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Opinion on owning multiple 125's?

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lilredmachine
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PostPosted: 17:24 - 01 Mar 2018    Post subject: Reply with quote

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I also think that people forget just how good 2 stroke bikes are, even compared to the modern 250cc class.

If you were to "top trump" the new GSXR250 against a TZR125 or a similar Gilera, the 2 strokes would probably win on most counts.


*Cough*90's 4 stroke 250 class*cough*

https://s13.postimg.org/8kamchvh3/28472195_10156183680333485_138352431679550488_n.jpg

If you were to top trump the modern 250 GSXR versus the old 90's 4 pot one it would be destroyed. The old ones AFAIK aren't even legal for 47hp restricted licence holders due to power to weight.

Everything was better back in the day, it wasn't just the 2 strokes. It's a real shame that these 250s were never imported, there are hardly any about and a lot of people don't realise they exist. I once spent a good 20 minutes talking to a chap about his CBR250RR and then he mentioned that the bodywork on his had been different and asked if mine was modified. I said that mine had the original panels and that all standard 250s looked like that. He was like 'Lulwut 250, isn't this a 400?'... so even people who own grey import stuff don't necessarily know about them.
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M.C
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PostPosted: 18:05 - 01 Mar 2018    Post subject: Reply with quote

lilredmachine wrote:
Quote:
I also think that people forget just how good 2 stroke bikes are, even compared to the modern 250cc class.

If you were to "top trump" the new GSXR250 against a TZR125 or a similar Gilera, the 2 strokes would probably win on most counts.


*Cough*90's 4 stroke 250 class*cough*

https://s13.postimg.org/8kamchvh3/28472195_10156183680333485_138352431679550488_n.jpg

If you were to top trump the modern 250 GSXR versus the old 90's 4 pot one it would be destroyed. The old ones AFAIK aren't even legal for 47hp restricted licence holders due to power to weight.

Everything was better back in the day, it wasn't just the 2 strokes. It's a real shame that these 250s were never imported, there are hardly any about and a lot of people don't realise they exist. I once spent a good 20 minutes talking to a chap about his CBR250RR and then he mentioned that the bodywork on his had been different and asked if mine was modified. I said that mine had the original panels and that all standard 250s looked like that. He was like 'Lulwut 250, isn't this a 400?'... so even people who own grey import stuff don't necessarily know about them.

Wasn't that because the small Japanese bike market was really competitive? Over here the 250 market has been dead since the learner laws changed.

I looked for a 250 Hornet and other grey imports (VTR250) but they were all too expensive/rare/old. If I ever win the lottery I'll go over to Japan and fill-up a shipping container Smile
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lilredmachine
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PostPosted: 18:16 - 01 Mar 2018    Post subject: Reply with quote

learner law over here went 125 in '83, the first 250s in this vein started appearing in '85ish. The change in learner law essentially killed off the market here for 4 stroke 250s which was a real shame as they offer a very different riding experience to the far more common place 2 stroke 250s of the era. The MC22 that I have is essentially a 4 stroke motor in a lightweight 2 stroke frame, which is why the 400s (both CBR and VFR) have the designation 'NC' and the NSR250s and these CBR250RRs have the designation 'MC' it also explains the relatively cavernous 30ish kg weight difference between the 250 and 400 bikes.

Unfortunately what we have now are lawn mowers in comparison.
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M.C
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PostPosted: 18:31 - 01 Mar 2018    Post subject: Reply with quote

I guess the closest modern equivalent would be a KTM RC250 (not sold over here). 147kg (dry) vs. 143kg so close in terms of weight, but 32bhp vs 45bhp according to the interweb Neutral
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lilredmachine
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PostPosted: 18:41 - 01 Mar 2018    Post subject: Reply with quote

I refer to them as lawnmowers as they are mostly singles with the odd parallel twin for 250/300 these days. There is nothing even close to the 19,000rpm, 4 pot, 16 valve, gear driven cam screamers that were about back then, regardless of weight or power.

Even the Duke 390 only manages a real 38hp at the back wheel and weighs about 160kgs on the kerb, still considered a superlight these days though.
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stevo as b4
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PostPosted: 21:26 - 01 Mar 2018    Post subject: Reply with quote

I've always said it, but if Kawasaki wasn't bound by the A2 regulations and wanted to spend proper money they could have done much better with the 250/300 Ninja twins.

I personally don't see that you need 4pots on a bike under 350cc to make power, and I'd prefer two 125cc cylinders over four 62cc cylinders for maintenance alone, and also if you did do engine work, it'd be very hard to mess with such small internals like valves, springs and ports maybe?

The first GPZ250 allegedly made 45bhp at 12800rpm. Kawasaki only ever de-tuned the motor from GPZ to GPX > ZZR then Ninja. With the 300cc version 50bhp should have been quite possible going by the original figures.

Put the resulting motor into a proper light weight sportsbike chassis like an Aprilia RS125/250 and you'd have a decent little 120mph bike with four stroke reliability.

Obviously doesn't stand comparison with the smokers, but that's hardly the point in new bikes anyway.

Even in the 250cc TZR/RGV days, there were still some people that wanted or preferred a small four stroke, maybe the ones that commuted all year, did big miles, or just had no mates with 2strokes?
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lilredmachine
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PostPosted: 21:57 - 01 Mar 2018    Post subject: Reply with quote

stevo as b4 wrote:
I've always said it, but if Kawasaki wasn't bound by the A2 regulations and wanted to spend proper money they could have done much better with the 250/300 Ninja twins.

I personally don't see that you need 4pots on a bike under 350cc to make power, and I'd prefer two 125cc cylinders over four 62cc cylinders for maintenance alone, and also if you did do engine work, it'd be very hard to mess with such small internals like valves, springs and ports maybe?

The first GPZ250 allegedly made 45bhp at 12800rpm. Kawasaki only ever de-tuned the motor from GPZ to GPX > ZZR then Ninja. With the 300cc version 50bhp should have been quite possible going by the original figures.

Put the resulting motor into a proper light weight sportsbike chassis like an Aprilia RS125/250 and you'd have a decent little 120mph bike with four stroke reliability.

Obviously doesn't stand comparison with the smokers, but that's hardly the point in new bikes anyway.

Even in the 250cc TZR/RGV days, there were still some people that wanted or preferred a small four stroke, maybe the ones that commuted all year, did big miles, or just had no mates with 2strokes?


Figures vary, but the GPX/ZZR/EX250 officially made 37hp at 11,000 RPM, and was gutless. For some reason Kawasaki geared it at a bizarrely long ratio that meant it would actually top out at under 100mph, unable to pull past 12k in top gear. That means that the CBR that I have is around 20mph faster at the top end. If you read actual road tests at the time you'll hear of journos complaining of the peaky nature of the twins for comparatively little pay off.

Most of the confusion stems from people miss-quoting the ZZR 250 horsepower from the ZXR 250 horsepower figure of 45hp. The ZXR being the full fat 4 pot version. A lot of this is the Americans confusing shit by calling things like GPXs by the name Ninja and (late model) GSXs by the name Katana etc.

Small engines don't make big torque. So they need to rev to make power, hence why Honda's small capacity race bikes had tiny cylinders and lots of them for the capacity.

The CBR motors will break over 150,000 km easily with just oil changes and the odd clearance job. They can burn valves as the revs are so high that as they get older and valve springs loosen, control gets sloppy and they let gasses blow past the edges of the valves.

Compare that to something like the GPZ305 which was a Z250 motor bored out and with a hotter cam, most of which failed before 10,000 miles due to catastrophic top end failure. The ones that are left now all sound like a load of nuts and bolts being let loose in a tumble drier. I should know, I've owned one. And I can tell you from experience that a GPZ, even in 305 form, can hold no candle to the 250 4 pots.
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GSTEEL32
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PostPosted: 22:51 - 01 Mar 2018    Post subject: Reply with quote

I think whats also important in the "old vs new" argument is that , unlike the 80's bikes which sometimes had "wooden" brakes, the 90's equivalent were usually floating rotor affairs, which would park the bike bolt-upright if you wanted it to .......

That cbr250rr is a bl00dy good example actually, because the modern stuff simply can not hold a torch to that, or indeed the ZXR,Hornet or NC30 which were also available at the time......

I'm also pretty sure those high revving 250's would still manage 20 - 40k on the same engine build ....

About 3 years ago, I was about to put my hard earned into a NC30, but that was before I physically saw one and realised how small they are .....
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lilredmachine
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PostPosted: 23:12 - 01 Mar 2018    Post subject: Reply with quote

GSTEEL32 wrote:
I'm also pretty sure those high revving 250's would still manage 20 - 40k on the same engine build ....

About 3 years ago, I was about to put my hard earned into a NC30, but that was before I physically saw one and realised how small they are .....


A) like I said, 150,000km on a CBR motor is not uncommon. They are VERY well built. You can't rev a motor to 20,000 rpm without it being perfectly balanced.

B) how tall are you? I am 6"1 and fit on the CBR250 just fine. I had a Buell XB12-R and ended up selling it as I was far too large to fit on the fucker. Really disappointing as I had always wanted one.
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Teflon-Mike
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PostPosted: 23:27 - 01 Mar 2018    Post subject: Reply with quote

The 90's Jap-Market pocket-rockets were, to a large extent, a bubble of legislation. Japanese Home market licence & tax laws were punative against the big-bikes; anything over 400cc, really, and 250's and under enjoyed peculiar favour in the regs.

The hot-snot 250/400's are probably best explained by the 'Baby-Blade' CBR400... it looks more like a 900 blade in many ways than a 900 blade! Only smaller! The 900 'Blade, despite lack of any racing pedigree, was for a while 'the' bike the world wanted, and sold by the boat-load.... in the US.. and were on the cover of every-magazine... but in Japan, you couldn't buy one! They were an 'export only' model. Hence they built the Baby-Blade, a scaled down replica of the 900 that Jap-Market riders could buy and ride.

At variouse points, Japanese home-market regulation was particularly perverse, and while they showed bikes like original GSX1100 Katana or the GPz900 at domestic expose's.. for the Japanese public roads, anything with an engine over 750cc was taxed/licenced as a car, and you had to provide proof-of-parking to be able to even register one, and the only way some 'rich' Niponese managed to get export-market exotica into the country, was to buy it in Australia! Then, domestic licencing made you lay the bike on a matress on its side and show you could pick it back up, to get a registration plate to ride it!!! Heck, I'm 6'2", and 14 stone, and struggled to do that with 575lb of VF1000! Judo MAY be about using your oponents strength against them, BUT I dont think that a typically 5'4" 10stone Nipponse would have easily Bruce-Lee'd one of them off a futon!

The cult of 400/grey-bikes in the UK, was a similar side-effect of Japanese tax laws, that increased the tax tarrif year on year to promote sales of new-bikes, and the only way to avoid paying tax on an older bike was to officially 'scrap' it, never to be returned to Japanese roads; hence they came over the water to UK and Australia by the container load, as 'scrap'.

The 250's and 400's were actually restricted by Japanese Domestic regulations to 45bhp... an early Yamaha TZR250 two-stroke, was just over the limit, and for all the techno they chucked at later pocket-rockets, they were no faster or more powerful for it... Just more expensive to build!

It costs much the same to make a motorcycle no matter what the cc is. Still needs two wheels, a pair of handlebars, a seat etc, and takes as much labour to bolt all the bits together. Actually scaling down 'big-bikes' to meet artificial licencing regulations, in many cases made them MORE expensive to make than thier bigger brothers, due to holding tighter tolerances on the smaller parts, and the demand of using more exotic and more expensive materials to keep the weight reasonable.

The 1983 VF750 was a bit of a flop for Honda, who had pinned so much on the 'hype' that a Vee-Four was the 'only' way to build a more bulky water-cooled four-cylinder engine that made the same or more power than an air-cooled one... when the VF750 actually made LESS power out the crate than the air-cooled CBX750... and weighed a shed load more for it! Oh... and the Kawasaki GPz600/900's that proved them utterly 'wrong' about the Vee-Four concept! The VFR 750 launched 18 months later, with vaunted gear-driven cams, in the face of the chocolate cam consternation the VF750 launch models quickly established, was then a GREAT bike... but rather like the Porshe 911 a feat of development over design... the later homologation special 'racing' RC30 even more so.

BUT they reckon that rather like the Austin Mini, until the launch of the VFR800 in around 2002, it actually cost Honda as much or more to make every single VFR than they made from selling them in the show-room!

Now ponder, that the VFR400 had just as many 'bits' and cost pretty much as much to make.... it was only viable because the Japanese domestic market could absorb enough examples to find an ecconomy of scale A-N-D because they were as much as the market was allowed... so tolerated an enormousely inflated show-room price tag!

The CBR250, 20,ooo rpm super-screamer, still stands out as one of those bubbles of technology produced by the punative Domestic-Japanese market regulation. At 45bhp it was no more powerful for all that technology than a reletively 'tame' two-stroke TZR.. just heavier, and more expensive, and for ALL that techno wizzardry.. it lines up pretty closely to a 1980 vintage Moto-Guzi V50, that with half the number of cylinders, 1/4 the number of valves, no water-cooling AND push-rods for crissiks, managed as much or more power at the crank, and 'handled' even with a shaft drive without all the aluminium mono-shock techno suspension! Just twice the size of fire hole in its engine!

It's revealing that since the Japanese domestic manufacturers have lost a lot of the Yen advantage thier currency offered, more, the favour of discounted investment loans, thier offerings have been ever more 'expensive' on the world market, and the 'advanced' technology reeled in. Even more revealing that since they relaxed domestic licence regs to allow Japanese to own 'real' 600+ siper-bikes... first so many haven't... and second that the availability of larger displacement world-models has seen the virtual 'death' of the home-market pocket-rockets... without that artificial regulatory incentive to make them, there IS virtually no market for them as 'just' the techno marvels they may be... and they are not commercially viable otherwise..

Interesting as they may be, it really shows just how irrelevent the Hot-Snot Jap-Market 250/400's actually were and are simply as motorcycles, and quarter of a century on, how much power they may have claimed at the crank remains pretty much of accademic interest only... yes, interesting, and perhaps a little spectacular just how high they got them to rev and how much power per cc they achieved... B-U-T, they never would have, had they not had to work within the punative Jap-Market regulations, and all that 'awesome' pales into insignificance along side a bike of half the displacement and a tenth the technology, that sold for a fraction of the show-room price where artificial regulations didn't influence matters...
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lilredmachine
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PostPosted: 23:38 - 01 Mar 2018    Post subject: Reply with quote

Teflon-Mike wrote:
*snip*


All I got from that *massive* wall of text is that bikes with twice the capacity could put out the same amount of horsepower and that a bike that had a power stroke twice as often could put out the same amount of power.

Explain to me again how these aren't incredible marvels of technology?
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lilredmachine
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PostPosted: 23:45 - 01 Mar 2018    Post subject: Reply with quote

Quote:
Kawasaki GPz600/900's that proved them utterly 'wrong' about the Vee-Four concept


Also this.

How many of the modern full fat MotoGP/WSB bikes aren't V motors, or motors that emulate a twin firing concept? I'll wait.
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stevo as b4
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PostPosted: 00:24 - 02 Mar 2018    Post subject: Reply with quote

Early 2ma TZR250's were actually 50bhp. The 45bhp was at the back wheel. Im sick of people swapping bhp figures between engine claimed power and rear wheel bhp just to suit their argument, or worse still using crank bhp figures from one bike and comparing it to wheel bhp figures from another!

Very sloppy TM!
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lilredmachine
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PostPosted: 12:05 - 02 Mar 2018    Post subject: Reply with quote

stevo as b4 wrote:
Early 2ma TZR250's were actually 50bhp. The 45bhp was at the back wheel. Im sick of people swapping bhp figures between engine claimed power and rear wheel bhp just to suit their argument, or worse still using crank bhp figures from one bike and comparing it to wheel bhp figures from another!

Very sloppy TM!


Manufacturer crank figures don't really mean much though, only hp at the back wheel on a given bike.

If you look on youtube there are no dyno videos of CBR250s making less than 43hp at the back wheel, with up to 47 being made with jetting/pipes. I was reading an article on tuning them a little while ago and the OP made 56rwhp out of one with a polished/ported head, removing the backlash cam gears and a slight overbore (like 20cc). That's pretty much what a stock CBR 400 puts out.

It is difficult to find any totally stock dyno results as people only have them dyno'd when they are tuning otherwise it's an expensive waste of time!

There are also 250cc class speed run bikes using these motors because they are the fastest and best built things ever to be 4 stroke and that small readily available. Some are turbocharged, some are supercharged and can make over 100hp on the stock bottom end.

https://s13.postimg.org/qglwty6uv/20140614_180938.jpg

https://s13.postimg.org/9jwu1hwpz/four.jpg

HurHur.
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stevo as b4
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PostPosted: 13:10 - 02 Mar 2018    Post subject: Reply with quote

Way off topic, but I do get that and the fact that bhp at the rear wheel is what is easy to measure and compare between bikes.

The problem is that chassis dyno's have an awful reputation for inaccuracies and fiddling figures and incompatible measurements between brands and even different models of the same brand. Also alot of them were till quite recently inertia dyno's, and this is not always an accurate way to measure power curves especially on very powerful bikes or tiny mopeds that struggle to spin the weighted drum etc.

And like you say there's no industry standard for how you prepare and test a bike on a chassis dyno. Things like tyre pressure,chain and sprocket condition and type, tension and lubrication all affect it, as does brake pads or drums binding etc etc.

That's why I'm interested in what a manufacturer tests an engine at at the crankshaft or even the gearbox output shaft, as it's very controllable and repeatable, even down to running the same coolant and oil temperature on every run.

I just hate it when magazines pick up say a new R1 that has a manufacturer claimed 200bhp, and then dyno it and it makes say 185bhp. Then they say Yamaha are full of shit and the 200bhp is total lies! It gets even worse when a manufacturer quotes a bhp figure for a ram air bike doing say 160mph. The magazine thicko journalists can't comprehend that, and coupled with the fact there are very few dyno's that can properly simulate Ram air effect, they say the manufacturers are talking pure fantasy.

Prove it or shut up I scream in my head. Laughing

I'd forgive them if they had accurate bhp figures at the wheel for every single bike tested on the same dyno in exactly the same way. But when they quote one bikes claimed bhp in road test against another bike they have dyno tested, without stating how and where the power figures were taken from, it's fucking poor IMO! And I've not yet seen a magazine that doesn't do it in nearly every issue.
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Teflon-Mike
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PostPosted: 14:45 - 02 Mar 2018    Post subject: Reply with quote

Not quite sure what you are waiting for, Red....

When Honda launched the VF series, starting actually with the Magna/Sabre series for the US market, ahead of the 'Interceptor' series of 'Euro-Style' sports-bikes, they did so on a bow-wave of publicity 'Hype' claiming that it was the 'only' way to make a water-cooled, multi-valve motorcycle engine compact enough that it wasn't even wider and bulkier and more cumbersome, and difficult to package into a motorcycle frame, that might actually 'handle' and not be overly tall and ill-balanced; which were criticisms roundly leveled at the last across-the-frame air-cooled 'fours' of the muscle bike era.

However.. when launched the VF750, turned up, full of cams and cam-chains, and threatening to self destruct, tipping the scales at just under 250Kg for a claimed 86bhp..... compared to Honda's own air-cooled 'four' CBX750, that claimed 93bhp for 215Kg... rather making mockery of the original claims for the VF series!

The GPz600/900's, launched to market within months, with water-cooled 'accross the frame-four' engines, also proved Honda's claims that they 'had' to make the VF a V to stop it being unduly wide and bulky, rather erroneous!

Relevance of modern Moto-GP and WSB bikes using V-Config motors, as hinted at, as much for power delivery as for ultimate power, or handling, is rather skew and irrelevant.

Again, a lot of the comparison is perverted by regulations. Blue-Ribbon GP racing used to be a pretty unconstrained 'build what wins' class.. which lead to the last of the 500 two-strokes that bore so little relevance to production road bikes at the end. Super-Bikes, notionally based on over-the-counter production models, 'should' be more closely related and more relevant to road bikes.... B-U-T Honda drove a mac-truck through the loop-holes of the regs in the late 70's, and through the 80's building 'homologation-special' virtually hand-built HRC race-bikes, in 'just' sufficient numbers to meet Homologation quota's to race them as 'production' machines.

The Honda CB1100R is case in point, they made barely 1000 for world-wide distribution each race year, and yet, like the VF1000R that followed it for proddy-racing, they failed to find enough road-riding customers to buy even that small number of 'specials', and were stock-piling unsold examples; of the VF1000R notably for 'years'! Some of the last of those not sold until almost six years after launch year!

Interesting that Ducati, challenging the dominance of the similarly Regulation-Cheating RC30, in the late '80's and 90's, exploiting, again, regulations, that limited four-cylinder machines to 750'cc, while a twin could be a full liter or more, but were taken to brook with their own Homologation applications, where they were shown to be playing Fararri's game of trying to homologate bikes on paper pre-sales and parts in the shed, that in no-way reflected what customers may actually buy over the counter, or the number of bikes they might, even if they wanted them! A-N-D running foul of the mods regs, with things like carbon-fibre fairings few of the 'production' bikes ever got, unless it came with a special paint job and 'limited eddition' certificate!

Ultimately brought to a head when Ducati, announced that all's fair in love and Road-Racing, and Honda had the same rule book, they did..... Resulting in the Honda VTR1000SP, to meet the challenge that they didn't have to try and win with a V-Four and could exploit the same regs to build a better Ducati....

In Moto-GP..... last of the 500-two-smokes were scaring 200bhp and potentially less than 100Kg, and were renown as evil handling beasts, as well as technological irrelevances, using two-stroke motors, threatened into extinction by emission regulations for the road.

Last of the line 'Big-Bang' motors, tipped the hat at Yamaha, who stated at the time, it wasn't about building the most-powerful or lightest 500 bike they could, but the 'best' all-round machine that got round a track fastest, and had been sacrificing the ultimate power they could get from a motor, and even the lightest weight they could get from a chassis, for 'tractability' to make them rideable, and less want to spit Raynie into orbit with Schwantz or Doohan !

At one point, ISTR they were having to 'ballast' bikes with up to 30Kg of lead weights to meet the race-regs, and some-one in the Yamaha camp, commenting that the racing was becoming almost a side-show, and the 'real' competition was in the pits to discover the best place to put the ballast!

The later 4-stroke Moto-GP bikes, devoid of the homologation rules for production racing, still have to comply with race-regs, where the minimum weight limits, are just as perverse, in that there is no great incentive to find so much weight-saving, when they would have to ballast to meet limits, hence favoring 'heavier' four stroke engines over the two-strokes, and more convoluted, heavier bulkier ones toboot, and where a V-Config engine, can be made as 'heavy' as anything else, and just need less ballast, and might have power-delivery advantages, as claimed for the 'big-bang' concept motors....

Which may or may not hold as much merit as far as 'tractability' is concerned, as Yamaha pointed out with the parallel twin TLR850 umpety years ago; power pulses don't actually depend on the angle between the cylinders, but that between the crank-journals!

Either which way... Honda vaunted the V-Four concept when they launched it, and it was soundly proved 'flawed' even on their own claims, even by their own engineers, at the time!

OTMH I can only think of one manufacturer who followed them down the V-Four road, and that was Yamaha with the V-Max, built to 'ace' the Magna cruiser on the US market!

It is interesting to note also, that Honda at one point claimed that they persevered with the V-Four, as much for 'market presence', the V4 a Honda 'trade-mark', like a BMW Boxer of a Ducati 'L-Twin', as much for any potential and probably spurious technical advantage.

Just as interesting to note that in 1986, in the face of having to build the RC30 Homologation-special to make the VF750 remotely competitive on the track, they hastily reverse engineered a GPz600, and launched the CBR600 'straight-four', at the time, completely re-writing corporate history, and making great claims to have 'invented' the 'four' cylinder motorcycle engine, with the CB750 in 1969..... err.... I remember the outraged cries of 'SQUARIAL' or even 'Hendee' let alone Nimbus! at the time!!!

But then, Honda's press department has always had a rather teniouse grip on 'history'.... in 1980, Swede, Ulf Karlsson won the FIM World trials Championship on a Montesa 349... Montesa was, at the time still a wholly independent Spanish company, owned mostly by the Permanyer family, and in part by the Spanish Gov't... yet THAT title is so often claimed as the 'first' World-Trial-Championship, achieved by HONDA in their press releases, vaunting the string of titles taken on (Spanish built!) 'Honda' HRC Montesa 315's, in the late 90's and early 2000's, despite the fact Honda never even owned any of the company at the time, and no more than a part share of Montesa until 1985! While their first 'act' of 'partnership' was to effectively 'kill' competition trials Montesa's, to allow Eddie Lejeune a chance of the title on a wholly Honda designed and built four-stroke, derived of the XL250!!!

It remains, that the mini-marvel 250/400 Japanese Market sports-bikes of the late 80's and 90's, were just that; mini-marvels. Fantastic examples of the manufacturers capability, BUT, they were only created because of artificial, and perversely Japanese domestic regulations that made them economically viable, and technologically necessary. Where and when those regulatory advantages didn't exist, they rapidly became extinct. There were much better ways to make a better, cheaper, motorbike.

Ste? I don't recall quoting ANY power specs for the launch year TZR250... only stating it was a little over the later Jap-Market 45bhp licence limit... isn't 50bhp just over that?

Does beg mention of the Benelli 2c though Wink What was the first 250 proddy bike to lap the island at over 100mph?... In a race..... then define 'proddy-bike'! Lol.

OTMH the credit probably has to go to the TZR with Mat Oxley on board, racing one imported ahead of euro launch, and only just behind Japan market launch, in the loop-hole that the TT was an international event and the TZR was available over-the-counter 'some-where' in the world at the time... and marginally less tweeked for class than the Benelli had been half a decade earlier. But still.... it was, at least still notionally more 'road-friendly' than when Kawasaki stuck lights on a sit-ifrikan KR250 racer, and claimed it a 'production-road-bike'.... it had a DUEL SEAT! Lol!

Brings to mind the Greeves Silverstone! Built in the mid-to late 1960's, it was an over-the-counter 250 class road-racer, with a very heavily modified Greeves/villiers two-stroke single motor. Based on the Greeves trials and MX bikes that sold in much higher numbers, I believe that it 'briefly' was eligible for "production" class racing, certainly in the US, and I recall one or two being fielded in the 80's in the UK against X7's, 250LC's, and even the immortal TZ's in the 250 'open' class, and not disgracing themselves! Not 'bad' for something more closely related to a lawn-mower and silver-cross pram, built in a shed in the Cotswolds like a push-kart, than one of the Niponese techno-marvels!!!
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redeem ouzzer
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PostPosted: 15:24 - 02 Mar 2018    Post subject: Reply with quote

stevo as b4 wrote:
Early 2ma TZR250's were actually 50bhp. The 45bhp was at the back wheel. Im sick of people swapping bhp figures between engine claimed power and rear wheel bhp just to suit their argument, or worse still using crank bhp figures from one bike and comparing it to wheel bhp figures from another!

Very sloppy TM!


I've just been doing some dyno work on a mate's TZR race bike. Standard you'll do 40-45 RWBHP on these providing the barrels aren't as worn as Smiler's gums. The best run we had was 57.9bhp at the wheel and that was on standard carbs and airbox, plus "homologated" shit Yamaha CDI and YPVS controller.

Anyway, I don't get what teffers was on about as I couldn't be arsed reading gibberish from someone who hasn't a fucking clue about building and developing fast engines. I assume he doesn't like 250 and 400 4t 4's for some inane reason, probably autism related.
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stevo as b4
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PostPosted: 15:49 - 02 Mar 2018    Post subject: Reply with quote

Blimey! That's alot of power for a TZR with the limitations of a std ignition!

I expect it has some very trick pipes, and lots of internal mods too! Whoever built the motor certainly knows their shit that's for sure!
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lilredmachine
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PostPosted: 10:34 - 07 Mar 2018    Post subject: Reply with quote

stevo as b4 wrote:


The problem is that chassis dyno's have an awful reputation for inaccuracies and fiddling figures and incompatible measurements between brands and even different models of the same brand. Also alot of them were till quite recently inertia dyno's, and this is not always an accurate way to measure power curves especially on very powerful bikes or tiny mopeds that struggle to spin the weighted drum etc.

And like you say there's no industry standard for how you prepare and test a bike on a chassis dyno. Things like tyre pressure,chain and sprocket condition and type, tension and lubrication all affect it, as does brake pads or drums binding etc etc.

That's why I'm interested in what a manufacturer tests an engine at at the crankshaft or even the gearbox output shaft, as it's very controllable and repeatable, even down to running the same coolant and oil temperature on every run.



It's also an issue that there are often many variables when manufacturers claim power figures at the crank. If one engine has been run with tweaked injection maps, unrealistic exhausts and other tricks (such as 0wt low friction engine oil) and one is dyno'd and claimed under more realistic conditions that more accurately reflect the engine's behaviour in the machine, then the actual power figures when the motor is in the bike will have larger or smaller differences at the rear wheel compared. Engine and transmission mileage on the test motor will always have an effect, too little and it will be tight, too much and a few of the ponies will have escaped. You can damn well be assured that most figures are going to be dyno'd/claimed at the ideal time in a test motors life!

There are some manufacturers, such as Suzuki, who are known for having stronger ponies from the crate when compared to similar bikes from other, more optimistic manufacturers claiming the same power.

I can see the appeal of using the claimed crank figures over the crazily variable conditions chassis dynos can be run under, but the truth is that most, if not all power figures are going to be skewed, whether manufacturer or independently obtained, crank or wheel, on purpose or accidentally.

Even with the same manufacturer, crank figures can be bauked. Check the FZ1 vs. the MT-10, both Yamaha, the FZ1 claimed 150hp and dynos anywhere from 135-138hp at the rear wheel stock, the MT-10 claims 158hp at the crank and dynos 137-139hp at the rear wheel. Either the MT-10 has a shit, inefficient gearbox or Yamaha are outright lying about the crank horsepower of the MT-10.

If you believe FactoryPro, a stock Hayabusa only puts out 145hp at the rear wheel on their 'realistic' dyno. The fact that just about every dyno test on every other stock Hayabusa anywhere on every dyno ever has pegged them between 160 and 165 doesn't convince them they are wrong!
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