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Kawasaki ER6f - larger engine alternative

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lilredmachine
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PostPosted: 13:33 - 20 Sep 2017    Post subject: Reply with quote

MINI twins are heavily restricted, SUPER twins used in road racing are not, the JHS motorcycle svs are kicking out 100+ rwhp from the sv (ish) motor. One of these is a 120mph lap machine at the TT.
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stevo as b4
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PostPosted: 17:44 - 20 Sep 2017    Post subject: Reply with quote

That explains it, two very different race classes using the same engines and bikes.

Supertwins are pretty cool IMO and a 100bhp 650 is some major race team engineering development and testing and special one off parts inside I'd expect.

I bet they destroyed quite a few engines to make a relatively reliable 100bhp 650, and as you say a 120mph TT lap is some going on a 650 too!
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Teflon-Mike
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PostPosted: 19:15 - 20 Sep 2017    Post subject: Reply with quote

What is proably more remarkable about the mini & super twins ISN'T how much power they 'may' get from them, but how much they DONT make to start with!

Back in the Cafe Era, they could get 60-70bhp or more from an air-cooled, push-rod two-valve Bonnie motor pretty easily. The Small-Bock Guzzi was probably one of the last air-cooled , two-valve, push-rod motors designed, and delivered 100bhp-per-litre matching then best Jap DOHC fours of the time....ACTUALLY, the CG125's air-cooled push-rod motor is possiby a tad 'later', with common lobe push-rod valves to keep manufacturing costs and maintenance down... at 1/8th litre even that is pushing 80-90bh per litre!

So what is then the more remarkeable, is not that they may get 100bhp from a 650 twin.... with four-valve heads, DOHC and water-cooling, etc etc; that is actually not such a huge achievement, nor is that such a 'granade' tuned motor with forged crank, shell bearings and high-pressure lubrication, can survive a handful of laps of the island... at 37.5 miles a lap, that's what? Do these do three or five laps? It's still less than 200 miles!

The remarkeable thing is, that as standard, these motors have all that more 'advanced' technology, by way of over-head cams, multi-valve heads, water-cooling, fuel injection etc, and YET, only deliver 'similar' power to 'old' air-cooled, two-valve, push-rod motors, of a similar capacity!!!!!

It shows how much modern engines have been 'strangled' to meet modern emmissions controls, and for manufaturing 'easement' to go into a more usually cost concouse 'ecconomy middle-weight commuter'.

With bikes like the S1000R, built to meet 'road' C&U regs and emissions, and consumer reliability, offering 200bhp per litre, from 1000cc and 4 cylinders... then 'half a 1000R' 500 twin (rather like the 60bhp GPz500 was reputedly 'half' a ZX10) aught to be able to deliver 100bhp straight off the stops; and a 650cc version, aught to be able to offer around 130bhp, BEFORE tuned beyond 'consumer' levels of reliability and C&U emmission regs!

For twenty-odd years, though, particularly in the larger-displacement classes neither 'power' nor 'reliability' have been such significant factors in what wins races; but making the whole package 'manageable'. Yamaha were happy to sacrifice power in the 90's to the fire-breathing Honda's or 'wild' Suzuki, for something less likely to spit the rider into the weeds, and won titles because of it!

It's interesting that whlst that still remains with the big-bruisers like the S1000R, in the lower classes, and mini-twins was originally concieved as a 'real world' and more 'affordable' class for more every-day road-based bike, even there, they are now punting the sort of power, reliably, and manageably, the sort of power that won Barry Shee more metal pins in his body than he got magnums of champagne to splash all over like cheap aftershave!!

Doesn't offer suggestion to the question of a more powerful commuter-twin... but does make you wonder where 'racing' and road bikes based on race evolution is headed, and how much 'progress' any of it has really made in the last 40 years or so.
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lilredmachine
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PostPosted: 07:21 - 21 Sep 2017    Post subject: Reply with quote

Quote:
It's interesting that whlst that still remains with the big-bruisers like the S1000R, in the lower classes, and mini-twins was originally concieved as a 'real world' and more 'affordable' class for more every-day road-based bike, even there, they are now punting the sort of power, reliably, and manageably, the sort of power that won Barry Shee more metal pins in his body than he got magnums of champagne to splash all over like cheap aftershave!!


Again, MINI twins have heavy restrictions on modifications and are pretty much power limited to 72hp. This is still a very affordable racing class compared to most others. The pretty much prototype SUPER twin class is far more expensive but you can still build a competitive bike for less than the outright cost of a new S1000RR. The engines will also manage more than a 'few laps' of the TT course even in that state of tune.

It's all relative.

It's also the case that at one point the SV was 4k brand new, which is the same cost as the new BMW 310 Indian built learner thing. So crazy motor development was never on the cards. The whole point of the SV was low budget, friendly approach-ability to new riders, smooth power delivery, low cost and light weight. Not mental specific power rating.

But do not think that there isn't incredible potential in the chassis of the SV, it has been proven time and time again.

I am also quite experienced with classic racing, having spannered for my mate when he ran several rounds of the Lansdowne and I know that sort of tune on an old british you are describing usually requires insane maintenance, and have seen guys boiling oil in a kettle and injecting it into the head so that the motor will expand enough for the internals to rotate... Looks very user friendly.

The CBR-250 I own was making 45hp back in 1990, which is 180hp per litre. It took litre bikes 20 years to bridge that specific output gap in a production bike.
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Teflon-Mike
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PostPosted: 10:01 - 22 Sep 2017    Post subject: Reply with quote

lilredmachine wrote:
It's all relative.

That's kind of the point..

The power being obtained from modern 650cc twins isn't all that impressive 'relatively'... even tuned.

What is interesting, is how you rate the handling on an SV650.. a bike that out the crate isn't much less powerful than the Sheene era 500GP bikes, that were fickle, prone to nipping up shedding tyres, going into violent weaves and wobbles and spitting riders ..

But, now out the crate bikes like the SV with that level of potential performance, are now considered a not particularly 'exiting' beginners bike or 'boring' every-day commuter!

The remarkable thing is how much bikes have been 'sanitized' and made 'so' consumer and environmentally 'friendly' along the way.

MAYBE, in that lies the answer... maybe what's needed to put the excitement back into biking isn't ever more audacious brochure stats.. maybe its under-damped twin-shock suspension; flexible steel frames and cross-ply tyres! Maybe cable operated SLS brakes, 'just' for that bit of extra Russian roulette 'spice'!?!

Point was 'sort' of how much expectations of everything have shifted, yet out of everything that has, power is one that hasn't actually moved that much... 'relatively'.. whilst so much else has.
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lilredmachine
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PostPosted: 20:39 - 22 Sep 2017    Post subject: Reply with quote

Teflon-Mike wrote:


Point was 'sort' of how much expectations of everything have shifted, yet out of everything that has, power is one that hasn't actually moved that much... 'relatively'.. whilst so much else has.


Ah, the joys of ever encroaching emissions laws.

Also, the idea of the SV650 being a 'modern' V-twin at 19 years old is somewhat laughable. The original SV is only 6 years off qualifying for classic insurance. The twins we have today are ultra short stroke, large piston architecture motors that all have their roots in Erik Buell's design for the Rotax twin in the original 1125CR Buell from 2008, that share very little with old tech twins.

Quote:
What is interesting, is how you rate the handling on an SV650.. a bike that out the crate isn't much less powerful than the Sheene era 500GP bikes, that were fickle, prone to nipping up shedding tyres, going into violent weaves and wobbles and spitting riders ..


The SV came from the factory with an aluminium trellis frame. It is held in whispered rumours that when the SV began to become known as a budget track rat, Harris began testing to see where it came up wanting in order to develop a better version for racers. The rumour follows that they gave up, deciding that the frame was essentially perfect. Indeed if you look through various reviews you will see comments like this from most sources:

Quote:
We even noted that Harris of England, a renowned chassis designer (involved in the current WCM MotoGP project), gave up on its efforts to build a chassis for the SV650 motor that surpassed the stock chassis for racing purposes the stock chassis was that good.


Like I said, not sure if this has been substantiated, but it's repeated mention speaks volumes for the bike.

The dangerous bikes you mention are old skool trouble. Dodgy frames with too much power delivered in too much of an aggressive fashion, trying to support too stiffer a fork/shock. The SV is the sweet spot, a beautifully designed frame with an underpowered but incredibly smooth motor, the capability to accept upgrades without compromising the frame and most importantly, the retention of sensible sized tyres that do not blunt turn in in the interests of fashion.

It was spot on, a revelation at the time and a proven contender even today.
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