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leepick
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bennell09
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Kickstart
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 Posted: 21:18 - 22 Oct 2011  Post subject: |
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Hi
Depends to a large extent on how much performance you have and use.
I managed to get 74.5mpg from my RS125 during the fuel strikes by riding it VERY carefully (trust me, it isn't worth the effort except in exception circumstances).
Only time I have had a 2 stroke and a 4 stroke of the same capacity and rough performance was when I had an H100S and then a CB100N. The 2 stroke H100S was better on fuel. Although that is probably an exception it does show you how close they can be.
All the best
Keith
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leepick
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demon9374
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| Posted: 22:11 - 22 Oct 2011 Post subject: |
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Haha, reserve, I knew it was there for some reason. Might have saved me hassle last week 
I always ride with the tap on reserve as a while ago in the 'on' position, the bike would die, I should go back & take a look at that.
ie, last week, was riding home.. Ran out of petrol, good job I was 2 mins from the gf's and her dad took me for some petrol lol
Feel like a wolly now. |
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| unitynotsocri... |
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unitynotsocri...
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| Posted: 22:15 - 22 Oct 2011 Post subject: |
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two strokes can generally run on shittier/lower octane fuel,as the compression ratio's are lower and they have no traditional type valves,
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nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS |
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| Teflon-Mike |
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Teflon-Mike
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| Posted: 22:52 - 22 Oct 2011 Post subject: |
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| unitycrippledatmo wrote: | two strokes can generally run on shittier/lower octane fuel,as the compression ratio's are lower and they have no traditional type valves, |
Err, nope.
The octane rating an engine needs is all dependent on its state of tune, as well as the compression ratio.
The 'effective' compression ratio of a two stroke does depend on when the ports close in relation to the piston stroke, as well as such things crank-case compression ratio, then varies according to the engine speed, and the porting and trapping effeciency....
While 'Quoted' compression ratio's for two strokes are anomolouse; generally there are two; the 'theoretical' C/R which is as a 4T, swept cylinder volume divided by combustion chamber vol, normally around 10:1 for a 4T, or the 'Effective' C/R which is normally a lot lower, and the swept volume of the cylinder above the ports, divided by the combustion chamber volume. Some also quote 'Equated' C/R which is the theoretical C/R you would have to get the measured cylinder pressure, measured on cranking.
Octane rating is important to avoid pre-ignition, higher the compression ratio, more advanced the ignition, the greater 'knock' resistance you need to avoid the charge self igniting, ahead of the spark, or burning to rapidly on ignition. And octane rating is ONLY a measure of knock resistance, and does NOT define 'Fuel Quality'. Many properties may effect how 'suitable' a fuel is for a certain application, and the 'quality' may be measured against any number of them, depending on whats important, from clean burn, to maximum power, to fuel cost, to calorific efficiency.
And, on part throttle, the throttle is choking the supply of air hence charge into the engine, causing a short fill, limiting the amount of cylinder pressure.
Hence, the actual compression in a running engine is rarely that of the measured C/R..... which presumes a full cylinder 'fill', its normally a lot less, so if you have a 500cc engine and 50cc combustion chamber for a 10:1 C/R, at 1/4 throttle with only 125cc of air sucked in and squashed into a 50cc combustion chamber, you only get maybe 2.25:a C/R.....
Even at full throttle, the cylinder rarely sucks a full displacement volume of charge into the pot, and higher tuned engines, especially on higher revving engines where they can afford to loose fill, and make power from making more fill cycles, to pump same or higher volume of charge.
However, on a two stroke, where the question of trapping efficiency and the 'effective' compression ratio is used, presuming a 'short' cylinder fill from the volume above the ports, the ACTUAL compression in the pot MAY, be a lot higher, as due to lag effects possible to get closer to a full pot full of charge squashed into the combustion chamber.
So the numbers are anomolouse, but two strokes don't always have less compression, they often have more, especially more highly tuned ones.....
Keith has offered that Aprillia quote the RS engine as having a 15:1 ish C/R. Yamaha quote more like 6:1 for thier two-strokes. And as said, four strokes tend to be around 10:1.... and the two strokes are likely to not be much difference in practice, the variance in numbers most likely down to the measurement regime used.
Meanwhile, the two stroke engine completing a combustion cycle every revolution, and not having the un-powered strokes of a four stroke to wash and dissipate combustion chamber heat, tend to be rather a lot more prone to knock, pinking, nipping up, siezing and melting pistons, and I'd be dissinclined to run anything but the lowest tuned 2T agri-motor on 'low grade' fuel!
Oh.... adding oil to the 'charge' of a two stroke engine, either as 'pre-mix' in the fuel, or injected down-stream via an auto-lube system, also tends to effect the octane rating, of the mixture actually being burned in the pot.
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jamesrs250
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| Teflon-Mike |
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Teflon-Mike
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| Posted: 00:46 - 23 Oct 2011 Post subject: |
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| jamesrs250 wrote: | i think the rs125 is good on fuel well compaied to my car especially how fast they are they are pritty good on fuel, |
I don't.
Full power 28bhp & and used as they ought to be, they can struggle to better 30mpg.
My 'car' is a 4.0l Range Rover, with nearly 200bhp, and that can manage 25! At two tons, it's hardly 'quick' but its still genuinely faster than a full power RS!25! OK, its £200 a year to tax compared to £15, but even so!
And thats just the petrol going in the tank. Add a litre of high grade two-stroke oil for every fifty liters of fuel, bumps fuel cost from £1.35/l to £1.55/l.. or drops cost per mile to that of a bike doing closer to 25mpg.... like my Rangie.... which actually is running on 70p/l LPG, so returning effective miles per £ as a car doing around 40mpg......
Then you have the small matter that pistons and cylinders are deemed a 'service spare', and top end rebuilds are required at frequent intervals, with the crank shaft 'lifed' like a pure GP bike, before you get the fact that these things run 'big-bike' sized, sports tyres, with big-bike prices and mileages to be expected; they are FAR from 'cheap' machines to run....
And yeah, they are 'relatively' fast..... in full power form....... for a 125....
But in bigger picture, thats still not all that amazing.
Available performance is not a lot different to my Honda Civic 1.4 Auto 'run-about'! Which, returning 30-40mpg, is bettering that of the RS, and on running costs, even with the higher road tax, beating it hands down, not having demanded more than an oil change, in the last twenty thousand miles! Its probably also cheaper to insure, depending on circumstances!
Having one of their balls lopped off, to ride on a learner licence, yeah, can get around 70mpg.... which isn't bad, but isn't exactly great either, I can get that from the 750, without dumping in 20p's worth of silkolene to every litre of petrol, and merely replacing the screw on oil filter every couple of thousand miles, not the piston... and its faster, and its cheaper to insure.... and... and?!?
| jamesrs250 wrote: | a yzfr125 will be a bit better on fuel but it will be slower |
Restricted RS verses standard YZF-R125, power isn't a lot diffent, performance isn't a lot different..... top speed will be within one or two mph of each other, while the four strokes 'mid range', for all its likely to get wheezy up top, more likely to put more useful power to the road, more often, making it point to point faster, certainly in the hands of a newbie. And doing it for less fuel, and no oil.....
Yeah. RS125..... an interesting and engaging riding experience; but far from a cheap one.....
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Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
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| unitynotsocri... |
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unitynotsocri...
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| Posted: 02:58 - 23 Oct 2011 Post subject: |
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Thanks TeflonMike,i'm an old giffer who remembers points and grew up on drum brakes but you really teach me a lot,especially when to keep my gob shut,once again thanks for a decent education.
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nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS |
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temeluchus
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Supermotard37...
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| Posted: 07:31 - 23 Oct 2011 Post subject: |
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my ktm 125 exc does about 65miles before it needs a refil i think the tank is about 7ltrs  |
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Kickstart
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leepick
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demon9374
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| Posted: 11:20 - 23 Oct 2011 Post subject: |
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| leepick wrote: | loads of great posts. teflon mikes has to be the most educating. ive had the RS125 and yeh its fun to ride exspecially if ur riding in the powerband BUT mine spent more time being fixed than it was on the road so this time around im gonna get the yzf r125. all u have to do is put fuel in and go, hardly any risk of breakdown and i wont have that worried feeling of breaking down somewere and having to push it back like i have before. so yeh the yzf r125 is definetly my choice this time around. thanks for all the posts lads |
The YZF can still breakdown, electrics can go, starter motor could go, you're not safe from breakdown, but atleast for the overpriced sex machine, you'll get your warranty etc & shouldn't die on you anytime soon. But most things that go wrong on an RS, can still go wrong on the YZF
I was going to get a YZF, thought against it now. I can't keep selling up RS's everytime something breaks. I sat down, stripped it & fixed most problems. Quite pleased with fixing the starter motor, clicky pen springs, clean armiture, tissue paper  , jobs a good'un, brushes now doing their job lol |
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leepick
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| Posted: 11:25 - 23 Oct 2011 Post subject: |
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| demon9374 wrote: | | leepick wrote: | loads of great posts. teflon mikes has to be the most educating. ive had the RS125 and yeh its fun to ride exspecially if ur riding in the powerband BUT mine spent more time being fixed than it was on the road so this time around im gonna get the yzf r125. all u have to do is put fuel in and go, hardly any risk of breakdown and i wont have that worried feeling of breaking down somewere and having to push it back like i have before. so yeh the yzf r125 is definetly my choice this time around. thanks for all the posts lads |
The YZF can still breakdown, electrics can go, starter motor could go, you're not safe from breakdown, but atleast for the overpriced sex machine, you'll get your warranty etc & shouldn't die on you anytime soon. But most things that go wrong on an RS, can still go wrong on the YZF
I was going to get a YZF, thought against it now. I can't keep selling up RS's everytime something breaks. I sat down, stripped it & fixed most problems. Quite pleased with fixing the starter motor, clicky pen springs, clean armiture, tissue paper , jobs a good'un, brushes now doing their job lol |
lol. yeh both could break down anytime but with the rs its all about rebuilds new con rods new pistons etc. id have to get an 09 or 10 plate. just gonna try the yzf this time. 4 strokes are more reliable
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Kickstart
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| Posted: 11:32 - 23 Oct 2011 Post subject: |
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Hi
Have a search around for the thread on the YZF that Pete rebuilt after it had blown up. Made a bit of a mess.
The rod and main on an RS should last reasonably. Would expect around 20000km from them. Pistons and rings are just service items and easy to change.
If you want 2 stroke that needs less maintenance at the expense of a bit less performance (but still far quicker than the 4 strokes) then consider an NSR125.
All the best
Keith
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demon9374
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leepick
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Teflon-Mike
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| Posted: 18:50 - 23 Oct 2011 Post subject: |
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| Kickstart wrote: | Hi
Have a search around for the thread on the YZF that Pete rebuilt after it had blown up. Made a bit of a mess.
The rod and main on an RS should last reasonably. Would expect around 20000km from them. Pistons and rings are just service items and easy to change.
If you want 2 stroke that needs less maintenance at the expense of a bit less performance (but still far quicker than the 4 strokes) then consider an NSR125.
All the best
Keith |
| leepick wrote: | thanks keith. i do like the nsr125 a lot. and it makes sense to either go for the nsr or yzfr125, the nsr seems a good choice because like u say they dont need as much maintenance as the rs. so its either yzfr or nsr for me |
You know I am really strugling to understand your perversity in sticking with a 125?
You have been riding over 5 years, on CBT... and as said, if you cant get your act together and pass the tests in that time, you probably never will, and you don't deserve a licence, full of provisional!
And my my standards high time you legitimised riding around on unrestricted bike you dont have licence for, getting the licence!
Other thread, pointed out that a GS500 is the same insurance group as your RS125, makes more power, does more mpg, demands less maintenence, and offers more all round biking for a lot less money or hassle.... all it takes is a licence to ride one 'legally'....
And five years on CBT, even if you were 16 and did your first one on a 50, you ought to be over 21 and eligible to test DAS..
So you have all options open; current test regime still allows you to test for full A (restricted) on a 125, you could, provided you offer proof of restriction, take tests on your RS and get it out the way.
You could hire a School 125 to Test for A (restrict) if cheaper / easier then providing proof of restriction.
You could do full DAS course, and get full unrestricted A licence straight off.
Talking about De-Restricted NSR's you ought to have full licence for to begin with, or even brand new YZF-R1.... just doesn't make sense.....
Getting another 125, ANY 125, is merely holding you back, and perpetuating the problem, wallying around on L's!
Was outside Busters a while back and they had an R125 in the window next to a Hyosung 250; to my eyes they looked nie on identical, styling wise. Chap was pulling the roller blinds down as Snowie & I had a fag and warmed motors, and asked him about them, and price difference was such that you could, for price of R125 buy Hyosung 250, a four stroke, with R125 styling, RS125 kind of power, and YBR type running costs, AND full Rider Training Course course AND have change.... and thats a naturally 33bhp coimplient bike; and any 17 year old that could afford R125 could do just that; Think Roger pointed out that while Suzuki's discount offer was still on till last month, sums worked similarly for a brand new SV650, restricted or unrestricted. While running perms on the scenario and bringing second hand bikes into the equation, almost ANYTHING is possible with the £4K budget to get an YZF-R125!
So, given that there is no economic insentive to percevere with tiddlers; given there is no legislative incentive to percevere with tiddlers; given there is no practical incentive to percevere with triddlers....
Why-oh-WHY!? Do you keep coming back to alternative 125's?!
I no understandie!
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
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demon9374
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Old Thread Alert!
The last post was made 14 years, 348 days ago. Instead of replying here, would creating a new thread be more useful? |
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