Increasing NSR125's compression ratio

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Increasing NSR125's compression ratio

I would like some advice about increasing the compression ratio and boosting the sadly lacking horsies. What parts need replacing upgrading to acheive this. I have thought of a better carb, and possibly a different camshaft (do two strokes have one)

Welcome m8 i'll av a pint of Stella.No cams in 2 strokes.if the bores ok, stick piston and rings in it and have the head skimmed

go to Carnellsthey sell compression in tins- be carefull not to open it before u get homethey also sell spark plug gaps - about 50P - cheaper than new plugs

Doing anything to a two-stroke to get more power is guaranteed to make it go pop even sooner but the best options are:Polish the ports to get the air flowing more smoothly.If there's room, open out the ports a bit.Big (relatively speaking) bore kit.Race type ignition advancer.Arrow exhaust.Of the above the only two I'd recommend for everyday use are the polishing and the exhaust.Assuming you don't do too many motorway miles on an NSR125 you could just fit a one tooth bigger rear sprocket to make more of what you have already.This will greatly improve acceleration at the expense of top speed and mpg.

Cheers mate. I will have a go but it is really beginning to piss me off. Ah well I will try the new exhaust failing that I will chuck the crappy piece of shit.

Either Trade it in for summit ElseAs it appears you've no Idea what your doing, I'd surgest you talk to Stan Steven's he's the Two Stroke Guru (see bike press for phone number ect)Any Tuning work on a Two Stroke will shorten the life of the engine Components, particularly the Piston and Rings and to a lesser extent the Crankshaft, you can raise the compression by lapping the Head to the Barrel and removing the Head Gasket, but I'd avise you Leave it well alone.

couldnt agree more .......more cc's fella!

Easiest root to more power is more CC. Find a big bore kit! Also fitting aftermarket pipes can unleash a few ponies. Finally check with a Honda dealer and see if they have a deresitctor kit for it. Upping compression or advancing the ignition are good roots to melting your piston. If you decide to polsh ports, ONLY do the exhaust. Polishing the inlets and trnasfers affects fuel atomisation and robs power.I wouldn't bother with Stan, while he used to be "the man" I think he has as much interest in 2 strokes now as most people have in eating shit.

I thinks I am going to put on an enlarged carb get a new reed valve, polish the exhaust ports o and get an arrows exhaust this should bump me up to about 33bhp. What about cutting lumps out of the CDi unit in an effort to remove the 5000-6000 power limiter.

There's an internet sight around somewhere with all the info you need to get it up to 35bhp. They said the highest you could get without altering the CDI was 27bhp.

I had it up on a dyno. Got it derestricted, and now just want a bit more power. I have now fitted a k&N and a new set of race plugs. Its just that the damn thing dies at about 5-6k due to the whole environment bollox. I can only find sites relating to derestricting prilias. Ah well

I wouldn't go putting a bigger carb on without matching the ports and exhaust.. I prefer to fit big carbs to ported engines to increase the air/fuel as the engine will be demanding a lot more than a standard carb can give. I'm no tuning expert, but know some basics. Sounds like you have a flatspot caused by the K&Nm filter bouncing back pressure waves at the wrong time. Can be cured by fitting a length of tubing between the carb mouth and filter.CheersPaul

I think I ironed out the flat spot with a bit of carb tuning. I haven't done it yet but have found sites that suggest replacing one of the valves i think its the needle valve for better 5-7k revving.

or just try moving the clip on the needle. Down for more air and less fuel, up for more fuel and less air. There are a lot of needles to try and they aren't cheap!

thanx reading it again that was what it suggested.

should have suggested that to begin with. Having a lot of mixture woes with mine at the moment...let me know how you get on.

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