www.t20suzuki.com

[windmill john]

Okay, now more confused!
2Stroker kindly sent me a link to piston sizes
BTW, I have a 1975 engine in a 77 GT250
It appears to have X7 pistons fitted and I'm led to believe an X7 crank.
Okay, the problem. Robin Davies told me that X7 pistons can cause issues.
I cannot get above 40mph.
Speaking to Crooks, they tell me that X7 pistons are okay in GT250s and to look elsewhere for my problem.
Baffles spotless
Carbs cleaned and slides should be in right carbs as oil mark lines up in right carb.
Points gap looks good, so does timing; even purchased a dial gauge to make sure.
Before I put the barrels back on, can someone give me a definitive answer:
Are X7 pistons okay, bearing in mind they are 3mm shorter than GT250s
I've had a lot of four strokes, but am aware that port timing is quite critical with two strokes.
Any help please!
Cheers
John

[Admin]

Shorter pistons will affect the port timing. The power will be higher up the rev range, possibly losing low down power.

You say that you can't go above 40mph, but this info is useless without telling me what gear you are in, what revs etc. Can you nail it through the gears, revving to 8-9000 rpm in every gear? What happens if you try, where in the revs is the problem, can you rev through it etc?

My TZ350 for example is barely rideable below 8000rpm - it is really hard to keep it running when riding through the paddock to the start grid... but this doesn't mean it doesn't go well!