250 cylinder questions

[mxthunder2]

Im in the process of rebuilding a 1998 cr250 with a new piston kit and new cylinder. the problem is i can find cylinders from different years of my same bike, but i dont know if they will fit or not. I've heard that from 1997 to 2001 there was no change in the cylinder, but im not sure. If that was so than shouldnt all the part numbers be the same??? and the prices are different too. So anyone who knows if there is a cylinder from a different year cr250 that will fit directly on a 1998 cr250 could help me out it would be greatly appreciated. Thanx ?

[kuritaro9]

*edit*

you can use a cyl. from 92-01...all of those years are fairly interchangeable. however, for the 92-96 cyl., you will need to change the head studs, and run the 97-01 head...

the porting will be slightly different, but not earth shattering.

IMO the best cyl to run are-not necessarily in this order-96,93,95,99,01... ?

[skipn8r]

IMO the best cyl to run are-in this order-96,93,95,99,01... ?

Which characteristics cause you rank them in that order?

[kuritaro9]

Which characteristics cause you rank them in that order?

whoops, i didnt put them in order...

96,01,95,93,99...

having a newborn makes me forget a lot these days...

96,01 and 95 because the power was almost identical, 93, for a fairly smooth hit and 99 for the great low to mid power ?

[kuritaro9]

here is a quick "not fully detailed" description of the main difference between the 92-96 and 97-01 cylinders.

the one on the right is a stock 96, you can see where the arrow points to the difference. the one on the left is a stock 01...other than some minor port timing changes, this was the main difference between those years... ?

also, you can see that the 01 has a smaller and different shaped intake window...

[skipn8r]

having a newborn makes me forget a lot these days...

Congratulations! Hopefully, you're a future "sponsor/coach/mechanic/crew chief" ? . BTW, I'm finding that strong low end "snap" really depends on precise jetting. I'm getting closer. Darn bike nearly jumped out from under me today .

[kuritaro9]

Congratulations! Hopefully, you're a future "sponsor/coach/mechanic/crew chief" ? .

yeah, one day i hope...but, right now, i feel like a janitor....

[skipn8r]

Yeah, those days will pass. I can't believe my kids are 14, 9 and 7 now ? .

[kuritaro9]

Congratulations! Hopefully, you're a future "sponsor/coach/mechanic/crew chief" ? . BTW, I'm finding that strong low end "snap" really depends on precise jetting. I'm getting closer. Darn bike nearly jumped out from under me today .

i have been playing around with a 7 position needle, and it really livens up the bike. but, it also makes the carb a bit too finicky with the temps.that combined with the odd sized main jets, and you can really get it precise...I'm just playing with it now, and probably wont make it my normal set up. i still like the 1368NS and 172-175 combo...

[skipn8r]

i have been playing around with a 7 position needle, and it really livens up the bike.

Good deal. I'm close to a set up I really like. Right now, I'm choosing the best SJ/needle diameter combo. Once I've nailed it, I plan to "altitude correct" it using the JD spreadsheet and pass it on to you for evaluation. I finally switched over to VP 110 octane this weekend to finalize my jetting and that really seems to have made the engine respond more clearly and consistently to changes. Hopefully I can go back to pump gas without too much trouble....

[kuritaro9]

we cant get the race gas here very easily, but we can get a pretty consistant 107 octane from the pump...next up will be the 96 HGA cyl. with a HGA modded 01 head... i gotta feel what the works bikes were like... ?

[mxthunder2]

WOW thanks a lot man! Lots of good info here!! I will definatly look into it!

[sonobob]

i gotta feel what the works bikes were like... ?

A friend of mine had a retired pro AMA 94 CR250....had a decent amount of engine work and what I can only surmise was a 'one-off' custom PC pipe. FAT. That bike was a rocket. He could consistently smoke my 94 off the line by 4 or 5 bike lengths in about 50 yards.

But with the stock sprocket gearing, it fell way short on top end...at least 10-12 mph slower than mine geared at 13/51. (but of course, on a SX track noone has any use for 5th gear WFO)

[Faded]

Good deal. I'm close to a set up I really like. Right now, I'm choosing the best SJ/needle diameter combo. Once I've nailed it, I plan to "altitude correct" it using the JD spreadsheet and pass it on to you for evaluation....

If it's not too much trouble would you mind letting me know what you come up with? Just curious to see where you end up. ?