250r compression check

[jimeeatc]

hey guys, i'm wondering whats the lowest psi the motor will still run. the reason i ask is; my motor alway has kicked over too easily. i know it needs new bore @ piston /rings. but still runs great, but probably about to blow i assume because have run 2 set of pistons without rebore.- i know, not smart- but funds were low. i was curious to see what my reading was so i checked. shocked! 1st kick 20 psi, 2nd 40, 3rd 60, 4th 80, 5th 90, 6th 115, -well- it took me over 10 kicks to reach 155 psi. - (below minimum). can it really be this bad? bike runs fine. starts always with about 3 kicks. a little piston slap, but not too bad. is my gauge bad? anyone have similar situation ever? --------------------oh yeah, i did hold throttle wide open and choke was off. also,i would like to know how many kicks should you be up to for max comp?

[Liquid-Darkness]

10 kicks is about right. The manual says to kick it many times to get a good reading. The engine should also be warmed up before the compression check is done. Throw a fresh topend on that sucker, pipe it and jet it! Lots of power there. Run premium.

[jimeeatc]

hey bud , thanks. can you tell me how many rebore sizes over stock can you go on stock sleeve. .10, .20, up to? im .10 over now next size over may not be enough due to wear/use.

[jimeeatc]

again, how far can you go on stock sleeve?

[Liquid-Darkness]

.100 over or 2.5mm's? I think. Someone want to correct me if im wrong?

[jimeeatc]

thanks again.

[sandpuppi101]

I just had to go out to the shop and got some info for ya.The '85 R come's with a 66 x 72 bore and stroke ,and .100 would put ya at 2 1/2 over.And I see that I can get a wiesco piston at .140 which would be 3 1/2 over..In my opinion I would take it apart and see what ya have with the cylinder just cross hatched,maybe just new ring's is all ya need.If ya shop around ya can do the topend for less than 50.00 if it's only the ring's of course..

[GPracer2500]

What year? Wiseco makes +3.5mm over for the 85/86's. You can download a PDF catalog from Wiseco.


On the comp check--just keep kicking till the gauge stops climbing. In my experience, the higher the comp you're running the more kicks it takes. 10 sounds like a bit much for 155, but maybe. I've got a worked head that pumps 230. It takes a lot of strong kicks to get up there. Not so many from 0-150 or so but the higher it gets the more kicks it takes to gain X psi.

$0.02

[sandpuppi101]

Yep that's what my book say's ! I'm sure you can find the info from wiesco,but I'd have to scan it to post it up ,but yep that's what the book is telling me a 69.5 bore which is .140 for the '85 R's ..it's a Pro-Lite too, Part # 526P14

[Rustytinhorn]

If its 155 you should be good to go still. Most bikes besides the 250r are only made to run in the 150 in top condition. Was the engine warm? And what is your elevation?
I was riding at the dunes one time when I started to blow coolant out the reservoir overflow really bad. I mean it would empty my little tank in a half hour ride. Finished out the trip like that and when I got back home I took a warm compression test and got 120psi. Despite the low compression it still ran. Glad to say I have it fixed now with a new headgasket.