I did a compression test just for curiosity

[oachs83]

I bought my 86 250r with a hole in the piston and I rebuilt it. It is bored to a 265 and for some reason I just wanted to know what my compression was. From dead cold has been sitting two weeks in 40 degree weather I got a reading of 215-220 psi. Now I really don't remember but I thought a stock quad was around 190psi max? I run it on regular 92/93 octane and the plug color is perfect but isn't 220psi a little high? Does one need race gas? Or are there more of you out there running at this psi?

[01shee]

I always just compresion with two gauges. But with that compresion you should be running straight race fuel.

[oachs83]

It does not detonate at all? I guess I have always thought you gain the most HP from running the lowest octane you can without detonation? Maybe I will get some and mix it 50/50 to see if anything fun happens?

[Honda 250r 001]

somethings not right, your gauge is wrong, with 220, i guarentee that on pump you would deto. Hell im runnin 190 and im on the virg of detonating. If your running stock cylinder with no decking or anything then your gauge is defeneatly wrong. if you have the cylinder decked or something then it could be correct.

[oachs83]

have always used this gauge and seems to be accurate? Just used it recently on a truck and seemed to work. To get the gauge in the plug hole I did need to sharply bend it as I was doing the test but I don't think that has anything to do with it?

[oachs83]

Multiple post

[oachs83]

Multiple post

[05LSR250R]

I run a stock head and cylinder with a really thin head gasket and im running at 210 psi of compression. It was higher than that when I rebuilt the motor two years ago. Just my two cents.

[speedfreek]

Originally posted by Honda 250r 001
somethings not right, your gauge is wrong, with 220, i guarentee that on pump you would deto. Hell im runnin 190 and im on the virg of detonating. If your running stock cylinder with no decking or anything then your gauge is defeneatly wrong. if you have the cylinder decked or something then it could be correct. I agree with above.

When my R was at 220psi it had a shaved head. Or stock head and a CR head gasket.

Did you put on a CR gasket? What plug you runnin? Better not be a B8 or hotter. You'll be rebuilding it again.

If your gauge is correct you def need a blend of higher octane gas.

[oachs83]

I will try a second gauge but this gauge has not failed me yet. I am running a B8 because I was running B9 and all it would do is foul my plug no matter where jetting was unless it was dangerously lean I am sure. I would get a 1/2 hr out of a B9. Switched to B8 and have not fouled one plug yet and have a perfect brown color. I did buy the quad used and have no idea if the head has had work. I bought a 250r top end kit from Dennis Kirk.

[speedfreek]

Originally posted by oachs83
I am running a B8 because I was running B9 and all it would do is foul my plug no matter where jetting was. I would get a 1/2 hr out of a B9. Switched to B8 and have not fouled one plug yet and have a perfect brown color. . Are you doing a wide open throttle then shuting it down then reading your plug? What is your gas/oil ratio?

[oachs83]

No I didn't due a plug chop but I put a brand new B8 in have ran about 3 hours on it have yet to have it foul and it has a perfect burn color. I am using the 100:1 Amsoil and mixing it 50-1.

[oachs83]

Well grabbed a second tester today and tested each one three times a piece. I am averaging 225-230 psi. Yet my engine is not pinging. It should sound like marbles in my engine right? The only thing I can think at all is that when the engine first starts up from dead cold the zings are a little farther apart. By Zing I mean the noise a two-stroke make is zing zing right. The zings are tight like zing.zing.zing.zing. but when it is cold and warming up the RPM's are a little higher than idle and the engine does more of a zing...zing...zing...zing... Sorry the zing is a little corny I just have no idea how else to explain it on a keyboard.

[gandgracing]

I always warm the motor a little before doing a comp. check