rings?????

[catbed]

i did a compression test on my 850. from one to four they were 115-95-95-110. i added oil to the cylinders and all of them shot up to 135-140. i thought it is the rings, but its strange because the is no power loss when riding, although there is a flat spot around 2k, and it doesnt burn any blue smoke. is there any possibility that the head gasket is leaking? like, in between cylinders? also, the square o-ring around the cam chain area, is that supposed to go under the head gasket, or is it supposed to go inside the head gasket, like there is room for it in the square of the head gasket. i think mine is under the head gasket. its an MLS gasket, BTW.

[posplayr]

You went WOT right?

the throttle wide open during the tests right? I got similar reading till I went WOT and the compression poped Right up into the health range.

Posplayr

[psyguy]

the throttle wide open during the tests right? I got similar reading till I went WOT and the compression poped Right up into the health range.

Posplayr

sooooo easy to forget doing this... (and end up unnecessarily scratching your head over low compression readings)

[catbed]

yea i did do WOT, both times.

[DimitriT]

A couple of thoughts before you tear into it:

* cold motor or hot motor? You need to test it hot.

* the tester fittings nice and snug? The center fittings are sometimes hard to get snug.

* valve clearances? I know you said readings shot up after you oiled but I'd still check em.

The rectangular o-ring fits in a groove and the head gasket doesn't lay over it on my 550. I used the OEM head gasket so your's could be different.

[catbed]

as to the valves, i had just adjusted them and i need to order two more shims. two are a little tight.

i did test it cold. before when i tested it hot, it was still only at 110-115, not anywhere where i would like it to be, or where it was before i replaced a valve.(~150) i did take the head and barrels off but i did not re-ring it. the cross-hatch looked good and the motor only had 8k miles on it.

i got the head gasket from flatout so it supposed to be OEM. the tester fittings are snug on all of them.

[ddz]

rings

If you took the barrels off, did you check to make sure the piston ring gaps were in the correct position?#-o

[tkent02]

as to the valves, i had just adjusted them and i need to order two more shims. two are a little tight.

i did test it cold. before when i tested it hot, it was still only at 110-115, not anywhere where i would like it to be, or where it was before i replaced a valve.(~150) i did take the head and barrels off but i did not re-ring it. the cross-hatch looked good and the motor only had 8k miles on it.

i got the head gasket from flatout so it supposed to be OEM. the tester fittings are snug on all of them.

Could be the rings are not sealing if you did not hone the cylinders before re installing, your oil compression test indicates rings.

How much oil did you use in each cylinder?

[catbed]

i have this oil squirter can thingy. i put one squirt towards the front and one towards the back. i guess around a tablespoon?

i did make sure the ring gaps were in the correct position.

[tkent02]

Well, your two low cylinders being adjacent to each other, with identical readings, would indicate a gasket blown between the two cylinders, I have seen this on a few car engines. One small problem with this theory, there is a cam chain and about an inch of space between cylinders two and three.

How does it idle and how well does it run at very low power?

[catbed]

when it first starts, i have to start it on full choke which i never had to do before. it only idles at about 1k and if i turn the choke down to about 2/3, it goes up to like 2k. after it warms up, it idles fine. there is a flat spot around 1500 to 2000 rpms.

[tkent02]

when it first starts, i have to start it on full choke which i never had to do before. it only idles at about 1k and if i turn the choke down to about 2/3, it goes up to like 2k. after it warms up, it idles fine. there is a flat spot around 1500 to 2000 rpms.

Have you tried any carburetor adjustments?

[catbed]

yea, i tried using a colortune and it didnt fire every combustion stroke. i looked at the plugs after riding and tried to adjust them that way. 1 and 4 were a little rich.

[psyguy]

you know it can be a thousand different reasons, right? 8-[

anyhow, one thing not covered yet, the torque on the head nuts in spec?


btw, why did you need to replace a valve after only 8k?

[catbed]

torque is in spec, 27 ft-lbs. i had to replace the valve because it got stuck and was bent.