Compression Test

[prometheus578]

Ventriliquest?"

Also, like Prom said...

Hmm.. I don't 'member saying that.
I've seen single cylinder engines spin under pressure, but can't recall an inline 4 doing that. I just like to remove the wrench first... just in case.
T.C.,
I've read GTRMN's latest post: "...with the piston at the bottom of it's travel..."
Didn't we have an arguement (Uhm... I mean discussion) about this once; (TDC or BDC?)
TDC will show leak-down at compression, etc, but BDC will also show cylinder wall wear, out of round, or something.
I can't recall what my position was concerning this.

[ratbyk]

I would suggest that it is impossible to do a leak down test with the piston @ BDC. At the bottom of a power stroke the exhaust valve is open. At the bottom of an intake stroke the intake valve is still open

[GtrMn]

Does the exhaust valve start to open just before BDC?

[GtrMn]

Oh yeah...in the mean time I'm doing the MMO thing...gonna let it sit over night.

[Geezer]

I hate to put a fly in the ointment but doing a leak-down test at BDC would give you artificially good results since there is less wear at the bottom.

On the other hand a BDC leak-down would be a good comparison for TDC test to get an idea of wear.

BTW, the valve adjustment is usually backed off when doing a BDC leak-down test but I haven't done one since mechanics' school about 30 some odd years ago.

Geezer

[prometheus578]

Why were they odd years, Geezer?
Were you slowly coming out of the altered reality of the 60's?

[GtrMn]

UPDATE:

Did the MMO and 2 + 3 went up to 142 and 136...much better! 1 + 4 are still high though at...160+. Did the MMO again...plus just used some Seafoam Deep Creep on 1 and 4...it's setting overnight again.

[ratbyk]

If your compression is uneven I would suggest that you adjust the valves. Low compression is first caused by valves that are too tight and followed shortly after by burned valvs/.seats.

[GtrMn]

Thanks rat..The valves are adjusted perfect.......and it sounds like a watch running...gotta be too much carbon at this point....MHO

[petejw]

just out of curiousity
gtrmn had the bike been sitting 4 a while?
or had u been using it consistently?

i ask cause ive never heard of a sticky ring
on a bike being ridden consistently.

good to c that MMO works well,
thats a good result for 2 and 3.

[GtrMn]

No..I ride it almost everyday. Plus, last weekend did about 175 miles round trip.

[GtrMn]

New update after the Deep Creep...1) 162 2) 145 3) 135 4)162....Think at this point I'll keep running Seafoam for the next few tanks and see what happens. Amazing to me though is how smooth the bike is running with those numbers...hmmm.

[ratbyk]

Don't fret, ride the sucker. A few good high speed runs and it might improve even more.

[GtrMn]

120+? Haven't done that in a long time!

[ratbyk]

You should have come to the XS11 Rally at Olympia Wash this year. We did 5 over a lot. (double the speed limit then add 5)