K11 Owners Group

[Dimond]

An Owner of a 1993 K1100LT for sale provided the following test chart that he obtained from his mechanic. The mechanic advised the owner that the engine had low compression in 2 of its cylinders. The Owner had this compression test done about a year ago and the Owner has been riding the bike successfully ever since - without any corrective measures. The Owner's opinion is that the bike could be peppier but that it has run well enough for him. Can someone please interpret the test chart for me and advise on what the compression issue may be, what may be causing the problem, and how it may be fixed? Thanks!

[Number 6]

I just see no compression on cyl 2 and 4, not possible if the bike works properly.
Quite likely that the mechanic screwed up, should be redone to be sure.

Unless the graph shows only the low compression cylinders, but why? Cylinder number 3 is pretty low.
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I am not a number, I am a free man.

94 K1100LT

[Scott_Anderson]

Like #6 suggests, I'd recommend the compression test be redone.
Then I would have the valve clearances checked. Sounds like there might be a tight one or two, not allowing a good seal.

Then I'd read Shog's thread here.
http://k11og.org/forum/viewtopic.php?p=37839&highlight=#37839
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Ride safe.



1995 K1100LT 0302044
2017 FLHTK Ultra Limited
Garmin StreetPilot 2820
Garmin Zumo 550
Garmin Zumo XT
"One who does not ask questions is ashamed to learn" Danish proverb
1997 K1100LT 0302488(R.I.P.)
1997 R1100RT ZC62149(sold)

[Dimond]

Many thanks for the input!

[jr'sbmw]

Doesn't make sense, so as already advised, have a retest performed by a knowledgeable mechanic. Compression tests are easy to do, but a couple of things can happen. The valve core at the end of the compression tester can get dirt in it causing it to leak down, not giving a good reading. The throttle must be wide open or the reading will be much lower. Crank the engine over so it comes up on compression 5 times on each cylinder(compression tester needle should jump some). Not 3 on one, then 7 on another.

If you have a low cylinder, follow up with a % leakage test, where air psi is run into the cylinder at TDC. By listening to where the air is coming out of the cylinder, you can tell if it is an intake valve, exhaust valve, rings, or in case of coolant leaks, a head gasket........ On new cylinders, I have seen only 5% leakage, 10% is good, but going down hill from there. On small piston aircraft, this is the test used for pass/fail, which has regulated 80psi going in on one gauge and if less than 60psi on the second gauge on most engines(25% leakage), it's tear down time. Good luck