R11S Compression Conundrum....

[CE3]

Hey Folks......
I've got an '02 R11S Prep....It seems to have a compression issue. But, background first. Bought it maybe ten months ago, didn't ride it much. It has a cat eliminating pipe. In looking for a little more power I added a techlusion and Lennies Sprockets. No real improvement in performance. Adjusted valve to spec...sync'ed throttle bodies with Twin Max, cleaned BBS, set left throttle body voltage to .390 volts. New Autolite plugs...
I checked compression, engine pretty warm, throttle open, and I got about 145 on the right cyl. and almost 200 on the left. The weird part is: I then did a leakdown test with about 90lbs of air and came up with approx. 7% leakdown on both cylinders....which seems pretty minimal to me......I rechecked the sprockets and the indicating arrows are both perfectly horizontal......
So....there I am....anyone seen similarly contradictory numbers for compression and leakdown ?

Thanks for reading,
Bobsy

[bykemike]

Old but simple trick, squirt a little clean engine oil into the low cylinder and
retest. If the compression comes up it may indicate cylinder or ring issues,
if it stayed low it may indicate valve or head issues.
Not an exact science but gets you pointed in a direction.

Personally...I have had issues with leak down tests but it is another
clue you can use.

BTW, how many miles on the bike?

Mike

[CE3]

Hi Mike,
Thanks for the response.....I'll try the oil biz .... more anecdotal information.
Have you seen a cylinder and head that sealed up for a leakdown but not for compression? Seems like a pretty weird circumstance. A BMW tech at the local shop
mentioned something about a reed valve in the cases that might influence results ....but I'm completely ignorant on that issue....among others.
Anyway thanks for the input. I'll let you know the results of the oil for rings effort.
Bobsy

[SergioK]

You added a Techlusion/Dobeck controller and Lennies Sprockets yet noticed no difference in how the bike performs? Wow. That is odd.

[RBMann]

Could the timing be off on one side? I remember someone having a problem with the locating pin when they changed the sprockets.

[CE3]

Hey Sergio.....
Yes.... I probably should have worded that more carefully. The motorbike probably wasn't running that strong when I got it, but since it was new to me, I thought it was okay ....so I had no idea what to expect from the bolt-ons.
RB, as for cam gear timing, the arrows are perfectly horizontal at TDC. Which I think is correct.
At this point I'm going to do all this stuff over, double checking as I go. Hopefully something will show up.
Bobsy

[wswartzwel]

There are two top dead centers... timing marks should not be lined up at the same time. one should line up when its respective cylinder is at TDC... then turn engine 180 and the other mark should line up.

Originally Posted by bobsy

Hey Sergio.....
Yes.... I probably should have worded that more carefully. The motorbike probably wasn't running that strong when I got it, but since it was new to me, I thought it was okay ....so I had no idea what to expect from the bolt-ons.
RB, as for cam gear timing, the arrows are perfectly horizontal at TDC. Which I think is correct.
At this point I'm going to do all this stuff over, double checking as I go. Hopefully something will show up.
Bobsy

[SergioK]

Did you check the compression just the one time or performed the operation multiple times and always ended with the same result? 145psi (R) & 200psi (L)

[ckcarr]

Originally Posted by bobsy

I checked compression, engine pretty warm, throttle open, and I got about 145 on the right cyl. and almost 200 on the left.

Do you know what your standard should be for this engine?

According to my R1100S service manual:

Normal compression 121 - 142 psi
Poor compression < 121 psi

Maybe I'm misreading something?
It seems you might want to do a recheck on the left cylinder. Not sure how it's getting to 200 psi ?

OK, and this is a dumb question. How are you getting the compression tester seated and sealed in the plug hole? It's a long narrow tunnel through the cylinder head cover.

[CE3]

Thanks for the responses...........
Bill...you are right. I check each side after establishing TDC for that cylinder. Whether it is for valve adjustment or to view the cam sprockets. I think you mean 360 degrees.
Sergio... It repeats the same any number of times.
CK ...Now that is news to me. I assumed the higher number to be the factory spec. Also I recall seeing some pretty high numbers on these boards before. Still that is a good observation worth looking into. Carbon seems unlikely...@ 22K miles....pretty lean plugs, etc.
So.....I'm redoing everything including indexing the cam sprockets.
Thanks for all the input....It'll show up sooner or later.
Bobsy

[CE3]

CK...My compression tester has hoses w/ 14mm screw in threads for the spark plug hole and quick couplers for the gauge end.

[wswartzwel]

Thanks for catching my mistake.. was still working on my first coffee..

Originally Posted by bobsy

Thanks for the responses...........
Bill...you are right. I check each side after establishing TDC for that cylinder. Whether it is for valve adjustment or to view the cam sprockets. I think you mean 360 degrees.
Sergio... It repeats the same any number of times.
CK ...Now that is news to me. I assumed the higher number to be the factory spec. Also I recall seeing some pretty high numbers on these boards before. Still that is a good observation worth looking into. Carbon seems unlikely...@ 22K miles....pretty lean plugs, etc.
So.....I'm redoing everything including indexing the cam sprockets.
Thanks for all the input....It'll show up sooner or later.
Bobsy

[CE3]

Hey Bill............
While you were working on that first cup of coffee ...I was busy turning my engine backward....yes, with the tensioner removed. I think it jumped the cam timing on the cylinder at hand. So...it's all relative. I'm a big believer in "keep fixing until seriously broken."
So ...my new main concern is ...Has anyone reset valve timing at the internal sprocket?
I considered just hopping the cam sprocket but am concerned that if the sprocket diameters are different I will not have a proper adjustment.
In light of the current circumstance, I think 40 or 50 bourbons may be in order.
Bobsy

[brentw1]

sprockets must be the same diameter the 2:1 is in the front chain.
you can set it on the cam end,
also take a flashlight and inspect the guides and make certain they are not cracked
and the proper length. they can break at the ends.
I usually get 180 psi on a healthy bike

german bike schnapps

[brentw1]

blow some air in it with the bleed down and listen to the ports and see if you can hear the valves leaking, check the torque on the suspect head, follow the procedure they are angle torqued.
see if the bleed down is different at tdc and bottom of power stroke.
Ive never seen failed rings, but have seen failed valves.
pretty basic only 3 things can cause low compression., valves, rings gaskets, if the timing is good
also might look at the cams and lifters they can be bad but usually noisy.

[CE3]

Thanks Brent.....
So...if I read that right the internal sprockets are the same diameter as the external (at the cam) sprockets ? If that is the case I can just do the make up at the cam end.
Once that is sorted, I'll retorque the head. Then I'll redo the leakdown at top and bottom of the stroke.
Thanks for the suggestions,
Bobsy

[CE3]

For any of those who are still listening......
I have found the problem regarding my jumped cam timing. Yes, this specifically involves my turning the engine backwards with the tensioner removed. Thanks to Brent for the heads up about the cam gears (both inside and at the cam) are the same size. I'm not advocating making changes in this way but it did seem to work well.
As for the cam timing.......when I removed the cam gear to re-index I saw a small distortion of the mating surface at the cam. I seem to have torqued the gear without it being exactly centered in the index slot. This is probably why I had less than stellar results from the mod.
In the end I think I dodged a potentially major problem. Cam gear not straight, chain comes off, etc.
Regarding the compression issue.....I spoke with a veteran service rep for BMW who suggested that it is not uncommon to see this differential. Carbon build up on the kickstand side cylinder......he said to run it.....so I am.
Thank to all who responded to my initial post and subsequent timing debacle.
This a great forum,
Bobsy

[tjs]

If you flattened the index tab on the cam sprocket there is the possibility of it turning on the bolt that holds it on. This might cause valve/piston clearance problems. If I had any doubt I would replace the cam sprocket. 2cnts from tjs

[RBMann]

It will be interesting to see the compression #'s when everything is set right.

[brentw1]

I have checked compression on motors with 80k on them and not seen the compression
issues you have seen,
+1 on the cam index tab I should have some sprockets in the bin.