Boxerworks.com

Hummmmmm cold and 3 weeks of sitting

I installed my rebuilt heads and went for a compression test pulled both plugs installed the guage rolled back the throttle pushed the bottom 5 pumps later 125 psi with about 7 pumps topped out a 128 psi

next!


Installed the compression tester rolled back the throttle push bottom and 5 pumps later 120 toped out at 125 about 7 pumps later

tried a leak down test but pistion always go to the bottom and 40 Psi went down in about 5 minutes


Hummmmmm maybe a run and a couple heat cycles

today rode and retested

135 left and 138 right

same leak down at 40 Psi and 15 minutes to drop to 20 psi each side............... I'm ok now

motor uses no oil the used cylinders and pisions came from a 40,000mi 1974 R90S that the ower said will take too much to rebuild and get in shape from years of sitting

I maped the cylinders at about .001 of wear and old rings fitted at .015 of gap

I replaced the rings at the time of rebuild

Motorhead wrote:Hummmmmm cold and 3 weeks of sitting

I installed my rebuilt heads and went for a compression test pulled both plugs installed the guage rolled back the throttle pushed the bottom 5 pumps later 125 psi with about 7 pumps topped out a 128 psi

next!


Installed the compression tester rolled back the throttle push bottom and 5 pumps later 120 toped out at 125 about 7 pumps later

tried a leak down test but pistion always go to the bottom and 40 Psi went down in about 5 minutes


Hummmmmm maybe a run and a couple heat cycles

today rode and retested

135 left and 138 right

same leak down at 40 Psi and 15 minutes to drop to 20 psi each side............... I'm ok now

motor uses no oil the used cylinders and pisions came from a 40,000mi 1974 R90S that the ower said will take too much to rebuild and get in shape from years of sitting

I maped the cylinders at about .001 of wear and old rings fitted at .015 of gap

I replaced the rings at the time of rebuild

135 and 138 are very close and within spec. Compression tests need to be done on a warm engine.
I've never had to do a leak down on my beemer. I've heard that it can be accomplished by putting it in gear at TDC and locking the rear wheel by tightening the rear brake adjustment nut as far as possible. Or you do like I did on my Vanagon......put a breaker bar on the crank nut (allen screw in this case) and hang on tight.

mattcfish wrote: I've heard that it can be accomplished by putting it in gear at TDC and locking the rear wheel by tightening the rear brake adjustment nut as far as possible. Or you do like I did on my Vanagon......put a breaker bar on the crank nut (allen screw in this case) and hang on tight.

I did a leak down test on my bike last night just to see if my advise was accurate. Screwing in the rear brake adjuster at TDC with the tranny in a high gear worked perfectly to hold the pistons in place. The motor did not even budge when I pumped over 100psi in each chamber. Both cylinders tested at only 2-3% leakage (less than 5% is considered excellent, up to 15% is acceptable). I've got less than 300 miles on them and it seams like the rings have set in quite nicely. No leakage detected at the valves.

Good news for you Matt maybe I'll keep the ole /5 ansI'm in the same ball park

Hope you have solved the mystery of an MPG issue on your R75/5 with a 900cc top-end and different cam...

I both recommend and pray you take the "OM's" advice here (the "OM" will know what that means). Not like carefully considering that person's advice is not always something one should take under serious consideration if you get a reply from him anyway.

This becomes comical for me, considering that you're Lyman from Ditto M/C Service from the [5United] list - the moment I realized that, I turned my brain off.

Good luck man.

Who's this OM comment?

OM = "Old Man"

dwire wrote:OM = "Old Man"

Yeah, THAT really narrows it down.

Major Softie wrote:

dwire wrote:OM = "Old Man"

Yeah, THAT really narrows it down.

OK, Old Man that knows CW??? Does that help?

Did you mean CV?

Chuey