Very low compression K5

[Michael janowicz]

Hello everyone, I was wandering if the Kips valve has any thing to do with loss of compression if installed incorrectly?? Thanks in advance, Mike

I think I may have slid the right side out, not sure if I put it back in correctly

[sandblaster]

Rings, cylinder wall, piston, head gasket, head volume, head, plug threads, and distance from the exhaust port closing to TDC effect your compression.
There is some bleed from the kips reliefs in the cylinder wall to help with starting but that won't for the most part give you a low compression reading.
What compression are you reading and when was the last time a complete top end was done?

[Michael janowicz]

I'm pretty sure the top end is original, really low hour bike, I can crank it by hand!! Single ring piston!! Maybe a broken ring??

[Foxx4Beaver]

Single ring piston!!

no kiddin...what year is it?....'87 was the last year for the single ring...or is it a newer bike that someone installed a single ring piston into?

[sandblaster]

If you pull the head off and rotate the engine I think you will see the issue...
Look for any color differences in the cylinder wall especially by the ports..

[Michael janowicz]

The bike is a 86' single ring piston, I had the cylinder off and it all looked good, I may have slid the Kips valve out on the right side?? Not sure if it went in right?? Could this cause low compression???

[Foxx4Beaver]

Could this cause low compression???

not that dramatically.
just because everything "looked good" when you had the jug off, don't assume that it is.
I would go back to sandblasters 1st post, and make sure all your clearances are within spec.

what brand of head gasket did you use when you put it back together?...and did you lap the head and jug mating surfaces to be sure they were flat when you had it apart?   

post some pics too if you have a chance.

[Michael janowicz]

The bike was running mint and stalled out at an idle, found the problem to be the nut in end of crankshaft- water pump side backed off rubbing against water pump! The flat washer that locks nut wasn't folded down far enough from the factory. I put the bike back together as it came apart, loss of compression now???

[Michael janowicz]

I used Cometic gaskets!!!

[sandblaster]

Trapped compression is the amount of compression that your engine makes once the piston covers the exhaust and kips ports.
So, once your piston is on it's way up and closes off those kips ports they no longer play a roll in compression.
Ok, what makes the compression after those ports are closed?
Piston, ring, cylinder wall, gasket, head to cylinder mating surface, spark plug threads, spark plug, and the cylinder to head alignment pins.
It's gotta be there somewhere.
Remember, you can remove your kips valves completely and all you will loose is your bottom end to mid range power.
The top end power will come on like a scalded monkey butt.
Start with the cheapest and easiest thing first.
Replace the plug and make sure it torques to specs.
Then I would pull the head and make sure that the alignment pins are not too long and the mating pin holes are clean and free of debris.
I would mic the cylinder wall and have someone who knows what to look for inspect your cylinder.
If the cylinder mics correctly and there are no flaws in the plating, and if the piston walls are cherry, I would as a minimum replace the ring, lap all the mating surfaces, inspect and replace any kips parts not in spec, and clean it all up to look better then new.
Then use new gaskets to assemble.
Of course with the cylinder off I would check the crank to connecting rod clearance with a feeler gauge and compare to the factory specs.
If it is out of new spec, I would plan on a complete rebuild.
Upon finding anything not in spec with the cylinder or piston I would pull the cylinder and clean up the transfers, bridges, ports and boost ports, studs would be removed, the cylinder would go to the plater,  head would be re-chambered and compression release installed, lapping of mating surfaces would be done, new Wossner piston kit installed with oiling holes, new cylinder studs installed being careful to chamfer the stud holes, using only Cometic gaskets, everything cleaned to look better then new, and everything torqued to spec.
Probably missing a step or two in there but you get the idea.
Then again if it was my bike and it was a 86, I'd clean the air filter filter and just rebuild the whole motor  

[Foxx4Beaver]

still post some pics of this thing when you get it squared away...if it's got that little time on it, it would be cool to see an old '86 in good shape.   

[sandblaster]

still post some pics of this thing when you get it squared away...if it's got that little time on it, it would be cool to see an old '86 in good shape.   

+1 

[Brute]

Wow Sandblaster. Nice explanation! You must have an unusual amount of extra time this morning. 

[sandblaster]

I'm the fastest two finger typist I know of   

[Michael janowicz]

I appreciate the time of you all explaining this to me, I never pulled the head off of the cylinder I just pulled the cylinder off whole. I got to year it apart Againsnd look at all the things Sandblaster mentioned. I just didn't want to go through those motions if it was the kips valve!!

Thanks guys and Sandblaster!!!

I'd post pics, but not sure how to!!