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compression diminishes to nothing from 1 to 4

  • Thread starter Thread starter Paul's Zuki
  • Start date Start date
tkent02 said:
Ride it hard for a while, then see what happens.
New rings need to seat.
Click to expand...
I have read that but I do I even get it on with so little compression? Just did the wet test dropping a teaspoon of oil and the compression went up on average an additional 5 - 10 psi.
here are the #'s

Dry/Wet:
1 - 78/85 psi
2 - 20/30
3 - 26/30
4 - 30/35
 
Something is seriously wrong. I'd check the cam timing first. Next is to double check the valve adjustment. Lastly, something could be wrong with the rings you installed. I trust you honed the cylinders before installing the new rings?
 
Nessism said:
Something is seriously wrong. I'd check the cam timing first. Next is to double check the valve adjustment. Lastly, something could be wrong with the rings you installed. I trust you honed the cylinders before installing the new rings?
Click to expand...

Aside from what the manual says and what I see on the engine with the cam timing it is perfect. Everything seems to line up great. I just replaced 3 valve shims that had no clearance and now all have clearance between .03-.08 mm as stated in manual. I did not hone the cylinders..........so, I guess I'll be doing that next and will recheck my piston rings(those are new).
 
You need to do a hone when using new rings...ALWAYS.
The compression #'s should be higher even without honing. How did the cylinder walls look?
Did you test the valve seal after valve lapping by pouring liquid in the ports and looking for leaks?
 
Yeah, this is my first rebuild so obviously the learning curve is throwing a hell of one. Anyhow, The cylinder walls looked pretty decent no gouging at all, maybe glazed over from what I've read and how they should look and yeah, I just lapped all the valve seats and poured liquid and all good. no leaks. Even had to replace to bad exhaust valves.
 
I measured roughly the piston size and it is 55mm. what size ball hone would be good? I found one on ebay that is 55-57mm would that be sufficient?

Or could I use those 3 stone hone tools?(they have this available at the auto store near where I live)
 
Last edited:
what size should I get and what grit? current bore is about 55mm


They have a 57mm 240 grit. If I order this these usually come oversized correct? So I just order the exact corresponding size, Correct?
 
Last edited:
nevermind just found all the info i needed on that website. thanks.
 
i, personally, would get an engineering shop to do this for you...... easy to mess it up and then you'll need oversize pistons if you do...
 
sparki said:
i, personally, would get an engineering shop to do this for you...... easy to mess it up and then you'll need oversize pistons if you do...
Click to expand...

I actually know how to hone. I was once an industrial honer working on Sunnen & General Hone machines. I just wasn't sure how these ball hones were measured, giving some more play. well, with that said, I did hone out the bores and this is what I found. On cylinder 1 it looks like it has some scoring and cylinder 4 just some spots. I can't feel those, only in cylinder can i feel it. See photos below. What do you think? usable or am i needing a new head?

Cylinder #1
IMG_6686.jpg


IMG_6687.jpg


&

Cylinder #4
IMG_6690.jpg


Also found that the ring gap was oversize by about 5-10mm.
 
5-10 mm oversize ring gap?:eek: Are you sure you have the proper rings for that?
Thats where your compression is going.
 
that's what I was afraid of. ebay it is. damn. I just dropped about another $100.00 on gaskets and stuff and now this. damnit. damnit. damnit. Deep breath. Oh how I love you GS.

How will I even know if the one off ebay is any good. so far have found 3 and 1 says its scored, so I'll stay away from that one.

Other option how easy not easy is it to press out bore and put in a fresh one? and I know this isn't anything I can do at home, but for those that have gone thru this, what?
 
Do some searches on removing cylinders; it's been covered. If you're not married or you have a very understanding wife I think they fall out after a while at 400 degrees in an oven. Or you could just use the whole new cylinder block.
 
Okay just ordered a cylinder head that the seller said the bores were in very good condition and pictures proved it as well. We will see once it gets here and I have ordered some new piston rings and know exactly what the tolerances should be. Hopefully this will resolve my compression woes.
 
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