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Do these compression readings make sense?

  • Thread starter Thread starter shadow
  • Start date Start date
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shadow

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I've got a rough '78 1000 that I'm still trying to figure out what I'm going to do with. I'm in no hurry to get it on the road, and I don't want it to turn into a complete money pit, so it will be a slow project. It runs, but it's got a busted exhaust bolt, broken off flush, and I can't get to it because it's behind the frame. Eventually, if I continue with it, I want to pull the engine for cleaning and paint, but for now, I was thinking of just pulling the head to try and get at the busted bolt.
I thought I'd check compression, before I get too far into this.

These were my readings on a warm engine:
cyl #1-150
cyl #2-140
cyl #3-125
cyl #4-130

I was concerned about the compression being too low, but if anything, these values seem a little high to me, Especially #1 and #2.
I was hoping some of you more experienced guys could chime in and give me your opinions.
 
Those readings are not too bad, I would not be concerned until the motor has run for at least one hour and the valves have been adjusted
 
17% difference between lowest and highest cylinder. still above the 100 psi service limit. standard compression is from 128 to 184 Psi with no more than 28.5 psi lowest to highest cylinder. among other things, could be carbon build up that's the cause of the differing readings.

check the valve clearances and fix the broken stud.
 
Thanks for the quick responses. So I shouldn't worry about it. I'll try to fix the broken bolt, check valve clearances, clean carbs etc. I know I have to fix the exhaust leak, before I'll ever get it to run right.
 
:lol:
chef1366 said:
Those numbers scream one thing!
RUN ME!
Click to expand...

:lol: I'd love to, but I'm afraid it'll be awhile until this bike hits the road. Even if it was running, it's snowing as I type this.
It still needs alot of work, but it's encouraging that it probably doesn't need a rebuild.
 
One of these days I'll learn to say things as succinctly as Bill did.
 
If you do pull the head ? Pull the cylinder too. Don't necessarily need to change the rings? How many miles ?? The base gasket should be replaced, removing the head will disturb it and cause it to leak.
 
SqDancerLynn1 said:
If you do pull the head ? Pull the cylinder too. Don't necessarily need to change the rings? How many miles ?? The base gasket should be replaced, removing the head will disturb it and cause it to leak.
Click to expand...

Thanks for the tip. If I do end up pulling the head, I'm sure I'll have a bunch more questions.
 
SqDancerLynn1 said:
If you do pull the head ? Pull the cylinder too. Don't necessarily need to change the rings? How many miles ?? The base gasket should be replaced, removing the head will disturb it and cause it to leak.
Click to expand...

Might not. I did a head gasket on my 1000G and didn't pull the cylinder. So far so good.

Those compression readings don't look like needing rings to me, of course if the cylinder was pulled, a honing and new rings would be in order. I agree that it would be a good practice to pull the block.
 
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