Compression
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Tourer
Joined: Jan 2011
Posts: 376
Likes: 27
From: Ontario
Forged pistons likely came with moly rings. Cast rings will seal on most any honed surface, moly rings are more particular. How were the cylinders bored, honed and clearance setup?
Personally, I'd put some miles on it and check it again. If it runs well and doesn't burn oil, I'm not sure what you are trying to accomplish.
But if you want to do a cylinder leak down test and find any leakage, you will need to remove the pushrods and carb so you will know where the air is leaking from.
Paul
Personally, I'd put some miles on it and check it again. If it runs well and doesn't burn oil, I'm not sure what you are trying to accomplish.
But if you want to do a cylinder leak down test and find any leakage, you will need to remove the pushrods and carb so you will know where the air is leaking from.
Paul
Before that I did another cylinder compression test and got 110psi both front and rear
Ok so back to leak down
I calibrated the tester motor TDC on Comp stroke
Front cylinder had between 15-20% , no sounds from exhaust , no Bubbles in oil
Very very very faint sound of air through intake
Rear cylinder was a whoa!!! Gauge all the way to red...you could hear the air and out of the pushrod holes you can hear and feel the air just spewing out.
Again nothing from exhaust or oil tank
So intake valves? Possibly bent? But how could I get that much compression with such a leak?
Maybe before removing beads I can go in with a bore scope or at this point should I just remove heads?
Appreciate the help.
Road Captain
Joined: Oct 2020
Posts: 518
Likes: 593
From: Central Iowa
Hey, I got around to doing a leak down test I removed pushrods and put engine at TDC on the compression stroke.
Before that I did another cylinder compression test and got 110psi both front and rear
Ok so back to leak down
I calibrated the tester motor TDC on Comp stroke
Front cylinder had between 15-20% , no sounds from exhaust , no Bubbles in oil
Very very very faint sound of air through intake
Rear cylinder was a whoa!!! Gauge all the way to red...you could hear the air and out of the pushrod holes you can hear and feel the air just spewing out.
Again nothing from exhaust or oil tank
So intake valves? Possibly bent? But how could I get that much compression with such a leak?
Maybe before removing beads I can go in with a bore scope or at this point should I just remove heads?
Appreciate the help.
Before that I did another cylinder compression test and got 110psi both front and rear
Ok so back to leak down
I calibrated the tester motor TDC on Comp stroke
Front cylinder had between 15-20% , no sounds from exhaust , no Bubbles in oil
Very very very faint sound of air through intake
Rear cylinder was a whoa!!! Gauge all the way to red...you could hear the air and out of the pushrod holes you can hear and feel the air just spewing out.
Again nothing from exhaust or oil tank
So intake valves? Possibly bent? But how could I get that much compression with such a leak?
Maybe before removing beads I can go in with a bore scope or at this point should I just remove heads?
Appreciate the help.
Was this a running engine before the new jugs and pistons? Why were they replaced? Were they replacement to fix a problem or just to get fresh new cylinders on a tired engine?
Thread Starter
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Tourer
Joined: Jan 2011
Posts: 376
Likes: 27
From: Ontario
I'll start by saying that I'm not a fan of compression tests, dynamic or leak down either one. While they can be a tool to help pinpoint a problem when combined with other supporting evidence, they are a terrible method on their own of indicating there is even a problem, or to give any meaningful indication of the health of an engine, the fact you got different results on the second compression test compared to the first one is just one of the reasons why. Way too many uncontrolable variables.
Was this a running engine before the new jugs and pistons? Why were they replaced? Were they replacement to fix a problem or just to get fresh new cylinders on a tired engine?
Was this a running engine before the new jugs and pistons? Why were they replaced? Were they replacement to fix a problem or just to get fresh new cylinders on a tired engine?
Crank pin was no good so it got replaced
Pinion shaft same thing and the gear shaft as well
Had that all done at shop , not myself.
So I figured new jugs and pistons too
Road Captain
Joined: Oct 2020
Posts: 518
Likes: 593
From: Central Iowa
If it were me I’d carry on and fire it up, just pretend like you never did a compression test because I highly doubt there’s anything wrong. If (big if) there turns out to be an actual problem then deal with it but so far in my opinion you have no evidence of anything wrong.
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