Compression
Thread Starter
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Tourer
Joined: Jan 2011
Posts: 376
Likes: 27
From: Ontario
Compression
Did a cylinder compression test on an 80" shovel
New jugs
New pistons and rings (9.5:1 weisco)
Andrews A2 cam
Front Cylinder 95psi
Rear Cylinder 105psi
These seem like low readings????
Rings??? Even though they're new
New jugs
New pistons and rings (9.5:1 weisco)
Andrews A2 cam
Front Cylinder 95psi
Rear Cylinder 105psi
These seem like low readings????
Rings??? Even though they're new
Stellar HDF Member
Joined: Aug 2020
Posts: 3,192
Likes: 2,235
From: College Station, TX
It does seem little low and almost 10% difference between the cylinders.
So new cylinders and pistons. How long (miles) has it been run since the new cylinders and pistons were installed? Were the valves and seats refinished at the same time?
Did you hold the throttle fully open when checking compression? Did you let it crank over at least 5 times? If not, I'd do that and check it again. If you get the same or similar results, squirt a little oil in one cylinder and check it again. If it improves, that likely means rings not sealing well. Do the same on the other cylinder. And if you have a bore scope it would be worth while looking inside the cylinder with the piston near the bottom so you can see more of the cylinder bore..
How does the bike run on the road? Loss of power? Are you having oil consumption problems? Or smoke from the exhaust on acceleration? Or when you coast with the throttle closed and them accel again?
Paul
So new cylinders and pistons. How long (miles) has it been run since the new cylinders and pistons were installed? Were the valves and seats refinished at the same time?
Did you hold the throttle fully open when checking compression? Did you let it crank over at least 5 times? If not, I'd do that and check it again. If you get the same or similar results, squirt a little oil in one cylinder and check it again. If it improves, that likely means rings not sealing well. Do the same on the other cylinder. And if you have a bore scope it would be worth while looking inside the cylinder with the piston near the bottom so you can see more of the cylinder bore..
How does the bike run on the road? Loss of power? Are you having oil consumption problems? Or smoke from the exhaust on acceleration? Or when you coast with the throttle closed and them accel again?
Paul
Thread Starter
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Tourer
Joined: Jan 2011
Posts: 376
Likes: 27
From: Ontario
It does seem little low and almost 10% difference between the cylinders.
So new cylinders and pistons. How long (miles) has it been run since the new cylinders and pistons were installed? Were the valves and seats refinished at the same time?
Did you hold the throttle fully open when checking compression? Did you let it crank over at least 5 times? If not, I'd do that and check it again. If you get the same or similar results, squirt a little oil in one cylinder and check it again. If it improves, that likely means rings not sealing well. Do the same on the other cylinder. And if you have a bore scope it would be worth while looking inside the cylinder with the piston near the bottom so you can see more of the cylinder bore..
How does the bike run on the road? Loss of power? Are you having oil consumption problems? Or smoke from the exhaust on acceleration? Or when you coast with the throttle closed and them accel again?
Paul
So new cylinders and pistons. How long (miles) has it been run since the new cylinders and pistons were installed? Were the valves and seats refinished at the same time?
Did you hold the throttle fully open when checking compression? Did you let it crank over at least 5 times? If not, I'd do that and check it again. If you get the same or similar results, squirt a little oil in one cylinder and check it again. If it improves, that likely means rings not sealing well. Do the same on the other cylinder. And if you have a bore scope it would be worth while looking inside the cylinder with the piston near the bottom so you can see more of the cylinder bore..
How does the bike run on the road? Loss of power? Are you having oil consumption problems? Or smoke from the exhaust on acceleration? Or when you coast with the throttle closed and them accel again?
Paul
Engine has only ran for a
Road Master
Joined: Mar 2012
Posts: 1,050
Likes: 999
From: Ohio
I would suggest first verifying that the gauge is accurate. If you have access to another gauge, try it and see if it's the same.
There are some simple methods of testing a gauge for accuracy, you will need to fab up a test rig and have access to other gauges to compare to.
There are some simple methods of testing a gauge for accuracy, you will need to fab up a test rig and have access to other gauges to compare to.
Stellar HDF Member
Joined: Aug 2020
Posts: 3,192
Likes: 2,235
From: College Station, TX
So run for 5 minutes at a time. Does that mean you have done the warm up method of seating the rings? What type of rings are you using? Cast, moly?
If it were mine, I'd put some easy miles on it to see how it runs. Then I check the plugs to verify jetting and timing is correct and that is no evidence of oil burning. If those things look good, check the compression again and compare the numbers.
Paul
If it were mine, I'd put some easy miles on it to see how it runs. Then I check the plugs to verify jetting and timing is correct and that is no evidence of oil burning. If those things look good, check the compression again and compare the numbers.
Paul
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Thread Starter
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Tourer
Joined: Jan 2011
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From: Ontario
So run for 5 minutes at a time. Does that mean you have done the warm up method of seating the rings? What type of rings are you using? Cast, moly?
If it were mine, I'd put some easy miles on it to see how it runs. Then I check the plugs to verify jetting and timing is correct and that is no evidence of oil burning. If those things look good, check the compression again and compare the numbers.
Paul
If it were mine, I'd put some easy miles on it to see how it runs. Then I check the plugs to verify jetting and timing is correct and that is no evidence of oil burning. If those things look good, check the compression again and compare the numbers.
Paul
I.purchaded the V-Twin cylinder and piston kit
Came with 9.5:1 weisco forged pistons and rings.
I could do a leak down test ... Idk what those Amazon kits are like, but I don't mind purchasing one
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Stellar HDF Member
Joined: Aug 2020
Posts: 3,192
Likes: 2,235
From: College Station, TX
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
Last edited by pgreer; Aug 6, 2024 at 03:54 PM.
Thread Starter
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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 hones 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
If it runs good and like you said doesn't burn oil. Them I guess it will be good to go
