Just rebuilt still low compression? - Page 2 - ArcticChat.com - Arctic Cat Forum

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post #11 of 29 Old 11-13-2011, 09:05 PM
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Quote:
Originally Posted by 04 EDGE View Post
And there is your problem.
Can you elaborate on your reply about winderosa gaskets? Everyone I've talked to speak highly of them.
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post #12 of 29 Old 11-14-2011, 07:03 AM
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On a cat I only use cat oem gaskets, if I have to replace them. Compression should be within 5 % on a rebuild. Before I would worry about low compression I would try another known good tester. Testers should be recalibrated every year to make sure they are accurate. If it runs good and has good power I would ride it. As said before you could be looking at even 150 miles before the rings are seated if the hone was light and possibly never a good seat if they were not honed at all.
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post #13 of 29 Old 11-14-2011, 09:18 AM Thread Starter
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I didn't hone my cylinders, I bought replated ones. How do you calibrate a compression tester? I hooked it up to a tire that I knew the pressure of and it was right on. What do you mean by compression should be within 5% on a rebuild?
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post #14 of 29 Old 11-14-2011, 11:26 AM
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Example: if one of your cylinders has 100 and the other 95, that means there is a 5% difference. Ideally you don't want more than that.
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post #15 of 29 Old 11-14-2011, 11:31 AM
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The OEM gaskets are metal and the Winderosa appear to the fiber, or paper type. They are thicker than the OEM gaskets, which will result in lower compression. When you reassemble the top end there will (should) be plenty of oil on the cylinder and rings, so you should have the best seal, a wet seal, in the cylinder, so the compression should be a s high as it ever will be. I don't think you should expect to see any increase in compression reading from a fresh top end to after break in.

It should not be necessary to calibrate your compression tester. Absolute numbers are not important, but what is important is that you use the same gauge and assess the relative readings from cylinder to cylinder and before and after. You can reuse the OEM base gaskets many times, if they are not bent during removal. Use a little bit of sealer on them and you're good to go.

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post #16 of 29 Old 11-18-2011, 03:01 PM
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Originally Posted by 94ZR580 View Post
I don't think you should expect to see any increase in compression reading from a fresh top end to after break in.
Really? Everyone I have talked to have told me the rings need time to seat with the cylinder wall and this could take up to 1 tank of gas. Compression should go up once rings have seated.

How can you back up your statement I quote from you?
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post #17 of 29 Old 11-24-2011, 04:10 PM
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Quote:
Originally Posted by mosabi View Post
Really? Everyone I have talked to have told me the rings need time to seat with the cylinder wall and this could take up to 1 tank of gas. Compression should go up once rings have seated.

How can you back up your statement I quote from you?
Refer to the sentence before the one you quoted, it is probably about as explicit as I can get. I'm just going by my experience, my engine, my compression gauge, etc. Your experience may vary.

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post #18 of 29 Old 11-24-2011, 11:03 PM
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Quote:
Originally Posted by 94ZR580 View Post
The OEM gaskets are metal and the Winderosa appear to the fiber, or paper type. They are thicker than the OEM gaskets, which will result in lower compression. When you reassemble the top end there will (should) be plenty of oil on the cylinder and rings, so you should have the best seal, a wet seal, in the cylinder, so the compression should be a s high as it ever will be. I don't think you should expect to see any increase in compression reading from a fresh top end to after break in.

It should not be necessary to calibrate your compression tester. Absolute numbers are not important, but what is important is that you use the same gauge and assess the relative readings from cylinder to cylinder and before and after. You can reuse the OEM base gaskets many times, if they are not bent during removal. Use a little bit of sealer on them and you're good to go.
Well this is intresting. Wouldnt Winderosa know what OEM specs are for the thickness of a gasket before and after they are torqued? I have used them, OEM and Wiseco gaskets and never had a problem. Next question is, Every machanic that I have talked too said that you will see a increase in compression after break in because od the rings well seat to the cyclinder. Please explain why you dont think there will be a increase. Mind you I am not a expert, but have rebuilt alot of 4 stroke engines so I am interested in this.

Last edited by icr242005; 11-24-2011 at 11:13 PM.
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post #19 of 29 Old 11-24-2011, 11:07 PM
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Quote: Originally Posted by 94ZR580 You can reuse the OEM base gaskets many times, if they are not bent during removal. Use a little bit of sealer on them and you're good to go.

Wouldnt sealer changed the gasket thickness? I never use sealer on head/cyclinder gasket
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post #20 of 29 Old 11-25-2011, 12:06 PM
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Quote:
Originally Posted by icr242005 View Post
Quote: Originally Posted by 94ZR580 You can reuse the OEM base gaskets many times, if they are not bent during removal. Use a little bit of sealer on them and you're good to go.

Wouldnt sealer changed the gasket thickness? I never use sealer on head/cyclinder gasket
Sealers are designed to squeeze out and only fill in tiny irregularities, so they are generally regarded as not adding dimension to the gasket. However, on an absolute, molecular level, you could probably expect to see some change in overall thickness. This is a process recommended in my factory service manual when re-using base gaskets, but you can never go wrong using new gaskets.

The heads on all the liquid cooled engines, that I've seen, use rubber o-rings, so no sealer required when re-using those. Little dabs of grease, or silicone can be helpful in hold the o-rings in place while setting the heads.

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