No compression after base gasket replacement
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Thread: No compression after base gasket replacement

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    Member c.salt's Avatar
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    No compression after base gasket replacement

    09 TW 7500 miles. Just did a base gasket change out. Pretty straight forward. I did slip a ring out when installing wrist pin and gently worked it in by hand. Put it all back together and would only idle. Give it throttle and dies out. Pull it apart expecting a ring out but all seems ok. Valves look good. Put it back together (again) and same thing. Plug comes out very black. Put a compression check on it and showing 60psi cold. Bike was running good before I pulled it apart. Did not do a compression check before starting first attempt, so I don't know what it was before.
    I see in the supplement to manual (01 and above) that it has an extra o-ring between head and cylinder that I did not put in because there is no recess in the alignment dowel for it to fit correctly (FWD center dowel). Could this be an issue? How does one tell if the rings are bad? I did pull piston out and looked at rings, removed rings and cleaned grooves. Put piston back in cylinder. Put some gas in cylinder and had no leak down for an hour. Scratching my head here and would appreciate some ideas.
    Thanks, Doug

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    Senior Member Dryden-Tdub's Avatar
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    Quote Originally Posted by c.salt View Post
    09 TW 7500 miles. Just did a base gasket change out. Pretty straight forward. I did slip a ring out when installing wrist pin and gently worked it in by hand. Put it all back together and would only idle. Give it throttle and dies out. Pull it apart expecting a ring out but all seems ok. Valves look good. Put it back together (again) and same thing. Plug comes out very black. Put a compression check on it and showing 60psi cold. Bike was running good before I pulled it apart. Did not do a compression check before starting first attempt, so I don't know what it was before.
    I see in the supplement to manual (01 and above) that it has an extra o-ring between head and cylinder that I did not put in because there is no recess in the alignment dowel for it to fit correctly (FWD center dowel). Could this be an issue? How does one tell if the rings are bad? I did pull piston out and looked at rings, removed rings and cleaned grooves. Put piston back in cylinder. Put some gas in cylinder and had no leak down for an hour. Scratching my head here and would appreciate some ideas.
    Thanks, Doug
    Did you get the cam chain back on and then verify your timing?


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    Senior Member Fred's Avatar
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    I believe compression should be checked on a warm engine. However there should be no omitted O-rings during the reassembly.
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    Ken
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    Mine did the same thing. I used a compression gauge and it was bad. It was running before. I put s shot of oil in the cylinder and compression didn't increase, bad valves. I pulled the head and just to double check I poured oil in the exhaust chamber and oil ran right out around the valve. None ran out of the intake side. I took it to a guy and he did a valve job on it for me. It ran great after that.
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    Senior Member Tweaker's Avatar
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    I am no expert but did you put the rings back in the same grooves and in the same orientation that they came out ( not upside down) and with the gaps offset correctly ? Some rings are tapered and if upside down would affect compression.
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    Member c.salt's Avatar
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    Cam timing is good. took pic before. Put it back same.
    Was always told compression check while cold. Heat expands piston and increases comp.
    Will double check the valves.
    Put rings on same way they came off. No expert here obviously.

    Does anybody know how to check rings? I think it has to do with the measurement of the gap but not sure. I do not have a service manual and need the gap also.

    Thanks and keep them coming please

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    Member c.salt's Avatar
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    Searching the forum looks like the ring gap needs to go in same spot when reinstall of piston. Hone cylinder and install new rings. Others have re used rings and simply slipped them back inside with no problems. I got problems. So can anybody tell me proper ring gap?

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    Senior Member admiral's Avatar
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    Quote Originally Posted by c.salt View Post

    Does anybody know how to check rings? I think it has to do with the measurement of the gap but not sure. I do not have a service manual and need the gap also.

    I see in the supplement to manual (01 and above) that it has an extra o-ring between head and cylinder that I did not put in because there is no recess in the alignment dowel for it to fit correctly (FWD center dowel). Could this be an issue? How does one tell if the rings are bad?

    Thanks and keep them coming please


    It makes some sense that you are losing compression from a missing o-ring if you are missing one.

    I'm gonna address the o-ring/dowel pin questions you have with the first set of pictures. I will then follow with some piston, ring information.

    O-rings and Dowel Pins. It gets a little confusing here as you found out because I snipped a page from the 2001 and up supplemental and then from a parts cataloge for a 2016. They both should match as they are allegedly for 2001 and up right. Anyway, the only real confusion is dowel pins and not gaskets or o-rings.

    Here is a copy of the head to cylinder from the supplemental manual. On this page, it shows 3 dowel pins and one o-ring or rubber gasket (as I will call it). I'm gonna answer the extra dowel pin in a minute below. Don't do anything yet with this picture.

    Here is a copy of the parts manual for a 2016 TW. Notice it does not have the front left dowel pin. For the record I don't believe on should be on the front left, again I'll answer that in a photo in a minute. I'm just setting up my final answer for you with these other pictures.


    Here is an actual picture of my 2005 TW engine as I'm putting it back together after replacing the piston. I have the right rear dowl pin in with the o-ring or rubber gasket. I don't have the left rear (back of the engine) dowel pin in yet. If you look at the front left cylinder hole, it does not look like it's machined to have a dow pin in it but I can't be certain until I get home and check.

    I have an engine torn apart at home and will verify everything I'm mentioning here in regards to the cylinder pins, o-ring or rubber gasket.



    Pistons and rings.

    Here are some pictures of and copies of the manual which will tell you how to place the piston in, ring locations and indexing the rings.




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    Member c.salt's Avatar
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    Thanks admiral. The o-ring in question is #10 in the first supplement manual. Was pretty sure the dowel was in the front center when disassembled, The same parts l
    fische also shows 3 dowels.
    Last edited by c.salt; 12-07-2017 at 05:43 PM.
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  11. #10
    Ken
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    Quote Originally Posted by admiral View Post
    It makes some sense that you are losing compression from a missing o-ring if you are missing one.

    I'm gonna address the o-ring/dowel pin questions you have with the first set of pictures. I will then follow with some piston, ring information.

    O-rings and Dowel Pins. It gets a little confusing here as you found out because I snipped a page from the 2001 and up supplemental and then from a parts cataloge for a 2016. They both should match as they are allegedly for 2001 and up right. Anyway, the only real confusion is dowel pins and not gaskets or o-rings.

    Here is a copy of the head to cylinder from the supplemental manual. On this page, it shows 3 dowel pins and one o-ring or rubber gasket (as I will call it). I'm gonna answer the extra dowel pin in a minute below. Don't do anything yet with this picture.

    Here is a copy of the parts manual for a 2016 TW. Notice it does not have the front left dowel pin. For the record I don't believe on should be on the front left, again I'll answer that in a photo in a minute. I'm just setting up my final answer for you with these other pictures.


    Here is an actual picture of my 2005 TW engine as I'm putting it back together after replacing the piston. I have the right rear dowl pin in with the o-ring or rubber gasket. I don't have the left rear (back of the engine) dowel pin in yet. If you look at the front left cylinder hole, it does not look like it's machined to have a dow pin in it but I can't be certain until I get home and check.

    I have an engine torn apart at home and will verify everything I'm mentioning here in regards to the cylinder pins, o-ring or rubber gasket.



    Pistons and rings.

    Here are some pictures of and copies of the manual which will tell you how to place the piston in, ring locations and indexing the rings.




    I dig the red hammer. Maybe that's the magic tool he didn't use which caused loss of compression.
    admiral and maddawgj like this.

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