Clinician
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Post by flexo6 on Apr 14, 2013 15:29:21 GMT -6
Lost compression..did a compression test. Exhaust valve is burnt. What do you thik I should check?....When adjusting fuel/air mixture screw....does turning it in give it more air or more gas? Before I replace valve do you think I should up the jet some? Spark plug didn't look all that bad color wise. Thanks for any input!
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Post by Alleyoop on Apr 14, 2013 18:19:48 GMT -6
Question, before the valve burned out was it backfiring. have you changed the muffler or anything else?
Alleyoop
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Post by Bashan on Apr 14, 2013 19:23:08 GMT -6
Backing the A/F screw out adds fuel to the low speed circuit. I really doubt that burned up your exhaust valve. The main jet is what makes it run lean or rich. Also adjusting the needle up or down can affect that. How do you know it's burnt, are you able to visually inspect it. If you had a leak at the exhaust port that was letting air to get to the valve it can warp it and boom...compression loss. What was your compression on the dial by the way?
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Post by Alleyoop on Apr 14, 2013 19:33:18 GMT -6
Just because you lost compression does not mean the valve is burnt. To say it is burnt you actually have to take the head off and look at it. It could just be that the EXHAUST valve is tight an needs to be adjusted and is staying a little open therefore loss of compression. So first check the valve adjustment and adjust the Valves: for 50cc INTAKE .003 inchs and .004inchs EXHAUST for a 150+cc INTAKE .004 inchs and EXHAUST .005 inchs.
THEN CHECK your compression again.
Alleyoop
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Doc's Anything Goes
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Post by jct842 on Apr 14, 2013 19:49:40 GMT -6
Thats what I question too, how can you know the exhaust valve is burnt? Unless it is apart there is no way to be sure.
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Clinician
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Post by flexo6 on Apr 15, 2013 13:36:19 GMT -6
Backing the A/F screw out adds fuel to the low speed circuit. I really doubt that burned up your exhaust valve. The main jet is what makes it run lean or rich. Also adjusting the needle up or down can affect that. How do you know it's burnt, are you able to visually inspect it. If you had a leak at the exhaust port that was letting air to get to the valve it can warp it and boom...compression loss. What was your compression on the dial by the way? Checked compression..it was 30...took apart...definetly burnt....no exhaust leak. |
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Clinician
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Post by flexo6 on Apr 15, 2013 13:37:17 GMT -6
Just because you lost compression does not mean the valve is burnt. To say it is burnt you actually have to take the head off and look at it. It could just be that the EXHAUST valve is tight an needs to be adjusted and is staying a little open therefore loss of compression. So first check the valve adjustment and adjust the Valves: for 50cc INTAKE .003 inchs and .004inchs EXHAUST for a 150+cc INTAKE .004 inchs and EXHAUST .005 inchs. THEN CHECK your compression again. Alleyoop Head is off...and its burnt |
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Post by flexo6 on Apr 15, 2013 13:37:51 GMT -6
Thats what I question too, how can you know the exhaust valve is burnt? Unless it is apart there is no way to be sure. Head is off...its burnt |
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Post by Alleyoop on Apr 15, 2013 14:27:22 GMT -6
For it to burn you must of had a leak by the Flange where the pipe connects to the Head or you were running really lean from some other leaks not enough fuel.
Alleyoop
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..BAD TO THE BONE..
