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Gas Yamaha Gas Yamaha Golf Cars; G1 through "The Drive" and U-Max Utility Vehicles |
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09-05-2013, 07:02 PM | #1 |
Not Yet Wild
Join Date: Sep 2010
Posts: 4
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Spark Plug Causing Compression to Drop???
Customer cart G16: Said ran fine, then suddenly wouldn't start.
I did a compression test and it was 30psi. I replaced the valves, valve springs, lapped the valves and adjusted to valves to .004. The push rods and rocker arm assembly looked good so they wasn't replaced. Then I ran a compression check and it was 150psi. I put the spark plug in and tried to start it. It would crank but wouldn't start, so I ran another compression check and the compression was back down to 30psi and the valves had moved out of adjustment. I went back and checked my work and everything was like it was suppose to be, so I readjusted the valves to .004 and the compression came back at 150psi. I put the spark plug in and tried to start it and it wouldn't start. I checked the compression again and it was back down to 30psi again and the valves were knocked out of adjustment again. I tried several times and keep getting the same results. What is causing this? I get 150psi as long as the spark plug is not screwed in, but only get 30psi and the valves knocked out of adjustment when the spark plug is in and after I crank it over. Any ideas? I've had several other people look at it and called Everything Carts mechanics and TNT Carts mechanics and no one seems to have an answer. |
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09-05-2013, 08:14 PM | #2 |
Gone Wild
Join Date: Oct 2010
Posts: 6,730
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Re: Spark Plug Causing Compression to Drop???
If the valve lash keeps changing, something in the valvetrain is loose. Start at the crank gear and work your way to the valves. Check everything.
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09-05-2013, 09:48 PM | #3 |
G8 Specialist
Join Date: Jun 2009
Location: Phoenix
Posts: 7,799
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Re: Spark Plug Causing Compression to Drop???
The bracket that the rocker shaft goes through, is it ovaled out? From no oil getting to the top rocker galley.
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09-07-2013, 10:09 AM | #4 |
Not Yet Wild
Join Date: Sep 2010
Posts: 4
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Re: Spark Plug Causing Compression to Drop???
Thanks for responding. I checked the rocker arm bracket as Mike suggested and it's fine. I'm getting to tear it down to and start the drive chain check. Will let you know what I find.
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compression, spark plug, valves |
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