2001 400ex spark but won’t run - Honda TRX Forum
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post #1 of 3 Old 12-09-2018, 12:41 AM Thread Starter
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2001 400ex spark but won’t run

my 400 wasnt idling so bought carb rebuild and orders new carb so quad wouldn’t be down replaced all that won’t fire up tested for spark had spark it was just rebuilt by previous owner with paperwork on top end and bottom end don’t know what it could it ran fine before the cold weather hit. gonna do compression test this week figured y’all would know more than me and could help me out with the problem i’m new to 400 thanks in advance
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post #2 of 3 Old 12-09-2018, 03:23 PM
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If the previous owner had the flywheel off and didn't tighten it properly, it may have sheared the flywheel key throwing the spark out of time. But compression is necessary also - check the compression with the throttle held wide open and let me know what you get - anything over 120 is fine anything under 100 is bad.
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post #3 of 3 Old 12-19-2018, 03:47 AM Thread Starter
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wet compression test read 125 pulled apart down to piston and cylinder. cam had little scarring, head gasket was in good shape, valve were fine, spark plug was fine, didn’t see any scarring in cylinder wall. i’m thinking rings are the problem also had white stuff on piston lip which doesn’t make any sense to me since it air cooled so no coolant running in the motor
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