rear cylinder is miss-firing…everything checks out

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01-19-2017, 03:07 AM

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senor honda

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rear cylinder is miss-firing…everything checks out

james
hi! i just put together a new top end for 1988 sportster with nhrs stage 2 thunderstorm heads and new pistons/cylinder work by nhrs…i’ve completed the “heat cycles” and took her for her first easy mile ride…i’m using a mikuni hsr 42 carb and cycle shack 2 into 2 pipes…running compu-fire 21850 selectable electronic advance ignition…static timed it…my prob is the rear cylinder is miss-firing…everything checks out…no intake manifold leaks or exhaust leaks…rear cylinder feels cooler than the front cylinder…timing?? carb?? i can’t figure it out…thanx!! -james.

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01-19-2017, 03:08 AM

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senor honda

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Customer Service Techs Hi James
Make sure the pushrods are adjusted correctly.
Check ignition timing
Try swapping the spark plug wires. Front to rear / rear to front. See if anything changes.

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01-19-2017, 03:09 AM

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senor honda

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james
hi! did a compression test with engine at op temp, front 195+ rear 195+….readjusted pushrods, rechecked timing, good spark, battery good…still misses on rear…plugs?? starter solinoid?? havn’t checked charging system, not sure how to…nothing changed swapping plug wires…i don’t get it… ugh.

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01-19-2017, 03:09 AM

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senor honda

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01-19-2017, 03:10 AM

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senor honda

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Customer Service Techs
Hi James. As far as testing compression goes; it is typically better to test Compression, cold, when you are trying to diagnose a performance issue. Testing compression @ running temperature is fine, but expansion from heat can sometimes disguise a problem.
Make sure that you are adjusting your pushrods, cold. Also, you need to be confident that your Andrews cams were installed/timed correctly.
You may have a failing ignition, or coil.
Check your charging system and check for an intake leak.