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cold rear piston

Old 04-15-2019, 09:33 PM
boss hogg
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Default cold rear piston

Hi; I own a 1994 harley Electric glide classic when i went to try starting it this spring i notice it was cool to touch the rear piston head. the front piston was getting warmer as it run? can anyone tell me what it might be causing this. i pulled the plug and found it dark looking no oil though just black cleaned spark plug then restarted it did try see if it had spark and did piston did seem to get warm to touch after. but noticed left rear dual exhust was cooler than right side, shut it down after a bit then pulled spark plug out again see it had black look to it again. can anyone give me any idea what might want to look for?
Old 04-15-2019, 09:54 PM
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Welcome to the forums from Texas. This is the new member area but try posting your question on the forum below and see if anyone there can help. Good luck.
Old 04-15-2019, 10:10 PM
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Old 04-16-2019, 01:59 AM
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Old 04-16-2019, 05:10 AM
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Old 04-16-2019, 07:41 AM
boss hogg
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Default cold rear piston

hi: I own a 1994 classic ultra electric glide harley does anyone know why my rear piston when first started for the season was cool to touch after running 5 or so min ? didnt act like it was firing plus i pulled spark plug and it was black in color no moisture or oily to see. cleaned it off tested for spark and did have on. put back in and started bike, bike seem to run smoother and noticed when i touched piston was warm not like before. i noticed some black around on some of the piston fins near exhust outlet any ideas what from? Thanks for your time
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Sure sounds odd.
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Old 04-16-2019, 08:23 AM
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Old 04-16-2019, 09:14 AM
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my first suspect would be the plug. swap cylinders and see if trouble follows. then do wires.
not unusual for the front to be dominate. if swapping does not seem to help, next step would be a dry compression test, numbers low, do wet test, the follow with leak down test.
shouldn't happen but never say never, possible for the rings to be stuck on a long term shut down. an iffy lifter could also be an issue, bring her out on the road for a good run.
Old 04-16-2019, 09:19 AM
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It's because the oil that's flung off the crankshaft flywheels mostly hits the rear cylinder first. Long story short, don't over-modify your Evo unless you wanna run it pig rich. Also, get the bike on the road and get back to us. Freaking out over an idling engine not heating up consistently isn't newsworthy IMO.

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