Engine noise on decel
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From: Canada
Engine noise on decel
I have 5000 miles on a 95 upgrade (17k total mileage), Andrews tw26, and fuelmoto tuner, everything else stock. Bike was dyno tuned shortly after upgrade (86 hp/ 100fp) and has run great until recently developing a rattle that only occurs when decelerating from higher rpms (eg 4500+) and when totally off throttle. If I decel gradually it doesn't occur. *Have checked primary chain tension, heat shields, and other usual suspects that sound like engine noise. I am convinced that this is coming from front cylinder and it is in time with engine. Not real loud but audible and best describe as a rattle. When it does occur it only lasts a moment, and disappears as soon as rpms come down to maybe 3500. No smoke, no popping, plugs are perfect, and otherwise running as good as before. I have read dozens of posts that describe engine noises but nothing that occurs only on decel like this. I'd like to write it off to valve train noise? But sounds more like piston slap or wrist pin ?? Maybe has nothing to do with 95 upgrade? Has anyone experienced similar and if so what was the problem?
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From: Canada
Just a quick update. Just returned from Sturgis and other points west, put about 2300 miles on this week. The noise I previously described has evolved into what is best described as a rattle that now occurs prominently after startup, becomes somewhat quieter when hot, but now I can here it when accelerating, at constant speed, and especially when decelerating. Stopped in at Cody Cycle (sorry if I've got the name wrong) and they were very helpful. Put the scope on it and diagnosed as piston slap. So, if they are correct, that means I got about 6500 miles on this 95 upgrade and it's coming apart again.
Any opinions on how to avoid a repeat. How tight should these forged pistons be fit? And by the way, I did the recommended breakin: 3rd gear, full throttle to 60, full off to 30, ten times.
Any opinions on how to avoid a repeat. How tight should these forged pistons be fit? And by the way, I did the recommended breakin: 3rd gear, full throttle to 60, full off to 30, ten times.
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Joined: Jun 2006
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From: san antonio
I would guess piston/cylinder fitment was not right to start with. Bore to .010" OS and fit with SE cast flat top pistons. They can be fitted tighter than forged and run quiet for many miles. Whether you run forged or cast, make sure the machinist knows what needs to be done, has torque plates and has bored/fitted H-D pistons before. If you are not sure, it would be worth the shipping to ship your cylnders to one of the forum sponsors where they will bore/hone, fit pistons and gap rings; all you have to do is assemble and break in.
Cast flat top piston to cylnder clearance is .0006"-.0015" and forged setup at .002"-.004" depending on manufacturer.
Cast flat top piston to cylnder clearance is .0006"-.0015" and forged setup at .002"-.004" depending on manufacturer.
Last edited by djl; Aug 13, 2012 at 03:33 PM.
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