Big Bore Install - Issues
Big Bore Install - Issues
I had a Big Bore kit installed recently on my 2001 FLHTC. I have about 1200 miles on the build and I'm getting, what I call "Piston Slapping" if the engine gets near lugging. I can really hear the crackling or pinging of either rigs or pistons slapping.
Is this normal? I know lugging the engine is not a good thing, but sometimes when I miss gear it really makes a lot of noise. Could there be something wrong with the 95 build? I have an Andrews 26 cam also and my bike is carbed with a Mikuni 42 Flat side. The bike runs great, its just this ring slapping that got me worried.
Any help or advice would be appreciated.
Is this normal? I know lugging the engine is not a good thing, but sometimes when I miss gear it really makes a lot of noise. Could there be something wrong with the 95 build? I have an Andrews 26 cam also and my bike is carbed with a Mikuni 42 Flat side. The bike runs great, its just this ring slapping that got me worried.
Any help or advice would be appreciated.
Last edited by FL-kruzen; Sep 25, 2013 at 07:37 PM.
Outstanding HDF Member
Joined: Nov 2012
Posts: 2,422
Likes: 14
From: Fla
That's what I'm thinkin too...
Are you running a fuel/air tuner, or carb? You might be able to tune the ping out, but you may be sacrificing power if you adjust it to take care of a ping on a lugging engine.
Piston slap sounds more like a bell ringing. And it isn't very loud. When you hear it, you won't forget it!
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
"Piston Slap" occurs when the cylinder wears into the shape of an hourglass, or the bore is too big and the piston is just kinda bobbling around.. either condition will show as poor compression.
pretty sure you don;t have piston slap, that can take alot, alot of miles.
bored motors are more likely to experience PS.
mike
pretty sure you don;t have piston slap, that can take alot, alot of miles.
bored motors are more likely to experience PS.
mike
Last edited by mkguitar; Sep 25, 2013 at 11:13 PM.
Road Warrior
Joined: Apr 2010
Posts: 1,648
Likes: 37
From: Monroe, Louisiana
Sounds like high compression to me. Could be slight detonation or pinging. Richer mixture may help or some octane boost. Some one mentioned gas. I think some one has changed the gas as I have heard of and seen more pinging this summer than ever before. I suspect the 10% ethanol may have expanded. The only other thing is you can go to 1 step colder plug and it may do better. If you have carbon build up in the quench area it can cause hot spots and do the same thing. I doubt very seriously it is piston slap as it occurs more when cold than hot. Too much piston clearance will tighten up as the engine warms up. If you run lots of clearance say .010" you may hear it cold, but I doubt you have that much. Putting the pistons in backwards on some auto engines can also cause noise as the pin offset is to the wrong side and makes lots of load on piston skirt. Makes more power but doesn't last long.
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Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,898
From: Bedford UK
You say you had it installed, but what did your builder do to optimise your build's performance, like tuning it on a dyno? I suggest you go back to him and talk through your concerns, so he can test your bike himself and make any necessary adjustments.
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Thanks for the help guys. I put a whole freaking can of octane booster in and she quoted right down. Your right, I do have high compression pistons. The other issue I have noticed is after shutting down the engine when hot, it tends to be hard to restart for some reason. My bike Is Carbed with a Mikuni 42. What would cause a hard to start condition when hot?
Tourer
Joined: Jun 2011
Posts: 335
Likes: 5
From: Vermont
Thanks for the help guys. I put a whole freaking can of octane booster in and she quoted right down. Your right, I do have high compression pistons. The other issue I have noticed is after shutting down the engine when hot, it tends to be hard to restart for some reason. My bike Is Carbed with a Mikuni 42. What would cause a hard to start condition when hot?
Do you have compression releases? When hot, my bike will start hard if I forget to push in the releases.