About the bike:

2002 FXDWG 1550 kit, flat top pistons, gear drive cams, flat top pistons, ported /milled heads. The bike has 61k miles on it. The 1550 kit was done at 41k miles.

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I was riding to work in the morning as usual. Just cruisin' and taking it easy. BOOM, I can tell I just lost a cylinder. So, I barely make it to my mechanic and says I got a detonated piston with a hole blown through it.

This bike is my primary transpo, so I take very good care of it. Top synthetic oil, regular fluid changes, premium gas, regular maintenance. So what's the deal? There was no sign or warning of anything going wrong. How do I keep it from happening again?

Engine is getting rebuilt now, but it's costing me serious $$$. Anybody know what might have went wrong?


Thanks for any help you can give.


-Johnny

 

Usually happens to a lean AFR and timing advanced a bit too much.
Carbon buildup on the pistons can also raise compression beyond safe levels and contribute to the problem.
How did the other piston look? And the spark plugs?

 

The spark plug looked alright to me. A little old, the bike was due for a tune up. The shop is breaking the engine down now. My mechanic said he'd call when everything is apart and he knows exactly what needs to be replaced. He's already told me that I have to do the other piston also and that I have to redo the kit again. Again, I'm ok with cars, but really don't know much about bike engines.

 

An HD engine is a lot more simple than a car's. I did my BB kit having never worked on an HD before. Just followed the Service Manual's and kit builder's instructions.
Telltale signs of detonation (ping) is aluminum spatter on the plug's insulator.

 

Ok, the shop called me in last night to look at my engine. Luckily the pistons are not blown like they thought. One of the push-rods snapped and busted the lifter, so I just need new rods and lifters. So, that's cool.

For some reason, the mechanics don't like the 37G gear drive cams I had installed at the same time as my 1550 kit.

They seam very anti gear drive cam setup to me. If I understood correctly, they think the tolerance is so low, that it doesn't take much wear on the teeth to make the gear chatter very slightly, but enough to have a catastrophic failure.

Does anybody know if there is a history of problems with these gear cams on TC88?

They are suggesting that I stack some cheddar and invest in a new cam chest kit, since they have no idea how worn mine is, without take them out, which would be about another 4 hours of labor and they'd have to time it again. The gear drive cams where installed 20k miles ago.

Any thoughts?