My pride and joy is a 2007 Ultra Classic, with the 103 Big Bore Kit, SE255 cams, SE Air Cleaner, D&D FatCats. I've got 22,800 problem free miles on her, except for the starter the dealer replaced last fall.

On Saturday, my wife and I took a nice ride along the Ohio River in beautiful southern Indiana. Everything was great, the weather, roads and scenery. Gas was getting low, so I pulled over and filled up with premium go-go juice.

I hit the starter, and the motor backfired. I previously experienced this occurrence last year too. Just had to wait 30 seconds and try again. Pressed the starter and it fired right up. I took off down the road, but something was just not right.

Between 2500-3000 RPMs, the bike felt like it was running on rumble strips. It was a vibration that seemed to go away once I was out of that RPM band. I kept an eye on the oil pressure guage, and it appeared to be within normal range.

I rode it home cautiously, trying to stay out of that vibration zone. Once home, I looked the bike over to make sure there wasn't anything obviously wrong, but to no avail. This morning, I took it down the road, hopefully thinking that the previous day was just a bad dream. Just like yesterday, the vibration appeared within 2500-3000 RPMs.

I have an idea about what may be wrong, but I would like to hear from the motorheads on this forum. Do you think the crank scissored? What other possibilities should I look for? Any suggestions welcome.

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Kevin

 

If the crank scissored you would likely had a sudden loss of oil pressure.

This is a challenge since we can't see inside the engine to find the exact cause.

Maybe this has something to do with the cam chain tensioner coming apart. Get it checked out ASAP.

 

how bad was the backfire? was it a kinda mellow one?...or one of those ones that scares the crap out of anyone near the bike? Like a bomb going off...if it was really brutal, I would check along the exhaust pipes and look for a loose muffler/pipe mount bracket....you might luck out and find it to be something external of the engine...

 

Do you know if it spit back through the intake as well? I would check intake gaskets, vac lines, even the plugs for damage.

 

Start by replacing the spark plugs.

 

I know this sounds dumb but I had the same vibration on my 95 in...It turned out to be the bolt for the D&D exhaust...the one on the transmission was ready to fall out.

 

My 06 spits back thru the intake all the time . Its something to do at cold start with the PCIII. never hurt any thing though its just annoying as hell ... Mostly does it if I try to start it just before the engine light goes out .

 

Thanks for all your replies, I'll check the FatCat bracket and spark plugs when I get home tonight.

Its weird that it only vibrates in the RPM range of 2500-3000...

It has backfired before, usually after its been ridden for awhile, and restarted while it's still hot. It tore up my starter last year, and the dealer replaced it under warranty. I'm about to call my service manager for ideas in a few minutes...

--
Kevin

 

One of my friends had that happen, and it damaged the rubber ring between the intake manifold and the (in his case) carb. I believe the throttle body is mounted the same way. Just one more thing to check.

 

Ding, ding...we have a winner...

I just went through this. Take a can of WD-40 with the straw and squirt a dab around the intake with the bike running. You will notice a huge difference in idle when you hit the offending blown gasket.

Is it under warranty, if so take it to the dealer.

Good news, not terribly expensive....Bad news labor intensive.