Bought my sporty with 7700 miles on it last July, never had a lick of trouble with it at all. Changed the oil, put on a S/E intake and jetted appropriately in the fall. It had a slight knock on cold start, but it went away once the bike warmed up. Stored it for the winter with a battery tender and sta-bil in the tank, left it sit undisturbed all winter. Pulled it out in spring, fired right up and let it warm up before riding. Had the slight knock, went away again, and it's been silent until now. Started it up yesterday morning, pulled the same **** again, and it was quiet about a block from my house, went to work fine. Was riding back home and it lost power, I thought I was lugging so I downshifted to 4th, no change. Pulled off the main road on to a side road, found the bike was only running on the rear cylinder. Pulled off the front plug wire to confirm, then the rear, nothing in the front. Bike is on the trailer now and waiting for the autopsy on Sunday. Plug looked perfect, oil pressure was fine and it didn't do anything out of the ordinary prior to going. Always ran 93 in it and Mobil 1 20w50 VTwin.


Kicker is, she went right as it rolled over to 10,000 miles. It has 10,002.8 on it now. I'll keep this thread updated as I find out more. May be the time for some cams and headwork while it's apart....

 

Did you check the wire harness connector to the ignition coil? Reason being, I lost a cylinder and it turned out that one of the three wires inside the little weatherpack connector that plugs into the coil had become disconnected from its corresponding pin; I ended up pulling the weatherpack connector apart and resoldering it. I only discovered the cause when I accidentally bumped the harness and Cyl #1 came alive again.

 

+1. check all connections. ie plug wires, coil wires, connection under the bike that comes from the ignition module.

 

I agree with the others. It could be something really simple, so don't start any major surgery just yet! Best of luck finding the cause of the problem.

 

swap plugs , see if problem moves , "looking at a plug is usless"
even if you see it fire, it my not fire under pressure..
I once spent hours trying to troubleshoot a single that wouldnt start after complete service..
new plug fired out of the cylinder , so wasnot that ....WRONG!
finally put the old plug back in a bam , it started .

if it still doesnt run , do a simple compression check ,,that will tell you if valves/piston are ok , or not..

 

I dropped it off today by my uncles friend, he does phenomenal work - has two gorgeous panheads of his own. He said he'll start with seeing if it spins over alright, then move on to the compression test and so on.

 

Guy had a chance to look at it today, somehow, some way the exhaust valve was stuck open, even without the rocker acting on it. Possibly the guide, spring, who knows. Having both heads done to be safe, luckily the pistons and bottom end are safe.

 

good deal , a simple compression test found that

 

Update, I'm pi$$ed to say the least. Front cylinder head had the exhaust valve guide come completely out, jamming the exhaust valve open, and the intake guide was starting to come out as well. New guides, two new valves, seals and a valve job on both heads. Total bill of $750. This should NOT have happened on a bike with 10,000 miles on it. Hopefully I'll get the old parts back so I can dump them on the front desk at the MoCo.

 

You are going to blame problems with a 12 year old USED bike on Harley? LOL