I got the bike running. It ended up being the Ignition Module, and a wireing harness that melted on the exhaust. I am now having an issue with the rear cylinder not fireing. I am 100% positive that I am getting spark(found out the hard way OUCH!~!) The bike was running fantastic and then when I went to take it to work she was really slow when I got to work (15 min ride) the rear pipe was cold. It still starts right up with no problems. I have gone through the Manuel and cold not find anything about this. I was wondering if anyone could point me in the right direction. Iron Mick if you are out there could you please give me some words of wisdom?

 

id do a compression check to verify your valve terrain is working properly. THEN, try replacing the plug to see if plug is FIRING for sure. Even though it might fire outside of the cylinder, when placed into a harsh environment such as a cylinder where air and fuel is COMPRESSED, it may not wanna light/fire and do its job.. If u got spark back to cyl 2...not much left. lol although, i guess it could maybe be firing at the WRONG time?..but mick will have to answer that one. lol he's the guru...not me!

 

Try swappping plugs front to back, and back to front. Do you have compression on rear cylinder. Take out plug and put you thumb on the hole and turn it over. I think if the front is running the spark timing can't be out on the rear, both plugs use a common coil. Are your rear pushrods adjusted too tight and are the valves are closing? really don't think its a valve issue. Most likely the coil or plugs. Did you try swapping plug wires on the coil? Spark Plugs.. Wires .. Coil .. Do the cheapest first....

Really sounds like the coil, not running when warmed up.

 

Suggestions already made ...

swap plugs
swap wires
replace plug
compression test
pushrod adjustment

When it starts up cold is it firing on both cylinders? Does it lose the one cylinder only after it warms up? This is a classic symptom of a bad coil. There are resistance tests for a coil, but the real test is to replace it with a known good one. If it works out to not be the coil then you would have a good spare.

What ignition module are you using now?

 

I put in a known good coil. I switched the wires, but I didnt switch the plugs. After the plug bit the crap out of me I was kinda at a loss. Starting up cold the front cylinder heats up great, but the back cylinder dosn't heat up at all. I have to take the kids out to kinder camp I will stop and buy a new set of plugs and give that a try. I am just suprised that she starts up so easy on only one cylinder.

 

Mustangwagz Does your 81 have electronic ignition or points? Mine has electonic but I am not sure if they all came that way. Some people say yes and some say no. I do know that the po had installed many upgrades such as the altenator. I ahve had many people tell me that I have a very nice knucklehead. I just smile and say its an ironhead but thanks.

 

really need to do a comp check, if it has fuel,compression, and spark it has to fire, so you have spark so you need to check comp if it is low look into valve adj.may have a bad valve,make sure you dont have a very bad intake leak also

 

So I swamed out the plugs and problem solved. I just dont understand how the plug could spark when I pulled it out but could not ignite the fuel. Any who she is running like a raped ape once again. Thanks for all the help guys!!

 

1981 came stock with electronic ignition. The only source of info is in the factory service manual, available from many sources - HD dealer, eBay sellers, J&P Cycles, etc.