Bonneville America Forums Forums Technical Forums General Tech Only running on one cylander

Ok so I switched the coils and still only the right side will fire any other ideas before I tell my wife I need a 260 dollar CDI for my bike.

So you switched the wires side to side and the problem didn't move?

Yep wire and coil

Since you said $260, I assume you are talking about the Procom CDI? There is another option, I think, search here for it. Either way, you should check the output voltage of your R/R. I have the procom and have not 100% determined this yet, but indications are that the procom CDI is voltage finicky. Mine does not seem to like 12.5 V, which is what I get at idle with my RR. So, it is possible that you will have to upgrade to a MOSFET R/R, which is where I may be heading. You could start with the r/R mod, though. Others on the procom thread indicate cold bloodedness after going from stock to procom.

Does the left side ever fire, or is it totally dead? If totally dead, the R/R check may not be possible/accurate if you can't get good engine RPM's. You could check your stator output for that.

I was thinking Procom but I may go with one of the other one's what ever way you look at it, it's a 200 dollar bill.

R/R what is that?

Its the right side that will not fire sorry and no it is not firing at all and you can smell gas so I would think it is getting gas.

Regulator/Rectifier. Takes the AC voltage generated by the stator and puts out a steady charging DC voltage to the battery.

I saw $140 for the 270-degree unit on TTP.

Sounds like the CDI unit is toasted. Just make sure the spark plug and ignition wire to the right side are ok. Switching the primary and secondary wires on the coils only confirms the coils are ok.

What on earth would a bad rectifier have to do with not producing a tick to fire one of the coils?

Its the CDI.

"Its the right side that will not fire sorry and no it is not firing at all and you can smell gas so I would think it is getting gas."

I still don't understand, when you switched wires did the opposite side start to fire?

Have you taken the plug out, grounded it to the cylinder head to see if it is firing?

I had a similar problem (Thruxton), was ready to spring for a CDI. Turned out to be a stuck open float. I accidentally found out by finding the bike in the garage standing in a puddle of fuel. Just a thought.

The symptoms on my Thruxton was that after turning on the petcock and starting it would idle fine. Once I got two blocks away it would begin running on one cylinder.

looking back, I sometimes wish it was the CDI, a lot less work. I'm lazy, good luck.

When my cdi went bad I would intermittently lose my left cylander. Switched coils and plug wires around and still would only lose the left cylander. After 3 weeks off messing with it I bit the bullet and bought a Pro Com, set it to the number that matched the stock unit, installed it and haven't had any trouble since. My bike has always seemed to be cold blooded so it doesn't seem to take any longer to warm up than before. I have seen that some speculate that the Pro Com likes a higher voltage, I'm not totally sold on that. I have another theory, I think that it likes a higher idle. After reading a thread over in the performance section on the efi bikes needing a higher idle I started paying more attention to mine even though it is a carb model. If I set my idle below roughly 1150 rpms I noticed that my neutral light flickers, set it at 1150 and its solid. I think that the stock maps from Pro Com may be set to run at a slightly higher idle than the stock unit. Some guys have said that with using the custom map options they have been able to eliminate the cold starts. This makes sense if the custom map also lowers the idle. It seems to me that a lot of people suffer from "Harley Idle Syndrome" as in they set their idle low because it sounds cool. I bet if those of us with the Pro Coms set our idles slightly higher, like around 1150 which the efi models seem to like, or altered the idle in the map the Pro Com issue may be resolved. I think that using a low idle with a stock Pro Com map may unknowingly be responsible for the cold starts. It is just a theory, I may or may not be right, after all I am not a motorcycle mechanic I'm just forced to play one in real life!lol