Backfiring right cylinder...think it's electrical. Need help!

[jradvantage]

I have a 78 650e with stock coils, points, etc... Got it running pretty good. Put about 70 miles on. Had a bit of a stumble, when I'd take off, but overall, pretty nice running.

Noticed the timing was off on the right cylinder. I started messing with it while it was running. To make a long story short, I touched something that I shouldn't have, there was a big spark with whatever I touched with the screwdriver, followed by a big pop and the engine stopping.

Went in today and lightly sanded the points, put everything back together, adjusted the points did the timing with the 12v bulb and the wires, sprayed some electrical cleaner on a thick business card and cleaned any residue/oil off the points.

The good news is it started first kick. The bad news is the right cylinder is popping like a fiend.

I'm pretty sure I did something to the electrical when I was screwing around with it earlier. I suppose the "pop" could have done something to the carb/boots or some such thing.

Any thoughts on what and how I should go about checking the various electrical bits to determine what I screwed up?

I know it was a boneheaded move, so please, no grief. I just need some help.

Thanks,

John

 

[TwoManyXS1Bs]

An el-cheapo trick you could try is to switch left/right ignition, see if the problem switches sides.

Where the points wires plug into the harness, switch left/right.
Then, switch the plug wires left/right.

Fire it up, see what happens...

 

[weekendrider]

Check to see if the carbs are fully seated in the boots.

 

[jradvantage]

I will try both and see what happens. Thanks!

John

 

[Broder]

That happened to me too. In my case I have barbs on the boots used to attach the vacuum hose when syncing the carbs. One of the barb rubber covers came off allowing air to inter the cylinder and it started to backfire like mad.

 

[jradvantage]

Good point. I will check that, too. I have non vacuum petcocks and have covers on the barbs. Certainly could have blown one off. Thanks.

 

[retiredgentleman]

Good point. I will check that, too. I have non vacuum petcocks and have covers on the barbs. Certainly could have blown one off. Thanks.

Those cheap rubber caps that go on barbs, are a real bad idea on these bikes. They are of such poor quality, that they will likely split within a year or so. When that happens your engine will run like crap and idle speed will wander/hover. You will spend hours trying to figure it out.

The best way to deal with the open barbs is to run a length of high quality 3/16" fuel line between the 2 barbs. The fuel line will not split or leak air, and be good for at least 10 years of use.

 

[jradvantage]

Ended up getting the Pamco ignition. Now she runs like a champ.