Running on one cylinder
 

Any ideas of what could cause one cylinder to cut out. The really old thing is what would cause therear cylinder to cut out then switch to where the rear fires, but front cylinder cutsout.

I start the bike up some times it will run on both cylindersfor a few min or so then gets rough and is running on one cylinder. I check by pulling one of the spark plugwires off if no change in I know that cylinder is not firing, if stall I knowthat is the only one working. I thought I was crazy, but have done this severaltimes and sometimes it’s the front and sometimes the rear that is not firing.
On occasion it will smoth out for a few seconds I assume its running on both. I notice when that happens the battery voltage jumps up to a normal 13.5 otherwise its charging at 12.5

Not sure if related, but the tachometer also stoppedworking.
any ideas?

You running the stock R/R? Definitely sounds electrical, and seeing as it's springtime, the wave of failed R/R's is upon us.

Coils may be going out or have a loose/corroded ground, but if the tach is funny, voltage is wavering and electrical is being strange, the R/R is at the top of the list for this bike.

this happened to me last spring but my issue just ended up being fouling plugs due to bad gasoline... even though it was stabilized it still didnt run so i took the opportunity to get new plugs and air filter for some easy maintenance and emptied the tank and voila she was back to all the v-twin glory.... but id go with 7moore7's suggestion first... sounds electrical

Agreed I've been going down the electrical route. To give the whole story. Bought the bike, drove it 200miles with unsealed battery (unknowing at the time) bike died because of dead battery(boiled the water out of it, charging at 17 volts). I replaced the battery, replaced rectifier w/ stock one, replaced rear coil, CDI box, and changed the plugs. Both plugs were a little sooty,rear a little worse. any ideas of what else to check?

Wish i could be of more help. That's really weird if that really whats happening (firing on one or the other cylinders).

But the only time that i THOUGHT this was happening is when i OVERFILLED the gas tank to the brim and the tank would create a vaccuum and not let the gas flow out of the petcock. What would happen when i did this was that the bike acted and sounded like it was only running on one cylinder.

The trick was to not fill the gas tank up to the rim any longer and IF i did, you can simply pull over on the road and open the gas tank lid and let some air IN. Every since i stopped filling the tank so full, this is NEVER came back. And i was running into this issue like every 2-3 weeks and i was baffled as hell. Once i learned what i had been doing, i just laughed myself silly as i have never heard such a thing before.

But yeah, the VTR is ONE OF A KIND alright.......lol!

I've had the tank on and off a 100 times. Plus has only a gallon or 2 in it, yes fresh gas. I even set up a seporate full bottle to run with the tank off. I did do a rather scetchy test of the petcock, let it run and pulled one fuel line from the tank at a time. fuel flowed from each side, but I did notice that when on the side stand and pulling the fuel line on the high side fuel did not pour out until I stood the bike up.

Any ideas from the rest of the forum. Even if off the wall, I dont know what else to check/replace.

I just had the same problem. Turned out one cylinder wasn't getting any fuel at all. The fuel filter was bone dry. I took the tank off and flushed it out. Put on fresh fuel filters and made sure my vacuum line was hooked up good. I put new plugs in and cleaned the air filter while I was in there. Seems to be running fine now. If it happens again, I am going to replace the petcock diaphragm.

I wonder if you fried your computer during the overcharge?

I'm guessing the initial cause for all of this is the R/R and not the battery. Because this is a very common failure on this bike, it probably ruined your battery and possibly a lot of other things. Where are you located? It might be nice to swap the ECU with a known good one to make sure that's not the issue. A failed R/R has been known to take out many different parts of the electrical system.

Hi, mine is doing exactly the same thing. I'm waiting for a MOSFET reg rec to arrive. Any update on your bike??

kurt999- when you say same thing you mean this crazy switch from fron to back cylinder cutting out?

7moore7 - when you say ECU do you mean hte large of the two black boxes under the seat in the tail? I tried swaping that out with one I bought from a salvage yard. I'm in hte Baltimore, MD area. What are the odds that one was bad too.

No not quite, starting on 2 cylinders then dropping the front one. I thought it was spark loss following a reg rec failure, but turns out it was crap in the front carb somewhere causing an overfuelling problem.

Sorry I can't help, watching with interest for your updates though