Mysterious Problem with DOHC

[doodsaibot]

Last weekend I was riding on the highway at 75MPH. I hit an extremely rough bump in the road and instantly my bike started to bog down and lose power. I was able to pull over into the shoulder and come to a stop as the bike promplty cut out. I waited for a few minutes after inspecting the bike and fired it back up. I rode it back home and it would occasionally bog down on me again. It was as if the power was being cut in half when the issue would arise.

At any rate, I noticed at idle that the bike would cut off when I lock out the steering to the left. I have checked the wires and cables and don't notice anything out of the ordinary. I checked the probes that go into the gauge cluster and noticed the tachometer side probe was not screwed on so I fastened it back on and the bike no longer dies when I lock out the steering..well, not always. I checked any wiring from my HID kit and none of it is being stretched when the steering is locked out. I am scratching my head on this one.

All my basic maintenance is up to date.

Aside from the routine, I re-checked the vacuum on my carbs and I am pulling 7 in. Hg on both sides (per the manual) and even synced with the manometer afterwards. Checked inline gas filter and its all good. Petcock vacuum line is on snug and petcock is not leaking. I drained the tank out and refilled with fresh gas just to be on the safe side. Air filter is in great shape.

After the routine check ups, I rode about 25 miles (riding through various RPMs) with no issue until I got home and parked the bike, at which point it goes back to bogging down again. To keep the idle up I have to screw down the idle screw. The RPMs jump back up and I set the screw back to where it was. I can go ride another 20 miles with no issue until it randomly bogs down again. I have noticed this problem at all RPM ranges from idle, to mid, up to main jets above 7000RPMs.

I am going to give it another look over but if anyone else has had this issue or can give me a tip as to what I should look for, it would be greatly appreciated.

SIDE NOTE: I COMPLETELY rebuilt the carbs last year save the diaphragms since they were in great shape. I have been riding with the rebuilt carbs for several months without issue.

Is it possible something slipped passed the gas filter into the carb? Did a wire or cable come loose from the rough bump on the highway or is that part all coincidence? The problem itself is completely random so I am leaning towards carb cleaning...

 

[16VGTIDave]

Based on your description, my first thought was "TCI module", followed by wiring in or around the steering neck, and lastly the ignition switch.

See the pattern?

Electrical.

That's where I'd be concentrating my efforts.

 

[drewpy]

could have damaged the battery, depending on how hard that bump was

 

[doodsaibot]

Yes! You are right, Dave. This morning I had some time to give it a quick look over. I stuck my hand into the spine of the frame and pressed on some wires. The idle would bog down every time I pressed on the wiring. I am almost sure it was the spark plug wires that go up to the coils. Not sure what's what though since my time to check was limited. I will have to educate myself more with the electrical system tonight.

Drewpy, you may be right. I may test the battery on another vehicle just to see if it's in good shape.

A side note: If it does end up being TCI related, I read that there are two different TCI module designs for our DOHCs floating around out there, one providing more quality than the other but again I will research more into that.

 

[XSLeo]

It may be a bad ground. The hard bump further loosened the ground enough to cause your issues. Check your grounds, especially around where you press on the wires to cause the rough running.
As the bike runs ok the ground maybe ok, when you press on the wires it shifts the wires enough to loosen the ground.
Leo

 

[doodsaibot]

Leo, you may be right. I did notice that the ignition coils are not mounted onto the frame as they should be. They are just floating around inside the frame. I'll need to loosen the engine mounts to get to them and screw them back on. However, I won't rule out a bad ground elsewhere. I will have time to give it a thorough look over tomorrow.

 

[doodsaibot]

So I had some daylight to work with. Drewpy, I installed the battery onto another vehicle and it worked just as it should so I ruled out any problems with the battery.

Dave and Leo, I inspected as many wires as I could find on the bike including the ones you guys recommended that were in the problem area. Lastly, I took a very close look at the spark plug wire/cap connections and saw that the right side wire was frayed and chewed up where it makes the connection to the cap. I decided to trim both left and right wires just a bit in hopes they had a better connection to the caps. Not sure if that is a full proof repair aside from getting new wires but I figured I could give it a shot.

Afterwards, I took baby steps with the Maxim and eventually rode a solid 45 miles through different RPM ranges from idle up to 9000RPMs, also going up to speeds of 80 MPH using normal and aggressive acceleration. At idle, I would lock out the steering left to right and did not experience any bogging or performance loss. I also went over a few speed bumps at low speed and did not notice any problems. I fiddled with all the wires in the problem area and again did not notice any power loss.

I am going to keep a close eye on this one but my guess is that the right side spark plug wire was chewed up and loosened up enough that it was simply coming loose from the cap whenever I hit bumps in the road or what not, somewhat pulling the wire from the cap. I believe this may have been leaving me running on only one cylinder which would explain why the bike would suffer a huge power loss.

I suppose this was somewhat of a face palm moment for me. Such an easy task that I overlooked before. On top of that, my superbrightleds LFS-1-Flat LED flasher showed up in the mail after I had finished remounting the engine for the day. Could have killed two birds with one stone on that one. Oh well, I'll save that project for a rainy day.

 

[drewpy]

glad you got it sorted