This probably sounds odd, but want to get you guy's opinion. Sometimes, when I do a wheelie, I lose power and seems like it's only running on 1 cylinder.
Any guesses? R/R connection? or R/R perhaps?
Thank you.
Could be a wire or connection that rubs on something with the new angle, but I would think there would be other times when this would occur also. Might be something to do with the fuel level in the carbs too. Does the problem stick around once you are back to riding normally or is it just when the front wheel is in the air?
Jeff
Over Tach cut off wire runs between TCI Unit and tachometer. BDC
On a modern bike you would have to pay extra for that feature (anti wheelie electronics). ;)
Is it when a momentary lift is occurring or a deliberate long duration wheelie? Are you twisting the bars for balance when skyward? What's your technique, clutching or fork compression/bounce?
Finally, are you sure it's a Vision? :o
Quote from: dingleberry on March 12, 2014, 08:02:10 PMFinally, are you sure it's a Vision? :o
I wondered about that myself. BDC
patient: "Doc, it hurts when I do this..."
Doctor: "stop doing that" ;)
Sticky float valve or some other carb difference?
Bad fuel pump = no gravity siphon when you make the tank next to the carbs instead of above them :)
Wheelie on a Vision? Impressive. Please post pics!
I'd reckon it was the over-rev cutoff taking you down to 1 cylinder to prevent damage. Chop the offending wire coming out of the TCI unit and you can happily blow up your engine.
I bought my 83 vision, new off floor, in 1984. As all of you do also, I know "her" very well. Having grown up racing motocross, riding on 1 wheel is pretty common to me. I've done this hundreds of times. Only the past few years has this been an issue. It may happen when it comes back down to earth. My technique is throttle and clutch.
Just went out and started it since this happened last year. It's still only hitting on one cylinder.
Tac cut off? What is the purpose? I've never had it shut down when running it hard. If it were a float, would it be instantaneous? I really believe it has to be electrical. If the R/R is malfunctioning, "could" it behave in such a way?
It seemed like I fixed it for a while with my last R/R, but I've forgotten some of the details of that event. As you can see, I have R/R on the brain. But I am open to other suggestions. Wish I was close to someone that knew these puppies inside and out. I am in NW Iowa.
Thanks for the feedback.
what about a vacuum tube? Would that create such a behavior?
If you do a search for "rev limiter" at the Forum home page you will see that unexplained running on one cylinder is quite commonly attributed to a faulty signal from the tachometer that detects an over-rev condition (12000 rpm). This cuts out the front cylinder.
The quick fix is to disable this feature by simply cutting through the black and yellow wire coming from the rear of the TCI unit.
After that, it is a process of elimination. This sounds to be electrical since you say the engine is only running on one cylinder permanently. It is unlikely to be a R/R fault if your battery is charging OK or you have a full battery.
After chopping the rev-limiter wire, I'd start with swapping the coils over and see if the other cylinder runs instead. The problem could be a dead coil. If there is no change, work through the obvious electrical connections as a process of elimination. Loose spark plug connections, a dead spark plug?, swap your resistor spark caps, replace your HT wires. clean up your coil ground connections and engine ground connection, etc. Then, if there is no improvement see if you can borrow a known good TCI unit from another forum member to swap in to your bike. You can use an XZ400 TCI unit for testing OK.
All the best.
To confirm some apparent uncertainty, ms you are saying that the problem ONLY happens under wheelie operational conditions, and that under all other operational conditions the bike runs as normal?
Hey, put new plugs in and see what happens, had the running on one cylinder issue once, new plugs, purred like a kitten again. An easy cheap item to eliminate.
I even met QBS after I did that in Colorado!
Spent some time working on it last evening (finally). There have been a number of questions, and I hope to answer them all here.
Doing the wheelie, last fall, put me in this predicament. In the past, sometimes it has come out of it. It sat all winter. I kept battery charged, treated gas, etc.
I can start it, but it still sounds like it's only running on one cylinder. I checked spark on both cylinders, and it has spark. Additionally, the plugs were "slightly" wet so I think both are getting fuel. I suppose that could still be an issue.
I pulled the R/R and it looks like it hasn't over heated.
So, I am considering cutting the rev-limiter. Someone mentioned fuel pump, perhaps that's still an option. Would the fuel pump stop working on one cylinder and not on the other?
Thanks for everyone's time!
If it has spark on both cylinders, like you say, cutting the rev. limiter wire shouldn't make difference.
As far as the fuel pump suggestion, a full tank will usually negate this being the culprit...
All bets are off when the carbs aren't level. That's the main thing I was getting at. Could be any number of other things.
So the bike does this all the time now? I misunderstood and thought it was only when you were one one wheel.
It might be time to check your compression and replace the spark plugs. Do you have a vacuum gauge?
As long as the battery is charging I can't see why the R/R would have any effect on driveability. Check the charging and address as needed. If the problem persists, it's not the R/R. :)
There is no reason to guess if both carbs are getting fuel. A wet plug may simply mean incomplete (or non-existent) combustion. Fill the tank, turn the petcock to "ON" and start the bike. After a brief run shut it off and drain both carbs individually into a clean container and compare quantities. Someone may be able to quote a volume to expect. You might also note water or particulate in the fuel drained from the bowls.
I'm guessing when you checked spark it was with the plugs out of the cylinder and watching the arc across the gap. This does not guarantee spark when installed and running. Compression will suppress a weak spark. I've even seen circumstances where at idle it had spark but not at high RPM's.
Rik might be headed in the right direction. Check for water in float bowls.
Thanks for everyone's replies.
Yes, it does it all of the time now.
I'll proceed with the feedback.
Thanks again.
Quote from: QBS on April 24, 2014, 05:55:22 PM
Rik might be headed in the right direction. Check for water in float bowls.
Thanks for the support but I'm not necessarily suggesting water is the issue. Rather, as a matter of course, whenever I drain the carb bowls I examine the contents for stuff that shouldn't be there. :)