2004 Suzuki Volusia, 40k miles, ridden near daily. Starts and runs, but increasingly quits while running. Either at an idle in the garage, or at speed while riding around. It begins to run rough, then completely quits. Backing off the throttle while riding will allow it to recover, then throttle back up to previous speed - it dies again. During the dying, backfires/flames out the exhaust. Back off the throttle, engine catches again, and will run. When it first appeared, it only happened at 70mph or higher. The speed it occurs at has been slowly decreasing, where it can now be reproduced at 55-60mph. The last time it happened, I was down to 40mph before I could get it to recover. It also will just quit if sitting at an idle for 15 minutes or so.
My brother is fairly competent at maintenance, and has done his own on everything he owns for years, and this has him stumped.
What's been done (not in this order, just trying to remember it all):
-this bike had stock pipes debaffled (back plate and baffle removed, front plate intact).
-changed jets and airfilter to higher performance. These have since been reverted to the stock jets and airfilter. No fix.
-inspected carb, nothing to note. Looks clean through and through.
-checked carb float, best measurement we could make appeared slightly to one side of spec, but still within spec. Tried adjusting dead center of spec, no fix.
-replaced fuel line. No fix.
-inspected fuel pump by removing and disembling. nothing to note.
-valve clearances checked. Within spec.
-spark plugs look in good shape, but they're cheap - replaced, no fix.
-pin testing wiring harness, did not find any bad wires.
-swapped out control unit with a known good (new) one for test purposes, no fix. Reverted to original control unit.
-replaced stator, no fix.
-coil wires appeared to be getting brittle, replaced with similar copper core, no fix.
As you can imagine, a considerable amount of time has been spent on the air/fuel considerations, but we have not identified any issues there at all. Tried determining if there was a bad seal/crack in the intake anywhere, but could not find one or evidence of one. Obviously, we have done extensive testing on electrical components where we could (coils are not easy to test). So far, I've bought a new stator, which was not the problem. I cannot afford to throw parts at this. My brother's bike is also near 40k, and he is experiencing similar behavior, although mine appears to be much worse. Any ideas or help would be greatly appreciated.
I am having the same problem with my 2003 Volusia. Have you found out what the problem was?
Have you try to rev it up stationary (no load) and with load on its centre stand, any RPM drop or struggling?
Have you checked the jet seats, idle jet seats, perhaps fuel filter.rectifier/regulator state, float bowl seating impedement, vacuum line and oil level.
Does it burn any oil or have low compression in cylinders or valve are not closing properly?
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Thank you for your response. All valid questions. Answers to your questions:
- Bike has no trouble throttling up, either on the stand, or in gear. Plenty of power overall.
- All jets are all back to factory set at this time, and have also been inspected to ensure they are clean and clear.
- Fuel filter has been taken apart and inspected, no sign of any trouble. Fuel flows freely to engine.
- Rectifier/regulator checked with meter, looks good.
- Float/bowl nothing impeding it, float measures within factory specification, bowl is clean.
- Vacuum line is clean and clear of any obstruction.
- Oil level is maintained, regularly changed between 2-3k miles.
- Bike does not burn oil.
- Valves are within factory specification.
- Will have to run a compression check on cylinders. Bike has plenty of power, but will do this to get a baseline anyway, and to see if there has been loss compared to factory specification.
This bike's previous owner kept it outside, and lived near the coast, so there is a bit more rust/corrosion than average. Will also be checking the battery ground and other grounds to ensure they are still good.
Start the bike, leave it in neutral on the kickstand. In roughly 20 minutes, you can sense the engine is running rough, then it will die. It will immediately start back up.
Thank you for your response. All valid questions. Answers to your questions:
- Bike has no trouble throttling up, either on the stand, or in gear. Plenty of power overall.
- All jets are all back to factory set at this time, and have also been inspected to ensure they are clean and clear.
- Fuel filter has been taken apart and inspected, no sign of any trouble. Fuel flows freely to engine.
- Rectifier/regulator checked with meter, looks good.
- Float/bowl nothing impeding it, float measures within factory specification, bowl is clean.
- Vacuum line is clean and clear of any obstruction.
- Oil level is maintained, regularly changed between 2-3k miles.
- Bike does not burn oil.
- Valves are within factory specification.
- Will have to run a compression check on cylinders. Bike has plenty of power, but will do this to get a baseline anyway, and to see if there has been loss compared to factory specification.
This bike's previous owner kept it outside, and lived near the coast, so there is a bit more rust/corrosion than average. Will also be checking the battery ground and other grounds to ensure they are still good.
Start the bike, leave it in neutral on the kickstand. In roughly 20 minutes, you can sense the engine is running rough, then it will die. It will immediately start back up.
I completely forgot this post was out there. Problem resolved on that bike. The PAIR valve had been removed. The PAIR valve recirculates exhaust back through, in order to burn more cleanly. This has the effect of causing a little more backfire and rough idle, and is often removed by Volusia owners. In this instance, the homemade block off plates that covered where the tubes from the PAIR valve entered the case were no longer sealing properly - the gasket used was burned off, and the plates were no longer smooth. Therefore, they were allowing just enough air in to cause a vacuum leak. And, I imagine, this was also affected by heat as they expanded/contracted. The plates were removed, buffed smooth on a grinder wheel, and placed back on with new gaskets. Bike runs great. May not be the exact same location, but this behavior is a symptomatic of a vacuum leak somewhere. Hope this helps you.
Where is the pair valve located
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