sputter

[10spd]

On my 1988 at around 3000 rpm on up it has a sputter. It also doesn't seem to want to rev above 3500. up until then runs pretty good. also seems like it has a dead cylinder. haven't gotten into that yet. any suggestions where to start? also only getting 35 mpg I know these bikes will get better than that. Man I really enjoy riding this bike!!

[Flyinfool]

I only get 35 MPG when it is running good.

 

First is see if you are running on all 4. start the bike cold and see if all of the pipes heat up at the same rate.

[10spd]

I have always thought that. With the coils mounted on top of the engine could the heat be affecting them? just a thought.

[cowpuc]

Right there with Flyinfool.. Then check/change plugs, the little 10mm plugs in these things hate to be choke blackend. Check your carb diaphrams for holes/rips and your slides for stickyness. Toss a carb sync at it and try it again..

[Marcarl]

Check your fuel filter and make sure your petcock is all the way open. Sounds like it could be fuel supply.

[saddlebum]

Another thing you can try is to pull your air cleaner and battery. to gain access to your TCI module remove all the connectors and check for dirt and/or corrosion. Carefully clean all pins and terminals.I had the exact same symptoms and found this to be the problem with my 89 and it has run like a dream since. Another thing that will give similar symptoms is Carb flooding gives the same symptom as though it were starving for fuel.

[Great White]

A quick indicator of carb slides and diaphragms working as per is to pull the air cleaner lid and filter, start the bike and then blip the throttle lightly. You should see the slides and needles (for lack of a better word) bouncing.

 

If they're not bouncing or one or more are not moving, your diaphragms are suspect and warrant closer inspection. Pulling the carb diaphragm covers off will allow you to inspect the diaphragms for condition and security.

[10spd]

Already changed the fuel filter. pump seems to working fine will check the others this weekend. Thanks

[10spd]

Here is a new one possibly. My slides are bouncing. But it starting run really rough. Even backfired back through the carbs. So now where to look?

[Patmac6075]

Backfiring while the airbox is open? That's normal....

[10spd]

backfiring while riding down the road. wants to die with the airbox open.

[Patmac6075]

Could use more history to be sure...Has anything changed since the last time it was running well? What is the condition of each plug (pix help)? Are you up to date on maintenance (valves within spec, carbs clean, age of plugs, oil changed, how old is gas)?

I had a similar issue with my '84, except mine seemed to flatten out near 5k rpm, I had just resurrected it from a 10 year nap...I did all the routine maintenance to bring it back into this century....except I must have had enough stale residual gas left in the tank, once I ran a few clean tankfuls through the performance steadily increased.

In your case it sounds like you have an air leak, or perhaps a faulty diaphragm (which is technically an air leak)...I'd start with an unlit propane torch while she idling, move it around your intake boots and carb area, listen for an increase in rpm....viola, you've found your leak. Beyond that, I'd start knocking off over due maintenance items. Starting with Valve check/adjustment, carb rebuild and sync.

Good luck, let us know what you find.

I'd also start a new post in the 1st Gen Maintenance section.

[Condor]

One more thing to consider is since it's running strong up to 3000rpm, it might be caused by one of the valves floating due to weak spring???

[10spd]

It seems to have a dead cylinder. This weekend I plan on giving it a good tune. Wires plug caps plugs. Running Seafoam through it seems to help. Love the way this old 1988 rides & handles. Just want to get the performance back.