Carb or Electrical Issue??

[Hodado]

81 650g;runs out great until about 5000 rpm then stumbles'carbs have been rebuilt to stock specs;new o rings berryman dip have original exhaust and airbox,exhaust leak on one pipe[gasket].
Have spark to every cylinder;all cylinders firing idles fine,runs strong up to 5000 rpm.Acts like it needs fuel;Should I change to larger main jets?or could it be cdi box?Headlamp and all lights are bright.Confused

[cowboyup3371]

How long were the carbs dipped? Did you poke a small wire through the jets?

How's the vacuum line - is it the right size for the petcock? Did you replace the intake boot orings?

[BassCliff]

Hi,

Fix the exhaust leak and go from there. Could be a malfunctioning petcock. Do you use an inline fuel filter? Are you sure the airbox is sealed? Are the valves adjusted? Are the intake boots in good shape or have you replaced them? Sure, it could be the ignitor but it could also be that the cams have jumped a tooth. One thing at a time.


Thank you for your indulgence,

BassCliff

[Hodado]

I ran wire through jets as instructed on rebuild ;new vacuum line,replaced one intake boot ring.Petcock is new;how can I check to see if it is operating properly?Bowls are full of fuel
Thanks

[cowboyup3371]

For the intake boot orings - it's best to replace all just to be on the safe side if nothing else.

To test the petcock, suck/blow on the vacuum hose while the petcock is on run or reserve - if fuel flows it's okay there. Also turn it to prime and see if fuel flows that way. Fuel should stop flowing when you stop providing the vacuum or when you turn the lever back to run from prime. But if the bowls are full and fill up on their own then it should be fine.

[Hodado]

Thanks for reply;The bike starts and runs on either run or pri position.if its the petcock I don't understand why cause I'm obviously getting fuel I don't even have to choke it when its cold to start.Where else would I check for a vacuum leak?Thanks

[cowboyup3371]

Vacuum leaks will come from those orings so only replacing one of them doesn't always do the job. Also, how pliable are the intake boots? Do they have holes, even pinsized, or cracks? Did you put new weatherstripping tape around the air box? Are you sure your hoses don't have even pin-sized holes in them? Are they snug around the petcock outlets?

[Hodado]

Intake and airbox boots are good,airbox seems snug but as far as any weatherstripping around it there isn't any that I can see.

[Big Rich]

My bet is either on high rpm fuel starvation or your coils are too old to create spark at those rpm's. Any inline fuel filter (other than on the petcock)? There's a test for the coils in the service manual.

[Octain]

If you dont need any choke to start it cold it may be running a tad rich. What do your plugs look like?

[Hodado]

No inline filter,plugs are sooty.Stock main jets are 110;maybe try 130?

[tom203]

If you dont need any choke to start it cold it may be running a tad rich. What do your plugs look like?

Sooty plugs, no choke needed from cold start- yes, rich- assuming it had a decent run. My 650 won't cold start without full choke-even after a decent ride, if shutoff for an hour, it likes partial choke, but I'm sure mine runs lean. Check your gas tank vent to make sure it ain't plugged and not allowing enough fuel at 5000 rpm- but this doesn't explain the sooty plugs.

[Hodado]

Problem solved!! My buddy came over yesterday and after concluding that fuel was not the issue,we went through the cdi box but did not find anything wrong there,went on to the coils thought we would remove to have tested and discovered that the coil wires were mixed up,[don't know how it ran so good up to 50 mph] put the wires where they belong and its running good now.I can only assume that the p.o. had them in the wrong place.