Afternoon Guys. Exhausted my limited ability troubleshooting and in need of advice.

315r 2001

Sea level

Pbhl26

Pilot jet 36

Main 110

Needle one notch from bottom.

Fuel screw 2 out.

Dual stage boysens

Large opening air box lid.

All restrictors removed before I got it.

2 issues possibly connected.

Hunting idle. 1/8 throttle and il happily chug along smoothly but no throttle and it will chug erratically surging and dying.

Worse with a richer mixture.

Also taking a while for revs to die down after blipping throttle and front firing

Improved with a richer mixture.

Checked for air leaks and all good outside. Flywheel is tight with zero play.

Next idea. Rebuild carb with new seals etc

Failing that crank seal ignition side?

No sign of water in the oil either so the rhs seems sound.

Any other suggestions.

Cheers. Rob

Sure sounds like an air mix issue.  Are you using a spray bottle to check everything from the intake boots to the cylinder head?  Have had friends get a small leak in the bottom gasket causing this same symptom.  

 

good luck!

problems like this on a 2 stroke I always think crank seals 1st

 

Yup carb cleaner all over. No change in idle. Il have another check tomorrow just in case. Driving me nuts. Other than these issues she runs superbly. Pulls like a train from any throttle position including near stalling in all 3 gears on steepish climbs. Rev's out cleanly and develops power evenly across the board.

Should have seal kit for the carb next week. Fingers crossed.

My two cents worth

Usually on the magneto side air leak, you can run it with the magneto cover off and it will rev a lot higher as it gets more air into the leak than when the sealed cover is on the engine.

I thought that perhaps the carburetor needle retention plate was under the clip instead of above it. Making the needle float up and down? I've seen this a few times.

Or perhaps the sealing o-ring is missing from the top of the carburetor slide cap?

regards, Jim

Good idea. Guessing as the stator ect is fitted to the cover I could just back the bolts off enough to pass air without affecting it. Would leave no doubt it's crank seal then. Unfortunately I don't have a puller to hand or I would have checked it's condition with the mark 1 eyeball already.

Carb is as it should be but all old seals. And squeaky clean. Pilot jet is brand new too. Stepped up 3 sizes when I fitted reads. Air screw was right out previously.

I thought that perhaps the carburetor needle retention plate was under the clip instead of above it. Making the needle float up and down? I've seen this a few times.

regards, Jim

Umm actually. This might be it.

Only had to strip and clean the carb on my last bike and never really paid attention to the slides construction. Just hung it over the frame after a spray. When I checked the needle height earlier I was able to push the needle up inside the spring and get to the clip. It was above the plate the spring locates into.

After checking a few diagrams and pics this is definitely in the wrong position.

Relevant digits crossed as I've got a 300 mile round trip for a training day in the morning. Be great to have it cock on for the day.

I'll add this to the list of bodges I inherited from the old boy it came off.

Best one. Incorrect sparkplug no R rating and not even the correct thread diameter.

Problem fixed. It was the needle clip. Ticks over and crawls as smooth as a sewing machine now. Rev's aren't hanging either now. Cheers Jim your diagnosis was spot on.

These guys know their ****,, never let you down,, mine is hunting a bit on tick over,, runs fine starts first kick on choke,, revs do hang a little,, I bought a carb refresh kit,, but I mixed and mashed the bits,, new with old,, could this be an issue,, needle is in the middle btw 

Cheers