Idling Issues

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Charl
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Idling Issues

Post by Charl »

Hello All,

I have read the jetting pages but want to run this one past you anyway. Bike revs up when started from cold, and you need to nurse the choke (pull it up) to get the revs down for two or three mins till it settles to a decent idle. Idle settings are throttle stop full out, and air screw half screw out - if you screw the air screw out more, it revs up rapidly. When assessing peak revs for idle jet sizing, peaks at 3 turns out - revs very high.

My theory is a very lean idle jet, and a rich main. Any suggestions?
Isn't it funny how knee down is painfull off road, yet foot out is likely impending doom on a Superbikes?
Goofaroo
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Re: Idling Issues

Post by Goofaroo »

Is this bike new to you? It sounds to me like you have other issues besides jetting but before you start tearing the motor down, have you thoroughly disassembled the carb and cleaned it? Is the air filter clean and in good shape? What year and model is it?
Charl
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Idling Issues

Post by Charl »

Hi,

I have had it about a month and done probs 10 hours on it. Re powder coated frame and went from there - it was rather un loved.

Things engine related worth noting that is non standard (As far as I can tell) other than some hand milling on slide and Scratches on Needle!!! :shock: , Air box lid off.

Gasket maker on cases.... :mad:

I got the shop manual and started.

So far I have cleaned the carb, jets, lubed / adjusted throttle cable, new air filter, replaced chipped reed valve, sealed / tigntened all potential air leaks from cylinder head to air box, checked float hight plus float seal needle rubber condition, cleaned /routed all carb vents... Fresh fuel, 32:1 Mix. Compression 146 PSI, decoked / re-packed muffler, new plug / gapped (spark is solid). Kips movement OK, correctly set up and visually inspected.

Im thinking to replace all jets with OEM spec and the needle - after that the seal in the carb block -failing that a new slide.

Will strip the carb and pay special attention to the idle circuit and post a pic of that needle and slide... Will also get needle and jet no's.

Tx for all the help - will make and effort to take photos as I go along to contribute back
Isn't it funny how knee down is painfull off road, yet foot out is likely impending doom on a Superbikes?
Goofaroo
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Re: Idling Issues

Post by Goofaroo »

You will definitely need the carb issues sorted and then see what happens. You should also check for air leaks around the reed cage/intake boot. Hopefully that will fix your problems but if not it will be time to do a leak down test on the case.
Gasket maker on cases.... :mad:
Not good. I would be suspicious that he was trying unsuccessfully to fix an air leak. You seem pretty knowledgeable and mechanically inclined. If it were me, and I had gone to the trouble to powdercoat the frame, I would finish the job and completely disassemble the motor, replace all of the seals and gaskets, and be certain that the carb is dialed in with replacement parts if needed. If you have an air leak at the case halves or the crank seals you will never get this thing to run right and the life of the motor will be dramatically reduced.
Charl
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Idling Issues

Post by Charl »

Hi All,

As it would be I spent a restless night pondering.... It kept seeming to me that he Idle jet circuit must be lean. So before work, I brought out the mighty carb cleaner, attatched a nozzle to it. Took out air screw and blasted the circuit. Low and behold, all is now as it should be!

Jetting pilot circuit peak revs at 2 turns out, seems crisp response at about 1.5 turns out.... !!!

Engine cuts out when screwing air screw in full, as it should be. Strangely, lowest possible idle is with idel stop screw all out - anybody else got this?
Isn't it funny how knee down is painfull off road, yet foot out is likely impending doom on a Superbikes?
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bufftester
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Re: Idling Issues

Post by bufftester »

Pull the carb and clean it again, disassemble it fully first, pull all the jets and give it a good round of carb cleaner and compressed air. Clean filter, new plug, clean/repack the silencer, ensure the rest of the exhaust/intake tract is in good shape. Then follow the jetting guide (link in my sig). These are simple machines, but the benefit greatly from routine, correct maintenance.
Charl
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Re: Idling Issues

Post by Charl »

Sorted it thanks guys! Pulling like a tractor.
Isn't it funny how knee down is painfull off road, yet foot out is likely impending doom on a Superbikes?
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