runaway carbs.......

82 XJ650r seca......it sat for a year & a half in a hot climate with the petcock on "prime".....needless to say, it wouldnt run, and came to me.
washed out & blew out the carbs with laquer thinner & acetone. They were really bad. Inspected the diaphragms, no pinholes, supple. rubber Spigots are OK, one had cracks that didnt go all the way thru, I worked hi temp silicone into the cracks. Needless to say, I flushed the tank. The runaway part- it will go from idle to 4k in about 4 seconds-only happens when thoroly warmed up. I thought (hoped) the petcock diaphragm had cracked, unhooked it, plugged hose, & ran on "prime"- same runaway ......i can easily slow it down just by giving it a little clutch. Theres no external idle MIX screws, no settings were messed with, it ran perfectly when parked. Any suggestions?
I dont THINK its a carb to spigot vac leak, but Im willing to be told Im wrong.

 

I just read the well written step by step on proper overhauling. If the symptom dosnt ring any bells, I have acess to an ultrasonic cleaning tank.
i hesitated to break the carb bodies off the rack, I dont have a vacuum gauge bank, (got a colortune, tho) gat a flat surface for reassembly& the mix screws are secreted away.....and this runaway deal is irregular.....not a all the time thing. Would a vac leak at ONE carb be able to race it up to 4k?
this is a charity job, too. Rats. Never volunteer.

 

HAH! an enricher was hanging a tad open. Fixed it.
Tell you what, tho: were this my machine, I would hew closely to the really stellar carb cleaning advice offered here. Its running smoothly, & idles acceptably, but I have little doubt it would benefit from a major overhaul as described.
4 carbs are just too bloody many.........now maybe she can sell the machine. Beautiful bit of kit it is......

 

Isn't it nice when you can solve the problem on your own! Those carbs probably need a good sync still. There will be a carb clinic in the SF bay area this spring so if that isn't too far a trip I would go there and have some experts tune & sync your carbs while teaching you how to. Info should be posted sometime around March/April.

 

Oh, please let me know when that clinic will be!!!!

I'll be more than happy to drive 3-4 hours to make it to one of those with my bike.

 

I will post the info when it becomes available. This info get posted in the carb clinics rides and rallies forums at the bottom of the forums page. They are broken into regions so you can find one near you.

 

im sure they require a good synch....i used to run a 74 Triumph Trident, thats 3 carbs....that was plenty. Im damn good at twin carbs....and now that my ride is a shovelhead HD (with a Lucas headlight bucket & barrends- habits die hard- I just have one carb to diddle.
No, Im just getting it up & running so she can sell it- takin it on a long back country "test ride" today.
this is a heck of a fine tech site....Im on a ford 6 & a shovelhead HD site, & this here is up tho the others very high standards. Were I to own such a complex puzzle of a rocket, I would dwell here....
Thanks again, Mutt, San Diego....