Anybody have an suggestion?

[pmonty]

Hi,

I have two '79 Specials...I've done my own mechanical stuff for years on things, including the bikes...Done the carbs numerous times...BUT, I'm missing something this time, I guess...The bike starts right up but within a few seconds revs to 4-5K...I have the throttle cable disconnected...The throttle screws are against their stops...No airbox on so I can see if there's any binding going on...I can't see any...I did just rebuild the carbs...but I've done so many a time...and I took the bank of carbs off my other bike and believe it or not, same symptom...starts, but revs to 4-5K within a few seconds and of course, I hit the "kill" button then.

Any suggestions will be appreciated. Thanks.

Paul

[Snow]

This sounds familiar - did the carbs do this before you rebuilt them? Did you change any of the jets? Did you enlarge the main jets by chance? Did you put any K&L parts in them?

[pmonty]

Thanks...

Thanks for the prompt reply...Yep, I rebuilt the carbs, but reused the old internals, just soaked them (the ones I could remove) in carb cleaner...Have done this before many a time with success...

And, yep, I know about the K&L parts, I think? They supply the wrong size idle jet and idle needles that are way too pointed at the end...Been there...had to did one out using the method outlined on the site...It worked well...Hell, I tightened them to "light" bottoming with a small screwdriver and just two fingers...it still broke...have been reusing the old idle needles which aren't anywhere never as pointed...

No change in jetting...But I don't think that would come into play at idle...Correct me if I'm wrong...Now, I'm going back out to the garage to change the carb intake boots, as I suspect a leak, although I bought brand new ones last year...

Thanks...All you can suggest is appreciated.

Paul

[Snow]

Well, I didn't think Main jet size could affect anything at idle either, until jkorn said he had the same problem that I was having and the same problem you are currently having. The weird thing is the problem was the result of running too large of main jets for the both of us, once I dropped to normal jet size, my idle came right back down.

It was really weird and I still don't quite understand why the mains would make the idle jump to 4500rpm. Out of curiosity, are you using K&L float valves/float needles? They are actually the last things I have that are K&L in my carbs and as soon as I get a change, I am putting in my new carb kits from the motorcyclecarbs guys. I've heard nothing but good things about them, so I am exctied about putting the parts in and giving a report.

Btw, here is where my nightmare began:

http://www.xs11.com/forum/showthread.php?s=&threadid=1780&highlight=idle

[mitch]

choke

Sounds stupid but is ur chock stuck on ? if not try hooking up ur air box the start it up maybe gettin to much air just a thought , regards DOUG

[Jeff]

On any of the carbs that have caps over the pilot jets..... the pilot circuit feeds off of the main thru a small passage just below the main jet and just before the needle jet (emulsion tube). Main jet size has an effect upon the amount of fuel getting to the pilot jet. On the carbs without caps over the pilot jets... they feed independent of the mains.... directly from the float bowl.

[strom]

OK, the screws with the plastic caps on are idle mixture screws... DONT OVERTIGHTEN THEM... the tip brakes off... I should know...
Too lean mixture IMHO.

LP

[fusionking]

Carb swappin'

Was the carbs off the other bike working before? To double check put the first carbs on the other bike and see what it does. that is if it's a runner.

[pmonty]

Hey there...I just wanted to thank everyone that's taken time to offer suggestions...It's kind of a busy weekend, so I may not have time to tinker with the bike more for a couple of days. Thanks all of you!

Paul

[skids]

You are gonna kill me for asking this, but did when you found it rocketing to 4500 rpm, did you back off the main idle knob to compensate? Also, if I remember correctly, Rick J. once found that if the vent hoses (78 and 79's) are plugged, it can cause a big fuel imbalance.

Originally posted by pmonty
Hey there...I just wanted to thank everyone that's taken time to offer suggestions...It's kind of a busy weekend, so I may not have time to tinker with the bike more for a couple of days. Thanks all of you!

Paul

[Redbaron]

Think Simple

I had this problem when i worked on my cabrs, got the synch way out of whack. Search for the pre-synch article on this site, follow directions and try idle again. Just a thought. HTH

[jimg1au]

carbs

hi
i had this problem as well.what i did was screw idle jet screws out 1.5 turns.made sure all hoses were conected and no air leaks.if you are using air box reconect it as you need the right amount of air flow.MAKE SURE YOU HAVE A FAN BROWING ON THE MOTOR AS THEY GET HOTTTT.then sync your carbs.adjust idle then fine tune carb sync.let motor cool down then start again.should be spot on.if i left anything out can somebody fill it in