Throttle Hesitation, Carb Problems, Help Please!

[ponchopirate]

I know there is a lot of info on this problem and I've searched through it, but I have a CHP appointment tomorrow to get my engine # verified and I need to have the bike running so I can get there.  So I'm hoping someone has a fairly specific answer.  Here goes...

I installed new carbs yesterday.  They were jetted stage 3 but I have stock exhaust/air filter so I put it back to stock jetting and replaced the drilled slides with my old slides.  Now the bike will idle normally, but when I give it gas it hesitates and then shoots up to 3k and then stays there for a few seconds before slowly returning.  I did the WD-40 test for leaks and  came up with nothing.  I figure I'm running lean.  I didn't check my float heights, could that be it?  Could there be some gunk in there that I missed?  I'm going to pull the bike apart right now.  Any help would be greatly appreciated.  Thanks!

[70 Cam Guy]

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I figure checking the float heights ( http://www.gstwin.com/float_height_check.htm ) would be a good place to start as well as double checking the mixture screws and making sure your choke cable isn't binding anywhere.  I take it you checked the intake manifold boot things with the WD test?  Idle adjustment screw?

I wish I knew more about carb tuning on bikes, you're just over the hill from me

[scratch]

If you used the stock jetting, which is 37.5 pilot jets and 122.5 main jets, you're too lean. Size 40 pilots and 125 mains and shim up the needle is what you want.

[ponchopirate]

Thanks for all the info.  I pulled my carbs and checked them over.  It looked like the pilot jet in the left carb was plugged so I cleaned it out.  I also checked my float levels and everything is in spec.  I put it all back together and I have the same problem.  If I give it a little throttle it hesitates and then jumps up to 3k and then slowly falls back down.  Sometimes it just stays at 3k and if I turn the idle screw down the revs will drop.  I know stock jetting is lean, but I shouldn't have these kinds of problems should I?  Any other ideas on what this could be?

[70 Cam Guy]

I agree stock jetting is lean but I've never had any troubles with it.  just brainstorming here...

You're sure the vacuum lines are free of cracks or pin pricks?

could the throttle cable be binding somewhere?  I know when I swapped to drag bars (before I adjusted it) the r's would jump way up when I turned the wheel to full lock in one direction.

The O-rings/washers on the needle are all the correct order?  I remember reading about someone here that accidently got something reversed causing things to run funny

You're adjusting the idle when its at full operating temp?  If you set the idle when the engine is cold, it will not be too high when its warmed up in my experience

Shouldn't a lean jetting provide snappy throttle response off idle just revving it?  I'm just remembering how my nitro RC's would respond to lean mixture setting.  Fast off idle but zero top end and, of course, high op temps

When I had this old Holley on my Camaro, the needle and seat would get sticky or some crap on it and really screw up how the car ran.  Are these ever a problem on our bikes?  Do our bikes use the needle/seat in the carbs?

good luck with it.  wish I could be more help :dunno:
sucks your bike had to be such a problem child but I'm sure you'll get it worked out and running reliably soon enough

[ponchopirate]

Thanks for the help.  I'm going to pull it all apart tomorrow and maybe swap the floats with my old ones (I know they're in good shape).  I'll check out my needles as well.  Maybe the height is off.  Argh, this has been one frustrating bike.