Hello!

So I have a multilayered question! First, I appear to have some sort of vacuum leak. I have rebuilt my carbs, replaced most of the seals and wearable parts. The bike was raced before I got it and has what appears to be 260 main jets (this seems mighty big even with K&N's and a complete Yoshimura system what do y'all think? oh and I'm in Portland Or I don't know if that helps or not). The bike starts fine with the choke on and warms up. Only I can't get it to idle at the correct speed to sync the carbs. It wants to idle either around 1200 or it will jump to 5000 by itself, then after a bit it will drop back down by itself without me touching it. I have backed off the choke cable and throttle cables, made sure both mix screws are 2 turns out and I don't know where to go from here~!

I'm running a K&N filter and complete Yoshimura pipe on it, I also did an engine tune up on it to make sure the valves were happy before I got this far as well. I've poured a hell of a lot of work into this bike (it is completely rebuilt and repainted) and getting this far and not moving ahead is driving me bloody crazy! Crazy I tell you!  Any help would be greatly appreciated!! Thanks, Erik

260s are way too big dude

What year is the bike?  89-2000 should be about a 140 main with K&N
2001+  should be 147.5 or 150

It is an 89, I figured the main jets were too big! But that's what the idiot before me had! Ok I'll change those out first thing. Any other suggestions? Anyone?

The jets may be Dynojets or something. Their numbers don't relate to the hole size. If it does have a Dynojet main, then chances are the needles are not the stock ones either, and I have no idea how the needles will work with Mikuni jets.

Personally I think 140 is too big with just an exhaust and K&N's. 135 to 137.5 should be enough.

Turn the mixture screws out to 3 turns, and then you can adjust them in from there once you get it running semi-right. Check the idle jet, and see if it is a 40. Replace those if they aren't 40's, non-cross-drilled jets.

If that doesn't cure the flaky idle, you probably do have a vacuum leak. check the diaphrams very carefully, the caps on the vacuum ports, and the vacuum line to the fuel switch. Make sure you are getting good fuel flow - try it on Prime.

If you can't find the vacuum leak, take some WD40 and spray it around suspect areas. The idle should change when you hit the leak, and you will get white smoke in the exhaust as the WD40 gets sucked in and burnt.

Let us know if any of that works.

I know the needles are stock, I double checked the numbers. I'm not working on it until Friday so I am gathering info in the meantime.

I have the fuel line coming straight from the tank to the carb, I don't run the reserve crap as I've had 3 of them go out and I'm sick of messing with them. I'm going to change out the tank petcock in the next couple of weeks. So I doubt it's that, it's also all new fuel line. I have a fuel filter on the bottle line so I can see that the fuel as it is being pulled from the bottle and that looks good, I've even changed the angles of the line to see if that makes a difference and I haven't seen any coralation.

I think I'll start off with taking the carb off and checking the carb clamps, then change the jets and double check the carb itself. Then go from there and try the WD40 method.

I have been rebuilding the entire bike from the ground up and knowing I am so close yet so far is driving me utterly insane!

Thank you for your info and support!

Erik  

How is the vacuum port blocked off that used to go to the vacuum fuel switch? Any chance of a leak there?

Opening up the idle mixture screws to three turns may help too. 2 is pretty lean on most bikes, and can make the idle surge.

Even if you can't get the idle to stabilize, I'd try to do a rough carb balance. Can't hurt.

260 is so big in fact that mikuni doesn't even make them...Ok They dont have Keihein's in them either before you take that route....They dont make 260's either. Somehting is wrong and I believe you probably need glasses.
Cool.
Srinath.

Srinath,

Funny you should mentioin it, I already wear glasses! You goof!  :guns:  No seriously, I took a magnifying glass to it, the only identifying numbers said 260! I kid you not! I will pull it apart again and have several other people look at it and get back to you.

visualizing whirled peas.

Ok 126 maybe...and that funny square insde a square thing you you think its a 1260 and the 1 is obscured so it is 260??? How's that for stretching it...but hey its still more believable than 260. Full pipe and K&N pods will need 150's max with stock needles. That idle racing and dropping could be a vaccum leak and test it wiht wd40. Spray that around the carbs with it idling and see if idle goes up or exhaust turns white and smoky. Look for throttle cable hanging and rock the handle bars left to right to see if that affects it any. Else put in 150's with the stock mains and thne try it. Also strat with 3 turns out on air screw. I typically set them within 1/2 turn of 3 on most bikes.
Cool.
Srinath.

One more question!

What is the highest quality Jet Kit I can get? I'm not concerned with the cost I want quality. I apreciate the opinions!

Thank again, Erik

Factory is without a doubt the best, they use Mikuni parts for the GS.