2 into 1 intake...Bike revs hard and will not come down...

[remainincognito]

Have a 2 into 1 intake and have tried just about everything to get the bike to run right. Current settings are 159-p8 emulsion tube...pf6 needle...200 main and 25 pilot. Pamco ignition. Right now the bike just revs at around 3000 rpm and will not come down. I've tried all combinations of a 180,190,200 and 210 main with 20,25,30 and 35 pilots with no luck. Any ideas?

 

[mrkil]

I'm not trying to be a dick but is the cable to tight or caught? I ought my old XJ for 3 days trying to figure out why my idle was hanging so high and it was a pinched throttle cable in the end.

good luck man

 

[remainincognito]

Cable is fine but thanks. Just revving with current setup. But all others failed as well but in different ways.

 

[TeeCat]

How about your ATU? Are the weights returning to resting position? This happened to me, and it was an issue with sticking weights.

Also, what kind of carb are you using, and have you backed the idle speed screw out and allowed the slide to close completely?

TC

 

[scott s]

Stuck advance? Stuck slide in carb? Too lean? Intake leak?

 

[remainincognito]

I will check the atu. No leak on the boots and slide is all the way down. How exactly do I check the advanced timing unit? Carb is a 35mm mikuni round slide with round kn filter.

 

[swbill]

I know you said its fine but check that cable again. I just dealt with that crap on a customers bike and it ended up being I had the cable pinched in my tie down strap.
it could even be in your throttle assembly. Try running it with the cable hanging right out of the Carb.
I'm also running that intake. My settings are stock needle and needle jet. 200 mj, 27.5pj, clip in the center,air screw 2 turns out, no filter. Mine runs great other that terrible fuel mileage. I gotta change my needle and jet to fix that.

 

[sgallaty]

What are you using for exhaust? If you're using straight pipes you may have issues with too much ejection - meaning not enough backpressure. I know this sounds stupid, but try corking up your exhaust with some tapers with smaller holes in them for temporary baffles.

I've had a very similar problem, and so have friends of mine.

 

[zuehl666]

I know it sounds like a no-brainer, but if you're not paying attention its fairly easy to put those slides In backwards. It will drop down, but not fully. If you haven't already, pop your filter off and have a look to make sure the slide is at the proper height.

 

[Loffer]

I dont XS carbs that well but i know this , that is a needle , slide , cable problem. No matter how things are jetted/set you will be able to close those slides and lower any carb idle with the idle screw, somethings stuck , cable throw, length ect. .

 

[remainincognito]

Pulled the air filter off so I can see the slide. The slide is not hung up which tells me the cable is not sticking or the slide hanging up. Carb has been removed and cleaned and double checked. The jettings are correct for the setup. I'm at a stand still. First charging issue now this. When I check timing it is erractic. Using Pamco igniton.

 

[sgallaty]

You're ignoring my question.

 

[remainincognito]

sgallaty must have skipped you over. Pipes are not really straight pipes. Check my pics and you'll see what I mean and let me know what you think. Thanks.

 

[sgallaty]

what is the butterfly valve like when the throttle is at rest?

Since noone else has stepped up and mentioned this, I'll do that but I'm not familiar with your carbs.

There is an 'idle circuit' which is the air/fuel circuit that the bike relies on when the throttle is below 1/4 open. There should be an idle jet, and one or two pilot circuit correction screws (mixture and air correction)

If everything else is okay, which is a poor assumption to make, you will need to look at your idle circuit secondary adjustments and see if you're maybe running a little rich at idle which may be causing RPMs to creep up.

I don't know if you know what to smell for, but you should be able to 'smell' a rich exhaust.

Also, does it come down slowly from RPMs when you rev it over 3k?

This sounds f'ing stupid to say, and I apologize but it sounds like your choke might be stuck partly on.

 

[remainincognito]

Butterfly valve? I have my pilot jet at 25 which should be very close and the air/fuel screw 1 turn out which should be a good starting point. Not sure of any other correction screws. If I rev over 3k it does not come back to idle....just idles high. It did do that previously but not any more. If I use the timing light...timing seems erratic.

I did however take out the little air screw that is located in front of carb where 3 holes are on air filter side. Others who use this setup have taken that out. Maybe this?

 

[grizld1]

sgallaty, there is no butterfly in a VM series carburetor. No, incognito, don't reinstall that main air correction jet; it has nothing to do with your problem (the intake side is the back of the carbie; directions on a motorcycle are always referenced to the perspective of rider in saddle). I assume you have a VM34, as Mikuni produces its carburetors in even-numbered increments. Zuehl666 and swbill gave you sound suggestions: check that the slide cutaway faces the intake side, not the outlet side, and take the cable out of the twist grip to test for bind or insufficient slack. BTW there is no "pf6" Mikuni needle.

 

[remainincognito]

Grizld1....thanks for the info. The cutaway is does face the intake side as the slide only goes in one way. The carb is a vm36. I will pull the cable from the twist grip although while the bike was revving and having the air filter off there was no idication that the silde was off it's seat. Also the needle is a 6F9 thanks for the input.

 

[mrriggs]

It sounds like your ATU springs are too weak. This is easy to verify. When it is idling high, use the clutch to drag it back down to an idle speed (bike in gear, don't touch the throttle) then pull the clutch in again. If the idle races back up after pulling in the clutch then its probably a carb/throttle issue or air leak. If the idle stays low after pulling in the clutch then your problem is likely the ATU springs. To fix it, cut a coil from each spring.

 

[pamcopete]

When I check timing it is erractic. Using Pamco igniton.

The dual output coil produces a positive voltage for one spark plug and a negative for the other. The timing light works best on the negative because that is the polarity for a conventional distributor type ignition system, so try reversing the timing light clamp or use the other plug wire.

As for checking your ATU, the simplest test is the "snap back" test as shown in this video;

Notice how the weights snap back to the completely retracted position. They should not float outward.

 

[remainincognito]

Thanks Pete. Checking the weights as shown shows they are snapping back just fine. I will try the other plug wire.