Carb Curve Ball - The bane of my existance! ;) OPINIONS NEED

Sascha · Post by **Sascha** » Fri Jan 28, 2011 9:40 am

Hey Guys,

So as some of you may be aware I have a small carb issue (seems like an air leak) but I wanted to paint the full picture and get the opinion of a few of the veterans on here... So here we go:

When I turn the bike on, its idleing very high
When i give it gas, its reving even higher and the throttle is prolonged

I have been told its probably an air leak (which I am going to check)...
The two most likely places in my mind are:
1. At the manifold where it connects to the motor (via a mounting bracket)
2. the 'Cap' on the top of the carb is not on correctly

Now, having said that I have TWO CURVE BALLS for you to consider when answering:

Curve Ball #1. I am not running pipes (only headers with baffles welded in them) and I am told that this could be causing an issue with idle beucase there is no 'back pressure' given there are no pipes?!

Curve Ball #2. When I adjusted the float I had to bend the tab down to let fuel in, is it possible that its getting far too much gas because of this? could this be causing the prolonged throttle?

In short - I am hoping to determine what exactly is causing the prolonged throttle - Let me know what your thoughts are and if anyone can chime in on the 'curve balls' that would be apprecaited.

-Sascha

jensen · Post by **jensen** » Fri Jan 28, 2011 9:55 am

Hi,

I'm not a veteran, but I'll give it a shot.
I don't know what a curve ball has to do with it, but that's me, not knowing everything about Canadian (?)slang.

You say you run no pipes, only headers with baffles. I don't think that that's a reason for high idling, since a dream idles good without any header at all. That leaves the air leak and the float hight.

Float hight should be checked as described in many other threads, so make sure you set the hight right.

Leaves the air leak.

Check the flange on the carb for straightness, most of the time that is curved, because people over tighten the flange bolts or nuts. Zamac (material were the carb is made off), doesn't stand that, and over time and heat / cold will curve it.

Check the carb top gasket, and do not over tighten that part either, by letting the bike run and put tape around the top, if you hear any change in rpm, take a closer look (you could use this also for the flange).

Jensen

roadcapDen · Post by **roadcapDen** » Fri Jan 28, 2011 10:15 am

Clogged idle jet?
Slide sticking?
Spray WD or water around the carb when running, see if idle changes, would show air leak.

Good luck Sascha

Sascha · Post by **Sascha** » Fri Jan 28, 2011 10:41 am

Slide sticking - If this is the case, how can I lubricate the slide?
Not sure what I can and cant use to lubricate it...

-Sascha

Snakeoil · Post by **Snakeoil** » Fri Jan 28, 2011 11:13 am

Slides normally stick because there is something wrong with them, the carb body or dirt.

Clean both the body and slide well. Inspect the slide for scratches that would indicate binding somewhere. Check the small guide track for burrs or crud.

With everything clean, slide just the slide into the carb, no springs , no cable, no neede, just the slide and see if it settles all the way down without having to push it. It should slide freely and drop easily into the carb with just gravity but without being loose in the carb body. If it is snug anywhere along the path. Put magic marker on the slide and put it back in the body. Run it up and down once and take it out. See where it is rubbing on the slide. It could be a burr in the body or the body could be out of round. You can round out a deformed body sometimes with careful application of a vise, c clamp or other method of squeezing. I cannot stress the importance of going slow and being careful. You might get away with just a little polishing with emery inside, again going slow.

I had to round out two Amal carb bodies that were deformed to the point that the slides would barely enter the bodies. Both carbs remain in service for 2 years now with zero problems.

Good luck,
Rob

Sascha · Post by **Sascha** » Fri Jan 28, 2011 11:29 am

Hey Snakeoil,

Yeah - I dont think thats the issue, she dropped right into the chamber to the bottom, no problem!

-Sascha

Snakeoil wrote:Slides normally stick because there is something wrong with them, the carb body or dirt.

Clean both the body and slide well. Inspect the slide for scratches that would indicate binding somewhere. Check the small guide track for burrs or crud.

With everything clean, slide just the slide into the carb, no springs , no cable, no neede, just the slide and see if it settles all the way down without having to push it. It should slide freely and drop easily into the carb with just gravity but without being loose in the carb body. If it is snug anywhere along the path. Put magic marker on the slide and put it back in the body. Run it up and down once and take it out. See where it is rubbing on the slide. It could be a burr in the body or the body could be out of round. You can round out a deformed body sometimes with careful application of a vise, c clamp or other method of squeezing. I cannot stress the importance of going slow and being careful. You might get away with just a little polishing with emery inside, again going slow.

I had to round out two Amal carb bodies that were deformed to the point that the slides would barely enter the bodies. Both carbs remain in service for 2 years now with zero problems.

Good luck,
Rob

davomoto · Post by **davomoto** » Fri Jan 28, 2011 11:32 am

When I turn the bike on, its idleing very high
When i give it gas, its reving even higher and the throttle is prolonged

Sasha, have you tried adjusting the idle screw to lower idle? Is there any free play in the throttle cable? What is the condition of the throttle cable? New, used, and have you lubed the cable? Have you done a plug reading from idle? Check for intake leak and tight intake valves.

Davo