Engine Dies at 1/2 Throttle

[LarryA_Texas]

re-jet

Thanks everybody, I think I have something to go on now. I'll get the pods and rejet, I developed a grudge against the stock airbox when I first removed it. I'll install the new o-rings, I know that I am missing some on the air screws. Hopefully that will get it functional.

Others have probably given you enough to go on, but here's my take. You are getting too much air and at 1/2 to full throttle the mixture is going too lean.

That's because it's jetted to have the somewhat restricted air flow of a normal air filter. When you took the stock box off you changed that. Add the pods if you want, but you will have to add a stage II jet kit, or if you have changed from stock exhaust you'll have to go with a stage III. There is a ton of information out there about carb jetting. Read up and then go out and test your bike to get the proper jets. Since they are about $5 each it's not very expensive to change them, but can get to be a lot if you keep getting it wrong. Try this to get started:

http://www.factorypro.com/tech/carbtun.html

It's hard to imagine how much a little change in air flow can affect the carb performance. If your pipes have a significant air leak it will make a difference. You can try to cover the carb intakes...wrap a shop towel or something around the pods for a quick, very rough estimate, of what changing the air flow does to the carbs.

good luck.

[Guest]

Does your bike have a mechanical advance? Check and see if it's froze up.
Did you adjust the valve clearance?
What are your compression numbers.
The slides should rise evenly which makes me think you are not pulling the same vacuum through all the cylinders. (compression)
I would also check the diaphrams on the slides and also make sure the slides slide smoothly in their bores.

[Steve]

... It has no airbox.

I suspect that this is your problem.

The CV carbs need at least some resistance ahead of them to develop enough vacuum to lift the slides. Either a stock airbox/filter or a set of pod filters. For a quick check, take a shop rag, fold it in half, drape it over the carb intakes. Secure the rag to the two outer carbs with hose clamps or tie-wraps, making sure it's taut over the inner carbs. Now check your throttle response. This setup is even good enough for a ride around the block, but it's not good enough for jetting checks.

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