Know a thing or two about slide carbs!?!?

I am new to slide carbs, and I know they are a lot different than CV carbs. There is just ONE thing about this VM34 round slide carb that I don't understand.

If I am sitting still with the engine off, the throttle twists pretty easily (feels normal) and springs back quickly.

BUT, when I am driving, the throttle is pretty hard to twist. Like awkwardly hard to twist especially right off of idle. The cable isn't kinking or anything. I have check that. Plus if it was, it would be hard to pull all of the time, not just when running.

I am assuming this is because of the airflow through the carb pushing the slide into the slide wall.... or something like that. Just not sure if it's "normal" for slide carbs, or if I should be concerned.

Must be something there catching on that you dont see

treitz wrote: I am new to slide carbs, and I know they are a lot different than CV carbs. There is just ONE thing about this VM34 round slide carb that I don't understand.

If I am sitting still with the engine off, the throttle twists pretty easily (feels normal) and springs back quickly.

BUT, when I am driving, the throttle is pretty hard to twist. Like awkwardly hard to twist especially right off of idle. The cable isn't kinking or anything. I have check that. Plus if it was, it would be hard to pull all of the time, not just when running.

I am assuming this is because of the airflow through the carb pushing the slide into the slide wall.... or something like that. Just not sure if it's "normal" for slide carbs, or if I should be concerned.

Put some carb gauges on them and see how much vacuum you're pulling.

Carb gauge? How much vacuum should I be pulling?

It's a 2-1 intake on a KZ400 with a VM34.

Put one drop of motor oil on the slide and see if that makes a difference. If it does, then yes the vacuum is pulling the slide toward the engine, which is normal, but it shouldn't be that hard to pull.

If the throttle cable is not lubed, the extra resistance from the slide, while running, can cause the cable to bind up in the cable housing. Lubing a cable can make a world of difference.

Then there is always the possibility that something is not right in the carb.

When the cable resistance is normal, the slight resistance you feel on the throttle, while riding, is one way to determine how fast you open the throttle. Too little usually means you've opened too fast, and you'll notice the bike will not accelerate as hard as when you open it at the right speed.

So it turns out the throttle assembly I got with the carb was some kind of quick fire dirt bike throttle. It had a 90 degree bend going into it making it a 1/4 turn instead of 1/2 (I think). Anyway, I put my stock throttle assembly back on and it is much smoother now.