Which carb design is for what? Out of Curiosity

If I am looking at say Keihin carbs they sell round slides and flat slides (I’m talking new ones) the question is why? What are the advantages of one over the other? (I’m not talking CV) Any input would help.

flat slide carbs flow better than round slide carbs.

timebomb33 wrote:

flat slide carbs flow a better than round slide carbs.

They also are shorter and weight less then a similar sized round slide carb.

there is that as well.

Throttle response is better on a flat slide...

With roundslides you have to use a smaller diameter carb because if you go to big the engine will have good top end and thats it. With a smaller diameter carb you have better all around peformance but the top end suffers.

We went over this in snowmobile technology in college and I can't remember exactly why but the flatslide can run a larger diameter for good top end and still maintain good all around performance. I can't remember why or how it does it though.

So why are there so many round slide carbs out there if this is true? Seems odd that they would be used for so many years from the factory if they weren't "better" in some way.

Do they just provide better all around (low,mid) performance versus the flat slide carbs?

Don't know but been told that sometimes it's easy to tell the flat slides are working better, because they're rattling. :laugh:

Good Fortune!

Well, like I said, that is what they told us in snowmobile theory. On sleds you are on the throttle alot and so the manufacturers are looking for performance over economy. maybe the roundslides are more efficent MPG wise??

I won't pretend to know what manufacturers are thinking when they make these decisions.

Injected wrote:

Throttle response is better on a flat slide...

Bingo

I flowed and posted the numbers for RS34 Mikunis. The're not impressive in the flow department.

Size wise, you can get good throttle response out of a slightly larger flat slide as you can on a round slide without way over carbureting the engine.

Carbs meter fuel well or poorly based on the signal strength present at the fuel discharge point.

Patton wrote:

Don't know but been told that sometimes it's easy to tell the flat slides are working better, because they're rattling. :laugh:

Good Fortune!

That would be incorrect :laugh:

DoubleDub wrote:

So why are there so many round slide carbs out there if this is true?

rounds simply existed before flats... round slides are easier/cheaper to manufacture.

Flats have another advantage of rollers in the slide so the slides dont stick under high engine vacuum and need less spring force to close, easier on the wrist.

TG