CV secondery

1203 Views 5 Replies 5 Participants Last post by Allan, Mar 27, 2011

Jason S

Discussion Starter · Mar 26, 2011

I was thinking about this for the last couple of days and thought I might pass the idea along you fine folks to give some input and insight.

The idea is too put two carbs on each cylinder side-by-side. A thottle cable pull round/flat slide that is sized to a 125cc cylinder and set up like normal with all normal adjustment provisions on one side. On the other side/half would be a CV carb that only has the bowl, floot, needle + seat, main jet, thottle needle, slide, and air diapham.

The round/flat slide would be for half thottle use and the CV would kick in only when the engine needs and calls for the extra air and fuel. I think I could drill and tap the CV carbs slide hole to install a jet to tune when the slide starts to rise open. I think the big IF is the correct tuning of the CV slide. (Almost forgot to mention, the CV carb would also be of a size for a 125cc cylinder.)

I know it adds to the list of parts that can get gummed up and slowly shake out of tune but most of the bikes I work on have four carbs so it really wouldn't be that much of a bother. (I wouldn't try this on a CBX... 12 carbs... shreeeeeeeeeeeak!)

Anywho... What do ya think? Thanks.

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NightBiker07

· #2 · Mar 26, 2011

sounds like a LOT of work for minimal gains. and you wouldnt even really see the added 2 carbs.

I also question if there is even room

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NateDawg

· #3 · Mar 26, 2011

Jason In PA said:
I was thinking about this for the last couple of days and thought I might pass the idea along you fine folks to give some input and insight.

The idea is too put two carbs on each cylinder side-by-side. A thottle cable pull round/flat slide that is sized to a 125cc cylinder and set up like normal with all normal adjustment provisions on one side. On the other side/half would be a CV carb that only has the bowl, floot, needle + seat, main jet, thottle needle, slide, and air diapham.

The round/flat slide would be for half thottle use and the CV would kick in only when the engine needs and calls for the extra air and fuel. I think I could drill and tap the CV carbs slide hole to install a jet to tune when the slide starts to rise open. I think the big IF is the correct tuning of the CV slide. (Almost forgot to mention, the CV carb would also be of a size for a 125cc cylinder.)

I know it adds to the list of parts that can get gummed up and slowly shake out of tune but most of the bikes I work on have four carbs so it really wouldn't be that much of a bother. (I wouldn't try this on a CBX... 12 carbs... shreeeeeeeeeeeak!)

Anywho... What do ya think? Thanks.

Uh, you are just asking for trouble there. You only have so much vacuum. You can only efficiently burn so much gas in der. Take the motor out and bore it over and rejet and you will have better results than pouring more gas in there and fouling sparkplugs. We would all love to see a supercharger bolted up to a twin

Just dont ask us how to do it lol!!!

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Randall-in-Mpls

· #4 · Mar 26, 2011

NateDawg said:
We would all love to see a supercharger bolted up to a twin

Just dont ask us how to do it lol!!!

Do the electric fan conversion, and run it off the forward end of the camshaft.

Maybe some day, when I have gobs of money for custom machining.

R

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Jason S

Discussion Starter · #5 · Mar 26, 2011

I am not looking for more power. What I am looking to provide is more thottle response at lower rpm's while still having good high rpm control. A typical carb on any motorcycle has only two jets to control fuel. This idea would give me three.(low, middle, and high)

I do realize and don't care if it's harder to set up. This concept is nothing new to the automotive world as a Holley with vacuum secondary is the same thing. Plus, most 3-dual set up's are exactly the same with the front and rear carbs only controlled by vacuum. Yes sthey are harder to set up but the great control is worth the time spent. This is why you will never see a CV carb on any race type motorcycle unless the rules state it has too.(Which I never seen such rule in any roadrace or drag rule book.)

The only thing stock on my bike is the engine and that will be breathed on in do time. There is plenty of room for me to do this mod. and stated in the first post was the switch to smaller carbs.(All four) I not planing on four 36mm carbs but more like 24mm or 26mm carbs. You could run ten carbs on one intake and the engine will only suck in what goes by the jets, so the person jetting the carb/carbs is responsible for getting the mix right not the carb itself.

It's proble safe to assume every person has the same size jets in both of their carbs on their cx/gl. But if anyone ever cleaned or rejetted carbs on older Honda v-fours they will proble attest to four different jet sizes on one engine.(had to do with back flow in the airbox across the rpm range) Most all that installed pod filters on those engines and unified the jet sizes would say it hurt the power big time on the low end. It also sheds some light on the trap doors in the Yamaha V-max airbox.

I guess I'm really asking if someone can give me a heads up on the CV carb tuning. Thanks again! Sorry for the brain spillage. My mental valves are adjusted alittle tight?

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