Another couple of "if" "what if" and why not" carb questions.

Brad William /

Thought experiment.

For small cc engines I've read that a certain degree of tradeoff can be had between low rpm torque and better breathing at high rpm by ovalizing the carb throat. This seems perfectly reasonable actually. Why is this not better utilized? Why not a taller thinner oval section yet so that your're effectively starting out with a 16mm carb up to 1/3 throttle and end up with an area equal to a 22mm carb at full throttle?

I just took apart an electric choke carb for the first time. Interesting in that the circuit is separate little "carburetor" in itself. Needle valve, throttle slide, air in, mix out, sips out of the bowl. Why couldn't this, with a bit of modification, be used for a throttle/torque boost at mid rpms?

Re: Another couple of "if" "what if" and why not" carb questions.

Many stock carbs already have an oval shape internally.

But if you're looking for midrange power, nothing will beat reeds and massive 360 deg intake porting.

Don't fuck with jetting while riding.

If you need extra mix in your midrange, jet for it. Powerjets already exist and sometimes can be beneficial, but they can also fuck up your mix if you're not careful

Re: Another couple of "if" "what if" and why not" carb questions.

I have seen carbs with the bores more like egg shape - smaller radius towards the floor - perhaps for the effect you mentioned, it was on a rotary intake ported bike so could have been to just get some sort of low enough idle without the engine just spooling down from loss of vacuum signal over the jets.

Re: Another couple of "if" "what if" and why not" carb questions.

Brad William /

....and.....

...why are custom mounted carbs on Puchs (almost) always mounted on the left? There's actually more room to tuck it in out of the way on the right. The cylinder is offset to the left, and the e50 has more room on the transmission side than the magneto side. You'd have to do a little rerouting of cables and wires, as well as the coil on most models. No big deal.

Re: Another couple of "if" "what if" and why not" carb questions.

Dirty30 Dillon /

Yeah, many OEM carbs have ellipsoidal venturi for that exact reason.

Why aren't more carbs like that? Probably a combination of cost and footprint.

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