Bigger carb dosent help

im always hearing about how putting a larger carb on a ped will make it faster. My motobecane used to be able to do a constant 25+ on flat ground, which was fine, but now only cruises at 20.i heard that the biggest difference in the faster and slower model motobecanes was just the size of the carb and manifold. Well, i got the bigger manifold, i have enlarged the carb opening and jet, and i even tried my racing carb on it, which has a air/gas mix adjust on it. It seems no matter how much i play with the carb, its just not making it go any faster. So whats the deal? did i miss something? what else could i do?

Re: Bigger carb dosent help

Chris Robertson /

Hi Tim:

You are describing <i>lost</i> performance (instead of speed above and beyond stock). Assuming your carb is spic and span (and you haven't done something drastic like drilled out your jet), you should look at your exhaust (it might need to be decarbonized); your exhaust port (it may be clogged); and your engine compression (worn out rings or cylinder).

Not all problems have to do with the carburetor!

Keep trying.

Chris.

Re: Bigger carb dosent help

I think with the motobecane muffler there is no way to take it apart and clean the inside. I was told that they use a system of larger and smaller chambers to create the Venturi effect like a performance muffler. So if one or more of your chambers have carbon build up you have to buy a new muffler.

Maybe there

Re: Bigger carb dosent help

maybe i should have said this in my first post. Just cleaned the carb, muffler, ports, and the bike only has 2500 miles on it. engine is clean as can be. anyone have anymore ideas?

Re: Bigger carb dosent help

Chris Robertson /

It might be something outside of the engine:

Dragging brakes?

Bearings in the wheels need oiling?

Chain needs lubrication?

Gearbox have too much/too little oil in it?

Chris.

Re: Bigger carb dosent help

Hi! Remove your muffler and put it back on the engine either with a spacer washer or leave it loose enough so exhaust can escape without being forced thru the muffler.But don't put the gasket in until you're done test-running it,unless you've got a new one for later.If you see a noticeable increase in performance you've definitely got a partially clogged muffler.This is assuming you haven't gotten your bike out of whack by the carburetion changes.I hope you fix it.By the way,I'd say Chris is probably `dead on' with his diagnosis.BYE!

Re: Bigger carb dosent help

another thing to consider might be the jet size in your bigger carburetor. that might make a difference. another thing might be your manifold size. unfortunatley, it seems that often when you change one part for better performance, you might lose performance if you don't have the other changes that are also needed.

also i remember that two-strokes require a good clean muffler to help the engine run better. perhaps if you stepped up to a bigger carburetor, you might even have to step up the muffler? someone else can tell you more than i can about this.

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