Jetting 101

JuliusPleaser · Apr 26, 2003

I have an 03 XR50 with a Takegawa 82cc big bore & mild cam. I replaced the stock carb with a Keihin from an XR70, but it's still running a bit lean.

What's the best way to fatten it up? I have removed the jets, but I don't know what to do next. Should i drill the stockers, or try to round up some replacements? If i drill the stockers, how big should I go and which holes should i drill?

BTW, when I bolted the carb up, the bike ran like a mofo, but it poured gas out of the bowl overflow. Turned out that the float pin was missing, but when I replaced the pin, the performance really suffered.

I want the fiddy to run like it did before I replaced the float pin, but I really don't want to ride around on a Molotov cocktail.

Hep me - somebody HEP me!

Rich Rohrich · Apr 26, 2003

Based on what you've said it's worth trying to determine if the needle jet will pass enough fuel to feed the engine. You can get a pretty god idea of this by pulling the main completely out and seeing if it will run at WOT throttle. Generally when the needle jet is adequately sized it will pass too much fuel to run on the top end without a main, and gurgle till it dies.

Once you are sure the needle jet can pass enough fuel make it idle and transition to part throttle with the pilot and needle.

You might want to check with Powroll and see what kind of jetting they recommend for their big bore XR70s

JuliusPleaser · Apr 26, 2003

Are different needles and needle jets available for the Keihin? I have only a rudimentary understanding of how carbs work, so keep in mind that you're responding to a complete ignoramus.

I'll try the needle jet trick tomorrow. Should I try to ride it WOT or run it WOT unloaded?

Rich Rohrich · Apr 26, 2003

Needle jets should be available. Best bet would be to check with Sudco.

After you pull the main ride it and roll the throttle on as you accelerate till you are WOT. If it doesn't fall off hard from gurgling at the 3/4 to WOT point you'll probably have to go to a larger needle jet.

It's worth marking the throttle housing at the 1/4, 1/2 & 3/4 throttle points so you'll have some reference to the carb circuit you are using.

Jetting 101

JuliusPleaser

Too much of a good thing.

Rich Rohrich

Moderator / BioHazard

JuliusPleaser

Too much of a good thing.

Rich Rohrich

Moderator / BioHazard

Similar Topics

Jetting 101

JuliusPleaser

Too much of a good thing.

Rich Rohrich

Moderator / BioHazard

JuliusPleaser

Too much of a good thing.

Rich Rohrich

Moderator / BioHazard

Similar Topics

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