Rotax Max Carb Issue

2 Stroke Kart Engine Forums
1

Hi all,

I’m new to Karting and have bought myself an old pre evo Rotax max on a tony kart chassis.
I cleaned the carb prior to start up and fitted a new needle valve and seal. On start up the kart revs like it’s getting near full throttle although when choke is used it seems ok. I pulled the airbox to check the slide is ok (it is) but there is fuel squirting out of the hole in the centre of the carb and sendinging it into the airbox. Pic attached of were the fuels squirting out.
Any help would be great as I’m so keen to get it out on track! Thanks

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2

Check the floats. Sounds like they might be caught on the needle arm letting in a bunch of fuel.

3

The floats seem to be free and in good condition, if the floats were at fault would that also cause the engine to Rev hard at idle?

4

The easiest way to troubleshoot this is to swap the carb out with a known good one. If that’s not an option, go through the carb again and double check the seating of the needle valve seat. Another item to check again are the floats. You may have gotten them in up-side-down.
Link to a carb rebuild video. (143) Power Republic - Dellorto Carburettor Service For Rotax Max 125 - YouTube

5

It’s possible. I accidentally got a float stuck under the needle arm and it flooded the bowl and caused full to spill out everywhere including that hole you mentioned. I would take a close look at everything and set it up at stock settings. Also I would also double check the slide is fully closing. Maybe it’s getting hung up and you are actually at part throttle.