Cateye hitting speed limit

Flyboy7 · Feb 23, 2010

I have searched everywhere on google but I can't seem to find an answer. I have an older Cateye FS509 pocket bike. The acceleration is fine, but when it gets to 30 mph (I have installed a digital speedometer), the engine makes a weird noise and it will maintain 30 mph but never try to accel. It almost sounds as if the engine ignition is cutting off somehow, and this sound is only made when going top speed. I've already taken the bike apart looking for a governor but have yet to see one. I've replaced the carb with a walboro carb, put new ported piston, new ported head, new bearings, new rings, ported exhaust, bigger exhaust, hp clutch, air filter etc but I always get limited at 30 mph. The more mods I do, the faster the acceleration but I'm at a loss. I don't think it's a gearing issue because the engine makes a specific sound, but I am running stock gearing. I'm thinking it's an ignition cutoff somewhere, but I can't find any mention of it anywhere.

Any ideas?

StrayDawg63 · Feb 23, 2010

Welcome to the site Flyboy!!!
Sounds like it's sputtering at the top end. Which means it's to rich. Adjust the mixture screw (or the H screw if your carb has 2) a 1/8th turn in and ride it to top speed again. You may need to do this a few times but you should hit the sweet spot by doing it this way.

Than if that doesn't take care of it than I would try a new coil.

Flyboy7 · Feb 23, 2010

I have tried adjusting the mixture thinking it was too rich myself with the same end result. I will purchase a new coil.

Thanks for your prompt reply!

StrayDawg63 · Feb 23, 2010

Something else you might try is to take your gas cap apart and make sure the little vent hole is clear and not half plugged up. The way it looks like they put that vent hole into the cap is with a little hot poker that sometimes leaves it kinda plugged up. Gas can only get to the carb as fast as the air can get into the tank from the vent. So if it is slow you may not notice it until you hit top speed. Anyways it worth a look. I would also make sure there isn't a bunch of crap in the tank too.

Cateye hitting speed limit

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