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Help with Chappy LB50 at wide open throttle


wild03
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Hi all,

I have a 1980 Chappy LB50 with 3500 miles on it.

The bike runs good and idles fine. MY issue is that when I run it at open throttle it will run fine for 200 yards or so, reaching 25-27mph then the engine looses power, speed drops to 22mph or so. the engine feels like it has no fuel, it will drop RPM then PICK up again, DRoP and pickup. If I slow down and let the engine idle then go open throttle, it will again GO strong for 200 yards then do the same thing.

A little background. This bike was running fine a few weeks ago but it had a problem were it would dump all the fuel out the air filter when left parked in the garage. I go the idea that maybe the float was not set correctly, I took the carb completely apart, clean it and assembled it using the same gaskets and a little silicone around these 30 year old gaskets for a better seal. I can't seem to find a carb kit for these bike anywhere. anyways I moved the float a little so it would close earlier. Do you think I went too far and now the bike is starving of gas? Seems logical.

Can anyone help with the correct carb settings? as far as float adjusting?

Thanks in advance.

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By altering the float so it shuts earlier you will actually lower the fuel level in the float chamber causing it to be starved of fuel at full throttle. What you need to do is take the carb off and reset the float height. Unfortunately am not sure what the factory setting is .Perhaps one of the helpful chaps here could tell you if they have a manual. Tony.

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  • 2 weeks later...

By altering the float so it shuts earlier you will actually lower the fuel level in the float chamber causing it to be starved of fuel at full throttle. What you need to do is take the carb off and reset the float height. Unfortunately am not sure what the factory setting is .Perhaps one of the helpful chaps here could tell you if they have a manual. Tony.

Well looks like less and less people have these old bikes, I was hoping for some help finding the carb rebuild kit and for carb settings.

Well I decided to give it another go today, I noticed that the gas was affecting the thin coat of silicone gasket I coated the old gaskets with, had to remove it and installed gaskets without it. Moved float 0.5mm and this seem to fix the problem.

rode for twice the distance as before and no issues. before it would stave at the same spot on the road. like clockwork. very happy with the results and now I hope gas stays in the tank as well.

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