I am new to this forum and hoping for some help.
I had bought a used 1987 LT80 for my daughter for Xmas. The quad has a severe problem with fouling the plug. It will start and run with a new (clean) plug, but it loads up and never reaches full RPM. After about 6 laps around the yard it dies and back to plug cleaning. Then we repeat the process all day. I noticed that about half throttle it seems to be where it starts anything past half throttle it starts to load up fast. The quad is all stock. I have rebuilt the clutch and regular maintaining. It idles fine til it loads up and dies. It starts very easy when the plug is clean and engine sounds nice and tight. When I pull the plug it is a dry black carbon not wet carbon. I thank you in advance for any and all help. Also on the carb (the side without the choke) there are 2 spouts on top. I know one is vacuum the other one closest to the front tires, what is it for and what should be connected there if anything ? I noticed once in a while a little gas will come out of it. And lastly, what is the float hieght supposed to be ?

 

Go down on the main jet size. Take the float down just a bit also.

 

Going down a main jet size is ok.
The float is not adjustable.
I think you have a plugged up pipe. If so, build a fire or use charcoal and get it red hot. Then blow compressed air thru it. This should make a world of difference.

 

Thanks for the suggestions I will try them tomorrow. Just curious would the injection pump cause this ? And any help on the carb spout question would be great.

 

the injector could be the cause like you said, it could be allowing too much oil into the fuel mixture..hmm, you could get a block off kit and just run pre-mix if it isnt an issue. good luck, hope you get that lil 80 rippin soon

 

try LT80's cure first. I rebuilt my engine, cleaned carb, new rollers... and had a similar problem to yours. after heating the pipe and blowing it out, that seemed to make the difference, and i finally got my top speed and RPM back.