if i could get some help, it'd be greatly appreciated. ive got an 87 lt 80. with a brand new bored out cyl and piston. new reeds, new carb kit. i have cleaned the carb, let it sit in carb dip and even tried another and i can not get it to stay running. it will start and run fine with choke on but when you take it off, it slowly idles down and dies. like its starving for fuel. any suggestions

 

Sounds like it might be an air to fuel mixture issue. Did you change your main jet when you did the mods?

 

no, the main jet that came with the carb kit, should have been stock

 

I think you are running out of fuel, is the vacuum line hooked up on the petcock. Also try running the bike on prime, this eliminates the vacuum line.

 

ive got the vaccum line blocked off on the carb, i do not have anything on the fuel petcock, i've been trying it with it turned to prime

 

Could be many things, but the first I would go after is venting. Is the tank vented properly? Take the cap off and give it a try. What about the carb?
My next thought is you have an air leak somewhere. Carb boot, gasket....................????
I would also do a compression and see what you get.

 

i have tried it without the gas cap on. no luck. the flange between the carb and reed cage has been replaced. and they bolt directly to the intake so i dont see a problem there

 

But is the o-ring inbetween the carb and insulator (black thing)?
It's sucking air somewhere.

 

had same issue with my sons 87 lt80 it was the petcock something with the prime. after i replaced it it was great goodluck.