I picked up an 82' 125 in pretty good shape for a Xmas present for the kids. I bought it in late Oct and I replaced the leaking fuel primer and it sat waiting for Xmas. Xmas day I fired it up and it idled for 30min no issues until I was ready to bring it out to the kids. When it was time for the big revel the bike wouldn't move 5' without dying,.as soon as I hit the throttle it would die. So the weather is warming up and I decided to look at the bike. I put fresh gas in it and if fired right up, I let it run for 30 seconds jumped on a flew around the yard. 2 min later once it got warm same thing happened it would die once I hit the throttle.

Any thoughts. The carb should be good a clean since I just had it out. it has fresh gas. Feels like a carb issues but I thought I'd ask incase someone else has come across this before.

Thanks

 

Most likely is not enough fuel getting to carb. The tank vent may be blocked causing a vacuum, check by running with cap loose. Or tap not letting enough through, or float needle not letting enough through. Other possibilities are the coil breaking down when hot, or one of the other ignition components. I always go for plug first, as it is easy and cheap to replace, check if it is sparking when the fault is on.

 

Took a look yesterday, I found that the vent from the tank was up over the frame rail instead of underneath, so when you put the seat on it was pinching the tube. Took awhile to start the bike (maybe 20 pulls) once it was running we ran around the yard for abit but it lost power again and stalled 4-5 times, by the end I could barley make it back to the shed.

I checked the valves an they seem fine spec is .08-.12mm mine were at .1. I guess I'll take the carb out and make sure it's clean but I just had it out and cleaned it when I replaced the primer.