2-Stroke Help............Pulse Line

[Fleabags]

I purchased an old Yamaha SnoScoot (80cc single cylinder 2-stroke – w/reed valve) that had been neglected for many years. I got it running (rough) a few weeks ago, however, now it won’t run. I am convinced it is fuel starvation. I have cleaned the carb so many times that I lost count. Originally, it was pretty gummed up, now it appears clean and all of the jets look clean. The bowl is always full when I pull the carb. The reeds have also been inspected and cleaned.

If I prime it, it will run and then eventually die. If I rev it up after priming it, it will stay running as if at higher RPM it creates more vacuum and finally draws gas in. The choke does not help get it started and seems to have no effect, although I have confirmed that it mechanically functions properly. The choke is not a butterfly style.

A few days ago I was able to prime it and get it running for ½ hour of riding around the yard. It ran surprisingly well at that time and even idled well. It eventually bogged then quit and wouldn’t restart without going through the whole priming thing again. So, I know that it is capable of running properly.

Today, I pulled the pulse line off of the fuel pump, in order to test it. I put my thumb over it and turned the key. I confirmed that the crank pressure is good. While testing it, the machine fired and started to rage (it has never fired so easy). I had to quickly shut it off so it wouldn’t take off and crash into the wall. With the pulse line open, it would start up instantly.

Do these symptoms point directly to a cause? Is it just the increase of air that causes it to run with the pulse line disconected from the fuel pump or does it have more to do with a change in the internal engine pressure/vacuum?
Any help would be appreciated.

[MX86]

i don't know much about the sled there, is their a fuel pump or is it an oil pump? i would check the hose comming from the tank is their a fuel filter on it?