YS828 stops running when warm

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YS828 stops running when warm

John
Hello,

I am trying to help a friend get their YS828 running properly. The problem we are running in to is the machine starts and runs fine for about ten minutes then stops running.

The machine is in very good condition. They had already purchased a brand new carb so I double checked all jets and part numbers before I swapped it. There is a full tank of fuel, petcock and lines let the fuel through, spark plug is good.

After the ten minutes of running the machine slowly dies. With choke it will restart and can be kept running with choke. Let it cool for a few minures and it will start right up and run for afew minutes and die out again.

I can bypass the fuel pump with the motor hot and the machine runs fine. It appears obvious that the pump is bad even though it appears perfect inside.

If it runs without a pump, since the tank can gravity feed, why is there even a pump???? I'm tempted to bypass the pump and jyst gravity feed the engine. Can anyone see a reason why this should not be done?

However, my ocd says I need to figure out why the fuel fliw stops with a warm motor..... I theorized the intake valve clearances have worn enough where, when warm, it fails to shut enough to produce a proper pulse in the intake to run the pump pulse line enough to run the pump. With a cold motor I have .oo5" clearance between the tappet and valve stem, same on the exhaust valve as well.

Any ideas?

Thanks.

John.
Fairbanks Alaska

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Re: YS828 stops running when warm

John
Forgot to add it is not a tank vent problem. It all appears to be heat related. They think the problem is worse in warmer tepmeratures.