bike stalls when ON but not PRI

[subvcd]

The bike sat for about 10 days of no use. When I first started the bike from rest and set to PRI it was all fine. Now, when I set it to ON, it stalls. When set to ON, the bike will get going for a few minutes but slowly fall down in RPMs. When I let the bike just idle after about two minutes, if set to ON and the choke is on all the way, the bike will slowly decline from 4000RPMs to a dead stall. But when it is set to PRI before riding and kept there for the duration everything works just fine. Please help and thanks for your time.

[EvilScooby]

Sounds like your vacum hose is not connect correctly, or it could be bent.
Also make sure your air filter is not blocked

[GRU]

fill up the gastank

[Kerry]

Given that fuel is supplied from the RES hose when the petcock is on the PRI setting, I can think of 5 possible explanations for your symptoms:

1) Like

EvilScooby said, the vacuum line between the ON/RES/PRI petcock and one of the carbs could be loose or cracked.  This would prevent the proper operation of the diaphragm inside the petcock, which would keep enough fuel from getting to the carbs.

2) The diaphragm itself could be "blocked" or defective.

3) The fuel in the tank could be down to the REServe level.

4 & 5) The ON hose or ON outlet from the fuel tank petcock could have some sort of blockage.[/list:u]To test the 1st and 2nd possibilities, try to run the bike on the RES setting.  If it runs well, then there is no problem with the diaphragm or the vacuum hose or its connections, since all are used in both the ON and the RES positions.  The PRI setting uses neither the diaphragm nor the vacuum hose, so it makes sense that it could still work.

If it DOESN'T run well, test the 3rd possibility by filling the fuel tank and trying the ON setting again.  Several of us have found, by sad experience, that the apparent fuel level in the tank can be deceiving.

If it STILL doesn't run well, test the 4th and 5th possibilities by switching the ON and RES hoses at the fuel tank.  (Leave the petcock in the ON position.)  If the bike runs well, then the ON hose is OK and the tank-mounted petcock should be inspected.  (We already know the RES hose is OK.)

EDIT: Fixed mis-matched "possibility" numbers.

[EvilScooby]

I'm getting good at this stuff

[KeLL]

This happened to me recently and I found my vaccuum hose disconnected from the petcock.


Kellie