I'm at a loss here. I picked up a 87' 650sx and rebuilt the motor, adding new pistons, rings, gaskets and replaced crank with newish one and new seals and rebuilt the carb. Added new primer, but after priming, it runs, then engine will die after a 10-15 seconds.
It's got an OEM Keihin carb on there, so here’s what I did to troubleshoot
Checked all the lines from the tank to the carb for any breaks or holes and for the heck of it replaced main and reserve lines.
Took the T fitting out and checked for clogs (blowing in each end, no prob).
Took off the pulse line from fuel pump to low speed fitting on carb and saw it pumping fuel when I turn engine over.
Checked fuel relief valve and it works
Blew back all lines going into tank to make sure no clogs….all good.
Checked fuel selector switch by moving to main and reserve by blowing lines and they worked.
New primer is pushing fuel to engine.
What should I do? Can’t get it to stay running.
Thanks for any help or ideas you guys can give me
Added new primer, but after priming, it runs, then engine will die after a 10-15 seconds.
This is a vacuum leak, most likely at the carb base gasket.
The primer is successfully starting the engine and opening the needle
and seat, but because of the vacuum leak, the needle and seat closes
and remains closed. Then the engine can only run as long as there is
fuel inside the float chamber. When the fuel inside the float chamber
runs out, the engine dies.
Find a new carb base gasket, and make yourself a flat sanding plate with
a 3/16" thick piece of glass, 220 to 320 sheet of emery cloth, and some
3M-spray 77.
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Originally Posted by LBI_Guy
