99 Yamaha 250 SW SII

[patmead]

I have been having problems with a motor I bought two summers ago. It has been to three different dealers and not one of them has been able to make it work. When I bought the motor it had been in storage for 4ish years and I figured it would have a few little things to address. Here is what it does. It starts fine and idles fine but when you give it the throtle to get out of the hole it gets to about 3200 rpms and then stalls out back to about 800 rpms. they have tried a separate fuel tank, checked the stators, pressure tested it, tested the O2 sensor, and multiple other tests to no avail. Can anyone help me?

 

[birdbrain]

Re: 99 Yamaha 250 SW SII

I'm not the expert on this forum, let the others confirm. I'd check the filter on the high pressure fuel pump within the VST. Because the filter is clogged, the high pressure pump cant maintain pressure in the fuel rail as you accelerate, but can at idol. If this is the case, It means your engine has not been maintained and you should probably perform a major pm on all systems as well.