2003 yamaha 250 ox66

[PAULDIDIT]

I having trouble with the engine running rich . I've changed the o2 sensor with a new yamaha because the old one was flacking out and intermitten , also I claened the o2 sensor chamber and tube . the injectors have been claened and tested, replaced the TPS sensor because it had and open in it , fuel pressure has been checked and dead on at idle as well as 4000 RPM's the one thing I have noticed is the the starbored head runs concideribly cooler than the port side head even after repalacing the thermostats . I'm wondering if the temp. sendor in the starbored head is sender a signal the the ECM that the engine is still cold. when the engine is still pretty cool after it warms up and before we leave the dock its sneezing , but if you run it for about 5 miles at 4000 RPM's and bring it back to a idle and in neutral it runs great until you let it cools all the way down again and then the it starts all over again.

Any in put with this concern would be greatly appricated

Thanks paul

[walleye1]

Loosen the bolts on your fuel pumps, pump the primer bulb and see if one of the is leaking fuel
in the block.

[PAULDIDIT]

the low pressure pumps where new of last year , yeah I'm aware of them leaking and going bad . I had one bad last year and changed all of them out .

[99yam40]

If you have a lean sneeze happen it can damage pumps