'03 Yamaha 225 VMax

[RB33]

2003 Yamaha VX225TLRB. Motor seems like it runs out of gas above 4000-4500 rpm, every time. Motor runs all day long at about 4000 rpm or below. As soon as you push it above this, it dies out and cuts off in about 1/8-1/4 mile. If you take off hard, motor will rev up great, nose starts coming down, and as you are trimming up motor will die. Wait a couple of minutes, crank it up, will do the same thing. If you plane off and stay below 4000 rpm, it runs all day. But will not run WOT.
1. Changed fuel line bulb with new. Bulb was not collapsing, but changed anyway.
2. Replaced all 3 LV fuel pumps with new Yamaha pumps.
3. Replaced high pressure fuel pump.
4. Ran motor on pony tank, with separate fuel line to separator on motor, to determine if there was a fuel supply issue to motor. Same issue with pony tank or built in tank. Both with plenty of gas.
5. Cleaned water separator under cowling.
6. Removed/cleaned O2 sensor.

Anyone experienced anything similar? Any ideas what I can check next?

[jdwo2212]

Check your plugs? Id replace those as well. Also could be the anti siphon valve not holding fuel pressure. Im no mechanic, but those seem to be some common problems.

[RB33]

OK. Good ideas. Thanks.

[bpicinc]

I'm having the same problem now, but at 3,000 RPMs. Have changed spark plugs and fuel filter with no change.

Where is the anti-siphon valve?

[RB33]

I believe it is just downstream of the filter assembly under the cowling. Yamaha calls it the fuel feed assembly. I could be wrong though.