Intermittent Power Loss

[JohnRennie]

I have a 2003 115 TXRB 2 stroke. I’m experiencing intermittent power loss, it’s almost as if my revs are being restricted. The problem comes and goes… no consistency or pattern.

I only experience the problem as I’m coming to a plane. If I get to a plane without an RPM drop she runs fine for as long as I’m on a plane. I can run for hours with no power loss. She’ll get to 5500 WOT but I typically run her at about 4200-4400.

If I lose power while climbing to a plane, the revs fluctuate between 2800-3700 and makes no difference if I throttle up. The only thing that will fix the issue is if I have someone constantly pump the primer bulb while I’m running. I thought it was an issue with the fuel pump. I replaced it, re-built the carbs and replaced the primer bulb but it made no difference.

Any suggestions?

[99yam40]

monitor the fuel pressure/vacuum while problem is happening to see if that is varying.
Monitor timing to see if that is moving around while problem is happening.

monitor spark while problem is happening to see if you are dropping spark to a cylinder or two. Meter or induction timing light may get that done.

If good compression,spark and timing then you are looking for a fuel problem