Walbro WYA question

[KE4AVB]

I have Kawasaki KTFR21-A2 with WYA that giving a problem that I haven't worked on before.

Starts and idles fine and accels to about 3/4 throttle then it dies as I open the scavenger port. Carburetor has been cleaned and rebuilt. It did have bad diaphragms.

My question does this sounds like I have air leakage somewhere in the intake path?

I do know that carburetor adapter is warped in the middle but spraying fuel mix around it but doesn't change anything. I have ordered a replacement adapter and gasket anyway. I did enriched the idle mixture quiet a bit so that may be throwing off my tests too. I did a compression and things are fine. I even pulled the muffler in case it was partially plugged.

I got to get pressure/vacuum tool but that is scheduled for next month's tool purchases as I had to get a new drill with new bits,a tire changer this month and a couple pairs of new eyeglasses. I got rid of those lousy Lowes drill bits that couldn't even cut one hole.

[bgsengine]

Sounds a lot like the Echo PB-500 stratified 2-stroke - does it have reed valves? Those reeds can cause a bunch of problems. (I also have a post a while back referring to how the system works - perhaps understanding what it is doing will help diagnosis?)

Also sounds similar to a CS-500 I used to see often with a similar issue (but only one owner had that issue - others never had it happen) - I suspect a fuel quality issue for that one - frequently fuel filter changes would often fix the problem for a few weeks, and then it would do it again.

I cant speak specifically to the kawasaki engines you are seeing though - they are actually pretty rare in this area.

[KE4AVB]

It is the first one I have seen in the 6 years of working on 2C.

There is only one reed valve and it is on the carburetor adapter. I have checked it and is sealing when no vacuum and is opening on vacuum. Two port covers but no reed valves there. Fuel, fuel filter, and the supply line is new. I even pulled the cylinder in case the cylinder gasket was blown of which I have had three of on Stihl trimmers this year.

I did read the Walbro service manual on the WYs. That's what is leading me to an air leak theory. These scavenger setups is fairly new to me; only seen a handful here and they were Echos but I know there will more of them.

This one will be one those to remember problems. I'm too stubborn to let this to get the best of me.

[Mek-a-nik]

Here's the post Brian mentions: viewtopic.php?f=3&t=1345&hilit=echo
That one was over my head.

[KE4AVB]

Problem resolved...

It turned out to be a warped carburetor adapter and bad gasket. The adapter had warped just enough to cause the graphite gasket to loose seal. Replaced both and re-tuned idle mixture. Now runs at full throttle position.