94 Yamaha 115 V4 rough low rpms and dies on take off

[Bricew]

I've researched for a while now and really thought I solved my problem.....but I was wrong.

My symptoms are these. And they appeared over night with no warning.

-Motor starts and idles fine. It requires fast idle and a little choke. But it's been this way for the 12 years or so that I've owned it.

-When in gear, it runs rough but consistent. Like it's missing one cylinder. Sort of sounding like its purring.

-When throttling to take off on plane, it boggs down and dies.

-HOWEVER....If I time it right, I can click the manual choke for just the blink of an eye and it will get past the rough patch and jump on plane.

-It runs normally on plane.

So, after some searching, I checked my fuel pump. Thinking it may be leaking and flooding one cylinder. And when I pulled the pump off and squeezed the primer bulb, I did in fact get some fuel leaking out the back of the pump. Leading me to think I had a bad diaphragm.

I replaced the fuel pump. But the symptoms haven't changed.

Now I'm not sure what direction to head next.

 

[99yam40]

carbs needs cleaning.
off idle ports are not allowing the extra fuel during the transition from idle to higher RPM would be my guess

do not forget to follow service manual procedures for link and sync after cleaning and putting carbs back on

 

[Bricew]

If that is indeed the issue, I should be glad, because it could definitely be worse things. But it still stinks, because I just had them professionally cleaned last year.

Is anyone here a fan of Seafoam treatments for cleaning without disassembly?

 

[Bricew]

I should also mention that this only happens when it is under load. I can put it in fast idle and get all the RPMs I want. Just can't get past that small window of RPMs when it is in gear.

Don't know if that changes your opinion or not.

 

[99yam40]

loaded requires more fuel

 

[Bricew]

Thank you for the input. I do appreciate it.