Yam 150 slow climb; unresponsive throttle

[Home Cookin']

2003 Yam 150TXRB 2 stroke carb.
Yesterday ran for first time in 10 days. A little funky on starting as usual. ran great at its sweet spot at 4000 rpm/28 mph. Decided to open up for a burn off. First time, no response, as if the throttle were disconnected. backed down, went back up to 4000, then to full: this time the engine made a slow climb to about 4900 and speed up to around 35 (have achieved top of 48 mph @ c. 5400, same load). Adjusted trim tabs and motor trim to find top end, no real help. If I hadn't seen better #s before I'd say it was underpropped.
Also got some rattling from the engine but it didn't feel like it was missing.
new fuel, stabilized, ring free and with a new seperator. New plugs <30 hrs ago by dealer service.
To distill: initial unresponsive to throttle above 4000, slow climb, not achieving top end. Rattling. New problem.
thanks!

 

[Home Cookin']

Re: Yam 150 slow climb; unresponsive throttle

bump

 

[cousinabe]

Re: Yam 150 slow climb; unresponsive throttle

check your fuel pumps.
Does pumping the primer ball help?

 

[Home Cookin']

Re: Yam 150 slow climb; unresponsive throttle

I'll try the ball next run; I was by myself. But I ran it again yesterday and it did better, but still not top. Had more wind and people, though, so not a good test. I also had sneeze/cut off, and cut -off at idle and difficult restart, difficult to hold an idle. possibly too lean? This motor is new to me in March so I don't know the whole maintenance record.
Sounds like everyone else here. Damn ethanol. Ran into a boat mechanic friend, who spends his days rebuilding or cleaning carbs, and HIS boat was suffering from it too!