New to SBT and really need some help

[Ski Man]

Hey everybody I need a little help. I've got a 2000 Yamaha XL 1200. The ski is stock except for primer. It ran great last year, was winterized by someone else, and this year gave the following problem. The ski will run wide open just fine at around 54-56 mph. If the throttle is released the ski dies. If the throttle is released very slowly the ski will continue to run at lower RPM's with an occasional squirt from the accelerator pump or primer if things get rough, also it won't idle. I removed the carbs to find everything very clean including the filters. The check valves in the ctr and pto pumps were busted. I installed new check valves in all pumps and verified all carb passages with compressed air. I also checked the fuel return when the ski was running to verify fuel pumping back into the tank. I reinstalled the carbs and the ski still runs the same. Any suggestions?

[Technical Support]

Re: New to SBT and really need some help

The power valves may not be working, Disconnect the cables and by hand open them up, see if it revs up.

[Ski Man]

Re: New to SBT and really need some help

Hey Tech thanks for responding. I removed all the power valve caps just to make sure all was well and everything looked fine. I rotated the valves by hand and everything worked smooth. When I turn the ski off the servo rotates the valves back and forth. I also have compression of M-105 C-112 P-107. I put everything back together and took it out again. I rode it WOT for a while and then would drop my RPM down in steps to see how low it would go. Eventually it was ideling around. When I jabbed the throttle from idle to WOT the RPM's would shoot up to around 2800 and hang. I would feather the throttle and things would snap into action propelling me on up to 7k RPM and running strong. After doing this for about 45 minutes it stopped hanging and would jump to around 6k RPM right off the jab from idle. If I spend a prolonged time ideling and move to a slow cruise it will still bog sometimes which can be corrected with feathering the throttle. If I don't feather the throttle the ski will die.

[Technical Support]

Re: New to SBT and really need some help

It sounds like its still in the fuel system, like its loading up at low rpms.

[dtd6string]

Re: New to SBT and really need some help

Check your butterfly shaft ring on the carbs. Some of those older I series carbs had problems with the ring heating up and expanding, thus binding on the butterfly shaft.
With the carbs out, take a heat gun and heat up the carb and throttle arm. Work the arm slightly and see if it binds anywhere. I have had two of them do this with symptoms you are describing. One I just replaced the carb, the other I honed the ring very lightly and solved the problem. Don't want to hone it too much or you will get an air leak.

Just a suggestion