Surging & Bogging with more than 1/2 Tank

[Tvivelo]

Hi Everyone,
I have a 99 GTX Limited that I just bought. It has 108 hrs & has great compression (125 on both), the fuel lines have been replaced (at least the feed lines, the pressure & vent lines are still gray). When I took it for a test ride it ran great. When I got it home I filled the tank, put in some oil and took off, but it would surge & bogg down & could not get past 5500 RPM when you called for full throttle. Part throttle OK, idle OK.

As I kept riding the condition lessened, & when I got down to about 1/2 tank it was running great all the way to 6800 RPM. I thought it just needed to be run, but when I filled it up again the same thing happened, & just as before when it gets down to about 1/2 tank it runs great. I have cleaned the filter but it was not clogged.

I asked the previouse owner but he just said he never like to carry around more gas then he needed for a day/ (No help there)

Anybody have any ideas on this please let me know. Thanks in advance for the help.

 

[rotaxrule1]

Almost sounds like a vent line from your gas tank might be plugged or something. I would check all those just for fun to make sure. 125 on each cylinder? From what I remember that might be a little low, but at least they are close. Does it have the 787 or 951 engine? Hopefully one of the more experienced guys might chime in too and provide more info.

 

[Carguy89]

6800 rpm? Mine does 6650