97 GSX 787, lack of throttle response, needs choke

[acarter]

Hello,

I picked up a 97 GSX (787) a few weeks ago. I got it cheap in "not running well" condition. It wouldn't get high RPM's without adding some choke while on the throttle. I checked the compression (140&141) and decided since it ran great if you get the choke just right I would rebuild the carbs.

I followed the "carb rebuild thread" and have rebuild carbs before so I'm pretty confident I did a good job. Everything inside looked pretty good, I used a genuine Mikuni kit. Also went ahead and replaced all the Tempo fuel lines while I was in there.

Today I had some time to get it all put back together and it's pretty much doing the same thing, though it is idling better now.

To go into a little more detail of the problem: while running in the water (river) it idles perfect at 1,500 RPM, but as soon as you give it some throttle it only increases RPM to about 3,000 and just maintains that RPM until choke is applied. If the choke is just right it will get to full RPM's and runs great (while holding choke).

After running in on the water I pulled the plugs (new after carb rebuild) and they are both showing very rich condition, which doesn't' make sense to me because needing choke should be lack of fuel. I also verified that the oil injection pump is adjusted properly, if anything it's leaning a little to the lean side but it's pretty darn close to dead center on the alignment marks.

I'm leaning towards it being an issue with the fuel pump, though the thing is so darn simple I can't see how i would have messed up the rebuild.

Any input is greatly appreciated.

Thanks!

 

[acarter]

Didn't get any bites so I thought I would give an update. Checked for leaks in the fuel system and it looks like I have a leaky selector switch or fuel filter housing. I bypassed them both and am no longer getting air bubbles. Unfortunately that did not solve the poor running issue though. It may have improved slightly, but still not great. Thinking about ordering a new set of carbs as I can't see what else it could be.

 

[WhiskeyD]

If fuel system was rebuilt properly and you're still having issues then you might have an air leak in the engine

 

[POPPS]

sounds like lean mixture,,sounds like leanness at the transition circuit from pilot to high speed,,,,and maybe even poor spark for the dark plugs,,,compression seems low,,,could explain dark plugs,,go through the carbs again with a fine toothed comb,

 

[Poormanracing]

How do the rave valves look?are they a little oily and moving or Carboned up closed or open.if the stuck open on a tired ski won't let it pull rpms.pull races off and look at Pistons to see if the burnt half way down or look scuffed up.

 

[mike1117]

Didn't get any bites so I thought I would give an update. Checked for leaks in the fuel system and it looks like I have a leaky selector switch or fuel filter housing. I bypassed them both and am no longer getting air bubbles. Unfortunately that did not solve the poor running issue though. It may have improved slightly, but still not great. Thinking about ordering a new set of carbs as I can't see what else it could b

Didn't get any bites so I thought I would give an update. Checked for leaks in the fuel system and it looks like I have a leaky selector switch or fuel filter housing. I bypassed them both and am no longer getting air bubbles. Unfortunately that did not solve the poor running issue though. It may have improved slightly, but still not great. Thinking about ordering a new set of carbs as I can't see what else it could be.

When you rebuilt carbs did you pull the tank as well to clean it. Any crud left will be reintroduced into fuel system if you didn't. Looks like a good winter project checking over the engine. Free pdf shop manual downloads are available online with factory troubleshooting specs. Two strokes like leak free top and bottom ends, to run correctly.