3/4 throttle great, WOT not so great

[physicistkev]

Started with not being able to get the boat on plane and lack of power. So I removed and cleaned the carbs several times. Ordered rebuild kit and fully rebuilt both carbs. Found my original issue was a clogged, forward carb filter, the one in the carb itself. This made the boat workable but far form great. I have emptied the fuel tank and cleaned it. Replaced all hoses with fuel injector 1/4 inch line. Which they were before, but I figured, what the heck. Disassembled and cleaned the fuel selector switch. Forward piston has 150psi and the aft has 148psi. Replaced both sparkplugs.

What I get is at WOT the engine is definitely misfiring. I find that about 3/5 or 3/4 throttle is about as high as I can go before it starts to misfire. There is also a delay with the throttle response, sometimes. Also, I have noticed that when executing hard left turns the engine RPM's drop a decent amount. Any ideas where to go from here?

Thanks,

Kevin

 

[timmyboy76]

yup....but first, needto know the boat ur talk'n about.

 

[physicistkev]

DOH!!!

In the middle of working on it so I completely forgot a few details.

It's a 1996 Sportster. 717cc motor. I seem to have found my issue. Or at least part of it. It feels like a fuel delivery issue. Like, once it's wound up, there isn't enough fuel getting to the carbs to maintain full throttle. I pulled the plugs and saw that the front plug looked fine and the aft plug was fouled? That didn't make sense to me. Then, I noticed, while staring down the carb intake, that when the throttle was closed that the front carb was slightly open, from the idle adjuster screw, and the aft carb was still shut.

Once I adjusted the carb linkage, the boat will now hold full throttle just fine. There is a bit of a lag still when opening the throttle, but I really didn't get too long to test after my last adjustment. It's not a hesitation, you move the throttle forward and the boat just keeps going for a few seconds and then it assumes the new throttle position RPM. It's like fly by wire with a 2 second delay, except this boat is not fly by wire :rofl:

Any ideas on the throttle delay or anything else I need to look at on the carbs for the delay?

Thanks,

Kevin