800 EFI low end hesitation

[redwolf_92]

I have an 02 MCat 800 efi (in my sig). Last year it started having a low end misfire. It is especially bad when the engine is cold, but it can be recreated to a lesser extent when it is warmed up. It is also pretty noticeable if the engine has been shut off for 20 min or more.

The symptom I am experiencing causes the motor to stall out if I punch the throttle from a crawl. If I feather the throttle up then it will grab and go. Like I said the problem is nearly unnoticeable when the engine is warm, but it never did this before. I have had it into the dealer twice and he has been unsucessful in finding the problem. He checked all the sensors and calibrated the exhaust valves. I cleaned the exhaust valves, removed the tank and dumped the old gas, checked compression (150 psi in both), and have playing with clutching (just for kix).

Read something about unplugging the throttle sensor. What is the procedure and what will it tell me? What else should I be looking at?

 

[fishtank]

Do you mean Throttle Safety Switch?

The throttle safety switch is part of the kill switch. Find that cable and unplug it and run it without a kill switch and see if that fixes it. Mine ran with a strange mid range bog for a bit and it was the throttle safety switch playing up.

Your symptoms dont sound quite the same as mine but its worth a shot. Takes 5 mins to check.

 

[redwolf_92]

Oh yeah, forgot to mention I already did that. Thanks for giving it a try though.

Should also mention that I pulled the fuel pump out of the tank and cleaned the screens.

Gonna be gone for the rest of the week. Heading out to the snowies!

 

[miko]

I had the exact same sled for about 5 years and ran into this myself. I replaced the kill switch, and took care of it. Later it happened again and found the compression was low so I refreshened the top end. THEN it happened again and had to replace the coil. I guess half the coil started going bad.

I loved that sled even though I had the same problem with different repairs every time!

 

[Rixster]

Check your reeds. They will affect the bottom end if they are getting chipped.

 

[redwolf_92]

Thanks for the responses guys. It could be a coil problem, I will look into that idea. Doubt its a reed problem because it is not running consistenly bad throughout the low range, just once in a while it will stall out and try to throw me over the handlebars. What would be the result of a bad servo motor on the exhaust valves? I noticed that when I hold the throttle wide open that it will level out at top rpm for a second or two then it will be like it just got an extra shot of juice and rise another 3-400 rpm.

I did get into a tree when we were out at the snowies last week so I half expect that insurance will total it out. It didn't have very much mechanical damage just tweaked the left a-arm, and the left side of the bulkhead where the plastics attach to (should be able to straighten it out easily), and creased the pipe pretty good. It does have quite a bit of cosmetic damage though (hood, hinge, bumper (and brace), left plastic, belly pan, plastic around steering post)

Totally worth all the trouble though! The snow was nuts. Had 3-4 feet of fresh on thursday night and into the day on friday. (in some valleys that we got into it blew in 5-6 feet deep! If you werent cruising you were stuck