5 replies to this topic

[tristan800mxzx]

I need help figuring this out I have a 2005 mxzx 800 HO rev. It runs good, when i slow down and come to a stop the idle hangs at 3000-4000. If i flip the choke on it will drop down to 1500 and stay there it will not climb back up. i have checked the reed boots and they are good. My fuel screws are set to 1.5 turns. What should i do.

[ThumperG]

One of the more common problems for a hanging idle is probably the pilots in the carbs, take them out and thoroghly clean them. If you have a dealer close its probably easier to just buy new ones. The little suckers are sometimes almost imposible to get clean even if they look good. Having said that there are all kind of things to check on this form in the FAQ section on hanging idle. Good luck.

[tristan800mxzx]

Does this sound like worn carb slides?

[tristan800mxzx]

I also had trouble with the idle screw not adjusting the idle. the sled has 7000 miles on it

[thumbdoctor]

Does this sound like worn carb slides?

First, check all your throttle cable routing, then check you oil pump cable for kinks. Make sure you have some free play at the throttle flipper and at the carburetor. If all that is OK, take off the carb rack and inspect the engine side of the throttle pistons. If the coating is worn right off to bare aluminum then you have 2 problems.
1) Throttle pistons are worn out.
2) Throttle bore & slide surface are worn out.

You can try new slides and cleaning up the throttle bore while checking with a straight edge on the engine side. You can install #20 pilots and suffer a hit on fuel economy. The biggest problem with TM40s and 800HO engines is the idle vibration literally shakes the hell out of the carburetor hence prematurely wearing out the throttle parts. Most fixes are temporary on these engines and require some time & money. Try the cheap route first and see what happens. Failing that, new carbs are in order.

[the meat]

Check for air leaks at pto seal, y-pipe, and reed boots.
Take out fuel screw and clean the hole it came out of as well as the jets real good. Set idle position and sync with .062 drill bit.
The fuel screw can be turned out to 2 turns to lower idle. Any more does nothing so a bigger pilot will be needed if you want to lower it that way. Fuel screw 1 1/2 - 2 turns, 1 1/2 = higher, 2 = lower.
Adjust the idle screw when engine's warm.
Going up to #20 pilots will help if the carb slides are worn a little, if they're worn alot a bigger pilot would be needed but IMO you'd be better off fixing the carbs at that point.