The other day I was servicing my 400 and I shot some 2+2 gum cutter thru the carb. Now it will not idle to save its azz. If I rev it 2 or 3 times it wants to take rite off to at least 4grand. The slide is clearly closed, but its still runing away. I turn the key off, the thing keeps rite on running. I took the bowl off and blew thru all the ports. But it didnt help. Has anyone else had this problem? Whats going on here? I swapped my reed cage out & put the stock one back, but no difference. ? ? ? Please help.

 

My buddys tb 250 did something like what your saying, The engine would not idle and it would rev really high and you could trun the key off but the engine would still run...

-We checked the carb and found out that it looked like the slide was closed all the way but it was not, we adjusted the throttle cable and it would idle...
The only way it could rev if its getting more air/fuel, I would just remove the carb check to see if everything is working free adjust things as needed... Make sure the carb has not come lose from the boot...

Hope this helps....

 

I was having a similar problem on my scrambler400. found out it was the throttle cable sticking, lube it up but didnt last long. Ended up replacing it, I guess they had a problem with the older throttle cables.

 

Come to find out I just had my crank case drain plug finger tight and it vibrated loose, causing a lean mixture. MAN IM GLAD I DECIDED NOT TO JUST "GO AHEAD AND RIDE IT"! The thing would have completely ruined!