Well today I loaded my ATV(yes an ATV, not a dirtbike, but this particlar models engine and carb was the same as several of the dirt bikes that year) into my truck and took it to a worksite. After unloading it from the truck it sat for about 5 hours in the sun with the fuel valve off...

The ATV is a 1984 TRX 200cc Honda, it has electric and pull start....

When I finally needed it I set the fuel valve to on, and I clicked the electric start but no matter what I would do it would not start...

I was getting frustrated because this morning it ran fine. I needed the thing badly to move a trailer full of Mesqiute so after an hour of trying to get the thing start I decided to spray some WD40 into the carb(didnt have any carb cleaner on me and was desprate)...

Sure enough within seconds it cranked over...except the the engine would run almost full throttle with out even touching the throttle...I had to engage the choke to get the engine down to a safe RPM...

If I press the throttle forward the engine revs even higher....I even tried adjusting the idel screw but it didnt do any thing...

What I need to know is whats wrong...I cant seem to find the answer in any of the shop manuals...

 

Look for a reason why the slide is being held open.....rusty cable, dirty cable, spring missing, cap on top undone, and so on. To hit those revs, it needs lots of air, and that means something is holding the slide open.

 

Do you know of a place that sales new throttle cables if I have to end up buying a new one...

 

A honda dealer should be able to track one down, or try denniskirk.com, or rockymountainatv.com.

 

Update: I replaced the throttle cable, sparkplug, and airfilter...and rebuilt the carb

First I rebuilt the carb...looked good inside, all jets where clean:
Started it up again it ran at full throttle...

Second I replaced the throttle cable, again I started it up it ran full throttle...

Third I messed around with the gap size on the sparkplug, I got diffrent running results each time, either high throttle or no run at all.

Fourth I replaced the spark plug with a new one and set it to correct gap size, after starting i have to floor the throttle to keep the it running, and at max throttle it runs at a very low rpm...


Any idea on what could be wrong?

 

The slide is being held open. Is it put back together correctly? is the spring missing? Does the slide move up and down in the bore easily? Theres a slot in the side if the slide...does it line up with the "key" in the bore? Is the gasket missing from the top of the slide, where the top screws on?Is the idle adjust all the way out?
For it to run at wide open, there has to be alot of air flowing thru the carb, which means the slide has to be open.

 

doesent have really old gas in it does it ? mine had a simmalar problem.. and my problems where that the carb was really dirty, Gas was old, and the timming chain had skipped a tooth .. im not really sure which was the root of the problem since i fixed them all at the same time.

 

The slide has a groove. The carb has a pin that fits into the groove. If the slide is not positioned right when assembled it will hold the throttle open.