I have taken off carb and cleaned, it did not help. so I replaced it with a new one, and it still would not run right. Then replaced the electronic mod in the front, did not help. It has new spark plug, that did not help. Where do I go next to try to get it fixed? It run great before and just started to not run well after idle, missed and backfired. we thought it was fuel so cleaned out the tank and carb , but it did not work.

 

Have the valve adjustment checked (.006 intake and exhaust) Plus sounds like what happens when exhaust cam lobe is worn down. Will idle,but no power and pops back. Pull the cam cover and check that the center cam lobe (exhaust lobe) is elliptical like the outer intake lobes and not ground down. Could be the problem as soft cams were a common problem on the 425 and early 500 engines. OPT

 

I checked the cam and it was real good yet. I will have just a little adjustment on the valves to be made, very good shape,and the exhaust worked fine. What next? I am going to change all fuel lines and vac lines, to rule them out. Any ideas?

 

"IF" you're sure the cam isn't the problem then sounds like you still could have a fuel issue. Fuel pump,either weak or trash contaminated. Pull the fuel line from the carb and see if you have a pulsing flow as you crank the engine over. If fuel flow is good,then you could still have an internal carb problem,air leak from air box/intake manifold,etc. OPT

 

changed all the fuel lines. checked fuel pump. it put out fuel fine. it still idles great, and now goes a little more past idle before the missing starts. it has black smoke and backfires. so I dont think it is low on fuel in carb. as soon as you let off, it goes right back to a smooth idle. what else could cause this.

 

Cheapest thing to do if you just "cleaned" the carb and didn't rebuild is to use a kit like this or a Moose carb kit.Black smoke is usually because of too much fuel, still running too rich. http://www.ebay.com/itm/NEW-SHINDY-C...79cf75&vxp=mtr Only other thing is to pull the black wire from the reverse limiter module under the front panel(just up from the cdi module)and see if runs better.Limiter could be failing. OPT

 

Went over to the shop this morning, and fired it up. It run great until I got off idol a little. Traced down the black wire you said to unplug, did that and it is running great. So that is what the problem was. It runs now better than it ever has. Can I just leave that wire unpluged, or do I need to change that module also. ? Thanks for all the help. I never would have found that to be the problem.

 

you can leave it unhooked, tape the end up so it doesnt ground out on anything, you wont have any speed limiter in reverse any more, will still need to push yellow button for awd in reverse.

 

You can replace this module if you want to spend about $60 or more for a new one or about half that taking a chance on a used Ebay part. In almost 23 years that I gave the customers a choice on this,I think only a couple people wanted their machines back to "factory specs" Most people just said no and that they could live with out it! This was an unnecessary "safety" feature as far as I'm concerned that always went out and that no other manufacturer installed that I'm aware of. If you own an atv you have to have common sense in using forward or reverse gear! Good luck OPT