I have a 1997 Polaris sport 400cc. This will be kind of long so please bare with me. I just had the engine totally rebuilt, I have a new carb, new ignition coil, primary coil, all my vent hoses are clean and work fine, I have a new CDI Box, new spark plug, new spark plug cap, checked all my wiring and my fourn wheeler is still messing up. Here is what it is doing. It will run all day long in Neutral, it will ride around fine low to mid throttle, and when I go wide open it sputters, back fires, and then will die, a couple mins later it will start and will drive slow and idle fine but as soon as i hit wide open it does it again. I know it is not the carb because a buddy of mine has the exact same four wheeler and his works great and has no problems running. I put it on my four wheeler and the minute I hit wide open it sputters and boggs down and backfires and then goes and then sputters and dies. I have checked all my hoses on the entire four wheeler and all are clean, I even drove with the gas cap off to see if this would effect it and it did the same thing. I am totally out of options. I checked with ritter about the stater and he said that this would not cause that, so if ANYONE has ideas PLEASE PLEASE PLEASE let me know I am totally clueless. Thank you so much

 

Im no expert here.But if it happens at wide open throttle,it could be something inside the throttle housing.You might check inside the cover to see if anything is obvious.Sorry I cant really help and this problem has got my attention also.

 

It might be in the throttle, with Polaris's Anti stick throttle system, mine was bad too, but I was planed to put on a twisty any way. Also, check to see that the fuel filter is clean, you might not be getting enough fuel to the carb. It really sounds like a fuel problem to me. Also check to make sure the float in the carb is working properly. If it's not opening up all the way, again, it won't get enought fuel. I'm also no expert, but from what I read, I do beleive it's a fuel problem.

 

I seen where you checked all your wiring, but are you sure every wire is where its supposed to be and making good contact. I had some loose wires one time and it did the same thing. It is easy for wires to come loose in the rat nest. Double check the rev limiter wire.

Jay

 

I have double and triple checked every wire, I even compared to my buddies which has the same exact four wheeler, the carb issue is totally ruled out simply because I took my original carb off, and swapped it out with my buddies all vent hoses included and his ran fine, and his working four wheeler carb was placed in mine and died as soon as hit wide open. I forgot to add I have a brand new fuel filter as well, I have taken the rev limiter totally apart and everything is good, and the throttle housing was in full working order. I have talked this over with several mechanics including ritter and he has given me several good ideas but even doing all of those it still does the same thing.
Thanks

 

It sounds like it is running out of fuel. This could be in the carb. Or in the fuel lines. I have seen more than once where the fuel line would get an air pocket in it and not allow the fuel to flow through as fast. Thus causing it to run out of fuel at WOT. Also, check the main jet carefully. I've seen a little varnish get built up around the small hole and actually restict it.

Put it this way, you are riding around at 1/4 throttle and everything is fine. Then you punch it. The machine revs up and goes like hell. How far does it go before it starts cutting out?
If it only goes about 25 feet than I would say its in your carb. Most likely in the main jet system(jet, jet needle, needle jet) somewhere. What ever it is, it is slowing the fuel down at WOT.
If it goes 100 feet or more than I would say look more at your fuel lines for a restriction or even an air pocket.

 

Did you check your reeds.Just a thought.?

 

I would check to see if the ETC (electronic throttle control) is working properly.

 

It is your jetting. NO QUESTION!!! You need more fuel!!!

 

If you can't get this figured out , maybe you can bring it over and I can at least ride and listen to it . An ignition miss and a fuel miss sound similar , but different .

I get awefully busy in the shop but I can spare a few momets for a quick check of your quad . Irratic problems can be very difficult to catch sometimes .