I am about at my wit's end with this bike...I took it out to LS OK and for the 2nd time in a row..It was supposed to be a 4 day trip, but I was loading
up and heading home after just a few hours....The problem occured after 5 hours or so of no problem riding...
Then all of a sudden the engine starts to sputter and back fire in every gear.....I got it started again
and the same thing happened within 5 minutes...Then the engine would only start with the choke
set to full and then promptly die when you gave it any gas...Now it won't start at all...
It turns over and cranks just fine it will just not fire...The spark plug is getting fire, but it is "dry"(no gas residue) even if you
take it out immediately after trying to start(I have already tried a new plug)....I have taken the carb completely out of the bike and cleaned
every component as stated in the manual.....The fuel is getting to the carb(flows readily when you open the overflow), I just don't
think it is getting to the plug at all....I have a K&N air filter, that is clean and run an outerwears cover on it which is also clean...I am not a mechanic by any stretch of the imagination, but if anybody has any ideas I would greatly appreciate it...Thanks

 

Try turning the fuel petcock to the "PRI" position. This will allow the fuel to just flow to the carb, rather than having to be sucked from the tank by vaccum like in the "ON" & "RES" positions.

How full is the gas tank?? After 5 hrs. of riding, in may just be way low, have you tried the "RES" position??

If these don't work, when you had the carb apart did you take the top cap off?? This is where the vaccum diaphram & needle are located. It also sounds like the diaphram may be tore/ripped, not allowing the carb to function properly.

 

I'm going to assume you have a pipe as well , are you using a spark arrester?
yeah its a funny question .i have seen the fine screen get plugged up, when that happens strange things happen.

 

Try twisting the little black **** on the carb a few turns .......

 

I have tried the petcock in every position...No change....The gas tank is over 1/2 full(and has been drained and cleaned)...
The diaphragm and needle look and appear to be fine....I have tried adjusting the idle(little black ****) up and down w/ no change...
I have tried the exhaust w/o the spark arrestor in place(HMF Ballance Series)..No change...It's beyond me at this point and I finally
broke down and took it to the stealership..I hate to think how much this is gonna cost me...As I said in my original post, I am just getting
sick and tired of working on this thing every other time I ride it...I would understand if I didn't do proper maintenance and just basically
tore the hell out of it, but I don't...I change the oil and coolant on a regular basis, lube all the fittings, clean/adjust the chain and air filter and it still let's me down....It's getting to the point to where riding just isn't much fun anymore...If I had to work on my car's and trucks
this much, I think I would just walk everywhere...I have never bought a brand new 4 wheeler..Maybe once I get slammed for this problem
it might be time to try that...If I still have the constant maintenance issues it might be time to find another hobby......I don't mean to sound like a whiney-***, but this is supposed to be for fun not add more stress to my life...Just my .02....I will post how it all turns out...Thanks for your replies and keep them coming if you have any other ideas....

 

thats why i would never buy a used sport quad. You don't know how they rode them, what maintance they do, most ppl buy these bikes, drive the living sht outta them for a year or so then sell em before it needs a major rebuild or tune-up. Seen it too often. A guy will buy a bike off ebay, take it on a trip, the bike runs good for the first hour, then it starts to show its problems. Good luck though, hopefully it isnt something TOO costly

 

how about ur parking break rev limiter? mine had a mishap a while back and i overrode it and it works fine. i barely got the bike home cuz it was sputtering and shutting off when i gave it gas. i have a friend who had same problem on a raptor thats how i found out mine was shot. u need to by pass it. u probably dont use the park brake anyway.

 

Timing posibly jumped. The stock timing chains seem to stretch pretty easily.

 

check your valves and valve timing, and you could have a bad cdi box

 

dont think 400 will run right with open air box try putting the lid back on