I have a 99 Arctic Cat 400 4x4 atv. It is near impossible to start when cold. When warmed up it idles good but bogs out and misses at high speeds. Cleaned carb, new plug, cleaned air filter, drained gas, new gas, new inline fuel filter, fuel runs good out of tank. Anyone have any more suggestions or things I could check out? I just don't want to take it to the shop and let them start bolting on new stuff........Thanks.

 

valve adjustment or check for a tear or hole in intake boot

 

What should the valves be set at?

 

Valve lash - Not sure on a 99 but my 03 400 the intake is 0.002 to 0.004 and exhaust is 0.009 to 0.010, better call a dealer or get a shop manual.

Won't start when cold - most likely the choke is not set right.

Bogs out an dmisses at high speeds - points to a weak spark or the timing is off. Could be your battery, magneto, coils, voltage regulator etc., or it could be something simple like a bad or loose ground.

Well start with checking your ground wire and battery terminal connections. Make sure your gap on your sparkplug is correct, incorrect gap can change the timing. If you have access to a timing light then check the timing. The timing is NOT adjustable so if it is off, then the chain is stretched and would need to be replaced. Check the valve lash.

I would suspect that the problem is electrical so keep that in mind.

The CDI (electronic ignition control module) is equipped with an RPM limiter. When approaching maximum RPM the timing is retarded, it could be misinterpreted as a high-speed misfire.

 

what does the spark plug look like after it been running for a while?
does it blow smoke? what color? might be hard to notice. revit up almost to the rev limiter and let off, see if you see any smoke. and note the color.
let us know.

HR.

 

The old plug was pretty black. It does puff a little black smoke.......

 

Black is good, well better than blue.
with that being said i would bet my money it's jetting. your main and or idle jets are either shot warn out or just the wrong size. with the wrong size being what i would guess.
you shouldnt have to worry about the valves if you don't want to. maybe do a compression check to see what that are doing but not a must do.
take your carb off, or remove the old jets, tame them to a dealer and ask for 2 sizes smaller. and either clean the plug real good or get a new one. it's runnign RICH. to much fuel, and it's bogging out. and stalling.
i thinkg i remember a problem wioth those older cats with teh main needle jet going bad.

good luck.

HR

 

valves