[chadman1997]

I recently bought a 97 300ex and have had it out a few times and it runs really good after warming up for about 10 min. My question is when first started it seems to run pretty rough and even some slight backfire/misfire for a few minutes regardless of where I have the choke set. The manual says to set full choke on a cold engine if below 90F. No smoky exhaust and the plug looks great. The engine is completely stock. Is this just the norm for warmup period or does it sound like something needs attention? Thanks! P.S.-This is my first atv so I'm still learning alot as I go.(I've had a few dirtbikes)

 

[Billy250X]

Hows the condition of your air cleaner?And have you ever cleaned the carb out?

 

[chadman1997]

Air cleaner is brand new and oiled properly. Haven't removed the carb yet, didn't know if I needed to go that far yet. I suppose it probably should have a full cleaning since it may have never had any service to it. I think the previous owner didn't maintain to well, had to replace alot of little things.

 

[Helmut]

I've owned a few 300EX and all of them had to warm up a long time or they would sputter. At least 5 minutes, maybe more. After they warmed up, they ran great. I don't know if they're all like that, though.

 

[TRX2fiveO]

Bump up the slow jet to a 40 that should cure the cold start issue

 

[Redracer]

Those machines are notorious for taking a long time time to warm up. Don't try to fix what is not broke. Put the choke on and start the machine, you want to turn the choke off ASAP. Just let the machine warm up properly and have fun.