Can anyone help me with a diagnosis? My 2002 Scrambler 400 has started running awful lately. It has an irregular miss. It always starts. At its worst it runs like when it is in reverse without hitting the reverse override button. I notice this usually occurs at low RPM especially if it has idled for a minute. The top end has a noticable lack of power too though (my buddy passed me on his Kodiac on a staight away). I thought it was bad gas Because I fill up every time I take it out and this all started one day and not over time, but I drained the tank to empty and put in fresh gas (tank looked clear of sediment) and that didn't help. I put in a new spark plug and that didn't help either. How should 2- stroke plugs look? Mine was kinda black and wet.

Thanks for reading and any help you can give me.

 

Is your choke on? I know but I've seen it before. You shoud do a compression test, has the machine ever been rebuilt? Sounds like you quad is running really rich, is your machine blowing alot of smoke?

 

Have you changed your airfilter lately. You'd be amazed how much a dirty airfilter will kill performance. before I went to the k&n I was having the exact same problem and was getting ready to head out to ride. I stopped by the polaris dealer grabbed a new filter and it was like I was on a new bike.

 

I am going to get an air filter and try that. And the choke isn't on, but that's kinda like how it is running. I actually have done that one before in the snow. I would guess that I only have about 200 hours on it so I don't think that it is ready for a rebuild though. Besides basic lube and fluid changes, I haven't given it much of a tune up. I changed the plug and I blow the air filter out once in a while. Am I missing some important PM?

 

if its doing it only at idle, could be a clogged pilot jet. try pulling the choke out and see if it runs better. if so, then thats my bet.

if its overall running bad, might check the fuel filter? fuel pump?


just some ideas.....


X

 

Holy %$#@! I went to go get my mail and since my mailbox is about 1/4 mile away I took off my air filter and I'd have to say that is definately the problem. And it sounded kinda cool open like that. Thanks, ScramaDamaDingDong! What kind of K&N are you running and where did you get it? Round clamp on sounds like a universal type application with out the box.

ScramblerXrated, Where is the fuel filter located? I thought about that while I was poking around trying to drain the tank and I couldn't find one. I thought that it was odd that there wasn't one.

 

Follow the fuel line from the petcock(why they ever named it that). The filter is usually behind the plastic next to the cylinder head. If you take the line off the carb you can pull it down and the filter should appear. I don't think there is a fuel pump. Never under estimate the power of an air filter. Get rid of the stock paper, they plug up fast and don't come clean. K&N you can clean all day long and know it's good to go.

 

If you ride in any water then dont get the clamp on. Get the drop in. It will do almost as good and you wont have to rejet. If you get the clamp on you may have to go up a size on the main. The K&N is the way to go.

 

I use the K&N Ru-0820 that fit's the neck on my tmx 38. You can get the filter for 29.99 from 4filters.com. there are many different sizes and styles that will work. You can go to the k&n website and pull up the specs for all their universal clamp on's find something that will fit and you'll be good to go. PL-1002 is the stock drop in type K&N. www.kandn.com

 

If you want the best of both worlds then you can get a drop in filter and cut out the entire front section of the airbox and have an "almost like" clamp on. Then if you are gonna do water crossings then you can put the snorkle on and cover up the the big hole. Consider that you won't have the divider wall that directs the water around the filter if you do this. But it is still a good mod if you aren't gonna be just dunking your quad in the water. My .02.