Ok, this is going to be hard to write. Here's the question, what could be causing periodic spuddering? example...RRRRRRR,GG,RRRRR,GGG,RRRRR...
I feel very little, its just the sound. So, what do you think I should try? thanks

Bruce L. Hall
99 Sport 400

 

Bruce,

It could be any one of a number of things, when does it happen? What throttle setting? I have a feeling I know what it could be, but I need to know when it's happening.

 

I hope, you can help. My dealer has ajusted the carb twice, I'm loosing faith in the and now I'm off the warrenty. It happens most at slower speeds when the throttle is held steady. Its seems less frequent when excelerating, but still it does on occasion. Does this help? Thanks

Bruce L. Hall
99 Sport 400

 

this sounds normal for a two stroke. you could try a smaller pilot jet.

 

My dog sounds just like that. Sorry couldn't help myself

 

Bruce,

That problem is caused by the normal operation of a two stroke engine that isn't "on the pipe". The pipe and porting controls when your engine makes most of it's power.

At lower throttle settings, the engine isn't making very much power and is relatively ineffiecient. The exhaust flow isn't enough to hold all of the fuel/air mixture in the cylinder. Some of the fuel/air mixture escapes and this is called scavenging (the thing that environmentalists hate most about two strokes, unburnt hydrocarbons).

At higher RPMs, a pressure wave builds up in the expansion chamber of the pipe. This pressure wave is caused by more exhaust coming out of the exhaust port than is flowing out the back of the pipe near what is called the stinger. When the pressure wave of the exhaust rebounds off the back of the pipe during higher RPMs it keeps the charge of fuel/air completely in the cylinder and the engine "comes on the pipe" or allows it to become much more efficient.

What is happening, is that at the speed you are running, the engine isn't completely burning all of the mixture and it is allowing some of the mixture to escape. I know the feeling. It seems like you need a tune up if it were a four stroke, right? Well this is normal and doesn't go away completely, Even if you were to get your motor ported for low end power and to use a low end pipe, it still would not vanish completely. I'd just live with it. You'd be surprised how much my Sport does this (mid-top porting job, mid range pipe). But when the motor comes on the pipe, watch out!

 

How long has your dog had gas?

 

Try super no-lead gas.

 

Mike,

Man. you took the words right out of my mouth. That is exactly what I was going to say. Except fo the "coming on the pipe" part. I try to keep it clean in a public forum LOL.

Seriously, excellent response!

Long riding weekend and lots 'o mud up here ... We have Monday off in lieu of July 1st. Most of you guys taking Monday and Tuesday?

DJ

 

Before I had bought the 6x6, I had a 1996 Sportsman 400L 4x4. I had a problem with it sputtering a lot and not giving full power. I was towing a cultivator one time and the thing just sat there boging and sputtering(I had the petal to the metal too)Comes to find out I bought a new Pre-Filter(the yellow one)and a new air-filter. When I put that on,OMG, the thing hauld major a$$. It pulled like it had never pulled before and out ran many ATV's out here!!!!!!See if that helps if you haven't tried it.