1994 sportsman 400 4x4. I cleaned out the carb, put in a new spark plug, new air filter, fuel filter, replaced the fuel lines.

I start the atv and let it idle for about 5 minutes. When it is in neutral, if i give it max throttle, the engine gets to about 5400 rpm and then seems to stay around that reading. If i keep the throttle pressed, it seems to climb above 5400 up to maybe 55-5600 or so. This might be normal but seems kind of strange.

Idle-max throttle- climbs to 5400 quickly-hangs at 5400 for a few seconds- climbs a few hundred more- wont go any higher.

Is this normal for this machine?

Also from idle rpm of 700, at what rpm should the clutch engage where the atv starts to move from a stop?

Thanks everyone

 

What are you using for a tach? A multimeter?

The clutch engagement/ATV moving point will vary depending upon the gear you're in (H, L or R), among other things. There have been cases where I can't get moving in reverse without pressing the override button, and usually when I'm in low it'll move at a fast idle. Lots of info on RPMs and clutches in the free manual that's floating around here. When I get to it, I might be able to help more.

OPT will probably chime in shortly and be able to tell you more.

 

Slightly leaking seals along with the reverse limiter module can cause slightly erratic action along with reed valves or the carb itself. Pull the black wire from the reverse limiter and check for any difference.If that's not it check the reed cage for any warped or split reed petals.As far as what rpm the clutches engage depends on the spring used along with the counter weights. Manual calls this out very well in the clutch section.https://www.tradebit.com/filedetail....repair-service

 

Check your muffler. I had a 96 Sportsman 400L with the 2 stroke, ran like crap, exhaust ran super hot. Took the muffler apart, the flame arrester was 90% blocked and a cup of soot/rust came out. After that, no more overheating and it ran pretty strong.

 

OPT, could this be similar to the carb issue I was just asking about? 5 minutes of idling? Perhaps while idling the engine is loading up with excess fuel, and when revved up initially it's being "enriched" for a short time until it can burn the excess fuel and return to it's correct mixture?

A quick way to test this would be to let the engine warm up, rev it up like this once until it reaches it's max RPM, then let it return to idle. Once back at idle, rev it up again and see if it still stalls before hitting max RPM or see if it just goes to the max.

 

Could possibly be the same thing,but you're making a mountain out of a mole hill. Any engine in neutral with no load can do this.It doesn't have any force to drag the rpms back down evenly as you would have driving one and 2 strokes are the worst on this because of their design. 4 strokes have the natural engine braking to drag them back down and take throttle more uniformly. If you sit and play with one at idle,a two stroke can run funky.Even worn clutch parts can cause one to hang up on idle a little,cause problems on acceleration if sticking slightly,ect.The main thing is how well do they run on take off and at speed.

 

thanks for the replies everyone. a little bit more information. I took my daughter for a ride on it yesterday. Went up the road, turned off and climbed a snowy / rocky hill. Testing out the forward, Low, and Neutral gears.

The ATV seems to run very well. If you were deaf, you would think the ATV was in top shape. By this I mean that there are no indicators others that the engine "bogging" sound. There is no loss in power, shaking, or vibration that you can feel when the engine sounds like it is bogging/hesitating.

After driving up the road about 400 yards, when I came to a stop, the idle seems to idle pretty good, sounded much smoother that in the garage, but the RPM was still going from 820 -910-870- and so forth.

Putting it in forward gear, slowly pressing the throttle to move from a stop, the engine makes a sound like it is bogging/hesitating. Once the throttle lever gets about 10% in or the atv is moving at about 3-5+ MPH, the engine smooths out and seems to run great and sound like it should. Any time we would slow down to navigate an obstacle, it would make that sound again until it was moving 3-5+MPH. Anytime I would let off the throttle it would come down smoothly to an idle RPM and idle great. Never acted like it wanted to die. Reverse, Forward, and Neutral all worked perfect.

However that "hesitation/bogging" sound when starting from a stop, it seemed more noticeable in Low gear and reverse, than high gear. We reached the top of the hill, and turned around and came down. I put it in low range, and let the engine do most of the braking. Come down the hill, the engine never backfired, stumbled, stuttered, or anything.

1-Currently I have the black wire disconnected from the circuit board. I did this because the engine would die anytime I gave it throttle, disconnecting that allowed it to run at anything above idle.

2- I took the carb out and cleaned it all out about 2 weeks ago. Every piece, corner, hole, and valve was sprayed and blown out. I have not checked the reed valves yet, I was not aware this would be a symptom of that. The manual says that hard starts are a good indicator that a reed valve is bad, and it seems to start pretty well. But I will give it a check for sure.

3- How do you open up the exhaust to clean/inspect it? The previous owner had it on a ranch, so there could be a nest or animal stuck in there.

4- I am not sure of the spring / weights on it. I assume that it is all stock.

5- For the RPM reading, I am using a universal 2-stroke RPM gauge I got on amazon. It wraps around the plug wire and gets it's digital reading from that.

 

Compressed air first then soak the exhaust with kerosene for a couple days. Not many around but radiator shops can vat an exhaust for little or nothing. Drive clutch uses a blue/green spring with s65 weights up to 3000'. Above 3000' springs,weights stay the same,but you can either leave the secondary spring at 2-2 or 2-1 position. Driven clutch spring position under normal conditions is 2-2. This would be a good time to check the belt and clutches,especially the 6 guide buttons in the drive clutch along with any clutch sticking and also the 3 ramp buttons in the driven clutch for wear. This can cause bogging/hesitation also that people tend to over look. Check the reeds for any splits or warped petals.Look inside the reed cage to make sure the reeds are laying flat.

 

Yeah I will check the reeds for sure and report back on those.

What are the clutch buttons? I see new ones I can order, but what do they do, and how much wear indicates that they need to be replaced?

When soaking the exhaust, do I just soak the muffler, or would I need to soak the muffler and pipe? I am trying to think what I could put something that large in, and how much fluid I would need to soak it? Does it need to be submerged

 

Just down load the cheap manual I linked to and it will answer most of your questions on clutches. Just soak the muffler only. Stop up the tail pipe and fill it with kerosene and lean it in a corner for a couple days.When you drain it a lot a black carbon will come out with the kerosene.