Hello all, I tried looking around online to find an answer to my problem, and I found some pretty good info on this site, but still couldnt find anything close to my problem.

So I got this 1996 scrambler 400 4x4 in 2 buckets full of parts, I rebuilt the transmission and got everything back together but it still wont run right. At first I couldnt find out why it wouldnt rev up in idle, then found out the darn thing wont rev in anything other than forward, it wont even rev in reverse, is this true?

Second big thing is the quad just doesnt have any power. Taking off from the line it will pull the tires high into the air, but it just wont go faster than 1/2 throttle no matter how much throttle I give it. I had a similar problem with a snowmobile and it ended up needing a top end rebuild. Is it possible Im looking at a similar problem with this quad?

Any info would be greatly appreciated, I have so much money and time already invested in this thing that Id hate to lose it.


Thanks

 

i dont know why you would cut the wires to the etc as its a just like a snowsled as it prevents the throttle from sticking wide open. if its that, that is casuing the problems it would be skipping or cutting out as it mskes it run like the reverse override isnt being pushed in reverse and you hit the limiter. now you said you can pull the wheels so it sounds like its running fine off the line and its not shifting out correctly. did you change or alter the driven (secondary) clucth? that would be a good place to start.

 

My polaris snowmobile doesnt have this throttle safety and this is the first time I ever seen anything like it so I ended up clipping the wire as part of my troubleshooting routine.

As far as I know the quad is bone stock, like I said I bought it and brought it home in 2 buckets.

I didnt think about looking at the clutch, it seemed to be functioning correctly Ive worked with this setup on many of my sleds so I kinda seen problems with them. The engine is acting to me like its starving for fuel under load, but I dont see why it would the carb is squeaky clean, runs up to full throttle with the rear wheels in the air and starts and idles perfectly unless its got something to do with ring wear and low compression, unfortunately I dont have my compression tester around to check it.

How many safeties are there on this thing? so it wont rev in neutral or reverse? I cant even get up the driveway in reverse, are these things confined to reverse in idle only?

Thanks for the response. If I dont figure this out its off to ebay with this darn thing as a handyman special.

 

Ok so I kinda had a feeling that there is something wrong with the engine. I did a compression check today and after pulling the starter about 8 times the best I could get was about 110lbs of cylinder pressure.

Now usually my 2 cycles have between 120 and 150 after about 3 pulls. Is 110 on the edge of running? could this be the cause of my lack of full throttle power? I dont feel like putting much more money into this thing and I was told if its one thing that will last on a polaris quad is the engine.

Thanks

 

110 is ok. Its a little low but it will run. Try removing the black wire on the reverse limiter. It's behind the oil tank. It should have a green, white, yellow and black wire(if memory serves) There is also a regualtor close to it so just pull the black wire. See if it raps up now.

Is the carb clean? Maybe the main jet is pugged?

 

Ok I found the black wire you're talking about. I pulled it and was able to rev the engine but it was just very slow to rev and it took a while to really get some r's out of it, but once there it would really spin hard if I kept on the throttle.

I went through this carb with a microscope, I had it apart atleast 4 times, most of it was to fix a leaking needle and seat. This thing starts awesome and idles great, but in gear under a load its just a dog. Ive been told this model quad should be fast, this thing is shameless.


So 110lbs of pressure is adequate for this engine to still run pretty quick?

As far as I could tell the clutches were working, is it possible something in either the primary or secondary is sticking?


Thanks for the ideas I really do appreciate em.

 

Pull the silencer off and see if it's better, they can plug up with carbon build up, what's the plug color?

 

Good idea on pulling the silencer it helped a ton, now it actually has power on the high end, however I think the needle is stuck because I cant run it at full throttle for long before it bogs. Once the float bowl fills back it it takes off again. I dont know how the silencer is designed but I tried blowing into it by wrapping my hand around the inlet and I had a hard time moving any air through there so unless if thats what theyre suppose to do it seems to me like its pretty well clogged up.

Thanks for the advice, I have one less thing to worry about with this quad.

 

Get a nice hot fire cooking with a thick layer of coals, chuck the silencer in there until its almost glowing.... pick it out with a shovel and bang it around it will loosen up the carbon, take a strong compresser and blow the remaining out.

 

I was just thinking, how are your reed valves acting? What about the Stuffer with your reed valve assembly?