I have a 2001 sportsman 90 that I am trying to fix for my nephew. This quad runs fine in its initial 10 minutes. After that it begins to bog when you try to take off. It does not stall out it just bogs and has no power. Here is what I have currently done.

1.) temporarily bypassed: fuel filter, fuel shutoff
2.) removed and cleaned entire carburetor
3.) removed air box and air cleaner
4.) began tearing into the stator area to inspect

I am running the quad w/out an air filter, fuel filter and fuel shutoff temporarily to remove them from the picture to verify that it still behaves the same. It seems to be getting fuel fine, now I am headed down the electrical path. I was just wondering if the way it is acting could possibly be caused by a faulty stator? I have been reading posts about how bad the stator covers allow dirt, mud, and water into the stator area causing premature failure. I have not taken the flywheel off yet but there is definitely mud caked all around the outside of the plastic cover and there was a bunch of leaves trapped in the cover too. Does anyone else have any thoughts on how to go about diagnosing this problem? Also, does anyone know of a service manual(pdf format) for this that can be bought online? The only ones I can find are hard copy.

 

Being a 2001, my guess is you need to start with a compression check.

 

Sorry I meant to mention that as well. Compression is 95 psi which looks ok from what I have read on this forum.

 

Could be a choke problem.The engine will like more fuel when its cold but will run poorly once its warm if its getting too much gas.

 

oldyeller,

That sounds logical but isn't the choke automatic on these machines? There is no manual choke that I can see. How can I adjust it? I am assuming it is the piece that mounts to the carb with a wire coming out of it that they call a plunger starter on www.ronnies.com.

 

Might want to check the jetting. I had the same problem with my Pred 90. I changed the main
jet and now it is running fine.

 

I just dug into the stator area and it was a mess. Dirt build up everywhere. It has not been having any problems with the charging system so I did not bother running any tests on that. However, I did test the ignition coil per Spike's past threads and it checks out as being ok. I am beginning to think it is still fuel related. I tried disconnecting what I believe is the electric choke that is connected to the carb and I did not notice any difference in the way it ran.(still bogged when I hit the throttle) I did play with the air mixture screw a little bit and did notice quite a bit of difference when adjusting that. Even with that set where the machine runs at its best the thing still bogs. Any other thoughts? Could that plunger starter be bad or something?

 

I'm certainly no expert on automatic chokes since our Viper has a manual one(as do all of my quads)..I have heard that if you disconnect the wiring the choke stays on rather than shuts off but I'm not sure about that.Maybe if you disassemble the carb you can figure out for sure how it works.One other thing you might try is using your hand over the carb like a choke since you have the air cleaner off.Try putting your hand over the carb until the engine starts to die then remove your hand and then nail the throttle.If it responds then the engine is too lean and wants more fuel...

 

I just remembered these quads came with a little "cap" that went over the exhaust tip to really restrict the exhaust and kill the power for beginner riders...Make sure it is removed.If the engine has been run along time with this on the pipe or muffler may be clogged and will really kill the power.

 

I will check the cap on the muffler, and try your carb idea. Thanks for the help so far.