What is the easiest way to tell if you have a worn cam on 2002 Sportsman 700? It runs fine up to mid rpm range then bogs and if I hold my hand in front of carb without air cleaner I get some gas blowing out of the carb when it bogs. Running it with the air filter housing on makes no difference. Inspected the carb diaphragm and look fine. Slide in carb lifts up as you accelerate so I assume the diaphragm is good. Been thru carb, new fuel pump, new plugs, new fuel filter, new intake manifold and compression is 150 psi on each cylinder. Would a weak valve spring cause this?

 

Cam issues are pretty rare in my experience on 6 and 700's. Lean out your main jet and I bet it will run just fine. What number main does it have in it now? Can look tomorrow and see about where it needs to be and let you know.

 

All stock carb. Never messed with the jets and it has always run perfect

 

I have seen a couple of units that did that. Rejetting took care of it. Its worth a try, not saying its the 100% fix. Plus its a lot easier than removeing the valve cover and trying to measure the cam lift and compare to specs, or remove the head, cylinder, and lifters and visibly look at the cam lobes. A lot of the info on these forums come from peoples experiences. We dont have the machine to diagnose ourselves, so sometimes we have to go with problems/cures we experienced.

A weak valve spring would cause valve float and more than likely make contact with the piston.

 

Do you think the cdi module could cause this? I connected a timing light and ran the atv with it connected and the light never quit flashing or interrupted when the atv bogged. The spring on top of the carb diaphragm did for some reason come dislodged and was sitting sideways under the cover. I took the carb off and dissasembled it to clean it and found that problem. I reinstalled it correctly and it has been find since then.

 

Cool. Glad to hear it. Also glad to see you reply your fix in case someone down the road sees it!!

 

The problem with the spring being unseated occurred BEFORE all of my problems started with it bogging down. It still has the problem. The carb was just the first thing I checked, that is when I discovered the spring being unseated. I cleaned the carb and reassembled it but still have the problem

 

I guess I read the other post wrong. sorry. I personally dont think the cdi will cause it. I realize it ran good before, but I still think lean it out with the main jet, Do you still have the original plugs you removed? Are they black? Running with the air box lid off will also make it run bad. Im guessing you tried it with the lid on too. Try taking just the snorkel off the air box lid and see if it clears up any. We have had some machines in the mountains before that were a little rich, remove the air box lid and they ran terrible, reinstalled the lid and removed the snorkel and it let a little more air in and allowed the machine to run way better. Still needed jetted but it was very usable.

According to the parts diagram your machine should have a 155 from the factory. According to the technical manual it came with a 162.5. If it were me(and what is going on that I think may be going on) Id stick a 150 in it and see how it runs after that(with air box and snorkel) One other thing we saw at our elevation(4200) the jetting charts were a bit on the rich side. If the book showed to use a 150 or so, we actually stuck 147.5 in a they ran great.

 

Yes I did run it with the air box on it and not much difference. The original plugs looked fine, maybe a tad lean if anything. We are at 742 ft elevation here. What do you think could have caused the spring above the diaphragm to get lodged sideways? There is a nipple on the cover that the spring goes over to keep it centered. I am going to pull carb off and go through it again. Anything special I should look for or pay attention to. Thanks the jet has never been changes so it has original in it now

 

No idea how that spring could have come off the nipple and got in there sideways. Thats a mystery. I would have thought it was a reassembly issue but yours did it some other way. Doing carbs - just make sure all the jets are clear. Don't use drill bits either. Make sure the passages the jets feed are clear to. Also there are some holes in the back of the carb that allow air through. Make sure they are all clear to. I have seen them get plugged and cause some issues. Test the needle valve if you can(mity vac with pressure adapter, should hold 5 psi for 5 minutes)

Did this start all of a sudden, or did it slowly get worse and worse?