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Remember the cv carb will not open properly for full throttle without the airbox and filter hooked up, as the vacuum signal changes. That is why spring changes are needed in some cases when using a cv carb.
 

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Remember the cv carb will not open properly for full throttle without the airbox and filter hooked up, as the vacuum signal changes. That is why spring changes are needed in some cases when using a cv carb.
This is not the case on my 500. I can run no box and no filter just fine. Also ran just a K&N air filter directly on the carb and it ran better. I was just trying things while diagnosing. I also did the CV modification. It definitely helps the slide cycle much faster. I didn't go all the way to .125", I did .104" on both vacuum relief transfers. Vacuum - pulse signal was one thing we checked, and you could watch the needle and slide whack or cycle very snappy. Since there are sooooooo many of these almost exact complaints here and only 2-3 of them actually fixed there problem, but neither was sure what fixed it exactly since they replaced so many things. 2 said cam and rockers, and the other said buying a whole new carb. No way I was shelling out all that money on a machine with 800 miles on it. Glad I carefully inspected , measured and tested each component using a manual. Just to find out a fuel pet cock would clog up. Then after 12 or more hours the red plastic shavings would slowly settle and dissolve some, allowing the machine to run fine for the first 1/4 mile. Good luck
 

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98 Explorer 400, bogging down

Reuilt carb. runs good but bogs at 1/3 throttle. Old plug had a lot of carbon on it.
If it is not electrical it must be the cam.
Can someone confirm that a new cam is the only fix? :cowboy:

Fuel pet cock ? Sure, the tank was full of varnish when I got this ol' bike.
I did clean the filter and lines, but not that ol' pet cock. I'll let ya know if this works.
Thanks for the tip.
 

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I was told by a dealer today that I need to pull recoil cover off, drain any water, put back together, and rtv the pull rope to the housing...Mine does it when going up hill, or out of a hole, hence the water is going to the back of the housing and killing the signal for ignition... Try it, I'm going to try mine tomorrow
 

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I've repaired around 20 ATV's since my last post. Boggin' down was a common problem on old, seldom used bikes. Fuel system was always the culprit. I suggest removing and cleaning the everything from the tank to the carb. Replace fuel lines and filter, they get old and fall apart inside, little rubber particles will stop up a carb. Cleaning the carb is a tedious and details project, use fresh carb soak cleaner and a clean work area, pay attention to the smallest details. One grain of dirt could spoil your project. Good luck and keep on riding.
 

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Well I couldn't find my problem by searching so here it goes.

A few days ago our 2000 Sportsman 500 started cutting out at about half throttle. Throughout the entire rpm range a hollow sound is made. It sounds like when I start my Honda without the air filter on. It has a near identical sound. It just feels like it doesn't have the power at the upper rpm levels.

I've replaced the spark plug, air filter, and dumped a pint of seafoam in a full tank. Ran it and it helped some but the problem is still there. Any ideas?
Hi I know this thread is very old but I am having same problem like a hollow stuttering and no power but after a min some times longer the power kicks in did you fix your problem and what was it if aI might ask thanks
 

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Hi I know this thread is very old but I am having same problem like a hollow stuttering and no power but after a min some times longer the power kicks in did you fix your problem and what was it if aI might ask thanks
So I too have been having a similar issue on an 02 500 HO. I'm actuually working on it right now and still have it apart.
Initially my problem started at the tail end of an atv trip. Ran no problem to our destination in the middle of town. Was off for about an hour or so. Started it up after walking around at a festival, ran fine, idled fine, then when heading back to the hotel with the group, I noticed at about half throttle I had no more power from there up to full throttle. It's almost like it was being governed and wouldn't go over 25 mph.
Once back at the hotel I let it sit and scratched my brain. Ended up loading it back on to the trailer and that's when I noticed a change in sound, almost like a hollowed out sound. If I remember right I thought I heard some popping out through the carb.
A quick Google search indicated alot of camshafts (exhaust lobe) for these motors would fail. To my dismay, this made sense based on the symptoms (loss of power, popping through carb because exhaust is not properly being vented from the combustion chamber/change in sound). But the one thing which did not make sense was the extremely sudden onset of the problem. A cam would wear down over time, not just instantly be a new problem once restarted. I convinced myself as wierd as that would be it still needed a cam based off the dozens of forums to which people confirmed this as thier issue.
This problem ended up turing into a whole top end rebuild (since I was already that far in there).
Anyway, as I disassembled, I finally made it down to and removed the camshaft expecting to see the root cause. To my partial surprise, it was perfectly fine. Further googling informed me that the cams were mostly a problem for the sportsman 500s from mid to late 90s models and the cams usually were never really a problem on the high output models. Of course I find that out as I have the camshaft in my hand...
Since then I'm on my way back together, had a machine shop hone the oem cylinder, machine the head, reseat the valves, port and polish the head and reinstalled those components paired with a new wiesco piston and rings.
I expect I did not solve the initial problem yet, but have learned alot and now suspect the fuel system. So I'll check the carb and particularly the fuel pump next. I created a list of leads to look into from several hours of researching this problem on these forums. Hope it helps.

-Worn camshaft (found to be good after disassembly, don't forget to periodically check/set your valve gap to .006)
-Bad/clogged carburetor
-Bad/clogged fuel pump
-Intake leak. Very short elbow between the head and the carb. (It has a gasket and is bolted on the head side of it, but just uses a hose clamp to attach to the carb which in my eyes has alot of potential to turn into a vacuum leak preventing a proper air/mix from being pulled into the combustion chamber.)
-Vacuum leak (vacuum line from the carb to fuel pump. Pump is vacuum driven)
- Fuel valve/shutoff. Read one guy post with similar symptoms, his was partially blocked with dirt/plastic particles.

Other oddball potential causes to look into...
-ETC/rev limiter. The speedometer module controls a handful of functions which can interfere with the atv operation (cooling fan not working, loss of power, ect.) There's a black wire to this module you can disconnect to check to see if your throttle is being limited but you won't be able to shutoff the machine from what I understand until you reconnect it.
-Water in your flywheel cover, rusting/interfering with the magneto/stator.
-I forget but one forum had a throttle adjustment in the small box that the throttle cable runs to right on the handlke bars. There had to be a gap set/adjusted properly.
-Plastic air intake near the fuel tank. One guys plastic intake was loose, when throttle was applied, being loose and because enough vacuum was generated to suck the intake against the fuel tank depriving the engine of air/proper air/fuel mix.

Anyway as someone who's already done alot of research, hope this info helps. Let me know how you make out and I'll do the same. Good luck.
 
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