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Discussion Starter · #1 ·
I recently got a 1996 sportmans 500 and it starts fine and idles fine. WHen you give it gas it revs fine for about 500 rpms or so (guess) but then it just boggs down and has no power. I have gone through the basics with it already like spark plug, air filter, fuel filter, oil etc. I still have to check compression but I am leaning towards a bad camshaft. Has anyone run into this problem or can help me out?
 

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Discussion Starter · #3 ·
no I havent pulled the carb apart yet to check it out. I would have thought that if it was a carb then it would do it all around in the rpms
 

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not necessarily.It's an easy check before doing things you may not need to do.Some carb cleaner might help.If the cam was bad it would still rev some but pop through the carb or exhaust depending on which lobe had the flat spot,unless it broke in half.
 

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That could still be the carb,but its up to you what you want to do.I would pull the carb and clean it before I jump in and do more expensive things.It dont hurt to try and see if it helps.The carb may not be your problem,but it's something I would try before spending too much money.
 

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I had the same issue, but a new plug fixed it up right. I may pull the carb too in searching for a damn clicking noise...

Good luck dude.

Jay-
 

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Yes,let us know how things go mudjunkie. Where is the clicking noise coming from s
Stalefish?Around the carb area.Have you checked the plug wire?Not saying thats the problem,but a wore spot in the plug wire can cause it to arc on something and make a clicking noise.
 

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My sportsman 400 startrd out doing the same type of thing and progressed to severe bogging and popping (backfiring). You might want to try some fuel treatment as it could be a sticky valve. Cheap and easy. I put some 2 cycle oil in the gas tank and the 400 works fine now.
 

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That is a good thing to try also,before you do a teardown.
 

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I too am working on a gutless 1996 Sportsman 500. It seem to do the same. starts, idles, runs but there is just no top end power. I have had the carb apart several times, stator resistances are ok (hot or cold), actually replaced the cam and one rocker, substituted CDI, disconnected the kill circuitry, clutches tore down and serviced, new belt, substituted gas tank and fuel pump. The bike doens't burn any oil and idles great, so I assume the engine internals are ok.

It does rev up when I manually raise the constant velocity slide with a screwdriver, but I can't see any tears in the diaphram. I would like to substitute the whole carb. Can anyone advise what other Polaris bikes used this Mikuni CV Carb, a BST 34??? Is there an on-line resource for for Polaris ATV specs, and I mean going back 10 to 15 years??

Thanks in advance!!
 

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I think some of the Sportsman 700 twins 05 or 06 somewhere around those years,use the BST 34.You might want to double check.
 

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1996 500 bogging at top end

I have a 1996 500 sptsman that is having the same problem of bogging down above 20 mph. Has anyone come up with a solution. I can't figure it out.
 

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Discussion Starter · #16 ·
I have a 1996 500 sptsman that is having the same problem of bogging down above 20 mph. Has anyone come up with a solution. I can't figure it out.
It was a bad camshaft. The lobes on it were gone! Mine would idle and go about 5 mph. Replaced the cam and it runs great
 

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400 are 2 stroke.
my 1996 500 a guy just gave me had the same problem, talked to my buddy who works on atvs said first thing cam lobs, replaced, ran great, now im going throught replacing gaskets and such.
 

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500 backfiring issues

I've repaired many of these machines while working at a Polaris dealership. Most of the issues were camshafts. It was not uncommon to fix 3 or 4 machines a week in the fall. The easiest way to find out if it's the cam is to take off the valve cover and watch the lobes as they go through their travel. The center lobe is the exhaust lobe and it usually is the problem.
 

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I've repaired many of these machines while working at a Polaris dealership. Most of the issues were camshafts. It was not uncommon to fix 3 or 4 machines a week in the fall. The easiest way to find out if it's the cam is to take off the valve cover and watch the lobes as they go through their travel. The center lobe is the exhaust lobe and it usually is the problem.
Hi Everyone

I've just got myself a Sportsman 500 HO, as ddwsr59 has pointed out, the center lobe on the camshaft has completely dissapeared.
Does anyone know any where i can get hold of a new camshaft (for a decent price), since over here in Spain they work out about 320 pounds + VAT.

Thanks
 
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