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1999 Polaris Sportsman 500
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Discussion Starter #1
My bike has had a hard 5400 miles put on it. I understand it is probably due for the cam but it dosnt show signs of the cam failure. Anyways the problem im having is it revs fine, no sputters or anything, but after a while falls on its face.
Please understand im new to this thing. Ive rebuilt the carb thoroughly and put a new air filter on it. Could it possibly be the fuel pump?
 

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Can you clarify “after a while falls on its face”? Does this mean after riding for 20 minutes it loses power, or every time you hit the throttle after a few seconds it bogs down? If the latter, I’d start by re-checking the float adjustment. Since you recently rebuilt it, you may have created a situation where the float bowl is being drained and it’s starving for fuel. They’re pretty touchy in this area. It needs to be correct, and the measurement procedure is a little odd. It’s described in detail in the service manual.
 

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137815

This is the only manual I have handy at the moment. It’s different year, but the procedure is the same. Maybe someone else can confirm the measurement for him?
 

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1999 Polaris Sportsman 500
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Discussion Starter #4
Its every time i punch the throttle, then it bogs down. Ill have to go through and check the float adjustments then. Is there a way i could do it without any special tools?

Cause id love to get this thing running right for the spring riding season. Also i would like to thank you for the speedy response!
 

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Have you checked valve clearances and cam timing both can cause these problems as it gets older valve clearances get tighter and the chain stretches retarding the valve timing
 

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1999 Polaris Sportsman 500
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Discussion Starter #6
Have you checked valve clearances and cam timing both can cause these problems as it gets older valve clearances get tighter and the chain stretches retarding the valve timing
No i have not, didnt even think to. I know how to check the timing on bigger engines and have a light, how would i go through and check the timing on this thing? Havent worked with small engines to much
 

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Not checking ignition timing cam timing. A little hard to describe but you need to remove the cam cover and gear cover, spark plug need to get motor on compression stroke both valves closed TDC you can now check valve clearances engine cold i will see if i can find and post the info but it late here now and i am trying to stay awake after a 10hr day i am stuffed brains shutting down see if i can post tomorrow cheers.
 

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After you make sure valve clearance is good and carb good if its still does it disconnect the black ground wire from the cdi and try it. I've seen a few of those late 90s to early 2000 machines that would bog/lack power on acceleration but it wasn't all the time. It was intermittent. Or sometimes it will start out bogging and then suddenly just kick in full power and run like gangbusters only to later do it again. That's a symptom of the cdi going bad. You can get a cheap replacement on ebay that works just a well as the expensive Polaris unit.
Note: The machine will not shut off until the black wire is grounded again.
I'm not saying that's your problem but something to try if the usual fixes don't work.
Here's a link to one of many. If you determine you need one, just make sure the wires/connectors match your old one.
 

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1999 Polaris Sportsman 500
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Discussion Starter #9
After you make sure valve clearance is good and carb good if its still does it disconnect the black ground wire from the cdi and try it. I've seen a few of those late 90s to early 2000 machines that would bog/lack power on acceleration but it wasn't all the time. It was intermittent. Or sometimes it will start out bogging and then suddenly just kick in full power and run like gangbusters only to later do it again. That's a symptom of the cdi going bad. You can get a cheap replacement on ebay that works just a well as the expensive Polaris unit.
Note: The machine will not shut off until the black wire is grounded again.
I'm not saying that's your problem but something to try if the usual fixes don't work.
Here's a link to one of many. If you determine you need one, just make sure the wires/connectors match your old one.
Thank you all for replying gonna be doing so work on it today. Ill keep you guys posted with results
 

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Its every time i punch the throttle, then it bogs down. Ill have to go through and check the float adjustments then. Is there a way i could do it without any special tools?

Cause id love to get this thing running right for the spring riding season. Also i would like to thank you for the speedy response!
Your really need a caliper to do it correctly. Fortunately, a cheap one will do... ...https://www.amazon.com/Digital-Caliper-Jsdoin-Calipers-Measuring/dp/B07P2CYXZC/ref=sxin_2_ac_d_pm?ac_md=1-0-VW5kZXIgJDIw-ac_d_pm&crid=3QKPJ04QYU0PA&cv_ct_cx=caliper+measuring+tool&keywords=caliper+measuring+tool&pd_rd_i=B07P2CYXZC&pd_rd_r=6a40faa6-a9ff-431d-8d14-999b416fec4a&pd_rd_w=cokIG&pd_rd_wg=kKJeR&pf_rd_p=0e223c60-bcf8-4663-98f3-da892fbd4372&pf_rd_r=VZDKYZ9BHCTR92NTM1B4&psc=1&qid=1585330463&sprefix=Caliper%2Caps%2C172
 

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Your really need a caliper to do it correctly. Fortunately, a cheap one will do... ...https://www.amazon.com/Digital-Caliper-Jsdoin-Calipers-Measuring/dp/B07P2CYXZC/ref=sxin_2_ac_d_pm?ac_md=1-0-VW5kZXIgJDIw-ac_d_pm&crid=3QKPJ04QYU0PA&cv_ct_cx=caliper+measuring+tool&keywords=caliper+measuring+tool&pd_rd_i=B07P2CYXZC&pd_rd_r=6a40faa6-a9ff-431d-8d14-999b416fec4a&pd_rd_w=cokIG&pd_rd_wg=kKJeR&pf_rd_p=0e223c60-bcf8-4663-98f3-da892fbd4372&pf_rd_r=VZDKYZ9BHCTR92NTM1B4&psc=1&qid=1585330463&sprefix=Caliper%2Caps%2C172
Nah, I haven't actually measured one for years. I just "eyeball" it!
Simply hold the carb up sideways and tilt it back and forth a little to make sure the needle seats when the float arms are level with the sides of the bowl. ALWAYS works just fine for me. Unless some dipstick has messed with the float level before you, its very unusual for it to be wrong anyway.
Its part of my routine to eyeball the float level as described above after installing the seat, needle and float and before putting the bowl on. Unless a quick eyeball shows it to be visibly out of whack it gets buttoned up and ready to go back on the machine. I've never had a problem yet doing it this way in many years of messing with carbs.
 

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1999 Polaris Sportsman 500
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Discussion Starter #14
i finally got it running good, i took the carb off and realized i overlooked the pilot jet. It runs phenomenal now, thank you for all the helpful suggestions everyone. I truly do appreciate it
 

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Nah, I haven't actually measured one for years. I just "eyeball" it!
Simply hold the carb up sideways and tilt it back and forth a little to make sure the needle seats when the float arms are level with the sides of the bowl. ALWAYS works just fine for me. Unless some dipstick has messed with the float level before you, its very unusual for it to be wrong anyway.
Its part of my routine to eyeball the float level as described above after installing the seat, needle and float and before putting the bowl on. Unless a quick eyeball shows it to be visibly out of whack it gets buttoned up and ready to go back on the machine. I've never had a problem yet doing it this way in many years of messing with carbs.
I don't measure them either - I have a calibrated eyeball like polman - I have found it better to set composite floats on the low side to allow for fuel absorption - most engines run better with the floats set low rather than high - high sometimes makes the engine run rich while low has very little effect - as long as the jets are submerged in fuel and fuel can enter the carb faster than it is used you will never know if the float is 'correct' or low.
 

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For the record, those of us who haven’t done 5,000 of them..... measure them. Two of mine were extremely finicky and only ran right when I got it within the spec.... by measuring it......with a caliper.....like the rest of the mortals.
 

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For the record, those of us who haven’t done 5,000 of them..... measure them. Two of mine were extremely finicky and only ran right when I got it within the spec.... by measuring it......with a caliper.....like the rest of the mortals.
LOL, I won't argue with that mico. I guess I did overstate it a little when I said I NEVER measure. I do sometimes if something don't look right or there have been problems and I'm trying to eliminate potential causes by making sure everything is exactly to spec. (y)
 

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LOL, I won't argue with that mico. I guess I did overstate it a little when I said I NEVER measure. I do sometimes if something don't look right or there have been problems and I'm trying to eliminate potential causes by making sure everything is exactly to spec. (y)
Thanks Gandalf ;-)
 

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Ditto polman and mico - I do have calipers also and I even have the special Honda float tool
 

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All that info is great guys. My 01 has unknown hrs/miles as the speedo seems dead.

Just got my high altitude jet kit and o ring from latebird (thanks)

Mine is going up to some prop of mine and I will check all this now. (only runs with choke pulled now)
 
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