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Discussion Starter #1
So i installed a new camshaft and exhaust rocker on my 2000 sp 500. Starts right up purs like a kitten. Can rev it up no problem in neutral. Couldnt do that before i replaced Cam. I put in new plug, new wire, cleaned carb, air filter, emptied gas tank and cleaned out fuel valve and diaphragm.

My problem is that when i head off down the road i cant get above 5 mph or give it any gas without it bogging and almost to the point of backfiring. Do i have a carb issue? Please tell me it is not the timing cause it runs so nice at idle and revs nice. I have these problems only when under load. Oh and i also changed oil and filter. Any ideas where i should start with this one?
 

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Discussion Starter #4
I can possibly understand Carb, but why do you think clutch related? Before Cam, clutch worked flawlessly. I am just trying to determine as to where something might have messed up in carb since i basically rebuilt it when i had everything apart.

What would be my symptoms if out of timing? Would i be able to rev it up nicely while in neutral?
 

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If the timing is off it could rev good without a load and not rev with a load on it. And it's not too hard to get the can chain off a tooth or two.
 

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Discussion Starter #6
If the timing is off it could rev good without a load and not rev with a load on it. And it's not too hard to get the can chain off a tooth or two.
OK. I think i will pull timing cover and do another verification. I was positive i had it set perfect at TDC with everything lined up correctly. Valves set at 0.006'. Should i look at my tensioner? Can that be adjusted? I have a completely stock setup. I will take pics of all my steps and try to post them. thank you. Timing check it is.

Quick question, will i be able to do an adjustment without removing front plastic? that stuff is a bugger on the olders sp's?
 

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backfiring is symptomatic of a lean condition

its your carb. It reallly has 3 stages. cold start up, idle to about 14mph and speeds above that. So your first stage is set up correctly, 2nd is iffy and 3rd is way off. Make sure the diaphgram and jetblock assemblies are working well-if those are good then tweak your jet needle to add more fuel, that's your 3rd stage part of the carb. Good luck.

Service manual in case you don't have it: Index of /ORV Manuals/Polaris
 

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Were you TDC firing stroke???
 

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Sounds like it's hungry. Feed it some additional fuel and see how it responds.
 

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Or could it be intake boots are cracked or loose? Sucking additional air would also cause lean condition..... but my vote would be on carb / carb related issue.
 

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Discussion Starter #11
OK, so i checked carb. Turns out somehow someway the main jet cam loose, fixed it up and thought everything would be perfect. NOPE.

I am now able to idle perfect rev it but when i drive it just feels so sluggish and no power. feels just gutless. I checked timing again and it looks bang on TDC on firing stroke. My question is this: If i adjusted timing 1 or 2 links, do i need to reset valves again?
 

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Discussion Starter #12
its your carb. It reallly has 3 stages. cold start up, idle to about 14mph and speeds above that. So your first stage is set up correctly, 2nd is iffy and 3rd is way off. Make sure the diaphgram and jetblock assemblies are working well-if those are good then tweak your jet needle to add more fuel, that's your 3rd stage part of the carb. Good luck.

Service manual in case you don't have it: Index of /ORV Manuals/Polaris
Thank you for your reply.

My diaphragm is now perfect. I have a 155 main jet. What notch should my retainer be on for the main needle? I think there are 4 choices?

What is the controlling factor of the 2nd stage?
 

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Discussion Starter #13
One thing i never mentioned as i hope it could not be an issue.

When i was removing some fuel lines i broke off the reserve line on the fuel pet cock. So i just put a screw in it and sealed it up. I plan on replacing it eventually but as long as it is sealed properly there should be no effect correct? I am using the main fuel line with lots of new gas in tank. I am about to replace all fuel lines also.
 

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Discussion Starter #17
I've done a bit of searching here and was wondering where i should start in troubleshooting my issue.

description/symptom:

replaced worn camshaft and bike will start and idle perfect. mid range and top range is terrible sluggish and boggy. I took advice that it was carb related and double checked cleaned for third time. same symptom.

I am going to triple check timing and valve clearance.

If i get same result, what should i check next? Clutch should be fine. New fuel, new plug wire(will replace plug also), oil change done...
 

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Any mods to airbox or exhaust to need that big of a main jet? Pilot jet and mixture screw controls idle to about 1/4 throttle. Then needle and main start to take over. Mostly needle from 1/4-3/4 and pretty much all main after that. 142.5 I think is stock on a 500. You may just be jetted way to rich on the main with a good clean carb or got the wrong main with a rebuild kit.
 

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Discussion Starter #19
Okay, i may be wrong but i thought 152.5 was stock. I do have that jet. I have the 155 in. Mods are clutch kit with KN air filter. It definitely seems i am running too rich. I will change out the main jet and focus on fine tuning mid range with the needle. Need to verify where the snap ring is set. What is stock?
 

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ok looked in my manual...non HO 500 jet is 162.5 in a mikuni BST 34

500HO is 152.5 BST 40 Carb

retainer ring 3rd from top
 
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