Snowmobile Forum banner
1 - 10 of 10 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter · #1 ·
Search Community



Conversations
1998 Polaris Indy 500 bog
ParticipantsSchmittyIndy500Polaris Matt Updated 13 h ago
Unstar

SchmittyIndy500
·
Registered
Joined 13 h ago · 0 Posts
13 h ago
I have a 1998 Polaris Indy 500 with 2400 miles and I've replaced all fuel lines and filters, flushed the gas tank out, rebuilt and cleaned and properly jetted both carbs, syncronized and set the choke and made sure the float height is correct and set both E-clips properly, set the idle correctly, set the air screws to stock, and checked the compression and have 120 in both cylinders. I also checked and I have spark in both plugs and I've gapped the plugs correctly also. The jetting in both carbs is a 330 main jet and a 45 pilot jet with the air screws turned out .75 of a turn. I am currently running the snowmobile in 5-25 degree weather. It will start up and sound great but when you quick blip the throttle you hear a bog from idle and if you take off it also sometimes bogs down. It seems like it doesn't have lots of power at quarter to half throttle but it GOES when 3/4 to full throttle. But then after a while or sometimes even right away it bogs WAYY down and then you can barely move and will either idle very low or just die
 

·
Registered
Joined
·
3,149 Posts
What elevation that will play into jetting. Also iirc those have a 350 from factory in them. The screw turn out should be .75. Here in Wisconsin it is 350 for -20 to +10F. 330 is for +10 to +40F. Personally I tried that on my '97 and it bogged. I went back to the 350 with running E3.31s and BR8EIX Iridium Plugs which last 3-4 times longer, and the plugs are perfect and no more bog. I would at least swap out the 330s and put in 340s and try a BR8ES or the BR8EIX. Polaris over jets their carburetors from factory and that is widely known. The old rules of running the BR9ES are long gone and have been on those engines since the late '90s. Even Polaris dealers around here tell people BR8ES or BR8EIX or the E3.31that I currently have in both of mine. Also make sure you clean both clutches, take apart the secondary and make sure the secondary buttons are not worn down or that you have a busted spring in there. For clutching go to a 120-300 in the primary and then for the secondary a Polaris Gold or Black that has a LB rating of 25-48/9 depending on which site has them listed. I now have that setup in mine and after testing it today after taking out a EPI it is much better through the back/upshifting. Also make sure the pump isn't shot with it being that old a replacement Mikuni is 30 bucks and the diaphragms inside could be collapsing as it tries to pull fuel through the pump pretty common on fuel pump that old.

Also click Polaris then 1996-1998 service manual for it


New Mikuni fuel pump DF52-73


Font Parallel Number Rectangle Symbol


Automotive tire Font Material property Circle Rectangle
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #3 ·
I have rebuilt the fuel pump on it and that's when I replaced the fuel lines too... I am running the 330 main Because I'm in the temp range of +10 to +30 degrees... Currently running the BR8ES plugs too... Clutching is all stock and I checked and it looks all good to me... Took it out last night and played around with the air screw and once I turned it out 2 full turns it seemed to run pretty good but still had that very slight bog... Drove it for probably at least an hour and a half and still ran good but also still kept that slight bog... Not sure if I trust it. It never bogged way down like before though just when I blip the throttle or on take off
 

·
Registered
Joined
·
3,149 Posts
Telling ya go back to 340s or 350s and see what happens. I tried that as they said to go to the 330s and it was nothing but bogging went back up to the 350 and 340s no more bog. Having it at 340 or 350 will not hurt anything you go by plugs as well not just elevation. Also rebuilding fuel pumps don't always work. I refuse to rebuild them for 10-15 bucks when I can replace with genuine Mikuni for 30 and know it will work vs a rebuilt which doesn't always work. That air screw at most should be 1.0. Regardless of it being stock take the secondary apart and clean the helix and check the buttons. Also it has a red spring from factory or should those are junk put a Polaris Gold/Black in it and it will improve a lot throughout the powerband from taking off to at full speed. Take the primary cover off and mark it or make sure you find the X as it is a balance clutch. Too many people I know have said "oh primary spring is good I can see it" then pull the cover off and find a busted spring. Both carburetors need to be setup the same as well with regards to jetting and air screws. Also pull the carburetors back apart all it takes is one piece of junk from old fuel or if you didn't pull the tops off and cleaned the slides & what not then you didn't clean properly. Try another cleaning it can take 3-4 times before they are done right, use a small piece of wire as well through each passage and good carb cleaner not walmart garbage. Re-check that the choke cables are set right as well and the throttle if those are off a bit it can cause this issue.
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #5 ·
Tried 350 mains but sled didn't like those either... I will try the 340s and play with the air screw some more too... Replaced the primary spring and put a gold one in and also went through primary and secondary last week... But yes I will try the 340s tonight and clean and let you know how it goes...carbs will all be synced again too and chokes set good again as well... What would you recommend for where my e clip should be set at? I have it at the 2nd slot from the top right now
 

·
Registered
Joined
·
3,149 Posts
Should have put in a Blue 120-300 in the primary. Much better engagement and top end overall. Perfect spring for that engine and clutch. Make sure that the X on the clutch plates match up or that you marked it before taking it off as it is balanced clip.

Put the air screw back to .75 and set the clip in the #3 spot from top of needle with 350 or 340 mains. That might be your problem right there. Go back to a set of 340s, set the clip at #3 and do a plug test run with NEW plugs. Get it full throttle wide open once you hit max speed hit the red off button on the handlebars and let it coast. Then pull the plugs and check.

I run mine with 350s right now with that exact setup in 0-30 degrees F with no plug issues at all. Tbh with the BR8EIX they are perfect.
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #7 ·
Thanks! The 340s are working right now and will keep posted on how it continues to work!But I have some more Indy 500s... And I have one in particular that's really bad. It's a 1998 Polaris Indy 500 Fuji liquid cooled with a little over 5000 miles. Everything has been gone through and rebuilt except the motor... I heard crank seals can go bad so I checked the clutch side seal and sprayed starting fluid and then the engine sped up... How hard are these to replace? What do I need to do? Should I rebuild the motor? If so what should I all buy and install? The snowmobile takes a long time to start and barely stays running and sounds almost like a 4 stroke because it has such a bad bog and it basically just bogs super bad when you try to give it gas and then once you feather it then it runs better but not good and then eventually bogs so bad it won't move and then if you don't keep giving it a little gas it dies... Like I've said before the clutches and pretty much everything besides the motor have been gone through professionally including the carbs. I really want to fix this one before the season ends!
 

·
Registered
Joined
·
3,149 Posts
You have to pull the engine out. Drain all the coolant that you can, pull the exhaust, pop the primary clutch off, basically tear it all down to the crankcase. From there you end up servicing the crankshaft and everything. You will need a complete engine gasket kit with seals. The '97 and '98 gasket kits FYI are different then the '96 and prior years I found that out the other night which kinda shocked me. You will need pistons and rings. SPI has a kit on eBay with both for 95-110. I would bore it out .10 if possible with 5K on it in mileage. I would rebuild and balance the clutch if you haven't meaning the buttons, spider and what not.

Service manual will have all that information in it on how to do a rebuild, grease the crankshaft & what not.
 

·
Registered
Joined
·
3,149 Posts
If you do you will end up paying a few hundred for it. At that point might be best to find a used engine to put in there for a couple hundred till you can get around to tearing down the engine yourself over the summer.
 
1 - 10 of 10 Posts
Top