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Discussion Starter · #1 ·
I’m having an issue fouling plugs on this sled, previous owner switched from oil injection to pre mixed which I don’t have a problem with, I’m running 50:1 as per the manual specs. I’ve read running hotter plugs may help, as of right now I have a br9es on pulley side and BR8ES on fan side. It’s running to rich I think but I’m not very experienced with carbs. I’m thinking maybe the air screw needs to be adjusted to lean it out possibly but just wondering if anyone has come across the issue with older sleds. And yes the simple option is upgrading haha it’s in the works hopefully next season
 

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I'm by no means an expert but what I've read is the following:


1) you shouldn't have two different spark plugs - check the NGK spark plug finder to see which one you should be using


2) don't run the sled for short periods of time. The plugs need to get hot to burn off the excess carbon. I've read to let it idle for a few minutes to warm up the machine then start to drive (not WOT) for a few minutes to get everything nice and warmed up (especially on cold days).


3) Use iridium plugs (they're more expensive but supposed to run hotter and last longer).
 

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I’m having an issue fouling plugs on this sled, previous owner switched from oil injection to pre mixed which I don’t have a problem with, I’m running 50:1 as per the manual specs. I’ve read running hotter plugs may help, as of right now I have a br9es on pulley side and BR8ES on fan side. It’s running to rich I think but I’m not very experienced with carbs. I’m thinking maybe the air screw needs to be adjusted to lean it out possibly but just wondering if anyone has come across the issue with older sleds. And yes the simple option is upgrading haha it’s in the works hopefully next season
Could possibly just be the mild temperatures we have been having, it would lean out when it gets colder.
 

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The first thing I would check for fouled plugs would be low compression.

Old fuel?, always use premium?
If its starting to have start up problems, low compression for sure.
 

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Could possibly just be the mild temperatures we have been having, it would lean out when it gets colder.
This is true. It may be set for colder temps than we are having now so perhaps have a test run during some colder temps before messing with it. Cold air is denser than warm air and thus more fuel required when colder and it may be calibrated for that.
 

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I’m a Cat guy but a Mikuni carb is a Mikuni carb no matter what it’s on.
1) do you know what size carb! VM32, VM34?
2) do you know the size of main jet and whether it’s the factory one in there?
3) where is the jet needle set at? There’s 5 settings. They’re usually set it the middle.
4) do you know how many turns the pilot metering screw should be at? And is it correct?
5) ethanol fuel requires bigger jet compared to using premium fuel which is highly recommended for seasonal equipment. I see too many ethanol related fuel issues.
And as Higgins mentioned. what is compression. It should be 110 at the very minimum and within 10% of each other.


Winter rig: 2016 AC Bearcat 2000 XT, Eskimo F1 Rocket 10”, Eskimo QuickFish 3i, Humminbird Helix 5 ice, 788Ci.
 
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Discussion Starter · #8 ·
So it’s a v34, I’m not too sure about any of the jet settings, I think it would be factory set but not sure. Sled starts great, prime it 2-3 times if it’s been sitting a while and she fires up no problem. This is my second winter with the sled, last year with the colder temp I was experiencing the same thing. I’d get about 4-6 fishing trips out of it before they would foul. I always use premium fuel, mixed 50:1 with 2 stroke snowmobile oil, and I put seafoam in it as well. From what I’m reading I’m gonna be tearing that carb apart and familiarizing myself with it. I haven’t checked the compression as it seems to start no problem. I appreciate all the info
 

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Checking the compression first would be the easier to rule out.
Then have at it with the carbs.:D
When you prime an engine you shoot extra fuel/oil into it and that helps the engine have better compression, as well as extra fuel to start.

Its actually a way to check a 2 stoke for low compression when they are hard to or not starting, bit off oil into the cylinder and it will have more compression to start, but if its bad won't run long.

You have a fairly old machine here, and a piston ring job is just a possibility.
I'm hoping its just the carb.
 

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Part of my yearly get the sled ready is I change the fuel line fuel filter clean the carbs empty the tank and put fresh #1 gas with stabilizer and change the plugs. I run a 1992 Polaris Indy trail 488. If I was you check for compression. That is like the first thing u do. Then disassemble the carbs. Clean those things till u could eat off them inside and out. Get a manual and make sure the carbs have the proper jets and that the floats are properly set. When u reinstall the carbs there are slides that go up and down inside the carb. There will be a long pin inside with a spring. There are slots on that pin make sure the c clips are installed to factory spec.

Have u thought about changing your mixing oil? Are you using expensive oil or cheep oil. Maybe if u are using expensive oil it needs to be mixed leaner???? Just a shot in the dark.

Keep us posted
 

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If the carbs are dirty they will cause the sled to run poorly air screws or pilot jets air passages get clogged and as others have stated ethanol fuels if left sitting for a while will cause grief in fuel systems! Also with older snowmobiles airbox foam and underhood foam breaks down and it can end up in the carbs!
 

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I forgot to mention that check your carb flanges while you’re at it. These mount the carbs on the cylinders. They cannot be cracked at all or you’ll burn down your motor. Also if your sled calls for BR9ES plugs, you can use BR9EYA plugs which are less prone to fouling. I used them in my 93 Cat.


Winter rig: 2016 AC Bearcat 2000 XT, Eskimo F1 Rocket 10”, Eskimo QuickFish 3i, Humminbird Helix 5 ice, 788Ci.
 

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Discussion Starter · #18 ·
Hey guys I use shell advance snowmobile oil in the yellow jug, this sled originally had an oil injection system that was taken out, and I’m wondering since when it idles or when drove at a low speed instead of the oil injector limiting the amount of oil getting mixed the motor is getting the 50:1 mix full blast, the fact that these plugs are black and wet, right at the tip, with no other discolouration is leading me towards this. As for ripping the carb apart that will be a summer project, I’ll switch plugs out for the rest of the season as need, cause the sled runs very well if the plugs are in good shape. Manual calls for the equivalent of br9es, I think I’m going to try BR8ES in there now, as I’m running the hotter plug on the fan side as per the previous owners instructions. I haven’t found any proof that this is the way to go and you guys have said both plugs should be the same, I’d just like to say I really appreciate the help and the info you guys are passing on.
 

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FWIW my 93 Pantera averaged about 42:1 with oil injection. Smoked like heck on cold start. My 05 Sabercat which come oil rich from factory had the pump turned down to average 33:1. Both oil injections still working. Never fouled a BR9EYA plug in them.
Double check your spark and make sure it’s a nice bright blue. Sometimes when there’s spark issues, guys remove spark plug boot and cut 1/2” off the plug wire. You may see a bit of corrosion there.


Winter rig: 2016 AC Bearcat 2000 XT, Eskimo F1 Rocket 10”, Eskimo QuickFish 3i, Humminbird Helix 5 ice, 788Ci.
 

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Hey guys I use shell advance snowmobile oil in the yellow jug, this sled originally had an oil injection system that was taken out, and I’m wondering since when it idles or when drove at a low speed instead of the oil injector limiting the amount of oil getting mixed the motor is getting the 50:1 mix full blast, the fact that these plugs are black and wet, right at the tip, with no other discolouration is leading me towards this. As for ripping the carb apart that will be a summer project, I’ll switch plugs out for the rest of the season as need, cause the sled runs very well if the plugs are in good shape. Manual calls for the equivalent of br9es, I think I’m going to try BR8ES in there now, as I’m running the hotter plug on the fan side as per the previous owners instructions. I haven’t found any proof that this is the way to go and you guys have said both plugs should be the same, I’d just like to say I really appreciate the help and the info you guys are passing on.
50:1 mix is the same mix throughout the RPM range, just different amount. Wet plugs indicate issues like poor compression or carburetor wear/adjustment required. Run factory recommended sparkplug heat range. As long as they stay wet and black you are assured that the motor has sufficient oil.
Do a compression test, I think Catman recommended 110+ on the low side. Ground the plugs so you don't damage the coil. I ordered the Mikuni carb kit on Ebay, delivered in 3 days at a good price.
 
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