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Old 02-19-2018, 11:29 PM
reddeerguy2015 reddeerguy2015 is offline
 
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Default Snowmobile Running Rich??

Hey guys,

Got a 98 polaris triple, 2 stroke.

Fresh top end rebuild, about 5 hours on it.

Sled seems to be running very rich with choke all the way off. Bogs, pops, farts, backfires and hesitation - until she catches, then she runs like a raped ape.

Seems to get a bit better when she's fully warmed up, but far from perfect - still getting a hesitation in low rpms, bogging down....then she catches her breath and WHHHHHHHAM!!! About 110mph in 6 seconds.

Starts in 3 pulls with full choke up to -20. Run it like that for about 30 seconds to a min, then switch her over to half choke and she'd run all day on half choke if I let her.

Only problem is when it warms up it idles better with no choke, but that damn hesitation, burping and farting when smashing the gas.

Jetted too rich ?? What say you 2-stroke wizards.

- running premium fuel (no ethanol)
- always run seafoam in the gas (for last 3 years)
- shell 2 stroke oil (most expensive stuff you can buy from Canadian tire)
- carbs are clean
- did the same thing before top end build, although seems more noticeable now ??
- brand new irridium spark plugs
- air intake not blocked or restricted

Help.
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  #2  
Old 02-19-2018, 11:36 PM
IL Bar IL Bar is offline
 
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To me it sounds like an issue with pilot jets. Might be on the lean side. Have you cleaned carbs yourself to know they are clean? What color are the plug tips after you ride it for a bit? Are they blackish, light brown, or whiteish?

Last edited by IL Bar; 02-19-2018 at 11:45 PM.
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  #3  
Old 02-20-2018, 12:18 AM
reddeerguy2015 reddeerguy2015 is offline
 
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Quote:
Originally Posted by IL Bar View Post
To me it sounds like an issue with pilot jets. Might be on the lean side. Have you cleaned carbs yourself to know they are clean? What color are the plug tips after you ride it for a bit? Are they blackish, light brown, or whiteish?
Good question. Will report back tomorrow with an exact answer.
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Old 02-20-2018, 12:27 AM
reddeerguy2015 reddeerguy2015 is offline
 
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Actually just reading around online, seems backfiring can be a symptom of a lean jetting condition??

Does this seem right gurus ??
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  #5  
Old 02-20-2018, 12:43 AM
reddeerguy2015 reddeerguy2015 is offline
 
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Okay the more reading I'm doing on this, the more it seems to point to a lean running condition.

Which would make sense, as I melted the top end down last winter doing a bunch of wide open runs across the hay field.

Sled is oil injected (seems to be working, at least at an idle as it's a smoke show when started and idling).

Water pump and coolant is good (mechanical gauge tapped into cooling rail by heads, doesn't seem to get much hotter than 130 degrees running in powder). Seen it get higher on hardpack but not much.

So where do I start ?? Main or pilot jets ?? Carb boots leaking ?? How can I test this ?? Maybe spray ether around the carbs and see if the sled revs up while idling ??
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Old 02-20-2018, 06:33 AM
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JustBen JustBen is offline
 
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1. Stop running seafoam in every tank. Only run it if it needs it. Maybe once per season.
2. Do a plug chop. Best way to determine if you are rich or lean. You should be able to review your current jets against recommended for your altitude and get an indication.
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Old 02-20-2018, 06:37 AM
Lites out Lites out is offline
 
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Check the color of your plugs as mentioned! Lien sounds more likely than rich. Will only take a 10min jet change to rectify! Pull airbox to get to bottom of carbs.Take apart bottom of carbs and remove jets with jet wrench or small socket. post which size of jet youre running and I can probably help as I use to own lots of polaris triples
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Old 02-20-2018, 06:53 AM
reddeerguy2015 reddeerguy2015 is offline
 
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Quote:
Originally Posted by Lites out View Post
Check the color of your plugs as mentioned! Lien sounds more likely than rich. Will only take a 10min jet change to rectify! Pull airbox to get to bottom of carbs.Take apart bottom of carbs and remove jets with jet wrench or small socket. post which size of jet youre running and I can probably help as I use to own lots of polaris triples
Okay, do I pull pilots or main, both ??

Obviously they'll have a number stamped on them??
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Old 02-20-2018, 07:27 AM
elkhunter11 elkhunter11 is online now
 
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If the engine bogs for a couple of seconds when you open the throttle, and then pulls hard, you need to adjust the needles. If it's lean, raise the needles(drop the clip one notch), if it's rich , drop the needles(move the clip up one notch).
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Old 02-20-2018, 07:40 AM
bubba300 bubba300 is offline
 
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Quote:
Originally Posted by elkhunter11 View Post
If the engine bogs for a couple of seconds when you open the throttle, and then pulls hard, you need to adjust the needles. If it's lean, raise the needles(drop the clip one notch), if it's rich , drop the needles(move the clip up one notch).
I would check these first.
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  #11  
Old 02-20-2018, 07:47 AM
Drewski Canuck Drewski Canuck is offline
 
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Default Carbs Cleaned does not mean Clean Carbs!!!

Had something similar on a Yamaha sled. It had no Fuel Filter.

Alberta Cycle pulled their hair out doing repeated carb cleans with an ultra sonic tank, and compressed air.

There is something called a "Welsh Plug". It covers a "mixing chamber" for the low speed jet.

The head mechanic took over, drilled a hole in the shiny silver plate and put back pressure on it. All sorts of black debris was forced out. No amount of any solvent could take out that stuff.

After the plug was soldered closed again, it worked perfect.

Your problem may be lean / rich settings and poor jetting, but I am going to guess the carbs were the same as before the rebuild on the top end. If the problem was there before, and jetting does not fix it, then you have to look at the model of carb, whether there is such a mixing chamber where debris can collect, and consider this solution.

Just because you bought good gas does not mean that your gas was debris free. It is easy for something to get into a tank, or a jerry can, and create a lot of problems fast.

Drewski
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  #12  
Old 02-20-2018, 09:08 AM
Joe Black Joe Black is offline
 
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melt down season before means leaned out. did all pistons go/heat damaged? may just be one carb(if multiple carbs) if not focus on air leak around carbs or crank seals. do the ether trick from outside around all connections and seals to see if you can get an engine rpm increase on idle. if not, then carb jets are plugged and caused a lean out.(or overall lack of fuel) fuel filter plugged? weak pump? increasing jet sizes will just mask the real problem, and if it cleans up, it will then run rich.

jets don't wear out, et, so look for the reason it melted(leaned out). will probably explain the crappy running now. keep running it as is and it will probably melt again.
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  #13  
Old 02-20-2018, 09:14 AM
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outofbounds outofbounds is offline
 
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Carb sync means more than just adjusting the air screws. After ensuringvthe carbs are clean.You need to get all three carbs set and pulling the same. I'm assuming seperate carbs on this sled.
If you don't have a manometer, you still need to adjust the slide height and throttle pull so that they are set evenly on each carb and also timed with the oil pump lever if the machine is oil injected. WOT requires max oil.
Ensure chokes are adjusted to open close fully for each carb.

Properly synced carbs result in better performance through reduced vibrations, improved throttle response, more power, higher mileage, and optimum operating temps.. No cylinder should run hotter, cooler, richer, or leaner than another. The synchronization adjustment adjusts the setting of each carb so that the air/fuel mixture passed by each carburetor results in an equal load placed on each of the cylinders.

Below is what I was told many years ago as I was eager to learn from the old timers that could tune everything from sleds to chainsaws.

1or 1.5 turns on the air screw should be fine to get it started. This jet is a fine adjust for the pilot jet at idle only. If the sled is dying out at idle, one must figure out if it is a lean or rich condition that is causing it. Fire it up and let it start to die, then blip the choke lever, if the sled dies, it's due to a rich condition, and if the RPMs pick up when the choke is blipped it's a lean condition. Most sleds will be lean at idle, and need a little choke lever babysitting until it starts to warm up.
Tune your airscrew for a hot motor. Turn in to richen, turn out to lean. Adjustment range is 1/2 turn to 2.5 turns. If you can't attain what you want, then it is time to re-jet the pilots.
Tuning the air screw on a hot motor will give you better throttle response while tuning on a cold engine will allow you to walk away from the sled while it warms up.
Throttle responce is more important to me, so i live with the choke babysitting. For the slides ensure they open all the way at WOT and start and travel at the same rate when the throttle is squeezed. The use of a vac guage is best practice, but if the carbs are set the same the engine will run.

Be aware that location/ altitude and temperature at intended riding location will affect carb tuning and performance.
Improperly tuned carbs will result in engine failure.
Like mentioned above spark plug conditions tell the story.
Nothing better than riding a properly tuned machine. Brraapp!
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  #14  
Old 02-20-2018, 10:59 AM
reddeerguy2015 reddeerguy2015 is offline
 
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Quote:
Originally Posted by Joe Black View Post
melt down season before means leaned out. did all pistons go/heat damaged? may just be one carb(if multiple carbs) if not focus on air leak around carbs or crank seals. do the ether trick from outside around all connections and seals to see if you can get an engine rpm increase on idle. if not, then carb jets are plugged and caused a lean out.(or overall lack of fuel) fuel filter plugged? weak pump? increasing jet sizes will just mask the real problem, and if it cleans up, it will then run rich.

jets don't wear out, et, so look for the reason it melted(leaned out). will probably explain the crappy running now. keep running it as is and it will probably melt again.
This is what I'm worried about - melting it down again.

And I'll admit I'm not that good with carbs. Most everything I can get my hands into pretty good, but never seem to have much luck with carbs.

Some good info in this thread so far guys. Thank you.

I'll check the plugs when I get home from work.
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