Backfiring
- Thread starter gep71
- Start date
Out of sync
snootbiscuit
New member
I believe that sleds got reeds, I would be looking at them=one missing or broken?
arcticgeorge
New member
a lot of good answers on Sno-Tech Magazines site
here's something i found on sno tech magazines web site about a sled that backfired.........................First off add some isopropyl to the fuel and see if it works better after the engine has run long enough to work it through the fuel and combustion system. Getting deeper, you could check the compression on each cylinder to make sure they are within 10% of each other. If they are, remove the carbs and check to see that all of the piston intake skirts are intact to allow proper intake vacuum for fuel. This could also be a matter of sucking snow dust into the combustion chamber, giving the impression that a plug is fouling. Plugs can’t burn water, and will act like they’re fouled.
here's something i found on sno tech magazines web site about a sled that backfired.........................First off add some isopropyl to the fuel and see if it works better after the engine has run long enough to work it through the fuel and combustion system. Getting deeper, you could check the compression on each cylinder to make sure they are within 10% of each other. If they are, remove the carbs and check to see that all of the piston intake skirts are intact to allow proper intake vacuum for fuel. This could also be a matter of sucking snow dust into the combustion chamber, giving the impression that a plug is fouling. Plugs can’t burn water, and will act like they’re fouled.
motor_slut
New member
Bad reeds, bad crank seal, or crank is out of phase. Ether will confirm a bad crank seal, visual inspection will confirm bad reeds, and some marking and measuring will confirm a crank phase issue.
I had the same issues on 500 I bought this fall. Thought that the carbs were dirty, old gas, old plugs. step 1, I cleaned carbs put new plugs and good gas. Still backfired on the PTO side. If I disconnected the TPS sensor on the carbs the backfiring would stop, Check carb sync and tps both ok. I moved carbs from onr sled to another ( 3 500's in the garage ) problem remained with the sled, then I tried a wire harness and the problem seem to go away, I ordered a new harness and install. The problem came back. After playing with this sled for a complete day I found that when the engine temps ran 150 degrees the backfire was very slight but would be bad at startup and until 150 degrees. The problem was crankshaft indexing and a bent rod on pto side.
My suggestion would be to check the carbs first and then the crankshaft indexing, if I would have done this in this order it would have saved me a lot of time
My suggestion would be to check the carbs first and then the crankshaft indexing, if I would have done this in this order it would have saved me a lot of time
1flatlander2
Member
is it backfiring when cold or after warmed up
1flatlander2
Member
all my xc's backfire when cold. they are cold blooded and need to warm up 99,01,05
toddspolaris
Member
could be, I would pressurize the coolant system, but easy for me to say cause I have the equip. to do so. has your coolant gone down?
indy_500
Well-known member
Check tps and make sure carbs are synced. Also, what does it idle at? My carbs were out of sink (slides lifted up too high) and it was idling super high (3000 rpm) and everytime i let off the throttle it backfired, but it wasn't a loud backfire.
I had coolant coming out of every gasket on my motor and it was due to a bad thermostat. It didn't allow coolant in and pressurized the whole cooling system making it seep out everywhere. You don't have head gaskets fyi, you have o-rings that can easily tear or not be seated correctly.
I had coolant coming out of every gasket on my motor and it was due to a bad thermostat. It didn't allow coolant in and pressurized the whole cooling system making it seep out everywhere. You don't have head gaskets fyi, you have o-rings that can easily tear or not be seated correctly.
Crank phase.
I bought a 2000 500 in rough shape but only had 1700 miles and was cheap!! Ran weird like yours, figured a carb problem, no big deal right. Wrong! If you can remove both plugs and insert a rod, dowel or screwdrivers in each hole. Slowly roll motor over. The two pistons should be 180 degrees apart and the rods should never move in the same direction. Mine did. Check it out and let us know.
I bought a 2000 500 in rough shape but only had 1700 miles and was cheap!! Ran weird like yours, figured a carb problem, no big deal right. Wrong! If you can remove both plugs and insert a rod, dowel or screwdrivers in each hole. Slowly roll motor over. The two pistons should be 180 degrees apart and the rods should never move in the same direction. Mine did. Check it out and let us know.