Switchback 600 cfi backfiring intermittenly

[mudorsnow]

Well, here's the deal. I purchased this sled this fall. It's an 07 polaris switchback 600 cfi. It came with a slp pipe and silencer on it. I installed the slp big horn air intake, and had the dealer replace the fuel filter, check the oiler cable and pump setting and install V Force 3 reeds plus a slp clutch kit and regear from a 22T to a 21T. I have NGK plugs in at .28 gap. I'm running polaris VES gold oil. As mentioned I just purchased it in fall...1/2 a tank of gas from previous owner. I filled the rest w/ 100% 87 octane. Played a bit and refilled the tank (about 4 gal. worth) of premium gas.

Here's the problem......

It backfires thru the exhaust intermittently on de-acceleration. When I'm coming off the field and going into a turn it backfires right before I get into the turn. I've put 240 miles on and its backfired maybe 5 or 6 times.

The other part of the problem is this....

It has the perc reverse and I had to back up a few times and when I hit the button, as the engine drops in rpm it gets to the low point, backfires then kills the motor. This happened about 4 times in a 10 minute period. Again, this problem is intermittently as well. I use reverse to back into my garage everyday and has never happened before.

I called slp and they are suspecting low grade gas at this point. I'm in the process of adding a bit iso-heat (the red bottle) and lucas octane boost(recommended by slp) and thru my calculations I'm at a 58 : 1 ratio in oil consumption which I thought to be on the lean side and slp agreed and said to put it about 40 : 1. Thur is my appointment to up the oil ratio at the dealer. Other than the backfiring issue, the sled runs GREAT, pulls hard, and has all the power that you would expect from that motor w/ its added goodies.

Am I on the right path??????
Any ideas????????

 

[maj16]

Not enough back pressure with the can

 

[jimfsr]

Sounds like unburned fuel in the pipe. Aftermarket pipes and cans will do that sometimes. The ignition reversal would easily ignite that fuel, and rolling off the throttle will do the same thing as the ignition timing changes with throttle and rpm input. Poor fuel might contribute to it, so try some premium in it, or mix it with what you have. Octane boosters and additives are mostly alcohol, which absorbs water, I wouldnt run too much of that in there.

 

[srt20]

Get rid of the NGKs put in Champion. Put premium fuel with no ethanol. Leave your oil ratio alone. Ride the heck outta it and enjoy. Backfire and stall will be gone. OH and most important, let the sled warm to 80*F before you touch the throttle.


P.S. I didnt read your post good enough. Do all of those things plus, check your donut gasket between the pipe and y-pipe. If thats good, also check the bolts and or gasket between y-pipe and cylinders. I missed the backfire on deceleration part.

 

[snow_monkey]

I second the backpressure issue, you need back pressure.

 

[snow_monkey]

Check for cracked porcelain on the plug, just in case, and all exhaust fittings for leaks.

 

[t660redrocket]

This is bad fuel. Dump it all out and start over. Don't leave any in there. When you put new in there just use the 87 octane at the pump, especially in December. Here's my theory on that.........Most people use 87 Octane in their cars which means the gas gets used faster which means it's fresh all the time. I hate to guess how old the premium fuel is at these stations in the yoop, especially in December. If your owners manual says 87 octane is good, then use 87 octane. It'll be way fresher gas and you won't need any of the additives either. JMHO.

 

[raceinsnow]

Don't use 87 octane in any Polaris sled!( If you have to because there is nothing else available there is a switch for that) They all call for premium fuel.The theory about the premium fuel being old and unused at the gas stations is wrong.You are right about the stations using more 87 octane then 93 but they use the 93 octane up also,think about it why would they want to sit on that much product and not sell it.When they receive the fuel they would get for example 2000 gallons of 87 and 500 gallons of 93.I would also use NGK plugs because the champions have a history of the porcelain breaking at the tip and falling in the motor and trashing the cylinder.

 

[mudorsnow]

Thanks guys. In the process of working the fuel issue out and that leaves one question.....how do I get more back pressure into the system? Checked the exhaust fittings.......no leaks. 4" fallin and still comin and I'm self employed....I think I need to call in sick and do some testing today!!!!!!

 

[xcsp]

Regarding the use of Champion or NGK plugs, I personally would stay with the Champion plugs if that is what Poo recommends. I put in NGK's in a Polaris a few years back (that had Champions plugs since new)and it didn't run well afterwards, put some Champion plugs in and it ran fine. Never had an issue with either brand of plug otherwise.

(I do recall reading that some have found that the NGK's did help with a stumbling issue with the 4-injector CFI engines.)

Curious to see what mudorsnow finds as the cause of the problem with his sled.

 

[t660redrocket]

87 Octane is just fine for a regular ol Polaris 600. Look at the owners manual. Don't take this as arguig because I'm not but unless you know the turnover of that fuel in the underground tanks I say the 92 Oct. is probably much less fresh than the 87 Oct.

 

[mudorsnow]

Well guys, I did some testing today. I had champion plugs and it didn't seem to like em. Changed to the ngks and the backfire still exists. I drained the gas and replaced with 93 100% gas with a splash of iso-heat and some lucas octane boost. No backfires yet but didn't get alot of trail time. But check out the pics below and this is what the baby can do. Still taking all advice into consideration and will keep you posted.

 

[snosgr8]

In Wisconsin, I alway fill up with 92 oct. Even though some say the 87 is fresher, it has ethanol in it. I try to keep that out of my small engines.