By REX EVRHART on Unrecorded Date: Edit

I NEED SOME HELP. I HAVE A 2001 MAX 4 AND EVER SINCE I BOUGHT IT NEW IT HAS BACKFIRED WHEN I GO TO CUT IT OFF. IT SOUNDS LIKE A 22 GOING OFF. DOES ANY ONE ELSE HAVE THIS PROBLEM AND WHAT CAN I DO ABOUT FIXING IT.

By david berger (Davidrrrd) on Unrecorded Date: Edit

REX YES THERE ARE A FEW FIXES BUT THAT HAPPENS TO ALMOST ALL OF THEM, HEH HEH HEH
HUMPHREYS TRAILS SOUND LIKE A SHOOTING RANGE WHEN A GROOP STOPS TO CHAT,BIG BALL OF FLAME COMES OUT THE EXAUST TOO!~ SOME TWEEK FUEL MIX AND SOME CHAINGE IDLE ADJUSTMENT, IM SHUR SOMONE WITH A FIX WILL RESPOND SOON, TILL THEN DON'T PANIC,
BUT DON'T SHUT IT DOWN IF THERES SOMONE NEAR EXAUST,(YOU DON'T WANT TOO BURN ANYONE)
I HAVE A SPARK ARRESTOR ON MY 2 STROKE, I OFTEN WONDER WHY THEY DON'T PUT THEM ON THE BRIGGS ENGINES, IT WOULD CUT THE FLAME ANYHOW

By Larry Houghton on Unrecorded Date: Edit

Rex.Try letting it idle for a few minutes before shuutting it off.This lets the exhaust pipes cool down a little and either won't pop as bad or not at all.

By REX EVERHART on Unrecorded Date: Edit

THANKS FOR SOME OF THE INFO,BUT THESE MACHINE ARE SUPPOSED TO BE GREAT FOR HUNTING AND THATS WHAT I MOST OF THE TIME USE IT FOR. AS I GET CLOSE TO MY DEER STAND THE QUICKER YOU GET IT TURN OFF THE BETTER YOUR DAY MAY BE. (NOISE THAT IS)I JUST HATE TO SET THERE (A FEW MINUTES) AND WAIT FOR WHAT I THINK IS THE RIGHT TIME TO CUT THIS MAX OFF.I HAVE ALREADY BE ASK BY OTHER HUNTERS AS TO WHO SHOT BEFORE DAYLIGHT. WOULD SETTING THE SPARK PLUG GAP MORE OPEN HELP?

By Garyb (Garyb) on Unrecorded Date: Edit

My Max II did the same thing and I put in a set of A.C. rapid fire plugs and it hasn't done it sense.

By Roger Smith on Unrecorded Date: Edit

Heh, a Man once told me that his Max always got the first shot off on hunting trips.. happens on Argo's too.

When you turn the key off, the spark plug of course quits firing, but the engine is still turning and air and fuel is brought into the engine. Since the plug doesn't light it off, it gets pumped into the exhaust, where some hotspot of carbon, or a glowing piece of wire from a wire fed welder protruding into the muffler, lights the unburned fuel.

Someone got a replacement muffler under waranty, forgot what vehicle he had.

Letting the engine idle before turning off the key lets the hotspot in the exhaust system cool. How long depends on ambient temp, engine temp, other things. Coming to a stop on a hot day after hard riding will take longer to cool than an easy ride in winter.

Spark plug has no effect since it's not sparking at the time of the bang. Mixture could affect it, a lean mixture makes things run hotter. The limiter cap on my Briggs didn't stay intact very long. Have to take the idle jet out to clean the carb anyway.

In the 80's when computer controlled car engines came along with very stingy (lean) carburetors, they had electric solonoids to hold the throttle open to idle speed. When the key was turned off, the solonoid dropped away and the throttle shut more completely, cutting off the fuel in the idle circuit. That prevented "diesling" or "run on", the failure of the engine to quit running immediatly. The AATV backfire and car diesling are different symtoms of the same problem, fuel getting lit in the exhaust side of things by something glowing hot.

I think the best fix would be an idle solonoid, I don't know if anyone makes a kit but the solonoids could be bought new or used and fabricated to fit the AATV.

By Russell Meixner on Unrecorded Date: Edit

hold it up to about 1/4 throtal and turen it off i have a 2000 max IV with the 25 hp and if i rember rightly right in the book that came with it on the engine it says to do that

By David Keeso (Argomag) on Unrecorded Date: Edit

Why would you want to give it more throttle when shutting down?? I don't mean to sound like a smart ass- I really don't know why. I would personally think that by giving it throttle, it would let more gas in allowing more to backfire. I have found that just letting the engine idle for about 10 seconds before shuting down solves the problem. The times my ARGO backfires are usually only in the summer months. If it hasn't been run for very long and the engine hasn't really warmed up much (engine oil temp gauge hasn't moved yet) and I shut it off before fully stopping it fires and scares the crap out of me, and anyone in earshot range. One weekend, I had a friend at the cottage and we were out on the road. Friends of ours came out of their driveway and I shut it off before I let the throttle off and it backfired. It scared the woman so bad after 10 minutes of talking she was still scared. She accused me of trying to make "her lungs jump" I don't know why the lungs but oh well. Just let the throttle off and idle for a few seconds and you should be alright.

By Kevin Percy on Unrecorded Date: Edit

Opening the thottle when the engine is turning over slowly at shut-down probably may reduce the amount of vacuum in the carb so the engine pulls less fuel into the motor. Just a guess, but if it works, it works.
I have two old snowmobiles (1970, 1973) and a lawn tractor (1982) that do the same thing.

By mikesmax on Unrecorded Date: Edit

MAX IV backfire on the max IV with the KOHLER the KOHLER comes with a shutdown solenoid thats why you have to give it about half throttle then shut it down.

By Pnorman on Unrecorded Date: Edit

Yeah, They make great Turkey locators ! Seriously let idle a little then hold throtle at 1/2 and shut down. If you still have problem and trying to be quite, kill it with the choke.

By Alfred Cushman on Unrecorded Date: Edit

Set Idle at 1400-1500RPM, that will fix it.

By terry harrison (Th3) on Unrecorded Date: Edit

i kill my 900-t with the choke when i dont want it to backfire. it takes a few more revolutions of the starter to get it fired back up but thats fine with me.

By Kevin Percy on Unrecorded Date: Edit

I would be worried about possible downsides to killing the motor with the choke.
You are essentially flooding the engine, and that extra gasoline is taking the oil film off of the cylinder walls. Then while you do that extra cranking to get it going again, the rings are rubbing against the unprotected cylinder. Also, the extra fuel may seep into the crankcase and dilute the oil in the sump, so the motor gets a little less protection while it is running.
Just my $0.02. This would only apply to a four stroke of course, a 2 stroke may benefit from the extra fuel/oil mixture (?) while it sits.

By terry harrison (Th3) on Unrecorded Date: Edit

im not much on combustion engines and correct me if im wrong, but if the key just turns off the sparkplug then the same amount of gas is going into the chamber as if you pull the choke to remove the air, with the key still on (which kills the combustion from lack of air not addition of gas?). i dont think the throttle position has changed. the only difference is less air because of closing the choke. the amount of gas does not increase. the choke just removes air and does not add gas, right? i would think holding the throttle 1/4 open when turning the key off would cause more wall washing than pulling the choke.

i think, by leaving the key on and pulling the choke, the sparkplug would still burn what gas is in the chamber till the air runs out. but if you kill the spark with the key, the chamber immediately fills up with unburnt gas and causes the backfire as it spills out into the hot muffler. the more i think about it the more it seems that less gas would be in the chamber because of leaving the sparkplug on and pulling the choke. i may be way off base with this. im just thinking out loud here.

By Attex Bob on Unrecorded Date: Edit

the choke just removes air and does not add gas, right?

Seems like it should be that way but it's not. When you pull your choke cable out, you are doing this: It pulls a big time vacuum on the main circuit, which adds a ton of fuel. It does not really do anything to the air except pull harder on the main circuit. There is another type of choke on most 2 strokes called an enrichment circuit. It just dumps a ton of fuel into the engine through a port.

Gas engines, like and run on pretty close air to fuel ratio's. Anything more than about 10 to 1 and it won't pop, anything less than about 17 to 1 and it won't pop. When you choke the engine you are putting that fuel ratio more than 10 to 1 so when the gas hits that hot spot in the muff it won't go off like a cannon!!!!

Like Kevin said, this is not a good thing for the engine.