SX Backfires

I

IgoFast

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Joined
Jan 7, 2010
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61
Age
37
Location
Wisconsin Rapids WI
My 1999 vmax 600 seems to have a backfiring problem.
It starts just fine when the motor is cold or if it had been sitting for a while.
If I shut if off at the gas station to put gas in it and then start it to leave it will backfire on the first pull and usuially stop the roap dead in its tracks. After it backfires I have to hold the thorttle open a little bit in order to get it to start.
I feel kinda bad when I scare the crap out of some little kid in a car seat or some old lady putting gas in her car.
Any help would be appreciated.
thanks
 
Sounds to me like it's the safety switch in the throttle handle. Unzip the handlebar pad cover and trace the wiring from the kill switch to the plug under the pad. Unplug the kill switch and see if it still does it. Don't confuse the handlebar warmers with the kill switch wiring. Just shut the engine off with the key when your done checking as unplugging the kill switch will disable it. I Had a similar problem last season with my 99 SX 600 and that's what it ended up being. Give it a shot.
 
I have a 02 vmax 600 that is backfiring exactly the same way you described in your message. Did you try disconnecting the kill switch? Did that work?
 
yeah I did unhook it but it still does it. I figured out if I pull the motor over slowly for the first pull then pull it, it wont back fire
 
I have to let my '02 600 triple idle for a few seconds before I shut it off or it'll back-fire when I start it up. Has done this since it was new.

Derek
 
I had a old SRV that did the same thing from new (only on a warm start up) I found that a 1/4 throttle when I pulled the rope was a quick cure.
 
AUGDOG said:
I had a old SRV that did the same thing from new (only on a warm start up) I found that a 1/4 throttle when I pulled the rope was a quick cure.
Click to expand...


Thats usuialy what I do, other wise it wont start.
I did turn the idle down to around 1200 rpm yesterday but I didnt get a chance to see if it made a difference.
I usuially let it idle untill I can get my helmet and gloves off the I will turn the motor off, it dosent seem to make a differnce.
 
let the motor rev down to an idle before turning it off. the excess gas in the motor /exhaust will cause it to backfire. old phazer does the same thing.
 
Here is a question for yas with the backfiring problem? When you come to a stop and let it idle down does the idle hang then come down or does it just go to normal idle?
 
I just logged on to post about this same problem, I am concerned about other possibilities for the same problem. I did the head mod earlier this season and everything was pretty good no coolant leaks. But last week went on a 3 day trip and this started at the end of the first day. So I will pull the motor over once or twice slowly to clean it out then it will start. I had to re-jet when I did the mod but I'm sure thats fine the plugs are perfect every time. It did it with pilot at 2 turns and pilot at 1 1/2 turns. Idle about 1500. It has always hung a little higher like 2000-3000 for a sec then down. Could this be reeds gone bad (getting oily in the air box) or a problem starting in the head gasket. Just seems like motor isn't right and is burning a little to much fuel. any idea's???
 
I have the exact same sled and had this problem. It ended up being the carb setup. However, one of the guys here in T.Y. mentioned that when they backfire the case reeds can be cracked. After getting the backfiring stopped by putting 45 pilots in and then cleaining and adjusting the carbs I checked the reeds. Sure enough, they were all cracked and had to be replaced. The new reeds really smoothed out the motor from idle thru WFO and gave me way better power and throttle response.

Here's what I did to my carbs:
1. swapped stock 42.5 pilots for 45's
2. Raised the clip on the needle so that it is centered on the second to last postion
3. Went (2) full turns out on the idle screws
4. Replaced all the case reeds.
Mills
 
Thanks Mills I was hoping for someone to have has this problem and fixed it! I was leaning on reeds a little since there seems to be a little more oil than usual in the air box. Had you done any mods to the engine to warrant the pilots being changed. The only reason I ask is they have been in there since new and never gave any trouble. and this problem is new. I will bee looking at the reeds later this week tho. Thanks!
 
On the oil in the airbox, I have that same problem with SX600. I've had the airbox and carburetors out about 20 times this winter (don't ask). And every time I pull the cover off the airbox, there is about 1-2 teaspoon fulls of oil in the airbox. Not sure why, but I'm leaning towards needing a new oil pump.
 
I did the head gasket, air box and silencer mods to my sled which is why I went with the bigger pilots. Oil in the air box is common with these sleds. I still get the teaspoon or two amount in mine during the season.
 
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