Backfiring

M

Morley

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Joined
Nov 8, 2004
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Canada - Above you
Is there a main cause as to why a sled will backfire?

It was fogged in march and cleaned the carbs.
Now I cleaned my carbs again on the weekend, made a slight adjustment on my
idlde air screws
to put them at stock spec and fired it up for the first time this season and
it runs semi ok, but when I give it gas up to about 3500rpms or so
it sends one nice loud backfire.. So I set my carbs back to where they were
at previously and still have pretty much the same condition.
Any ideas? Almost seems to be running on 2 cylinders.
I also noticed a bit of oil comming out the donut ring where the exhaust is.
Could it just be that theres alot of gas/oil in the bottom of the engine?
Im sure it would have burned off by now though?
Looking for some ideas?

I also adjusted my oil pump gap, it was at 33mm, now I set it to 26mm.
Maybe I should go back to where it was at? BEcause it ran pretty good like that?
Thanks


Sled= 97 sx700
 
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Sounds like you have a slightly fouled plug and once in a while it will fire and burn all the fuel sitting in the piston.. try changing the plugs.
 
have you done any mods to sled? I went through the same thing last year after I added a silencer. I had to increase my pilot jet one size other wise it would backfire all the time. Since then, no backfiring. Also I've heard that chipped or cracked reeds will cause a sled to backfire. Maybe check these if you have your carbs off again.
 
MrSled said:
mods for sure can cause this as blueballer has said.
Click to expand...

No I have not done any mods.
I'll try putting in some new BR9ES's tonight and see what that says
and post my results tomorow.
Thanks guy's.
 
my 600 triple has done this since day one if I don't let it idle for a few minutes to warm up, It runs perfect anyother time.
 
MrSled said:
Sounds like you have a slightly fouled plug and once in a while it will fire and burn all the fuel sitting in the piston.. try changing the plugs.
Click to expand...


Put brand new plugs in last night, took the exhaust off to make sure
there was no gas in there etc. And fired it up, runs good
let it idle for about 3 minutes or so, start to rev it up, when I hit
about 3500rpms it send out one nice backfire.
Take plugs off again, they are a little wet (fuel) on all 3 of them.
Whats going on?

Could it be something with my idle air screws?
I'm going to probably take it in to the dealer if I can't figure this out in the next couple of days :0(
 
make sure everything is set to stock on the carbs....is your TORS stuck.....how tight is your throttle cable?? Check the reeds for broken peddles. If you want give Larry at North Contry Yamaha a call 715-453-2626. The guy is a walking shop manual...very sharp.
 
MrSled said:
make sure everything is set to stock on the carbs....is your TORS stuck.....how tight is your throttle cable?? Check the reeds for broken peddles. If you want give Larry at North Contry Yamaha a call 715-453-2626. The guy is a walking shop manual...very sharp.
Click to expand...

Sorry not familiar with the TORS term? What is this?
The throttle cable is not overtight.
I took one reed off and it looked perfect.. Hope I put it back on properly?
They are pretty straight forward from what I can see right.
 
even after it warms up will it do this???? you should vary the throttle from 2500 to 3000 rpms while apllying a little choke as needed until it fully warmed up. Warm would be the when the heat exchanger on the running boards feel warm, then try applying throttle past 3500 rpm and let me know if it still backfires. At this point you may have so much unused fuel sitting in the pipe and it needs to be fully warm. TORS, is the throttle over ride switch....it 2 wires of the carbs , if need be we can bypass this.
 
Where is the backfiring occuring, @ the reeds or exhaust? Have you checked your pipes for any blockage?
 
MrSled said:
even after it warms up will it do this???? you should vary the throttle from 2500 to 3000 rpms while apllying a little choke as needed until it fully warmed up. Warm would be the when the heat exchanger on the running boards feel warm, then try applying throttle past 3500 rpm and let me know if it still backfires. At this point you may have so much unused fuel sitting in the pipe and it needs to be fully warm. TORS, is the throttle over ride switch....it 2 wires of the carbs , if need be we can bypass this.
Click to expand...




When you say unused fuel in my pipe, are you refering to the exhaust pipe?
Because I took it off last night and it was dry.

I will fire it up, let it run until the heat exchangers are warm
and then rev it up to 3500rpms or more and will post my results tomorow
morning. Pretty sure I had it warm when I tried this already, but I'll make sure tonight. Right now I am at work.


As for where it is backfiring, Im pretty sure that its at the exhaust side,
but Im not a professional, so thats just was I think is happening.
No I haven't taken my muffler off.. maybe theres a mouse in there.. lol
I'll be sure to check it.
 
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MrSled said:
even after it warms up will it do this???? you should vary the throttle from 2500 to 3000 rpms while apllying a little choke as needed until it fully warmed up. Warm would be the when the heat exchanger on the running boards feel warm, then try applying throttle past 3500 rpm and let me know if it still backfires. At this point you may have so much unused fuel sitting in the pipe and it needs to be fully warm. TORS, is the throttle over ride switch....it 2 wires of the carbs , if need be we can bypass this.
Click to expand...

Check this out...
I unplugged all of my wiring and re-plugged them in to make sure everything was
ok, and loosened my throttle cable a tad more, and checked the entire exhaust
and it was empty (no mice:0)
Installed the clutch belt (I was sure I was going to have to drive it on my truck to take to the dealer)
And fired up the sled, first pull no hesitation whatsoever.
And let it run for about 6 minutes until I felt the heat exchangers were warm.
Reved it up, no backfire...
Reved it up to 4000rpm, no backfire..
Reved it up to 8000 rpms, no backfire...
Kept trying to get it to backfire, but I couldn't..

Strange.....???


So could it be something to do with when I rev the engine up with
no load (no clutch belt installed) that it backfires, and when the belt is installed (giving it a load at 4000rpms and up) that it does not backfire?
I was tempted to take it for a run up the street and turn around to come
back home :0) Just to make certain that it's gone..
But what could my problem have been??
Can someone explain?

Thanks,
 
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it was either the TORS system or it was the cold blooded settings of that sled. If you dont let them warm up they will backfire or foul plugs....but it all fixed ;)!
 
Yes it is indeed fixed... I doubt it was the TORS because
like I said the throttle cable already had a bit of play in it.
I just gave it a tad more..
So I assume then that it was the "Cold Blooded Settings" of my sled :0)
 
I think it was your TORS............. Mine is plugged in half the time and bypased the other half.

Do you understand how to bypass it in case you need to do this on the trail?? If not several people can help.

Here is my way to describe it.... find the two wires that go to the carbs, unplug them and plug the two that are not on the carb into each other. Or if you are not sure which ones to plug into each other just do it to both pairs of wires.

Tod ;)!
 
Tod said:
I think it was your TORS............. Mine is plugged in half the time and bypased the other half.

Do you understand how to bypass it in case you need to do this on the trail?? If not several people can help.

Here is my way to describe it.... find the two wires that go to the carbs, unplug them and plug the two that are not on the carb into each other. Or if you are not sure which ones to plug into each other just do it to both pairs of wires.

Tod ;)!
Click to expand...


Thanks, I appreciate the info..
However the directions on how to exactly bypass TORS I am not exactly
clear on...
Can someone describe this to me differently perhaps?
 
Morley said:
I also noticed a bit of oil comming out the donut ring where the exhaust is.
Click to expand...

You might want to replace the Donut gasket and use an exhaust sealer on it. When that seal is cold it leaks and a little "New Oxygen" is all that is needed to relight the unburned exhaust gases.
 
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