Why is my sled doing this????????????????

Why is my sled doing this????????????????

Post by LBZ35 » Fri, 05 Jan 2001 10:30:22


When I stop it shoots a fireball out the exhaust!  Mostly after a long run
at high RPMs, like across a lake or field, doesnt happen with a quick blast,
most of the time when the sled is under load or driving in deep powder for
example.

The backfire happens 1-2 seconds after I shut off the sled...  What could it
be?  too rich on the mains causing a fuel buildup in the pipe???  I have a
330 main in now, stock was 350.

 
 
 

Why is my sled doing this????????????????

Post by Kevin 98 F583 » Fri, 05 Jan 2001 11:20:54

Quote:

>When I stop it shoots a fireball out the exhaust!  Mostly after a long run
>at high RPMs, like across a lake or field, doesnt happen with a quick blast,
>most of the time when the sled is under load or driving in deep powder for
>example.

>The backfire happens 1-2 seconds after I shut off the sled...  What could it
>be?  too rich on the mains causing a fuel buildup in the pipe???  I have a
>330 main in now, stock was 350.

   My sled would do this too, right from brand new. I'm just guessing,
but I figure it's because of unburned gas building up in the exaust
system during high RPM running.This might not be it, but I always let
my sled run for about 10 seconds or so after stopping, to let the RPMs
come down. I figure this also clears out the exaust of the unburnt
gas. I've never had a backfire since I started doing this every time.

Kevin 98 F583D

 
 
 

Why is my sled doing this????????????????

Post by Chris Tatary » Fri, 05 Jan 2001 13:51:45

you are not letting your sled cool down long enough before shutting it off.
after a high speed lake run at WOT let it idle for a minute to let it cool
instead of shutting it off.

chris


Quote:
> When I stop it shoots a fireball out the exhaust!  Mostly after a long run
> at high RPMs, like across a lake or field, doesnt happen with a quick
blast,
> most of the time when the sled is under load or driving in deep powder for
> example.

> The backfire happens 1-2 seconds after I shut off the sled...  What could
it
> be?  too rich on the mains causing a fuel buildup in the pipe???  I have a
> 330 main in now, stock was 350.


 
 
 

Why is my sled doing this????????????????

Post by kewx » Sat, 06 Jan 2001 01:42:58

Quote:

> >The backfire happens 1-2 seconds after I shut off the sled...  What could
it
> >be?  too rich on the mains causing a fuel buildup in the pipe???  I have
a
> >330 main in now, stock was 350.

////

Put the stock jet back in and see if it goes away.
kw

Quote:

>    My sled would do this too, right from brand new. I'm just guessing,
> but I figure it's because of unburned gas building up in the exaust
> system during high RPM running.This might not be it, but I always let
> my sled run for about 10 seconds or so after stopping, to let the RPMs
> come down. I figure this also clears out the exaust of the unburnt
> gas. I've never had a backfire since I started doing this every time.

> Kevin 98 F583D

 
 
 

Why is my sled doing this????????????????

Post by LBZ35 » Sat, 06 Jan 2001 04:35:00

no it did that ever since i bought it, that was one of the reasons I decided
to try changing jets.... along with the poor gas mileage!


Quote:

> > >The backfire happens 1-2 seconds after I shut off the sled...  What
could
> it
> > >be?  too rich on the mains causing a fuel buildup in the pipe???  I
have
> a
> > >330 main in now, stock was 350.
> ////

> Put the stock jet back in and see if it goes away.
> kw

> >    My sled would do this too, right from brand new. I'm just guessing,
> > but I figure it's because of unburned gas building up in the exaust
> > system during high RPM running.This might not be it, but I always let
> > my sled run for about 10 seconds or so after stopping, to let the RPMs
> > come down. I figure this also clears out the exaust of the unburnt
> > gas. I've never had a backfire since I started doing this every time.

> > Kevin 98 F583D

 
 
 

Why is my sled doing this????????????????

Post by kewx » Sat, 06 Jan 2001 08:21:30

For better mileage,.. I always just change the jet needle clips by 1/2 shim.
kw


Quote:
> no it did that ever since i bought it, that was one of the reasons I
decided
> to try changing jets.... along with the poor gas mileage!



> > > >The backfire happens 1-2 seconds after I shut off the sled...  What
> could
> > it
> > > >be?  too rich on the mains causing a fuel buildup in the pipe???  I
> have
> > a
> > > >330 main in now, stock was 350.
> > ////

> > Put the stock jet back in and see if it goes away.
> > kw

> > >    My sled would do this too, right from brand new. I'm just guessing,
> > > but I figure it's because of unburned gas building up in the exaust
> > > system during high RPM running.This might not be it, but I always let
> > > my sled run for about 10 seconds or so after stopping, to let the RPMs
> > > come down. I figure this also clears out the exaust of the unburnt
> > > gas. I've never had a backfire since I started doing this every time.

> > > Kevin 98 F583D

 
 
 

Why is my sled doing this????????????????

Post by at » Sun, 07 Jan 2001 00:28:32

Quote:

> When I stop it shoots a fireball out the exhaust!  Mostly after a long run
> at high RPMs, like across a lake or field, doesnt happen with a quick blast,
> most of the time when the sled is under load or driving in deep powder for
> example.

> The backfire happens 1-2 seconds after I shut off the sled...  What could it
> be?  too rich on the mains causing a fuel buildup in the pipe???  I have a
> 330 main in now, stock was 350.

That is, usually, a result of turning the sled off, before you let it
idle down to a normal idle. WOT causes the pipe to get really hot,
then, when you turn it off, the engine keeps on turning for a while,
which pumps the normal gas, and air, mixture through the system, and
into the pipe, without burning it. If the pipe is hot enough, it can
ignite the mixture, and since it is close to the optimal air to gas
mix, it all burns at one time (just like it would in the cylinder, if
the spark plug had ignited it), hence, the "explosion". Most of the
time, this is an indication that you are running pretty close to
optimal, and it doesn't seem to hurt anything, but, it is always a
good idea to let the sled idle down to it's normal idle, before you
turn it off. That way, it cools the pipe a bit, and it doesn't pump as
much fuel mix into the pipe, since it stops turning in less time.

Hope this helps...
--
From the PC of Doug Bissett
doug.bissett at attglobal.net

 
 
 

Why is my sled doing this????????????????

Post by JohnSowar » Sun, 07 Jan 2001 02:43:25

1/2? LOL

JJS