Suzuki KQ 300 carburetor advice
Sharky
running rich. I can tell this because of the dark black soot when I pull
the spark plug. Also, it will idle fine, but when you give it more than 1/4
throttle, it stumbles and hesitates, sometimes it will stall out. It has
the stock jet needle and needle jet and I have already pulled the carburetor
out and cleaned it, it was pretty clean. The only jet that is not stock is
the pilot air jet, which is 135 instead of 120. Will leaning out the pilot
screw 1/4 - 1/2 turn help the 1/4 - 3/4 throttle hesitation problem?
The top end of the engine was recently rebuilt on this machine, new piston
rings, new intake valve, both valve seals and both seats were resurfaced.
The timing chain and starter clutch were also replaced, as well as the head
and base gaskets. It was working very well, I even had it on a rally 3
weeks ago that was ~100kms and about 2500ft elevation. Up until then, I had
changed the oil and filter twice, and replaced the spark plug. The engine
at that point was not completely broken in, it had about 15-20kms on it from
me driving it around the yard. When I came back from the rally, I had to
fix the muffler because the homemade bracket that was welded on it broke and
it was rattling around. To remount the muffler, I moved it back about 1/2",
which I think may have pulled it out of the exhaust pipe, causing it to lose
backpressure. This may be why it was acting up, but I am not 100% certain.
I pushed the muffler back today and it seemed to help, but the midrange
throttle is still not right.
Any help with this would be greatly appreciated.
Sharky
Hustlin' Hank
There could be many things that cause your problem. First, it sounds
like it is getting LEAN and stalling rather than getting RICH and
stalling. But I can't tell you for sure unless I personally tested it.
It could still be a LEAN mixture in that throttle range, but the plugs
show black because it is run mainly above that "stall" range.
The loss of back pressure MAY cause your symptom too. Or, a
combination of the two.
IF you are sure it is running rich, you can do 2 things....Raise the
clip on the needle, or put the original pilot jet back in and see what
happens.
Hank
Sharky
Clymers manual and a few years of mechanical experience, plugs that run lean
show white or light color soot. Normal burning plugs have a brown or light
tan color. Dark indicates a rich mixture, which is what I believe is
happening with my machine. I've got the mixture screw turned out to about 1
3/4 turns and it is still very lightly sputtering under load, but not nearly
as bad as it was (it started at 2 1/4 turns out). It seems the more I turn
it in, the better it runs, but the more I have to turn up the idle speed.
The exhaust is now fixed, the exhaust pipe is now completely inside the
muffler pipe and clamped tight with a U-clamp. Before it was puffing
exhaust out where the two pipes join, which I believe was causing a
backpressure issue.
I still haven't ruled out the carburetor, or a faulty jet, to be specific.
As far as the oversize pilot air jet, I bought the ATV this way and
unfortunately, I don't have the 120 jet that it calls for from factory. If
I raise the clip on the needle, it will be at its highest position. On the
other hand, I have a second carb from a parts bike that has a P6 needle jet
and larger jet needle (the factory is a P4). I may swap these two jets into
my carb and see what happens. If it is right now running lean, like I think
it is, the oversize jets should make it run a tad richer and may resolve the
problem with the 1/4 - 3/4 throttle response. I won't be able to try this
until after work tomorrow, so I will give it a go and post the results.
Sharky
"Hustlin' Hank" <nineb...@aol.com> wrote in message
news:1db054fe-e3ce-44d8...@m15g2000yqm.googlegroups.com...
Hustlin' Hank
> Thanks for the reply. First off, from online searches, reading up in the
> Clymers manual and a few years of mechanical experience, plugs that run lean
> show white or light color soot. Normal burning plugs have a brown or light
> tan color. Dark indicates a rich mixture, which is what I believe is
> happening with my machine. I've got the mixture screw turned out to about 1
> 3/4 turns and it is still very lightly sputtering under load, but not nearly
> as bad as it was (it started at 2 1/4 turns out). It seems the more I turn
> it in, the better it runs, but the more I have to turn up the idle speed.
> The exhaust is now fixed, the exhaust pipe is now completely inside the
> muffler pipe and clamped tight with a U-clamp. Before it was puffing
> exhaust out where the two pipes join, which I believe was causing a
> backpressure issue.
>
> I still haven't ruled out the carburetor, or a faulty jet, to be specific.
> As far as the oversize pilot air jet, I bought the ATV this way and
> unfortunately, I don't have the 120 jet that it calls for from factory. If
> I raise the clip on the needle, it will be at its highest position. On the
> other hand, I have a second carb from a parts bike that has a P6 needle jet
> and larger jet needle (the factory is a P4). I may swap these two jets into
> my carb and see what happens. If it is right now running lean, like I think
> it is, the oversize jets should make it run a tad richer and may resolve the
> problem with the 1/4 - 3/4 throttle response. I won't be able to try this
> until after work tomorrow, so I will give it a go and post the results.
>
> Sharky
Now I am confused. You state in this post that you think it is running
lean, but in your original post you said it was running rich.
I suggest you start with stock jetting (both main and pilot jet) and
move the clip to the middle position and go from there.
Hank
Sharky
replacing the needle jet and jet needle might make it run leaner. As far as
the carb settings go, everything is stock, except for the pilot air jet, and
the setting of the pilot screw. The manual says it should be 2 7/8 turns
out, but it is more like 2 - 2 1/4, to make up for the larger pilot jet.
Without picking up a carburetor kit, I cannot completely restart from
factory settings. But because of the way it had been running before, I
don't believe I should have to start from factory settings.
It's pretty close right now, I've been slowly turning the pilot screw in 1/8
increments, and every turn seems to make it a bit better. The last two
turns haven't made much difference and I'm beginning to wonder if I might
have a loose wire/connection somewhere. Test driving it, sometimes it runs
perfect and then all of a sudden, it will sputter and bog. Usually it only
does this a couple times and then runs normal again. Especially in high
range under load. Low range it doesn't seem to happen as much.
I may end up having to rebuild the carb altogether. It was taken apart when
I bought the machine, but I used the same parts to rebuild it. The machine
was beat up quite a bit when I bought it, but once the engine work was
complete, was running very well considering the fact. I'll keep messing
with it tonight and see what I can come up with.
