Pinging Krusty

Hi again.. .

Well I am making progress on my 79 honda 750 Ltd...I checked the plugs
which looked litke they were running a bit lean, so what I did was see just
where the 4 lil screws were turned out to. They were about 2 turns out at
that point, so I turned them out to 2 1/2 turns and most of the sputtering
has gone away, in fact it doesn't start sputtering until at least 7000 or so
rpm. I turned them out another 1/4 turn to 2 3/4 turns.
My question now is how far out should they actually be before
considering a larger jet? I am running the kerker exhaust (4 into 1) with
105 jets. I am thinking that maybe a 110 would work with the screws turned
in a little bit would yield about the same settings but with more
flexibility in adjustment. Or would it be ok to keep the 105's and run the
screw at the 2 3/4 turn setting?

Fwed

 

The Factory Pro site says that the pilot screws have no effect after
about 3.5 turns. So that's when you'd go up one idle jet size.

You can stop tuning whenever you're satisfied with the results. #105
main jets sound a little small to me, it would cost you at least $20
for new #110 main jets, but they would pass about 10% more fuel
(assuming you have enough vacuum to suck the fuel out of the float
bowls).

Remember, though, the main jet has its effect at wide open throttle.

midrange. Changing mainjets won't help if you're not opening the
throttle wide open.

I suppose that you could tell whether you were just having that
well-known bad interaction with the 4-into-1 pipe if you could attach a
vacuum gauge to the synchronizing port on one cylinder and see what the
gauge reads at the RPM where you're having the problem.

At wide open throttle the vacuum will drop off. But carburetors will
always show *some* vacuum because of the venturi restriction. It seems
to me that if your Kerker is causing reverse flow through the carb, you
might see about 3/4 to 1 pound of *positive* pressure on the vacuum
gauge when it happens...

 

My question now is how far out should they actually be before

OK... well at 2 3/4 turns out, I am pretty satisfied with the
results....after all, although it is alot of fun to open it up at wide
throttle, I am not going to be racing this bike where I need to do that...it
excellerates much more smoothly, and I am even considering another 1/8 turn
on each screw, but I want to run it a little bit and check the plugs again
before I actually do this to see that I am not burning too rich, which I
really doubt at this point....
There has really been a tremendous improvement just by adjusting the
pilot screws.... I finally had some time today to go thru and check plugs,
regap to 26, and make sure the pilot screws were turned out the same
amount... I did find one (cylinder 2) which was out a bit more than the
rest, but thats taken care of now.... I am much happier with the way the
bike is running now... I think I will maybe make another small adjustment
and leave it at that....
Before it was sputtering and popping upon deceleration, now there is
barely any noticeable sputtering, and hardly an popping at all... so I know
I am going in the right direction here....and it you I owe many thanks to!!!

Fwed