Dual 44 Mikuni observations

[Mark44]

I would like to hear John from JSS chime in on this. I know he has done some bench flow testing on 44's hand has a pretty interesting theory I have tried a few different restrictions to change the signal and have found different outcomes.

Mark44

 

[freestylegeek]

I would like to hear John from JSS chime in on this...Mark44

I wouldn't.

 

[RMBC Freeride]

hmmm... let's close that can of worms...

Geek I'm sorry to hear you are having so much trouble with this. I have not tried this setup myself (yet), so take this for what it is worth...

But I do remember some (or all) OEM Yam carbs have that fine thread on the adjusters... hence you cannot buy the aftermarket ones with the crossbar to put in them. So it would not be a problem, nor uncommon to be 2 turns out there. Especially if it runs good.

my .02

BTW, holy **** I didn't realize we had Team Scream in the house! Awesome! Lots of good advice here!

 

[freestylegeek]

...
BTW, holy **** I didn't realize we had Team Scream in the house! Awesome! Lots of good advice here!

I know!!
Are we worthy?
I know I'm not.


I too agree with you on the 2 turns out isn't so bad - now that I realize they are fine thread.
That's why I'm thinking I may still be able to make them work.

 

[QJS]

Just finished dialing an 85mm Lamey Flattop with twin 44's today and ended up with 105 Lows, 140 Mains, 2mm Needle and seats and 115gm springs. The motor was very strong right through the rev range.
Chris.

 

[waxhead]

wow thats a wholw lot of fuel going in there
I guess it has to do with climate change
it wouldnt run that well down in australia with that jetting
but thne agwe are alot hotter so less dense air down here so we are going to be leaner

 

[freestylegeek]

Just finished dialing an 85mm Lamey Flattop with twin 44's today and ended up with 105 Lows, 140 Mains, 2mm Needle and seats and 115gm springs. The motor was very strong right through the rev range.
Chris.

How far out is your low speed screw?
I've been close to that set up (115/135/2.0/95) and I had a KILLER low speed hesitation untill I brought my low screws out to 2 turns.

 

[SuperJETT]

And, are they OEM 44's?

How far out is your low speed screw?
I've been close to that set up (115/135/2.0/95) and I had a KILLER low speed hesitation untill I brought my low screws out to 2 turns.

 

[freestylegeek]

And, are they OEM 44's?

Yeah, I forgot about asking that question.

 

[Big Kahuna]

I would like to hear John from JSS chime in on this. I know he has done some bench flow testing on 44's hand has a pretty interesting theory I have tried a few different restrictions to change the signal and have found different outcomes.

Mark44

Your kidding right............. Sorry........... Upon his recommendations, I followed and all it did was cost me money from smoking a piston.........." Nah, your jetting is all out of wack, you need to be running this................ sieze........................",,,, Smoke and Mirrors........... John has never run 44's, therefore he has no experience with them.......... his 38 mods are hit or miss.......... then he does not stand behind them when they dont run......... Ask Geek, Abe or Parrdaddy............ you ever wonder why he was not a Lanier, he live 4 minutes away.......... he wont show his face because of some of the PO'd customers.............

He has some good ideas, but carb tuning is not one of them........... I learned the hard way.....................

John "how ski running???" You.... Fine, thanks............ etc etc...........


You " John, got a problem with these carbs?" ............ Uh, it must be something you have done, carbs are perfect.................... etc.etc........ No John, ski works fine with regular carbs............ Yours do not work........... Oh yes they do, you dont know how to tune them right............ No John, I can tune just fine........... Your porting is out of wack............. John, I dont have porting............

These are quotes from a few years ago when everybody was having problems, I offered to help and put his carbs on and see if they was an issue of his carbs and a B pipe, that was the only common denominator..........

Oh, his last words............ " I am not worried about those 3 customers................. Referring to Parr, Abe and Geek...............


Sorry, I cannot recommend JSS for any Carb work unless it is exterior......... you can buy that epoxy paint he uses at Lowes............

 

[Matt_E]

One thought.
My 44's on my ported magoo motor seem to respond much better with a little more restriction. I tuned them and then played with screens on the inlet of my stock flame arrestor and found that running two screens worked the best for me, must be allowing the carbs to get a better signal with the restriction. Just a thought and a fun thing to play with.

Mark44

My set up as of now on new SBN 44's
112.5 H
117.5 L
2.0 NS
95G
2 screens for restriction on incoming air

I think what you're doing is creating a larger vacuum on the intake. You could get the same effect by lowering your popoff pressure.

 

[freestylegeek]

Well, pop-off is down around the 14 psi mark now.

120/135/2.5/80g
It wouldn't hold an idle without priming ocasionally at 1 turn out.
I went to 1-1/2 turns and it idles well.
Also there is no hesitation with a blast of throttle.
We'll see what happens when I get it on the water, but I may have found my solution (at least I hope so).

All I know is 14 psi seems EXTREMELY low for 44's with a STOCK dual carb airbox. But, if it works then braaaap!

 

[Mile9c1]

Well, pop-off is down around the 14 psi mark now.

120/135/2.5/80g

:bigeyes:

 

[freestylegeek]

:bigeyes:

I KNOW!!!!
This shouldn't be working.

 

[Mile9c1]

What's your fuel pump situation?

 

[freestylegeek]

What's your fuel pump situation?

The pumps that are on the carbs.
I just went through EVERY gasket and check valve.
They are in excellent condition.

 

[Mile9c1]

You might want to check your restrictors, make sure they're not drilled out.

 

[Matt_E]

It's not necessarily extremely low...yeah, it sounds like it is. But think about it. Really, you're just supplying more fuel down low through the popoff circuit, rather than low speed jet and high speed jet.
You've just changed where the fuel gets delivered and when,not necessarily the amount.
Example:

I started with 32psi popoff and 117.5 pilots. I changed to 115 pilots and 25 psi popoff - almost the same, a bit crisper. I then changed to 17 psi popoff with 110 pilots - again, almost the same, very very close to the first setup, but not as crisp as the middle.

 

[freestylegeek]

You might want to check your restrictors, make sure they're not drilled out.

You think I went through all that inspection in my fuel pumps and didn't look at my restrictors?
I laugh at your question! :smile:

They are there, and undrilled.

That was one of the first places I looked at.
It's too bad there's no way to get an accurate fuel pressure measurement at the output of the pump.

 

[freestylegeek]

It's not necessarily extremely low...yeah, it sounds like it is. But think about it. Really, you're just supplying more fuel down low through the popoff circuit, rather than low speed jet and high speed jet.
..

the pop-off circuit feeds through the low jet.
The needle and seat are used as a fuel regulator (when the suction is created by the vacuum the engine makes against the throttle plate).
The low jet is an orifice used as a fuel-flow limiter (when the suction is created by the velocity of the air moving through the carb.

If tuned correctly, the needle should be off the seat from 1/4 throttle on up.
Thats when the jets restrict the flow into the carb, and the remaining fuel heads down the return line.