CMB 67 low speed needle

[Craig Knight]

I'm setting up a new CMB 67 in my scale boat and was hoping someone could give me a starting point for the low speed needle.

 

[Duke Mordja]

Craig

I struggled for 2 years with low speed needle in my scale. I finally cut it off and took joe w.'s suggestion of setting the midrange (idle) at 0.110" and I can mill pretty good with my Miss Madison without it loading up on fuel. I can mill without using the throttle.

Before I cut it off, I would set my low speed about 10 points higher than high speed using a Boris meter and had pretty good luck.

The low speed needle would move and wouldn't stay consistent.

Thinking about that now, possibly a thicker oring to snug it so it would hold where it was set.

 

[JimZaremski]

what's the difference between a low-speed needle and a midrange?

 

[Duke Mordja]

I took mid-range as idle. Not closed throttle and not wide open throttle.

Looking forward to the new production run of Zoom Carbs.....Never had one yet.

 

[Hydro Junkie]

Low speed is exactly that, for idle and just above. Midrange, IIRC, is where the HSN takes over

 

[SayMikey]

Dont cut it out. The new carbs are as good as a 9b.

 

[Duke Mordja]

Mike

How do you get the neede tol stay put.

That was my biggest problem that caused inconsistencies.

Duke

 

[Samuel Hagan JR]

Is your low speed needle really loose.

Mine is pretty tight and stays where it's at.

 

[SayMikey]

On an early carb I used glow plug washers to hold the setting after I found the sweet spot. Newer ones seem to hold there setting

 

[Duke Mordja]

Is your low speed needle really loose.

Mine is pretty tight and stays where it's at.

I have three of them and all moved.

Newest one is about 3 years old.

Maybe they are better now.

Where do others set theirs to help Craig on his?

 

[Samuel Hagan JR]

I bought mine used and never touched it.

Mills great so I'm not really sure. I would like to know myself.

 

[Bill Brandt]

I'm setting up a new CMB 67 in my scale boat and was hoping someone could give me a starting point for the low speed needle.

Exactly 2 1/2 turns out from the throttle closed position. Same as 9B.

Bill

 

[Craig Knight]

Thanks Bill