Have a new CMB .67 greenhead. Had K&B .67 years ago with standard, basic carb/needle valve setup. I need help on how to setup the remote needle valve with this motor. Also, which adjustments affect the low and high speed idle? No manual came with my CMB and I was wondering if anyone has a website for the manual. Where should I set the low and high needle adjustments for breaking in the engine? What is the break-in procedure, and what % nitro should be used? Thanks a lot for any help
CMB .67 Carb/Needle Valve Setup
- Thread starter ReidCuddy
- Start date
Help Support Intlwaters:
CMB and manual ? ha ha ... If you're lucky there is 1 spare-part leaflet with it.
Is the remote-needle build-on or separate ?
In general .. the CMB needles should look like on the picture.
As for breaking in ... set the low needle that way that it idles properly
and set the main-needle on the rich-side ... run engine with short bursts from half to full open.
Do that for 1/4Gallon ... after that go some leaner on the main-needle , and repeat.
After 1 to 2 hours the engine is ready to run flat out.
Is the remote-needle build-on or separate ?
In general .. the CMB needles should look like on the picture.
As for breaking in ... set the low needle that way that it idles properly
and set the main-needle on the rich-side ... run engine with short bursts from half to full open.
Do that for 1/4Gallon ... after that go some leaner on the main-needle , and repeat.
After 1 to 2 hours the engine is ready to run flat out.
HendricX, thanks for your help with the break in. I still need help setting up the needle valve. Also, what are the adjustments for the high and low idles? I know the black plastic barrel spins on the remote needle valve but is that high or low? My CMB carb didn't come with the remote needle valve attached like the one in your picture. I took two pictures to show you what mine looks like. Thanks a lot for your help!!!
Last edited by a moderator:
steve wood
Well-Known Member
- Joined
- Dec 6, 2004
- Messages
- 1,777
CMB and manual ? ha ha ... If you're lucky there is 1 spare-part leaflet with it.
Is the remote-needle build-on or separate ?
In general .. the CMB needles should look like on the picture.
As for breaking in ... set the low needle that way that it idles properly
and set the main-needle on the rich-side ... run engine with short bursts from half to full open.
Do that for 1/4Gallon ... after that go some leaner on the main-needle , and repeat.
After 1 to 2 hours the engine is ready to run flat out.
these pics are backwards from what we run. we normally grind off the low speed needle completely, for best performance
steve wood
Well-Known Member
- Joined
- Dec 6, 2004
- Messages
- 1,777
mount the needle on a bracket, such as a piece of aluminum angle, where you can run a servo rod to it easily and as close to the engine as you can get it. adjustment will vary acording to your boat,pipe ,prop, nitro%, weather. just open it up 3 or 4 turns from full in, to start with, and turn out the low speed needle on the carb till you can see the o ring show. out is richer and in is leaner
Thanks Steve. My final question for you is this: When opening the high speed needle valve, four full turns from closed separates the barrel quite a bit and at about 4 and 1/8 turns, the barrel comes off and the valve separates into its two parts. Is it ok to have it near 4, close to that threshold?
steve wood
Well-Known Member
- Joined
- Dec 6, 2004
- Messages
- 1,777
the needle valve is the part with the hex head. don't open that too far out. the part with the arm on it that the servo hooks to can be turned out at least a turn from full in, then hook up your servo. there is no set adjustment on these motors/needle valves that any one can tell you exactly where to set them. it has to be done on the water. you need to start rich then lean it out till it's right
Hydro Junkie
Well-Known Member
- Joined
- Oct 2, 2006
- Messages
- 5,786
Another option that is very popular in the Northwest is to swap out the CMB carb for an OS 9B carb. Most find the OS easier to set and it's a drop in replacement.
Another thing to look at is internal flash from machining inside your engine. I have a brand new one that I was told by ALLRC needs to be torn down and gone through BEFORE trying to turn it over. Serious damage can result otherwise due to scoring the sleeve and damaging bearings. If you have any questions, contact him and he can fill you in as he sells AND RACES this engine. He and his son have been top 10 in R/C Unlimiteds season points using this engine for the last several seasons so he must be doing something right
Another thing to look at is internal flash from machining inside your engine. I have a brand new one that I was told by ALLRC needs to be torn down and gone through BEFORE trying to turn it over. Serious damage can result otherwise due to scoring the sleeve and damaging bearings. If you have any questions, contact him and he can fill you in as he sells AND RACES this engine. He and his son have been top 10 in R/C Unlimiteds season points using this engine for the last several seasons so he must be doing something right
Similar threads
