first run on a cmb .67

[avbrando]

i have an aeromarine sprint cat with a cmb .67 green head . i ran it last weekend for the first time and i think it was too lean, it just wouldn't open up, after richer settings it woke up but it was not consistent and the plug looked bad. the instructions are vague, there is no break in instructions or starting needle settings i am using the remote needle, but no third channel. can anyone help me to NOT blow it up? i do have a ton of nitro car experience but this is way different and this is way too mutch money to just ruin it . thanks brandon.

 

[carlnoki]

a few things need to be answered first:

1. what percent nitro fuel are you running?

2. what prop are you using?

3. what is your pipe length? (measured from the center of the engine (along side of it) to the high point of the pipe)

4. what pipe are you running?

5. and just one more thing, open the needle valve about 1/4 turn more at least.

let us know these answers and we can help you out.

thanks

carl

 

[avbrando]

a few things need to be answered first:
1. what percent nitro fuel are you running?

2. what prop are you using?

3. what is your pipe length? (measured from the center of the engine (along side of it) to the high point of the pipe)

4. what pipe are you running?

5. and just one more thing, open the needle valve about 1/4 turn more at least.

let us know these answers and we can help you out.

thanks

carl

thanks for the reply, i'm running byrons 45% the prop is an octura x460, the pipe is cmb 6780 fat pipe @ 11'' weld to plug. i do not race this boat!

 

[Dan_Cousin]

If the motor doesnt have a low speed needle on the carb, (I dont think the gren head with the silver carb does but the black car I think does have the low end needle) it will sound sloppy rich on the shore before launching. If it sounds clean and the engine RPM closely follow the throttle adjustments your too lean. It should have a definate hesitation of about a half second when going fomr low RPM to wide open.

If you do have a low end needle, richen it out all the way and set your high speed needle first.

The game is keep rihcening it until you cant launch it any more then lean it a little at a time until it cleans out.

At too rich of a setting the boat should run without taking out the plug. Once you start damaging the plug you're starting to run lean.

If you haven't done so, take your motor and make sure all of the screws are torqued properly (use blue locktite on mine) and that the gaskets are on one piece (no splits tears, etc).

Make sure your needle isn't spinning while you're running too. put a tie wrap around it so it doesnt spin with the vibration of the motor.

Once you get the high speed needle running reliably you can start leaning the low speed needle. This needle will make starting easier (you won't have to pinch the fuel line to start it) and provide good acceleration when you back of the throttle then get back on it in the water.

Good luck.

 

[Russell Bear]

How old is the fuel? Bad fuel will cause all kinds of problems....

 

[carlnoki]

if yuor fuel is ok then get rid of that prop and go to an X-457 or X-455/3 blade. i run the -x455/3 blade. works great. pipe length should start around 11 1/2" then slowly start to shorten it till it gets hard to get on the pipe. at that point lengthen it out about 1/4" and all should be well.

hope this helps you out.

keep us posted.

thanks

carl

 

[Roxyflash]

I run a sprintcat with a green head 67 .Im using a cmb big belly pipe at 12 inches.Mine does not like the 460/2 blade prop.Its ok with a 457/2.I would get a smaller prop and pull the pipe out get it broke in then try shorten the pipe.

 

[avbrando]

I run a sprintcat with a green head 67 .Im using a cmb big belly pipe at 12 inches.Mine does not like the 460/2 blade prop.Its ok with a 457/2.I would get a smaller prop and pull the pipe out get it broke in then try shorten the pipe.

thanks all, i will try to get out to the pond this week and try again with these recomendations. you guys are great!!

 

[carlnoki]

any progress yet?

 

[avbrando]

i have finally run the cat. it seems very rich on shore but when launched it seems lean and frys plugs almost every run. can anyone give me some baseline settings? is this thing that fuel hungry? prop now is an x457

 

[Chris Wood]

do you have a 90 degree pressure fitting in the pipe?? if so check to make sure it is not closed off otherwise this will cause all sorts of weird things

chris

 

[fun4ej]

I had this problem with my cmb 45 that I bought used. Turned out that the rear bearing was bad....I replaced the bearings and it lit right up. I also replaced the gasket, and no more fried plugs on every run.

The bad bearing was letting air in...leaning the motor. Is your motor brand new?

 

[avbrando]

the engine is new,i have checked the pressure line and fitting and all is good.

 

[FloridaScaleBoater]

Are you running a multi tank fuel system?

Check for restictions between them.

what size tubing are you using in the tanks, 5/32" is whats needed, with large fuel line

And be sure there is NO restriction in the fuel draw from the tanks.

I see you say the engine is new, I'm sure you have purchased something new, that has ended up being defective? check your bearings!!

if your first run was lean and a piece of the plug element went through the engine, thats all it could take to "roach" a set of new bearings.

The person at the factory could have put too much side load on the bearings during install, messing up a "new" set of bearings

Rick