New .90 rigger problems? Any ideas?

[jaso]

Well I'm just putting this post up in the hope some one might have a few tips for me? Recently I've been trying to get some run time on my new .90 CMB motor in my new rigger. Boat is set up as the builder recomended and I think I have it all pretty sweet but, I've had it out to pond about 4 times now with average to poor success so far . Any way this is the set up and basicly I've been having problems lauching the boat and successfully getting it up on the pipe. Seem to be very fine point between too rich and too lean. It's a 3 month old CMB.90 (from brand new), using 40 percent fuel, tried a std 1667 and a std h50,head clearance is at 15thou, pipe length at 305mm, mc9 plug, and getting frustrated . Any one got any ideas for me ? Please? Note: had some help from a few more experienced club members than myself, comments have ranged from engine still too tight to I will have trouble setting the needle till its more run in. I've also been assured that it should run a std 1667 but I'm not that sure???? Thanks in advance.

 

[jaso]

And I forget to mention something , today when I had my boat up and running it seemed to cycle between being too rich and too lean by itself. What I mean is it would do a lap or two ok then it seemed to load up for a lap then it would go ok again for another couple of laps, continued to do this till tank was empty? Seemed like there was a little man in the boat playing with the needle just to annoy me. It worked! :angry:

 

[Danny Bull]

Hi Jaso, I use to run a CMB 90 in one of Andy Brown's 67 eagles. Awesome little rigger, I first run it with the carby before changing over to an exhaust throttle. A few things to consider looking at is the fuel tank pick up, the size of fuel line, do you run pipe pressure to the tank ? Aslo check the needle valve itself for any bits or slices of silicone fuel hose or "O" ring material. Just sounds to me like its starving for fuel or........

Another possibility is to much or not enough water going through the cooling jacket thus causing it to overheat after a lap or 2. The H50 might be a bit big while your trying to sort it out, I'd stick with the 1667 (one of my favorite props)

There's a couple of photos of the 67 eagle with the CMB90 in it at My Website.

Cheers, Danny.

 

[Don Ferrette]

Pipe length is fine, both props are not too big either. I think Danny's recommendations on fuel issue is moving you down the right path. Check EVERYTHING from start to finish as in from your pipe pressure tap to carb-

pressure tap itself- not clogged?

pressure line to tank- no cuts, splits. kinks, etc

tank- first off what kind of tank is it metal or plastic?

if it's plastic are you running a header tank? (you need to)

is the brass pressure/vent line of either the main or header tank far enough away from the tank top so when the tank flexes in (and it will) under fuel draw it doesn't block the line - you'd be amazed how many times I've seem this cause EXACTLY what you are describing

check all lines between carb & tank(s) for the same kinks, cuts, splits.

check for any debris in needle (take the needle all the way out & shoot some WD40 thru it.)

Do you have a flow meter? Start out at about 9 to 9 1/2" of flow & lean it from there.

Now a twist-

How far is carb opening from tank? Do you see ANY open area around boom tube holes in the tub? Does cowling fit tightly forward of carb? I've seen water come in thru boom tube openings & from under cowl travel right to the carb area & you wind up injesting small amounts of water mist which will also cause same type of symptom. Seal up any open area around boom tubes & if your carb is any closer than one inch to tank try taking a clear piece of plastic & making a carb shield to steer any water that may get on top of tank away from carb.

Hope this helps!!

B)

 

[Don Ferrette]

"There's a couple of photos of the 67 eagle with the CMB90 in it at My Website.

Cheers, Danny."

....and what side is the rudder on? Sorry I just had to go there! Geez, I crack myself up sometimes ..... :lol:

I like the rigger stand you made BTW.

 

[Danny Bull]

****, You weren't supposed to notice that Don......lol. Just following the manufacturers recommendations in this case. It never liked the H50, I found that it really made it work. I sold that boat on e-bay to a guy, Joe from Florida. He says he's won heaps of races with it too which was cool to here.

Cheers, Danny.

 

[[email protected]]

One thing that the CMB's really like are a lot of fuel. Upgrade to large fuel tubing and it might be benificial for this motor to drop down to 30% nitro. That's just a suggestion to see how it runs compared to 40%.

 

Second, their carb/needle setting sucks. Close that off and go to a remote needle. It'll rattle and slide out that you'll never keep an acurate needle. If you want to adjust it by hand the K&B is fine. I've found for my CMB 90's and 1.0's that the Fuel Doctors worked the best. On my other boat's the Bob Violet's are better. To each their own.

 

I'd blow some water through the water cooled head and make sure there's no water restrictions because these motors will shut down quick style if they over heat. My .67 Gold Head EVO did it until I discovered I had a clogged line.

 

Good Luck....Let us know how it goes.

 

[Don Ferrette]

The H50 can make a motor work, but he should still be able to pull it. My favorite big block prop of choice has always been a 1667. B)

 

[Don Ferrette]

"One thing that the CMB's really like are a lot of fuel. Upgrade to large fuel tubing and it might be benificial for this motor to drop down to 30% nitro. That's just a suggestion to see how it runs compared to 40%."

30%?? What's that? :lol: I run 50 & 60% thru my CMB 90 with superb results, .013" head clearance. If you want to run a 3rd channel remote get the hi flow CMD needle from Andy Brown, I tried one & it's best I've used to date & practically bullet proof. BTW- one thing I forgot, is it single or dual plug head?? What color is the water jacket? :unsure:

 

[TimD]

What pipe are you using and did you put a MAC's products pressure fitting on it?

 

[jaso]

Ok, I'll try to give some more info. It's a purple single plug head motor, came with a remote needle setup which I'm using, running the pressure fitting from the widest point at the chamber and I checked it's not blocked, have a tin tank that the manufacturer supplied plumbed the correct way( pick up and breather), the fuel line is large size, I've cleaned out the tank after a days running with metholated spirits to stop any green goo from forming in the tank, had the needle valve apart several times to ensure that it didn't have a floaty in it ( last time it did a piece of silicon but not yesterday) I'm running the cooling as recomended by CMB with the water going in the top fitting and out the bottom, been clearly getting the water through as you can see it when running shooting out. OK

Now one thing that sounds like I need to address would be the lack of sealing around the boom tubes. I dont have any thing around them at present so I do that for starters. Thanks very much to all for your helpfull suggestions, I'll get this puppy going yet! Hpoe to get out this weekend and have another go so I'll let you know how I go.

 

[Don Ferrette]

"m running the cooling as recomended by CMB with the water going in the top fitting and out the bottom,"

For what it's worth I run mine just the opposite, in the bottom & out the top. I've done that on all of the double water jacket purple heads. I prefer more heat in the combustion chamber so I cool the case (lower passage) first & headbutton (upper passage) second. I never could get a good burn pattern esablished with it the other way around. B)

 

[TimD]

Again, what pipe is it?

 

[jaso]

Its a CMB nitro pipe with a muffler on the back.

 

[jaso]

I used the spare water fitting from the motor and I made a water outlet to shoot the water up to make it easily visable as I have done with past boats.

 

[jaso]

Don, When you say you couldn't get a good burn pattern what do you mean?

I was wondering about the water flow because I don't think I've seen one set up as per the instructions but you tend to do what the manufacturer says if unsure.

I'll change mine around to your setup I think, and fix the open holes at the booms, might also test the fuel system(tank and lines) under water to check for pin holes and if nothing shows up I'll just change the silicon lines anyway.

I like the sound of the water entry into the carb but, and I hope that is it.

Thanks again everyones input.

 

[Ian Inverarity]

I have heard that the reason for the recommendation to cool the head first and the lower cooling area second is that if the lower area is cooled first it can over-cool the top of the liner and may cause the piston to nip up.

But if Jaso already has it that way then I doubt it is his problem....

Ian.

 

[Don Ferrette]

" Don, When you say you couldn't get a good burn pattern what do you mean?"

The pattern that develops on the top of the piston should look like a nice round sunburst if you will. I was getting a very uneven pattern with the button getting cooled first. :blink:

 

[jaso]

Don, I spose this is an indication of the combustion and it's eveness across the piston which would be important for achieving the most complete combustion capable?== more power== more efficent== more good? :huh:

 

[Don Ferrette]

Don, I spose this is an indication of the combustion and it's eveness across the piston which would be important for achieving the most complete combustion capable?== more power== more efficent== more good? :huh:

Exactly!!