CMB 45 burning plugs

[fun4ej]

Hello.That needle isent it a bit small for that engine? change it to a bigger one that can handle the fule amount the engine needs.

Fredrik.L

I'm not sure, the needle assembly is for a .46 plane motor.....I figured it would work. I may end up getting another remote needle.

 

[fun4ej]

smaller prop and run it richer, that's kind of a heavy boat and needs a smaller prop than you would think.mike b

Yea, the hull is better suited for a .67 but since I had the .45 motor, I figured I'd give it a try.

I have another of the same hull that I am putting a gas motor in.

 

[fun4ej]

A couple of things to test or sure up.

1) With the tanks in the boat just like it is when running, pump your tanks full of fuel then draw the fuel out. Watch the fuel line going back to the pump as you pull the fuel out. There should be NO bubbles in the fuel line as you pull the fuel out until the tank is empty. If you see bubbles early woul have a tank plumbing leak (cracked tube)

2) take the tanks out and put a long (new) piece of fuel line on the vent side and plug the fuel side. Puch the tank underwater and blow into the vent side to put pressure inside the tank. There should be on bubbles form the tank.

3) I can't tell if you haven't already done so but add a tie wrap around that needle valve. Where it is, it will see lots of vibration and will spin if it is easily adjustable. it should be very hard to click when the tie wrap is set right.

4) You pipe length is very long for a 45 boat. Most 40 rigger are running close to 9" from plug to weld. Monos should not be too far longer that this. try 10.5" and prop accordingly.

5) That carb is going to sound rich on the shore since there is no low end needle. you'll have to keep working the throttle to keep it forn loading up on the beach. soo how rich you can run it before it stops getting on the pipe at all.

6) All of your plugs look like too lean and too much compression or load. Anytime the plug melts or moves its because there is too much heat being generated or held in the combustion chamber. You can cool this off by increasing the fuel, decreasing the compession (opening the head bubble) and reducing the prop.

7) set that motor for between .008 and .012" head clearance and forget it. Any adjustments should come from change the bubble. I'd start at .012 and get it running reliabily then drop the .008 and see if I can get it running reliably with the tigherter clearance nd higher compression (usually with more torque)

8) How old is your fuel? Moisture in old fuel can drive you nuts with this kind of stuff.

Hey Dan,

Lots of good info in your post....Thanks! You speak of "opening the head bubble". Does this mean milling out the underside of the head button where the plug comes into the cylinder? Can this be done on a drill press or does it require a much more precise method?

The fuel system appears to be good and sealed, no internal brass tube leaks and no external pinholes. I have 2 tanks, one in each sponson and when filling, I get no nitro squirting out of any lines and upon de-fueling, I get all the fuel out of the tanks. I am using brand new fuel so I don't feel moisture in it is a problem.

I'll run the shorter pipe to get it to the prescribed pipe length.

Thanks!

 

[Roxyflash]

I run the same motor i had to go to a 40cc head button was eating plugs.Also try running just one tank and see if that helps also.I think i have a extra head button thats has the bigger bowl.If your interested.

 

[ALLAN YUEN]

What kind of nitro company did you use ? <_<

 

[fun4ej]

It appears that the needle is plumbed backwards. It looks like the fuel line from the tank comes in the bottom and out the side. The fuel should flow down the needle from the fat end to the tip. Also, this motor is the CAM, not the RS. The RS has a disk rotor, the CAM a drum rotor, as previously mentioned. Another possiblity that was previously mentioned is bad bearings. Bad bearings allow the crank to break the oil seal at the front of the crank. If the bearing is too loose, the crank will hit the housing, and damage the seal bore, causing an air leak. If the crank has hit the seal bore, the case will need to be replaced or sleeved with a bushing.

Yea, that was my first thought when I purchased the needle valve assembly but by the book, it is plumbed correctly.

I guess I'll have to pull the whole motor apart and check the bearings

Thanks!

 

[Roxyflash]

I hope your running water to the head.

 

[fun4ej]

check the drive as well push & pull on the flex cable see if the flywheel moves alot in and out I have had this with my purple head which does mean the front bearing housing is screwed meaning New case.

Hey Shann,

Is "any" flywheel movement too much? 1/64"? 1/32"?

thanks

 

[fun4ej]

I run the same motor i had to go to a 40cc head button was eating plugs.Also try running just one tank and see if that helps also.I think i have a extra head button thats has the bigger bowl.If your interested.

I'll try out running one tank.

I may be interested if a bearing change does not solve this problem.....hell, I may just scrap this project if the bearings do not solve it.

 

[fun4ej]

What kind of nitro company did you use ? <_<

Powermaster 40%, 18%oil

It is the only fuel that is locally available that has 18% oil content

 

[fun4ej]

I hope your running water to the head.

lol, yea. It's getting plenty of flow...like I said, after a run, the head has never been hotter than 130-140 deg

 

[ALLAN YUEN]

What kind of nitro company did you use ? <_<

Powermaster 40%, 18%oil

It is the only fuel that is locally available that has 18% oil content

It is not good that is why! better buy Red Max or WildCat Good Luck!

 

[fun4ej]

What kind of nitro company did you use ? <_<

Powermaster 40%, 18%oil

It is the only fuel that is locally available that has 18% oil content

It is not good that is why! better buy Red Max or WildCat Good Luck!

Hey Allen,

Yea, I understand that it is not a high quality race fuel, but I don't see how it alone could be causing the problem I'm running into

 

[shann harrison]

check the drive as well push & pull on the flex cable see if the flywheel moves alot in and out I have had this with my purple head which does mean the front bearing housing is screwed meaning New case.

Hey Shann,

Is "any" flywheel movement too much? 1/64"? 1/32"?

thanks

Thats good your okay..If it does happen it will look like the flex hex has come loose.Steve Peterson has had this happen to him as well as a couple other people and myself..Thats one reason of many I'm swithching to the RS 45.tear that baby down ,Thats the fun part of it all...Be very careful with the needle bearings try not to loose any..Good luck..Shann

 

[lundahl]

Hello.That needle isent it a bit small for that engine? change it to a bigger one that can handle the fule amount the engine needs.

Fredrik.L

I'm not sure, the needle assembly is for a .46 plane motor.....I figured it would work. I may end up getting another remote needle.

A "high" nitro boat engine uses a lot more fule than a airplane engine. 12oz on 2 min, much more than an airplane dito.

Fredrik.L

 

[tnrcboatracer]

How fat is it on the beach. In muy opinion, the motor should not be quick to rev when unloaded. DEfinite hesitation when opening the throttle. Maybe some raw fuel out of the pipe. When the load is added the motor goes lean with the heat. It needs to be fat on the shore.

As for flywheel in/out movement, 0.005" should be the limit. I try for 0.002"-0.003".

 

[Dan_Cousin]

Hey Dan,Lots of good info in your post....Thanks! You speak of "opening the head bubble". Does this mean milling out the underside of the head button where the plug comes into the cylinder? Can this be done on a drill press or does it require a much more precise method?

The fuel system appears to be good and sealed, no internal brass tube leaks and no external pinholes. I have 2 tanks, one in each sponson and when filling, I get no nitro squirting out of any lines and upon de-fueling, I get all the fuel out of the tanks. I am using brand new fuel so I don't feel moisture in it is a problem.

I'll run the shorter pipe to get it to the prescribed pipe length.

Thanks!

Opening the head bubble typical involves a lathe and someone that knows how to use it. you'd be amazed at how little metal it takes to adjust by a fraction of a CC. Do you have a way to measure your head bubble? If so you can chuck it up in your drill press and sand the bowl to a larger side a little at a time.

I always suggest Marty Davis website. Its FULL of good information in these types of adjustements.

http://rcboat.com/past.htm

If you really think your head button is too tight try a good 15%-25% nitro fuel and see if you have the same trouble. Don't believe you can make decent power with low nitro. I raced with 15% redmax castor in a old OPS45 and was right there with the pack back in the early 90s. Glow plugs lasted FOREVER. Now that i'm less smart, I run 60% and burn plugs every time the wind direction changes. .

If you're using plastc tanks I'd recommend using the next size up brass tubing from 1/8" (5/32"?) for the and use large fuel line between the tanks. With dual tanks what happens is the when youre pulling from one tank you have three restrictions the fuel must go through. (pickup in tank 1, vent in tank 2, and pickup in tank 2) When tank 1 goes dry you only have one restriction which is the pickup in tank 2. This usualy causes the opposite problem you are having, you have to set the motor rich to compensate for the fuel drag of the two tanks, then when the switchover occurs, you get a slug of fuel and floods the plug.

Also about plastic tanks, don't use the airplane setup with the small length of fuel line with the brass weight in the end. That brass end will bounce and sip some air when you jump across waves. I recommend bending the tubing so the fuel pickup is in the bottom, rear left hand corner (looking from the back of the boat) and the vent is in the upper front right hand corner (max distance fron the pickup.)

 

[fun4ej]

Howdy All,

Thanks for all the replies! Lot's of great info from all of your experience. I ran today on 15% fuel and a x646/3blade and low an behold, one plug lasted through all runs this afternoon.

Ok, got one obstacle out of the way...however, the motor is still leaning out on the top end, even with my needle richened as much as it'll go, so I'm taking all your instructions and going to:

-replace bearings

-I've got a CMD remote needle valve assembly on the way

-Run one fuel tank

Thanks again for all your input, I appreciate it!

The boat doesn't run the greatest right now, but she looks pretty decent at rest on the water.....even for cellphone pics

 

[Dan_Cousin]

If it leans out when the needle is set for full rich there is a fuel delivery problem or a air leak. Be careful with this and get it fixed pronto or you risk loosing the engine.

When you say leaning out what is the boat doing? Does is rev up high then die? Does it sag then die? Does it happen at about the same amount of time each time out? (say after two or three laps it dies consistantly).

I would tear down the motor (you'll do it anyway to replace the bearings) and make sure all of the case screws are tight but not overtorqued. If there is a gasket between the carb plate and the case make sure it is in good shape.

Check the gasket between the tuned pipe header and the exhaust stub. That should be a shug seal. Also make sure the coupler between the header and the pipe is in good shape and air tight. Use large zip ties on both ends of the header to make sure it stays sealed with the pipe gets hot.

Check the pipe pressure tap to make sure it is open and not plugged.

Also make absolutely sure there is no metal to metal vibrations on the boat. if you servo jitter even a little on the shore, they may get worse when the boat is far away.

What usually happens is the throttle goes wide open and the rudder aims the boat at the hardest object on the shore. Sometimes you get lucky and the throtle servo pulls the carb closed.

Also, How new is this motor? I've had brand new CMB EVO motors that the piston would lock up when they are new until they were worn in and seated. It took about a gallon of running at half throttle with occasonal pulses to full throttle to get the piston seated. Then I could run it wide open.

 

[fun4ej]

If it leans out when the needle is set for full rich there is a fuel delivery problem or a air leak. Be careful with this and get it fixed pronto or you risk loosing the engine.
When you say leaning out what is the boat doing? Does is rev up high then die? Does it sag then die? Does it happen at about the same amount of time each time out? (say after two or three laps it dies consistantly).

I would tear down the motor (you'll do it anyway to replace the bearings) and make sure all of the case screws are tight but not overtorqued. If there is a gasket between the carb plate and the case make sure it is in good shape.

Check the gasket between the tuned pipe header and the exhaust stub. That should be a shug seal. Also make sure the coupler between the header and the pipe is in good shape and air tight. Use large zip ties on both ends of the header to make sure it stays sealed with the pipe gets hot.

Check the pipe pressure tap to make sure it is open and not plugged.

Also make absolutely sure there is no metal to metal vibrations on the boat. if you servo jitter even a little on the shore, they may get worse when the boat is far away.

What usually happens is the throttle goes wide open and the rudder aims the boat at the hardest object on the shore. Sometimes you get lucky and the throtle servo pulls the carb closed.

Also, How new is this motor? I've had brand new CMB EVO motors that the piston would lock up when they are new until they were worn in and seated. It took about a gallon of running at half throttle with occasonal pulses to full throttle to get the piston seated. Then I could run it wide open.

The leaning happens the same way every time. There is definite hesitation on the beach with no load on the prop....wont get on the pipe. Then it will come up to to speed when thrown in the water. It'll do about a half lap then it will sag for a few seconds, then pick back up for a few seconds, then sag again and then quit.

Exhaust coupler and gasket are good and sealed...I use hose clamps on the coupler.

The back pressure fitting is clear and sealed.

No metal to metal contact.

I'm not sure how new this motor is...I bought it used.

So, like I said, I'm going to replace the bearings (i'm sure they could use it), I've got a CMD remote needle on the way, I'll put fresh fuel lines on the whole system...I may just run one tank. When I tear the motor down, I'll make sure the case screws are not over torqued and I'll check the carb gasket.

As far as the head bubble thing goes, I have the means and ability to do it, I just don't have the experience or knowledge to do it right.

Since I am not a competitive boater, I am hoping that the above stated things take care of the problem.

Thanks for the help!