pirate one

i have a realatively new motor that has suddenly gummed up to the point that I cannot turn it over. it appears as if the left over oil and nitro residue has built up between the crank and the crank shaft housing causing the crank to bind. I have had no success soaking the motor in marvel mystery oil. Now it appears as my second boat motor has done the same thing. What can I do about this? help!!!!!

RCUOrbiter

If it really is gumming up then heat and a little fresh fuel will nearly always free it up.

Gumming up is only usually a problem if an engine is left a long time after using castor based fuels.
--
Steve

RaceCity

"Suddenly" gummed up? Two motors did this? Odd, because motors don't "suddenly" gum up. Were the motors running well the last time you used them? How long ago was that? Did something happen in the meantime? Perhaps they got wet internally? Is it possible that something in the driveline (external to the motor) is causing the bind? Something is fishy here. (no pun intended)

Some more investigation is needed...

Let us know.

'Race

j.duncker

My Feedback: (2)

Gumming usually results in an engine which is stiff to turn not seized.

If you run high nitro fuels the problem may be corrosion related. I am seeing more and more engines with seized bearings due to corrosion. Some have only been unrun for 6 weeks.

Remove back plate and inspect visually. If the bearings have corrosion damage they need replacing.

Fuelman

My Feedback: (6)

If you put them away with marvels mystery oil and let them sit for a long time, yes, that can lock them up like being filled with super glue.
Do as above mentioned and rule out corrosion.
If it is gummed up due to castor or marvels mystery oil, heat the engine up with a monokote gun to losen the gummy residue and see if it turns over. A complete disassembly sounds like it is in order and a cleaning with Demon-Clean.

bdtsr

My Feedback: (5)

I think you stated the important words here, "Boat motor". As previously posted, corrosion is what will "lock" a motor. Since your motor is in a high moisture environment, it only makes sense that your problem would be corrosion. Using an aircompressor to blow out the motor followed by a liberal amount of after run oil after the days running would prevent this from happening again.

piper_chuck

My Feedback: (12)

Au contraire, I had several that were completely locked up after being in storage for about 17 years. I KNOW they were not rusted, they were very well lubed before being put away. A combination of heat (oven at 300 degrees) and 91% isopropyl alcohol from the drug store were all that was required to free them up. Every one has run very well once cleaned and lubed.

Motorboy

Worst if you are running the modelboat in salt water, there are enough to corrode inside in the engine in short time..

Jens Eirik

pirate one

Can anyone recommend a place to send a cmb 100 evo for repair? It is gummed up and apart, I would like it lchecked out and repaired. Any suggestions would be helpful. Also any ideas what might have happened?

pirate one

it might if you could get it in the motor. I soaked the thing in diesel for 3 6 hours. it still was frozen. does not appear to be any scores or anything in the cylinder.

canadagoose

My Feedback: (2)

Have you tried heating it up? I had a small 049 cox engine that i had put some oil in that locked it up in a relatively short time (about 1 year) can't remember what oil it was. Heating it up was all that was required to get it turning over again.

piper_chuck

My Feedback: (12)

Hard to say without looking at it. Could be the bearings, could be something as simple as gummed up castor oil. If it's castor, heating in the oven, as I mentioned several posts ago, will free it up. Then you use something like isopropyl or denatured alcohol while it's hot to get rid of the castor.

However, if you're not so familiar with engines, sending it in is a great idea. I repair my own airplane engines, but when it comes to my MAC boat engines I send them in. Andy Brown is one of the best in the business. You can get contact info at http://www.cmdracing.com/updated/main.htm . While you are at his web site, be sure to check out the gallery photos. Lots of nice boats.

For future reference, the typical way to flush an engine at the end of the day is to spray WD-40 in the carb while turning it over with the starter. This flushes out the fuel and leaves some protection in there.

Fuelman

My Feedback: (6)

Give BJ's Engine Service a call. Expert model engine repairs at very reasonable prices.
Bill is a great guy and knows engines.
http://www.starcomposites.com/BJModelEngines/

wcmorrison

My Feedback: (2)

Once you get it un-gummed up, take a look at your after run oil. Use some transmission fluid or Marvel Mystery oil (or a combo of those two) as your after run oil. If you are using 3 in 1, that may be your problem causing it to gum up in the first place.

Cheers,

Chip

pirate one

I have only put after run oil in the motor. I never had the problem until I used it. I tried to heat the motor and nothing happened and it was pretty hot.

Loopman

My Feedback: (195)

Pirate One,
Try this. Get an old crock pot and label it so there will never be any possibility that it will be used for cooking again. Fill it 1/2 way with anti-freeze. strip your engine of any exposed rubber or plastic parts. submerse the engine in the anti-freeze and turn the crockpot on. Leave it overnight or about 12 hours, make sure the lid is on! After this time carefully remove the engine ( it will be HOT!!!!) let cool and try to turn it over. I have used this method on several engines that were frozen and on one engine that a guy threw away because the crank was so frozen that it would not budge. Be aware that exposure to the hot fumes from the ant-freeze is not good for your resperatory system but if you do this procedure with adequate ventilation and in a wide open space ( work shop, back porch, garage) you should be okay. Also keep in mind that anti-freeze is deadly to animals (pets) so don't leave it where they could ingest it.

Happy Flying!

Loopman

jaka

Hi!
....When it is so easy to just take apart the engine and clean it with your hands/mechanically.
Regards!
Jan K
Sweden

piper_chuck

My Feedback: (12)

Send it to Andy Brown. He lives and breathes high performance boat engines such as CMB. When I sent in my Mac he charged $25 for the service and about $30 for new bearings. He also noticed a problem with the sleeve and replaced it, no charge.

piper_chuck

My Feedback: (12)

I do this with my airplane engines. However, I draw the line when it comes to $400+ engines that regularly turn over 25,000 RPMs. I'm perfectly comfortable paying someone a reasonable fee because I know that when the engine comes back it's going to be as good, or better, than new.