I just picked up a Kyosho Nitro Brute and all electronics for FREE from a friend!! But with that comes some repairs. Everything seems fine except the engine and need some new batteries.

Here is my problem..... The engine is VERY stiff. It takes a lot of force to turn the thing over. I took the muffler off and slowly turned the engine over. I can see the piston going up and down. There is no grinding or other funny noises when I turn it. It's very smooth but VERY stiff.

The engine has OS MAX - CZ casted on block. I cant see any other markings. I'll probably have to take it out of the Brute to see any other markings. It's a spin starter.

The truck has been sitting for a few years so I guess age has done this to the engine. It probably has something to do with the oil in the gas getting old and gummed up. Any ideas how I can fix this?

Its probably just gummed up. You should just take it apart and give it a good cleaning and reassemble it. Don't forget to oil all the parts before you put it back together.

What sort of oil should I use? It may need to be rebuilt, is there any signs I should look for while it is apart?

Prock,
This is what I would do. Remove the engine from the model, then remove the glow plug and rear back plate/ starter assembly if it has one. Submerge the engine in a container filled with MMO (Marvel Mystery Oil). Let it soak for a day. During that time, attempt to "turn it over" a few times. This should loosen things up without a total dissassembly. Drain all the MMO and reassemble. Wipe down the outside of the engine and reinstall back into the car. I did this to a completely "frozen" model airplane engine that was sitting in the closet for over twenty years!! The engine now runs fine without any problems.

i had that same probelm all i did was use some of that marbel mistory oil and let it set for a few days and that cleaned it out real well and it should not be stiff........

I'll have to go pick up some of oil and give it a shot. Thanks for the info.

WD-40 should quickly penetrate the engine, freeing it up. You can also get it in 1 gal cans, but the spray might work faster.

yea man i got the same motor and all i did was took the engine out of the car and just pulled of the pull start off and the plate behind that there was like a one way bearing type of thing but the end of the conecting rod sat on and spins around on and i think that thing just pops out of place or some thing but after i did that it turns over great and seams like it would be a great engine but for some reason i cant get it to start but i think that might just be the mixture screw would you happen to know what the adjustment for that would be??

vee-dub, I believe that you may be a candidate for longest sentance of the day.
Just funnin ya, welcome to the fourm.
Try going to the OS website, they may list the factory settings if no one knows what they are.

Prock, Do what these guys said. The engine is probably good. If you dissassemble the carb to clean it then first turn the carb needles all the way in while you carefully count the turns. That way you can put them back where they were when you put it back togeather.
I've got an OS .10 engine in a street car that is over 20 years old and runs great.

ha ha yea i just type thing out i dont realy make it perfect cuz ya no were not in english class. but thanks that was gunna be my next step to clean the carb i dont know what the moter is besides a o.s. cz and it has a flat head on it and its in a kyosho but it seams like it would be a cool car to play with thanks again!!

Dude Methanol will fix it if its only gummed up.. Take out the engine remove the backing plate and fill it up with methanol and turn it over by hand it should free up within a couple of minutes..Put it back in the car and fire it up..

ok cool yea i got it i just have to figure out why it wont stay runing it runs for like 10 sec. then dies and then some times it starts back up and other times it fluds out

Look for air leaking into the crankcase could be as simple as the O-ring under the carb has gotten old , i always seal mine witha little (dont get carried away) of permatex #2 and hold down on it while I tighten the screws. It has made a world of difference on my engines. Look also to fuel restrictions.