I was trying to find out why my OS .82 four stroke wont start after 6 months of sitting and I found this. Great disassembly vid.

I am not experienced with RC vehicles yet but am thinking of getting a 4 channel plane with a live feed video camera on it. Extremely good video work to whoever did this video. Wow. Quality camera, good video editing, clear step by step instruction, clear words, necessary equipment, ect.... Very good video. I'm into drag racing but it was very interesting to see how similar these engines are to full size units.

Finally! an engine rebuilder on youtube that knows what he's doing! and has great camera work! Thank you! and btw i love these small 4 stroke engines

Thanks for responding so quickly. I'll give it a try. I got the cover off but the cam is stuck good. The cam followers were a bear to get out. A heavy magnet helped after I worked them up and down a while. I'll check out your site, Thanks again.

Amazing how they make these little engines almost like car engines with the valves and head, all those little precision parts!

Very interesting seeing how these things are built, thank you :)

@Luvtoflyhelis Use the drywall screw or a screw extractor to get the wrist pin out. If that doesn't work grind a fine taper on the drywall screw to get a better grip. If that doesn't work, heat the piston, there is oil residue or corrosion holding it in. If it's badly corroded it might not be possible to get it out and the only option will be cutting the rod. I've only had to cut one rod out of probably 30 engines.

There is no side load on the wrist pin so no wear of the pads. The pads used to be brass many years ago and worked without issue. OS made a FS-26 and FS-40 specifically for cars. The FS-26S-CII is still made but not sold in the US. People have modified other airplane engines for car use.

This engine is pristine and very easy to disassemble try one that has got some run time and residual fuel and castor oil in it helpful in showing how it comes apart but in reality most are not that easy.

@7bikerboy7 Many use airtool oil. In the FS-120S-III there isn't actually any contact between the crankcase and regulator. The diaphragm in the pump should handle it as it's mylar or something. Incompatible oils can turn to sludge in the crankcase. People have been using engine and airtool oil as after-run oils for years, seemingly without issue, other than pumped engines, in particular YS.

@7bikerboy7 I happen to have an FS-120S-III apart and it does have two gaskets. I didn't measure, but one looks like 0.2mm and the other 0.4mm. The listing on Tower shows two gaskets as well as the OS manual.

@MaxwellForce That happens sometimes due to tolerances or corrosion. The the flame can unevenly heat the housing and may not expand correctly to release the bearing. Thought the 91VRDF with it's bolt on front end shouldn't be a problem. The worst thing that can happen by hitting the case heard is distorting it or the mating surfaces. It's probably fine. Only time will tell.

Procedures will have to be changed some for anything other than an almost new engine. Any engine with some use will have varnish and other contamination holding the parts together. That makes disassembly more difficult. Will need at least an arbor press and some experience. If you have an old engine that you want to rebuild, buy a junk motor and learn on that so you don't ruin your good motor.

To degum and clean an Rc engine…get an old slowcooker. Disassemble the engine as far as possible. Place the parts in the slowcooke. Cover the parts in 100% auto antifreeze - the green stuff without water. Cook for 12 to 24 hours on low. Clean with a toothbrush and repeat as necessary. I saw this on another Internet forum and I kwow others that have cleaned auto Caribs the same way.

You are a real genius :) thanks for the vid, i'm looking for the same but for a 2 strokes version (OS-55 AX) :)

thanks for the vid now i know a 4 stroke looks like apart

@tycomypuppy1 There are only a few more parts. once you learn how it all works and goes together, no problem at all.

Great video...good job..new subscriber

Thank you!! very nicely explained. Too bad though that older engines put up much more of a fight.

cara, muito bom o seu video. me ajudou muito. parabens. guy, very good your video. helped me a lot. congratulations.

wow that looks way more complicated than my 2 stroke.. or are looks decieving?

I too have a 120 pumped and It's been sitting for quite a while, really gummed up. Any suggestions on a soaking solution to loosen things up? I don't want to force anything but I can't even get the cam cover off, and yours slipped right off. I'm seriously bummin'. I have lots of carbon in the combustion chamber and junk all over the crank and cam followers. Nothing moves hardly at all. Any help I really appreciate. Good vidoe by the way, lots of help right there. Thanks.

thanks, so there are just a couple of plastic caps on each end of the pin to keep it in place, does they wear out due to friction with the cylinder liner? well, about the parts my crappy force two stroke 0.15 has about 20 pieces less than that four stroke but is 20 times less reliable as well, i would reallyl ike to try a four stoke conversion for my 1/10 buggy :)

@rcdieselrc ok thank you, i used oil used for air tools, what do you think?

Awesome tuto! How do i extract the little bearing from camshaft?

@pipes81111 This was a new engine I disassembled for modifications.

Nice Video a verry thanks

I disassembled my OS91 VRDF engine to change the main bearing. I had a lot of trouble with the main bearing. It just wouldn’t budge. I used an open flame and gently heated the crank case of course. I eventually got it out, but I had to use more then a slight tab. I really had to knock it really hard before the bearing got lose. Now I am worried that I might have damaged the engine, is there any way to know or see if any damage has occurred. The engine seems to run just fine afterwards.

It's a machinist's grinding vise. A Chinese import costs under 40USD.

Nice. Make other part of it for refitting it.which scroodriver n key required for opening it.please reply

very informative ..thanks

A four stroke engine does have many more parts than a two stroke engine. No snap rings in this engine. The plastic pads serve the same purpose.

hi, question..i have an os fs 120III with pump. Do you know if this engine has 2 head gaskets or one, cause when i was cleaning i couls swear i only took off one but later found 2 on the napkin.

@rcdieselrc thank you

Nice Video Greg. Have never attempted to take apart a 4 stroke; used to race RC cars & have plenty of experience disassembling 2 strokes. I have a pumped OS 155@ engine that has been sitting for 3yrs & will attempt disassembly sometime soon. Is there any info you can give me before I tackle it ? Can you tell me where you purchased your torque wrench, & what are the torque values for most of the screws ?

think ill invest in one thanks good vid

god, this is a really complicated rc engine. so basically there are no snap rings to hold the wrist pin inside the piston?

nice job!!

Where did you get that little vice? I could so use one of those.

Thanks for the comments everyone. I'm getting ready to do a series on Saito four strokes soon.

No. It's just a 2" grinding vice.

Fresh fuel into the crankcase and heat from a heat gun will loosen things up. Please contact me through my website for further questions.

nice vice did you make that?

very good ,muito bom.

Great video. However I have one problem and I hope you have a solution. The piston wrist pin on my 52 is old and will not come out. The pad came right out. I have tried heating the pin with a heat gun and I have soaked it in wd-40. Any suggestions you have will be greatly appreciated.

has that engine ran

hi, is there a quick solution if the rocker arms are not moving and there is no compression on the engine?? or does it mean a complete dissemble? great video

hi, great vid! can you please tell me more about your little heater thing. I have lots of rc engines and have never seen one like it. aside from very specific bearing pullers this technique was fantastic!

Where can I get engines like that?

berapah harga untuk mesin seperti itu boss,,,

Reassembly videos are also up.

very cool :)

How does the cam turn? I've been trying to figure that out.

what you parsul me engine palees?

Where did you get the vice? Thanks

gulp... gulp... remove the pushrods... gulp... the valve keepers... gulp... hehehe... gulp... kinda like this video... gulp!

How do you fix seized up engines because I have one that has not Ben run in years and it moves just VERY tight?!

Kitanaka ha

Fine. Now show how to take apart a gummed up, used and abused engine, with stuck wrist pin, damaged bolt heads, cam cover glued in place, etc, not a brand new one just out of the box!

Kheyle mr30