By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by CML

Jammed OS engines

All Topics | Latest Posts

Search for:  in Thread Title in  
Talha Khan22/02/2020 05:53:24
1 forum posts

Hi, I have several OS engines that I have not been using for many years. Now that I have taken them out, they are totally jammed and cannot rotate at all. I have tried dipping them in petrol for several days but it has not worked. Can some one please suggest a way to get them going again. Thanks.

Denis Watkins22/02/2020 07:42:39
4168 forum posts
82 photos

It would help Talha if the lads knew if the motors were stored in the open air?

And the fuel used, was this castor based? Or synthetic fuel? When the motors ran.

After use this time, run the motors dry and use afterrun oil to lubricate them for storage

Edited By Denis Watkins on 22/02/2020 07:43:17

Nigel Heather22/02/2020 08:45:05
239 forum posts
7 photos

If you are lucky it will just be gummed up castor oil and a cleaning solvent like WD40 or white spirit or cellulose thinners or brake cleaner will break that down. Mind you petrol would have worked too - did you remove the carb and glow plug when soaking - and did you try turning the engine periodically.

If it is ceased due to rust they may be beyond economical repair or safe operation.

Have you tried taking the backplate off to look inside - will give you an idea of whether there is any rust.

The other trick is to heat it in a pan of water, that will soften any gunge and the expansion will help release the puston from the liner. Make sure you lubricate thoroughly and ideally run afterwards as you don’t want the engine left with any water inside.




Edited By Nigel Heather on 22/02/2020 08:46:14

Peter Christy22/02/2020 08:50:14
1716 forum posts

I've used contaminated diesel or red diesel in the past. Both cheap and readily available. Nasty stuff, though! You don't want to get it on your hands!

I use a large Kilner jar, fill it with diesel, take the carb, backplate and plug off the engine, and suspend it in the jar for a few days. The carb can also go in, but is removed to allow the diesel to soak into the inlet side of the engine.

Has worked for me on a couple of "solid" engines.



extra slim22/02/2020 08:52:23
465 forum posts
48 photos

Put prop on, heat with heat gun, then work it. When it moves then lubricate and continue to gradually work it

Paul Marsh22/02/2020 09:09:48
3832 forum posts
1110 photos

I usually warm them up and put fuel in them. After they are ran, then should be ok, by adding some light oil to keep it moving.

Jon - Laser Engines22/02/2020 09:11:55
5181 forum posts
236 photos

If wouldnt mess about with a solvent as they rarely give satisfactory results. If they are stuck just take them apart and clean them. Even if you do free them up with a solvent the bearings will still be locked solid so just bite the bullet and strip them down.

For the time cost and the cost of a few bearings its just not worth destroying the engine by doing a half job of freeing them up and then having a bearing fail a short time later.

stephen grigg 122/02/2020 20:49:57
11 forum posts

ive had some solid ones recently cos ive discovered my shed has rotted in a mega way ivwwarmed them with a heat gun and its worked every time and then wd 40

Allan Bennett23/02/2020 05:05:51
1602 forum posts
44 photos

WD40 has worked for me in the past. But it's not a lubricant so, once you've got things moving, follow up with lots of light oil (e.g. 3 in 1) before trying to start it. As others have mentioned, if rust is the problem you'll need a proper rebuild.

ken anderson.23/02/2020 09:17:42
8543 forum posts
776 photos

I've just freed up the stuck carb on a OS46,using my heat gun and wd/oil..

ken dept.

Engine Doctor23/02/2020 11:08:07
2402 forum posts
31 photos

Re gummed up engines. Beware ! I still have a damaged con rod (oval big end)from a OS Gemini twin on my key ring as a reminder of what damage castor can do when it sets like varnish inside an engine . I bought the engine in a clipped wing Cub many years ago. It was very clean and showed no signs of burnt on castor . Engine felt a little dry but not gummed or stiff as it had not been flown for a year or so ,according to the previous owner. Engine was thoroughly wetted with fresh fuel and started easily. After a short run it started making a knocking sound and was immediately stopped. On investigation both con rod big ends had been badly damaged ,fortunately the crank escaped and was reusable. The culprit was castor oil had set in the big end oil holes like varnish plugs. Had this happened today then the Gemini 120 MK1 would be scrap as con rods were only available second hand back then !

Since then I always strip clean and check oil ways are clear. Similarly I Never used castor based fuel on any glow engine two or four stroke.

And before any fuel gurus start on about the merits of castor ,yes it has its place in vintage engines and WW1 engines , and old vintage model engines that need a thicker oil.

Three - in - one oil was mentioned. What ever you do don't use it as a lay up oil. It's acidic ,will stain casings and sets up like varnish . A good quality air tool oil will keep your engines free and protected for those long lay ups or general after run use.

Jon - Laser Engines23/02/2020 11:43:01
5181 forum posts
236 photos

ED Has is spot on and his conrod example is a classic. I have had many laser's back over the years with broken rods following this type of failure. They have been stored for a while, then whipped out and run without a thought. A short time later there is a crunch and the rod breaks due to either blocked oil passages or a small amount of rust on the crank pin picking up in the bush.

ball bearings are a similar problem as they might spin, but the little balls are all locked solid in the cage by congealed oil. Running the engine will score the balls and when some of them start to rotate as the engine heats up and the oil softens they transfer this damage to the races and the cage. Loads go through though the roof when the balls are hexagonal and the cage will fail shedding steel fragments into the crankcase. This debris will not stop the engine, all it will do is sit in the crankcase as the conrod/crank pulverise it and spread it around the engine. I had one customer who had this happen and only decided to stop the engine when he noticed metal particles all over the wing where the exhaust had blown on it. Needless to say, his 200v was beyond economical repair by that point.

As for solvents. 3in1, wd40, petrol, cellulose thinners, acetone... Dont use them. It ruins seals and O rings, and in the case of petrol it really will not touch castor as castor is not soluble in petrol. If you must use a solvent use methanol as the engines are designed for it and it will dissolve any oil used in model fuel. Still, methanol is nasty stuff so dont leave an engine soaking for a long period.

Even then, as ED and i have mentioned, the only way to fix a gummed up engine is to take it apart and clean it as solvents will not do all the work for you. And, as already stated, castor is dead. Stop using it.

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!

Find RCM&E! 

Latest Forum Posts
Support Our Partners
Cambridge Gliding Club
electricwingman 2017
Wings & Wheels 2019
Sussex Model Centre
Advertise With Us
Latest "For Sale" Ads
Do you use a throttle kill switch?
Q: This refers to electric-powered models but do you use a throttle kill switch?


Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us