Bob-I

I'mI'm returning to flying after a 15 year layoff (kids, sports, etc) and I've have some nice old engines that I want to use again.

Saito FS-45, Enya FS-60, OS FS-90 are which were running great when I packed them away after carefully cleaning them and running Marvel Mystery Oil through them. Well.... the Castor did it's thing and now they're gummed up terribly. The Saito has a stuck exhaust valve, the Enya and OS are both gummed so bad that I can hardly turn them over, which I only did to make sure the valves were ok. All the carburetors are gummed and won't turn.

Is there a solvent or a method of removing this gum? Right now they're soaking in MMO again but no success.

Yes I know that engines are better now, and I fully expect to be buying more as well as experimenting with electric power, but I'd also like to use these older engines, especially in older design airplanes like my Sig Skybolt and some of my own designs that are still close to airworthy.

Thx in advance,

Bob

Jerry Sigur

Take the carbs off, heads, back plates, valve covers in the case of
four strokes, then soak them in fresh fuel over night, they will free
up.
Jerry

Ed Smith

Do a search on this Forum for "Cleaning engines in Antifreeze".

Ed S

Bob-I

Thx folks. I searched for the anitfreeze method so I'll try fuel first then antifreeze.

downunder

One thing you need to be certain of is that the conrod is free on the wristpin. Just soaking in fuel or antifreeze won't necessarily free this up, you need to be able to slide the rod along the pin to get any solvent in there. If this is gummed the pin then rotates in the piston bosses and wears them out quite quickly.

majortom-RCU

My Feedback: (40)

I tried the anti-freeze (ethylene glycol base) in the stew pot recently on an old Enya two-stroke, left on low overnight, backplate off, head off, piston & liner left in cylinder. Next day I had some mysterious crud in the bottom of the stewpot, plus some kind of crystalline precipitate all over the metal parts, sticking out like whiskers on a hobo (or Esquire male model in a thousand dollar pair of slacks). Carb barrel still stuck, would not rotate. I was so disgusted I didn't even try the piston for movement. I'll stick with the methanol bath. I will give a year of back issues of Model Aviation to the first person who can identify the precipitate,

Jerry Sigur

The anti-freeze bath usually cleans burned on crud but
seems to do little for the gummed up parts. The fuel bath
works best for that. I've noticed the crystalline stuff also
after using the anti-freeze, (don't know what it is either),
I usually use an old tooth brush and soap and water to
get it off.
Bob, let us know which worked best for you please.
Jerry

Sport_Pilot

Soaking in denatured alcohol also works well. Also heating the engine in an oven will free them up.

Bob-I

Well after a night of soaking 2 engines in fuel I've made lots of progress. The Saito 45's stuck valve is unstuck and moving slowly, so I'm sure it'll free up by changing the position and soaking some more. The OS-90 is now turning freely, both valves working and has decent compression. Both carbs are still stuck though. I'm thinking of alcohol next if a few more hours doesn't start to work.

I'm confident now that I'll be able to save these engines. I like them for semi-scale realistic flight style planes and I'd hate to have to buy new engines.

Next I'll take the Enya out of the plane and soak it, then start on some of my old 2 strokes. I have a Como 50 that's great with a Perry carb, that Perry-Como really sings. (sorry, long day)

LSP972

My Feedback: (13)

Groooaaannnnn!!!!!!!!!!!!!!!!!!!!!!!!!!

jessiej

I agree- also if you are in a hurry you can heat the engine enough to turn over then finish the job with alcohol or fuel.

jess

Motorboy

You can soak the engine in autodiesel over night and parts will be degummed..

Jens Eirik

piper_chuck

My Feedback: (12)

You are in just about the same situation I faced 3 months ago, just different engines, although I also have a Saito 45. I did not have to do any disassembly, I did take the valve covers off the Saito to make sure they moved ok and to check the clearance. I found that 10-15 minutes in the oven at about 300 degrees softened up the gummy stuff enough to allow everything to turn, including some stuck carb barrels. While the engines were still fairly warm, and using an oven mit to hold them, I found they would turn, although slowly. I used rubbing alcohol to cut the gummy stuff. This freed everything up. After a few rounds of alcohol and the engines were spinning freely. I heated them a bit to evaporate the alcohol and then oiled them up. So far all are running nicely.

Bob-I

I'm concerned now about heat, now that they've soaked in fuel for 2 days. Like I said 2 are spinning freely now and one of the carbs, the OS, freed up just about an hour ago. If the Saito carb doesn't free up I may use heat but it'll be outside for sure.

jessiej

I have had success in some instances with a heat gun rather than an oven.

jess

Flyboy Dave

My Feedback: (21)

I soak the carbs in rubbing alcohol. They free up overnight.

Dave.

Bob-I

Thanks Dave. The alcohol did the trick. Next, put them on the test stand and fire 'em up.