SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Mar 22, 2011, 05:25 PM
Learning to Fly
Canada, BC, Kelowna
Joined Mar 2011
12 Posts
Discussion
O.S. Max 40 RC parts

Hello everyone.

I've got an old O.S. Max 40 RC engine that hasn't been used in over 20 years. I tried to run it, but it had hardly any compression. I took the engine apart and gave it a good cleaning, but I discovered that it is missing the flat ring head gasket, thus no compression. I've contacted O.S. and they no longer make that gasket. Does anyone know where I can get one? Maybe someone has this engine as parts....I'd hate to throw it away just because of a missing gasket. I've tried Ebay with no luck. Any help would be appreciated. Thanks.
northern pointer is offline Find More Posts by northern pointer
Reply With Quote
Sign up now
to remove ads between posts
Old Mar 22, 2011, 07:13 PM
Registered User
Joined Jan 2006
270 Posts
You can make a gasket if it was a paper gasket, using brown paper, or even buying gasket material from a local auto parts store or use liquid gasket stuff. Their was someone that was laser cutting them for Model Engines but I haven't seen any reference recently. Rings are available for the ringmaster.

It is a good engine very friendly with a good high low ratio. It would be a shame not to run it.
gzkpez is offline Find More Posts by gzkpez
Reply With Quote
Old Mar 22, 2011, 08:19 PM
Registered User
Tucson, Az
Joined Feb 2007
8,510 Posts
Os .40

OS made different .40's. Engine will have model # on side. .40H/ .40 FSR. etc. All you need to do is trace pattern on cut up soda can. Scribe it and cut out with sissors. Might need to do it again and be more carefull. This should give a good seal. You can glue on some fine emeroy paper to small sheet of glass and hone top of cylinder to remove gum/ tarnish etc. I bet a LA .40 gasket would work or FP-40. If this is ringed engine ring could be bad or stuck.
Dan
dankar04 is online now Find More Posts by dankar04
Reply With Quote
Old Mar 22, 2011, 09:10 PM
Registered User
Joined Feb 2009
29 Posts
Might just want to try and see if another OS 40 size head gasket might do the trick. How much different could it be?
smithth is offline Find More Posts by smithth
Reply With Quote
Old Mar 23, 2011, 12:43 AM
Learning to Fly
Canada, BC, Kelowna
Joined Mar 2011
12 Posts
To reply to dankar04, the only indication on the engine as to what type is that the outside cylinder wall has MAX-H OS 40 inscribed on it (MAX-H on the top, OS in the middle, and 40 in a circle at the bottom). The "manual" that came with it identifies it as OS Max 40 RC. The idea of cutting a pattern on a soda can sounds hopeful, as the original ring gasket was made of metal. I wonder if the thickness of the can would be sufficient to meet both faces of the cylinder and the head. I'm waiting from OS to let me know if a different engine ring gasket will work on this engine.

gzkpez....what is a ringmaster? I don't understand your sentence...."Rings are available for the ringmaster".

I checked with the local hobby shops (all two of them) and one had a ring for the OS 60, but when we tried it on my 40, it didn't fit.
northern pointer is offline Find More Posts by northern pointer
Reply With Quote
Old Mar 23, 2011, 01:02 AM
"Unnecessary Necessity"
coriolan's Avatar
Canada, QC, Quebec City
Joined Sep 2006
5,902 Posts
If it is a ringed engine it is normal not to feel compression while just turning the shaft by hand. As long as you didn't remove the ring from the piston it should be Ok, if you did it will need to be replaced as it will be distorted. Not easy to find parts for old OS, they don't stock any parts for discontinued engines. If only a matter of head gasket you can make one out of thin aluminium as suggested (brown paper is only good for back plate cover!
coriolan is online now Find More Posts by coriolan
Reply With Quote
Old Mar 23, 2011, 01:58 AM
Registered User
Arceenut's Avatar
Canada, BC, Langley
Joined Nov 2007
1,334 Posts
Quote:
Originally Posted by northern pointer View Post
Hello everyone.

I've got an old O.S. Max 40 RC engine that hasn't been used in over 20 years. I tried to run it, but it had hardly any compression. I took the engine apart and gave it a good cleaning, but I discovered that it is missing the flat ring head gasket, thus no compression. I've contacted O.S. and they no longer make that gasket. Does anyone know where I can get one? Maybe someone has this engine as parts....I'd hate to throw it away just because of a missing gasket. I've tried Ebay with no luck. Any help would be appreciated. Thanks.
I think I have several OS 40 and magnum 49 and 45s that are only collecting dust. (have to look to see what I have exactly). Make me an offer I can't refuse.
Arceenut is offline Find More Posts by Arceenut
Reply With Quote
Old Mar 23, 2011, 03:50 AM
Registered User
Sweden, Stockholm County, Sollentuna
Joined Aug 2010
221 Posts
Quote:
Originally Posted by northern pointer View Post
To reply to dankar04, the only indication on the engine as to what type is that the outside cylinder wall has MAX-H OS 40 inscribed on it (MAX-H on the top, OS in the middle, and 40 in a circle at the bottom). The "manual" that came with it identifies it as OS Max 40 RC.
In post number 136 in this thread http://www.rcgroups.com/forums/showthread.php?t=955929 you will find the manual for the OS Max-H 40.

According to that manual the cylinder head gasket has part number 414A, which I didn't find anywhere in the few webb-stores I checked before writing this, but you may have better luck with a more thorough search.

However, I did find a gasket set called 23414000 which is quite similair, so it might be that OS has revised their way of writing part numbers (OK, it's a long shot, but it might be worth investigating). Tower Hobbies has stated the size of the cylinder head gasket with that part number to inner diameter:19.8mm(0.782"), outer diameter:26.1mm(1.030"), Thick:0.1mm(0.004").

Just my 2 cents...
SBS_Pilot is online now Find More Posts by SBS_Pilot
RCG Plus Member
Reply With Quote
Old Mar 23, 2011, 10:41 AM
AMA 8711, FCC K4WZA
DPlumpe's Avatar
Salem, SC
Joined Mar 2003
524 Posts
My Max-H .40P ("P" is for "Pylon") (bore=20.6mm) has an alum shim/gasket, but is too mashed to measure the original thickness. ID looks to be 20.5mm (0.807") and OD about 25.5mm (1.004"). I have a clapped out Max-H .40 (no "P") which has a bore of 21.2mm. Shim ID would have to be about 21.2mm, but OD same 25.5mm.

My 40FSRs (the model following the H.40) have a bore of 21.2mm and have shims between .0075" and .008" thick when new.

Make sure your head really doesn't have the shim - it's hard to spot after it's been mashed into the head groove. Usually you can see some of the edge where it intersects a screw hole, or spot where it's been squished and starting to ride up the edge of the head groove.

BTW, the term "Ringmaster" likely refers to Frank Bowman, who makes excellent replacement piston rings (not head gaskets) for our old model engines. Last I bought, I think the charge was $9 for the smaller rings plus $3 or $4 shipping. If you need a piston ring, Google him..

-Dave
DPlumpe is online now Find More Posts by DPlumpe
Last edited by DPlumpe; Mar 23, 2011 at 11:04 AM. Reason: "Ringmaster" reference
Reply With Quote
Old Mar 23, 2011, 11:04 AM
Registered User
Tucson, Az
Joined Feb 2007
8,510 Posts
.40

The .40H is ringed. Frank Bowman sells rings and is called the Ringmaster. Gasket from soda can will work and you could use two but I don't think you need it. Oil and clean ring but don't remove unless you have a new replacement. Good old engine.
Dan
dankar04 is online now Find More Posts by dankar04
Reply With Quote
Old Mar 24, 2011, 01:47 PM
Learning to Fly
Canada, BC, Kelowna
Joined Mar 2011
12 Posts
Thanks everyone for your suggestions. I really appreciate it. I've made a couple of aluminum gaskets from a soda pop can and installed them. After that, I found that the compression problem still existed (or so it seems), so I filled the engine with WD40 and let it sit for a few hours. When I checked it, I found that the gasket must be working, because air bubbles were escaping from the bottom of the piston, which leads me to believe that the piston ring is not sealing properly.....or is that normal? Coriolan, maybe you can expand on your comment. The ring has not been touched and the piston sleeve is not scored, but I wonder if after all these years, the ring has become "seized" to the piston, and it won't expand to form a complete seal. That's why I filled it with WD40, hoping that it would loosen the ring. Coriolan, your comment gives me hope. Arceenut, if you have a Max 40 kicking around and it's working fine, I'd be interested in getting it from you. What to you would be a fair price considering its age? SBS Pilot, I checked out your link, but could not spot any reference to this specific engine...only LA and others like it in the 40 range.
If it comes down to replacing the ring, how do you remove the piston from the cylinder, and do you need any special tools to replace the piston ring? I tried sliding the piston rod off the shaft, but it would only go about 2/3 off the shaft. Thanks everyone.
northern pointer is offline Find More Posts by northern pointer
Reply With Quote
Old Mar 24, 2011, 11:37 PM
Registered User
Joined Jan 2006
270 Posts
Try this link for the manual: http://www.rcgroups.com/forums/showt...955929&page=10 I copied the manual for my new just broken in OS 40 H.

Sorry about the lack of a better reference about the Ringmaster before, must of deleted a sentence.

After you dissemble, it is possible my Dad did it years ago when he was clean it up a little. Someone here probably can tell you correct way for that engine. if the piston should be up or down or remove the wrist pin or what. Regrettably I do not know.

If you need a ring, (better then OEM), it might be just stuck as you suggest.

The RINGMASTER
Frank Bowman
1211 N. Allen
Farmington, NM. 87401

ringmaster46@msn.com
gzkpez is offline Find More Posts by gzkpez
Reply With Quote
Old Mar 25, 2011, 02:23 AM
Learning to Fly
Canada, BC, Kelowna
Joined Mar 2011
12 Posts
gzkpez, Thanks for the link. I've printed a copy of the manual. This should help in trying to get my engine running again. I'm going to a friend's father's house next week to have him check the engine. He's been flying for many years and knows his stuff. He's sort of like an old fashioned mechanic when it comes to rc'ing..
I remember this engine only has about a dozen flights on it, so the parts should be good, just unused for so long. With no scoring on the cylinder sleeve, it tells me the ring is good too, but maybe just stuck to the piston so it can't expand to create a full compression. We'll see what comes of the check up.
northern pointer is offline Find More Posts by northern pointer
Reply With Quote
Old Mar 25, 2011, 05:03 AM
Registered User
JohnsPop's Avatar
LaGrange, GA
Joined Jun 2009
1,818 Posts
If the engine was run with castor, you may be right that the ring is just gunked up and not sealing but you would think that it would be gunked to the cylinder, not compressed into the groove it rides in. Either way, you might try a heat gun to see if that loosens it up and gives a better seal. With a ringed engine, you're probably not going to feel a whole lot of compression anyway. You said you tried to run it so I'm guessing it got plenty of fuel in there.... that was going to be another suggestion, just soak it in fuel and it might release. Some folks shoot carb cleaner in there to un-gunk things..... my favorite is the crockpot with antifreeze. You can take the head and backplate off (plus it's a good idea to remove anything plastic or rubber like o-rings and such) and dunk the whole thing in a crockpot of antifreeze on low overnight. If the ring is stuck that should definitely get it loose. Letting your friend's dad look at it is probably the best bet since he's been flying a long time. Possibly, you were just missing something when you tried to crank it and the engine is ok after all. I bet he'll have it running in no time. Good luck!
JohnsPop is offline Find More Posts by JohnsPop
Reply With Quote
Old Mar 25, 2011, 12:30 PM
Registered User
Arceenut's Avatar
Canada, BC, Langley
Joined Nov 2007
1,334 Posts
If I am not mistaken, this engine was one of the earlier engines with a "Dykes" ring. This type of ring depends on the combustion chamber pressure to expand the ring and create the seal. If so turning the engine by hand will have low sealing and low compression. Run the engine and if it operates normally, there is no problem.
Arceenut is offline Find More Posts by Arceenut
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Sold NIB O.S. Max .40 FP series with muffler h2oman Aircraft - Fuel - Engines and Accessories (FS/W) 3 Feb 13, 2011 09:44 PM
Sold (2) O.S. .40 Max FP's in very good condition ebreeden Aircraft - Fuel - Engines and Accessories (FS/W) 2 Sep 13, 2010 06:44 PM
Wanted Wanted: 3A carb parts for O.S. MAX FP .40 nakman8 Aircraft - Fuel - Engines and Accessories (FS/W) 3 Nov 01, 2009 04:18 AM
For Sale Super Tigre .40 O.S. Max .20 $40 each shipped fixed3d Aircraft - Fuel - Engines and Accessories (FS/W) 0 Dec 16, 2008 12:53 AM
For Sale O.S. Max 40 RC engine w/muffler joey49 Aircraft - Fuel - Engines and Accessories (FS/W) 1 Nov 05, 2008 11:10 AM