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Jan 15, 2020, 12:37 PM
AMA 46133
SeismicCWave's Avatar
Quote:
Originally Posted by 1967Brutus
Running all castor lube in your fuel or at least a 50/50 castor/synth package) might restore that compression back to usable values (where is my compression gauge when I need it?).

It did for an old Fuji outboard that I received maybe 20 years ago from somebody from Hawaii. Engine was very low on compression, hard to start (needed extensive use of an electric starter), did not idle well etc etc.

After putting through maybe 2 litres of fuel 50/50, 10% Nitro, compression was more or less back, and the engine could fairly easily be rope-started again.
If this engine has no piston ring the compression won't come back.
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Jan 15, 2020, 03:00 PM
Still gassin' it.
Quote:
Originally Posted by SeismicCWave
If this engine has no piston ring the compression won't come back.
Well... that little .15 Fuji outboard als did not have a piston ring.... so I don't see why not...
Jan 15, 2020, 03:06 PM
AMA 46133
SeismicCWave's Avatar
Quote:
Originally Posted by 1967Brutus
Well... that little .15 Fuji outboard als did not have a piston ring.... so I don't see why not...
Hard to say. In my experience any engine that does not have ring and has no compression is not going to get any better. The reason for the lack of compression is worn parts. Ringed pistons can be salvaged with some over sized rings.

Then again we have absolutely no idea about the OP's engine. We have not seen any pictures of it. For all I know it could have a cracked head. All we know is that the OP got it used.
Jan 15, 2020, 03:12 PM
Registered User
Thread OP

Fx


Well I now know what a peeled liner looks like. After reading your posts and some on line research I pulled the head and looked again. The liner is junk. No wonder no compression. Its a real shame because the engine looks like new. I now remember I bought it several years ago at a swap meet from a guy that sold it cheap. No wonder. Well after waiting about 5 years to start it,I now have added to my knowledge.It should have some value but at the cost of a new sleeve it will set for a while till I can find a parts engine. Thanks for your input.
Jan 15, 2020, 04:26 PM
Still gassin' it.
Quote:
Originally Posted by Mash P39
Well I now know what a peeled liner looks like. After reading your posts and some on line research I pulled the head and looked again. The liner is junk. No wonder no compression. Its a real shame because the engine looks like new. I now remember I bought it several years ago at a swap meet from a guy that sold it cheap. No wonder. Well after waiting about 5 years to start it,I now have added to my knowledge.It should have some value but at the cost of a new sleeve it will set for a while till I can find a parts engine. Thanks for your input.
You could hold on to it, and try to find ASP/Magnum spare piston/liner sets. There is a good possibility that those are a direct drop in replacement. They are at least for the FX 46. If not, look for a nice lightly used ASP/Magnum and just harvest the items. These engines should be on the used market for prices that still would make it worth your while.

Worth a try, and IF Lucky, at least the ASP/Magnum items are of definitely better quality than the OEM OS items, believe it or not….
And if they would not fit, just transplant the OS carb to that ASP/Magnum, because believe it or not, the carburation is 90% of what makes a good engine, and although those cheap chinese engines might not look like much, mechanically and thermally they are absolutely decent engines.
Jan 15, 2020, 04:31 PM
Registered User
deleted

oooops. Sorry wrong information.
Last edited by JimboPilotFL; Jan 15, 2020 at 07:23 PM.
Jan 15, 2020, 04:42 PM
Registered User
OS Max 61 is known as an engine that can have problems with peeled liner but that is known for many years. I the period I fly this engine it was perfect for me until at one flight I discovered problems, the engine stopped in the air.

After I landed the Taurus I disover the crankshaft had friction and a ball bearing had problems.

Conclusion the temperature must have been very high. So high the ball bearing came lose in the crankcase and the engine cooled down with the outer race in a wrong position, so the friction. Also the CHT (temperature) has been very high, the alarm light (HH) was showing more than 200 degrees.

Conclusion, lean running during flight and because of thermal directly mounted of the HSN it must have been evaporating of fuel, so bubbles.

I replaced the carburettor so not using the original back plate mounted HSN anymore and replaced ball bearings. End of problems and flying the Taurus many succesfull flights after that until I stepped over to MVVS because of better torque and power for my airspeed control system.

My idea is, when overheating had take place more times as maybe OP's engine, can it lead to peeling, I don’t know exactly.

After a short time there was another OS Max 61 FX, of another club member with the same problem, friction of the crankshaft and we immediately renewed the ball bearings.

After that we also discovered OS Max made a modification of the mounting of the HSN with use of a steel plate bracket instead of the one piece aluminium back plate. Thermal flow from crankcase to HSN was reduced and overheating not possible anymore this way like a snowball effect.

That’s why I asked a photograph and the suggestion problems at the head and cylinder fit could lead to compression problems.

A fotograph of the Taurus with OS 61 FX and K&B carburettor. You also see the fuel pressure regulator and pitot and static tube for airspeed measurement and control.

TF
Last edited by Taurus Flyer; Jan 15, 2020 at 04:56 PM.
Jan 15, 2020, 04:57 PM
AMA 46133
SeismicCWave's Avatar
Quote:
Originally Posted by JimboPilotFL
There are no piston/liners anywhere from what I have heard ........ You can order a set if you go to the Pattern Planes forum and get your name on the list. there is a thread at the top.
https://www.rcgroups.com/forums/show...tally-in-OP%29
The pattern planes forum thread are talking about piston/liner/con rod set for the OS 61 SF/RF's. Those are long stroke engines. I am not 100% sure but I believe the OS 61 FX's are back to short stroke. So the bore and stroke dimension from the SF/RF will not fit in an FX.
Jan 15, 2020, 05:01 PM
Registered User
Indeed OS 61 FX short stroke.

TF
Jan 15, 2020, 05:05 PM
AMA 46133
SeismicCWave's Avatar
I don't have the specs in front of me for the 61 FX so I am only guessing. It must have a 24mm bore and 22mm stroke like the older OS 61's I wonder if the .61 piston and sleeve set will fit. Or maybe the 61 SX.
Jan 16, 2020, 08:28 PM
Registered User
Thread OP
I will just put the engine aside and maybe someday find the parts to fix it from OS. I would not want to disable another good engine to fix this one, The price of a used FX is not that much but it may not be a good deal. I don't need a 61 size engine now so not a great loss. Thanks for all the response.
Jan 17, 2020, 02:54 AM
Registered User
I bought my OS 61 FX new and after solving the HSN problems by mounting the K&B carburettor it did function very well. Because of the better specs for power, torque and 'no nitro', I switched over to MVVS 10 CCM and the OS became spare for the plane. Mounting holes are identic. Now I have a second NIB MVVS so the OS 61 probably will not run anymore but I still have all HSN components and so it's a kind of collectors item of a period in my modeling history.
My Taurus started with HB, after that OS and now MVVS. Also the HB has the mounting holes at the same pattern, location in the lugs.
A photograph of my Taurus in the beginning, more than 15 years ago, the last one of the same Taurus these days.
TF
Last edited by Taurus Flyer; Jan 17, 2020 at 03:02 AM.
Jan 17, 2020, 12:58 PM
AMA 46133
SeismicCWave's Avatar
>>I switched over to MVVS 10 CCM and the OS became spare for the plane. Mounting holes are identic.<<

I have quite a few MVVs 10 and 12.5 ccm engines in my collection. I am flying mostly the 12.5 ccm now because it is 2 ounces lighter than anything else. Now a super power house but a nice, light and smooth engine.

25mm X 52mm are fairly standard mounting hole pattern for a lot of engines. OS, YS, MVVs, Dub Jett etc. all use the same hole pattern. The main difference is the length from the mounting hole to the propeller drive hub. I have found that the MVVs has the longest length from the holes to the prop drive hub. I have a plane with with the MVVs 10cc mounted. I wanted to change to an OS or a Rossi 10cc but those two engines prop drive hubs do not extend beyond the nose ring. Since I did not want to modify the plane I just put in a MVVs 12.5 ccm and be done with it.
Jan 18, 2020, 01:32 AM
Registered User
Of course this is a thread about the OS 61 FX and a lot is written about this engine but by coincidence at the end the MVVS 10 CCM is in the picture, so still a post and not to 'burn down' the FX!!

Indeed the weight is also an important fact.

For pattern flying we want a centre of gravity at the most preferred place we find out during test flights. When using the OS 61 FX I have to add some weight in the tail, for the MVVS it isn’t needed. Also the HB is a lightweight engine and I started with in this plane.

So when looking at the characteristic, power, torque and weight for me also the MVVS is preferable above the OS 61 FX.
There also is another interesting detail, but, in the carburettor, the LSN.

The characteristic of the LSN of the MVVS I can modify over a much longer travel than other brands and in two directions and not limited to one direction by removing material with the lathe. Also I can turn the spray bar in the carb throat in the right angle, just as the Supertigres!

For a while we even can switch over to another engine, an OPS I have and then we see a carburettor with HSN, LSN, rotatable spray bar and airbleed. For special application this also can be preferred but it will be clear, adjusting this carburettor is quite a different story than a HSN and LSN. Not writing about the stop screw all carburettors have and the RC function for that we normally use, throttle trim position.

Photograph 1, spray bar I use in the MVVS 10 CCM
Photograph 2, carburettor of the OPS

TF


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