OS FT160... rebuild needed? - RC Groups
Shop our Airplanes Products Drone Products Sales
Thread Tools
Oct 06, 2017, 05:09 PM
Registered User
Discussion

OS FT160... rebuild needed?


Hello,

I recently acquired a used OS FT 160. I started going through it to adjust the valves and found some corrosion on the valve train (springs, rocker arms, retainers (pretty much everything visible). So I decided to pull of the back case to see what was in there and there is just slight rust on the gears. The teeth seem to be fine. There is rust on the retainer cage of the bearings but can't see the surfaces of the races without further disassembly.

Compression seems fine and the motor turns smoothly without play. Thinking about just getting new heads with the valve train (cheaper than the valve train alone) and possibly getting pistons, rings, cylinder liners and wrist pins just in case.

I'm thinking I'll have to break down the engine to at least clean up the cam and crankshaft bearings so I don't risk rust breaking off and getting circulated through the rest of the motor.

Am I going overboard and what else should I look for?
Sign up now
to remove ads between posts
Oct 06, 2017, 07:02 PM
Registered User

Os 160


Parts for that engine are very expensive and a rebuild can cost you close to a new engine. I suggest at regular intervals you pull the rocker covers and give everything inside a good squirt of automatic transmission fluid. These engines are famous for lack of lubrication to the top end. Adjust the valves and run it until it drops.

Kip
Oct 06, 2017, 07:30 PM
Registered User
Thanks kip. I wound up disassembling enough to see the crank case and cylinders and that all looks good but needs some cleaning. A lot of what I thought was rust appears to be some kind of red wax-like buildup.

Any recommendations on a cleaner to dissolve that?
Oct 06, 2017, 08:53 PM
Engine Frankensteiner™
1QwkSport2.5r's Avatar
It's castor varnish. Either leave it as is or flush with acetone.
Oct 07, 2017, 09:57 AM
Hope to get out of life alive
kenh3497's Avatar
Quote:
Originally Posted by 1QwkSport2.5r
It's castor varnish. Either leave it as is or flush with acetone.
Qwk has it right I believe. Castor residue is often mistaken for rust. If you are comfortable with dismantling the engine it can be completely cleaned up and look pretty much like new.

Ken
Oct 07, 2017, 11:31 AM
Engine Frankensteiner™
1QwkSport2.5r's Avatar
Quote:
Originally Posted by kenh3497
Qwk has it right I believe. Castor residue is often mistaken for rust. If you are comfortable with dismantling the engine it can be completely cleaned up and look pretty much like new.

Ken
That's the beauty of castor varnish. It prevents rust really well.
Nov 07, 2017, 04:08 PM
Registered User
So, I got the motor torn apart and found I needed all new bearings and that was about it. Valve springs are iffy due to actual rust on them so I replaced those as well. I got a tip from another modeler to soak the motor parts in a hot (200F) antifreeze bath and that worked even better than acetone and helped get most of the bearings out of the case.

Old bearings were a PITA to remove... specifically the front cam bearing. Made a bearing puller with some 3/16" music wire folded over then ground out recesses with my dremel. Worked well after heating up the case a bit.

Something I was wondering though is when trying to restore compression if I can get away with just rings or if I need to replace sleeves and pistons too.
Nov 09, 2017, 06:55 AM
Methanol, The Cool Fuel !
Gary Cee's Avatar
The rings should do the job. Many people think that the compression seems a bit low on these engines. Don't forget, this is a pair of 80 size cylinders and won't "feel" as strong as a 160 when flipped by hand.

BTW, Were your cam bearings pretty sloppy?
Nov 09, 2017, 11:54 PM
Registered User
Individually, the cam bearings have some rock back and forth on the inner race. But with the cam supported across both bearings, there is barely any discernible play. You would need a dial indicator to measure the movement, a couple thou, if that. Its normal for ball race bearings to have some play within the inner race. its the play across the two bearings with the cam installed across the two you need to be concerted about.
Nov 12, 2017, 06:17 PM
Registered User
Quote:
Originally Posted by Gary Cee
The rings should do the job. Many people think that the compression seems a bit low on these engines. Don't forget, this is a pair of 80 size cylinders and won't "feel" as strong as a 160 when flipped by hand.

BTW, Were your cam bearings pretty sloppy?
The cam bearings were clicking/rough. I used to restore bearings in synchro servo systems but I just couldn't get these clean so they would spin freely and smooth. $60 is what it cost to get both the cam and crank sets from boca bearings.

I wound up getting another used 160 and the compression was noticeably better.

Interestingly on that second motor... it was pretty gummed up so I broke it down to clean it. When I removed the con rods 3 of the four bolts snapped off at the shaft of the bolt where the threads started with minimal resistance. Those things were just about to give up. Maybe that occurred from rotating the motor when it was gummed up? The one that didn't is slightly bent in the same place.
Nov 14, 2017, 10:05 AM
Methanol, The Cool Fuel !
Gary Cee's Avatar
Quote:
Originally Posted by pt_a
The cam bearings were clicking/rough. I used to restore bearings in synchro servo systems but I just couldn't get these clean so they would spin freely and smooth. $60 is what it cost to get both the cam and crank sets from boca bearings.

I wound up getting another used 160 and the compression was noticeably better.

Interestingly on that second motor... it was pretty gummed up so I broke it down to clean it. When I removed the con rods 3 of the four bolts snapped off at the shaft of the bolt where the threads started with minimal resistance. Those things were just about to give up. Maybe that occurred from rotating the motor when it was gummed up? The one that didn't is slightly bent in the same place.
I picked up a 120II Gemini a few years ago. The engine had only seen Cool Power (100% Synthetic) fuel. Not a lot of time on the engine but most came on floats in a Cub. The cam bearings had extreme play, more than I had seen in quite some time! A few months later, I had another Gemini but a 160 . It too had gobs of play in the cam bearings. Just curious if you saw an issue too. (Looking for real observation )
Nov 14, 2017, 02:07 PM
Registered User
Quote:
Originally Posted by Gary Cee
(Looking for real observation )
Quote:
Originally Posted by ClubFlyer
Individually, the cam bearings have some rock back and forth on the inner race. But with the cam supported across both bearings, there is barely any discernible play. You would need a dial indicator to measure the movement, a couple thou, if that. Its normal for ball race bearings to have some play within the inner race. its the play across the two bearings with the cam installed across the two you need to be concerted about.
This is a real observation. I own a FT160 purchased off Ebay, new bearings throughout. With the case stripped, and just the cam & cam bearings (back timing cover as well) installed, put a dial indicator on the cam followers, I made a small short rod off the cam follower to the dial indicator. With the cam follower (dial indicator side) positioned on the cam base circle. Then from the apposing side follower push against the spring tension of the dial indicator, and read the amount of lateral play in the cam bearings.Take readings from both the intake and exhaust followers, you will find the readings to be more than acceptable. Couple thou if that. As I mentioned above, individually, the inner bearing race has some rock to them (rocks back and forth) but very little lateral play.
Last edited by ClubFlyer; Nov 14, 2017 at 02:35 PM.
Nov 14, 2017, 04:25 PM
Methanol, The Cool Fuel !
Gary Cee's Avatar
Thanks, new bearings aren’t the focus. Plenty of first hand experience in that arena from toy engines to huge metal forming machinery.

I have seen a few cases now of Gemini engines with extreme radial clearances. One set measuring near 0.5mm. ( .02”). Interested in determining what the operating conditions were for those engines.
Nov 14, 2017, 06:47 PM
Registered User
20 thou play in the cam bearings.The engine I got off ebay had hardly any play in those bearings, even after all the caster goo was cleaned out. I could have continued to use those cam bearings, but the work involved in dismantling the engine, I installed a full bearing set.

I doubt the valve spring pressure would cause excessive wear, unless there was a lack of lubrication to those bearings, for that reason I always use plenty of after run oil in the crankcase to get some extra lube in those areas.

Possibly a lot more hours on that engine than previously thought, run with less oil in fuel than recommended, or someone ran the hell out of it for sustained periods.
Nov 15, 2017, 06:05 AM
Methanol, The Cool Fuel !
Gary Cee's Avatar
I knew the owner very well. The engine was in a Clip Wing Cub float plane It was not a high time engine The fuel was Cool Power All synthetic.

Gene and I flew together and accumulated similar fly times. I had engines with twice the time on them then. My present 160 has no hint of a problem in that area. Home brew fuel 14% oil, 2% castor,12% synthetics. 14% nitromethane.

Yes, it is exceptional wear. That is why I am curious.


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Help! Need your advice about rebuilding Lipo battery's! Turbotom2 Batteries and Chargers 13 Apr 24, 2016 11:11 PM
Discussion OS 61FSR rebuild mustangherb Engines 2 Apr 08, 2016 03:58 PM
Question Rebuilding OS FS-40: Lubrication & Cleaning?? Gemini2 Engines 4 Feb 13, 2016 08:02 AM