Thread Tools
May 20, 2019, 02:46 PM
Registered User
Thread OP
Help!

Engine Repair/Service


Hello,

Recently at my RC clubs annual auction I acquired an old O.S FS-91 4 stroke that is a perfect match for the Top Flight ARF T6 Texan that I'm currently working on. I'll be honest it needs a bit more TLC than my abilities can provide. It will need a mechanical once over, probably a part or two a good cleaning and a run up with tuning. Does anyone on this forum know of anyone that is trust worthy, capable and in the business of servicing engines for customers?

Thanks
Mike
Last edited by lucylu11; May 20, 2019 at 03:07 PM. Reason: new pic
Sign up now
to remove ads between posts
May 20, 2019, 05:02 PM
Pro Hoarder
turbonut's Avatar
Hi Mike
There is a number of guys here on RCG that can take care of that engine for you. Where are you located? If shipping cost is an issue
Latest blog entry: In flight
May 20, 2019, 05:50 PM
Registered User
kimchiyuk's Avatar
Sent you a PM.
May 21, 2019, 03:36 PM
Registered User
Thread OP
Hello,

I live in NJ. Shipping is not an issue.
May 21, 2019, 06:16 PM
Pro Hoarder
turbonut's Avatar
I work on engines all the time but I am in california. I am sure there is some one closer to you
Latest blog entry: In flight
May 22, 2019, 11:46 AM
Registered User
Cougar429's Avatar
Are you able to post a pic with the rear cover off? A lot can be told of how well it was cared for and stored after running by the condition of the interior. One of the bore with the piston near the top may also show what the liner looks like.

I have been restoring, repairing and resurrecting engines for 3 1/2 decades and nothing really difficult, just need care and patience to do it correctly. If relatively intact most often a set of bearings and O-rings/seals are all that is required. There can be a few other items such as valves, springs and keepers that can wear over time, along with the cam lobes and followers. Each are replaceable and should still be available.

I have had 4 or more of that engine and over time went through all of them. In fact, first was mounted into the kit built T/F Texan shown in the first 2 pics and flew it well even at a relatively heavy 12 1/2 lbs. The ARF had a Saito 100.

Best I could offer would be to have a boo and give you an estimate of condition and what it would take to get it back up and running. Once at that point you could decide if economically feasible. If so, could even tweak it on the test stand shown in the last pic so should be ready for mounting. Only difficulty is international shipping as I'm in Canada. Just had customs rake me over the coals yesterday so may be best to find someone your side of the border.
May 22, 2019, 12:41 PM
Registered User
David McIntire has an engine rebuilding service, he has an excellent reputation, he will probably respond to your request, or you can Google os 91 surpass engine repair and his name will pop up.

Jim
May 22, 2019, 01:18 PM
Registered User
Quote:
Originally Posted by Solomaster
David McIntire has an engine rebuilding service, he has an excellent reputation, he will probably respond to your request, or you can Google os 91 surpass engine repair and his name will pop up.

Jim
If you watch a few of his videos on the 91 surpass you could probably overhaul it yourself. He has done quite a few. (hundreds of engines)

OS FS-91 Surpass Customer Engine Video 1 (16 min 20 sec)
May 23, 2019, 04:15 AM
Engine man
dmrcflyr2's Avatar
I am no longer servicing OS four stroke engines and cutting back on much engine servicing. About the only engines I will do anymore are Saito's.
May 24, 2019, 09:52 PM
Registered User
kimchiyuk's Avatar

O.S. FS 91 surpass refurbish


So Mike has entrusted me to bring his FS 91 back to life. I sent him a PM the other night telling him that I'd be happy to take a look at his engine and let him know what it needs. We spoke on the phone and it turns out he doesnt live all that far from me and we have actually flown at the same field. Never met in person, but what a small world!!
Anyway, I received the engine today and you'll be able to tell by the pics; it wasn't pretty inside. It has quite a bit of corrosion and very dry. Practically no sign of any residual lubrication. It turned over pretty hard, VERY gritty feeling and after installing a glow plug- NO compression. I removed the valve cover to see if the valves were moving and they were not. Turns out the tappets were frozen. I continued and dismantled the entire engine. I put the head in LA's totally Awesome and put the tappets, crankshaft and camshaft in CLR (Calcium, Lime and Rust) to remove the corrosion.
Tomorrow I will remove the bearings and thoroughly clean all parts of the engine. I'll take apart the carburetor and clean it as well.
All it appears to need parts wise is a set of crankshaft bearings and a throttle arm.
More pics to follow tomorrow after cleaning.
May 25, 2019, 07:43 AM
Registered User
Cougar429's Avatar
kimchiyuk, good of you to do the deed and lucky you are so close.

If I had to guess this engine is low time, just stored badly, (usually I at least see wear or abuse on the rocker adjusters). Still, would think some rubber bits such as pushrod tube end seals or carb O-rings would also be needing replacement.

Could not tell from the pics and angles, but what is the condition of the cam lobes and followers?

To the OP, Mike, get yourself an inline fuel filter. 4-strokes are less tolerant of contamination making it to the carb.
May 25, 2019, 12:53 PM
Registered User
kimchiyuk's Avatar
Quote:
Originally Posted by Cougar429
kimchiyuk, good of you to do the deed and lucky you are so close.

If I had to guess this engine is low time, just stored badly, (usually I at least see wear or abuse on the rocker adjusters). Still, would think some rubber bits such as pushrod tube end seals or carb O-rings would also be needing replacement.

Could not tell from the pics and angles, but what is the condition of the cam lobes and followers?

To the OP, Mike, get yourself an inline fuel filter. 4-strokes are less tolerant of contamination making it to the carb.
They actually weren't bad. When the engine is as dry as it was it's difficult to tell if it's dried castor or corrosion as the both appear to look like flaking and pitting rust. As you can see from the pics, the cam followers and camshaft look good.
Last edited by kimchiyuk; May 25, 2019 at 09:27 PM. Reason: Typo
May 25, 2019, 02:35 PM
Registered User
kimchiyuk's Avatar

Cleaning, reassembly and first run.


Mike,
Here is all the pics of the cleaned parts, reassembly of the engine and the first run. It is tuned and ready to go. Obviously you may need to tweak very slightly depending on weather and prop selection.

Prop used was a Master Airscrew 14X6.
Lowest reliable idle: 1750 RPM
Peak high speed: 10,200 RPM

I did get a run video which I will post as well. It started pouring right at the end of the run. I'll get it lubed up with After-run, box it up and send it out on Tuesday. Good luck with it in your AT-6. Should be a great match!

In my opinion this was a pretty low run time engine. It appears is sat for a long time with no lubrication; hence the corrosion. This engine is now practically good as new and runs like it!
May 25, 2019, 02:49 PM
Registered User
Great job on that engine kimchiyuk. Better than professional I would say, more like a NASA quality overhaul. Do you take in stray engines once in a while? website? business?
May 25, 2019, 03:24 PM
Registered User
kimchiyuk's Avatar

Run video


O.S. FS 91 Surpass run (1 min 32 sec)


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Looking for a builder in Scotland to repair a customer's boat. ResinRay Scale Boats 4 Mar 12, 2019 08:50 PM
Discussion Horizon customer service for Hobbico products Ryguy Vendor Talk 0 Dec 21, 2018 09:24 AM
Rave Hitec Customer Service and Repair bobthenuke Vendor Talk 2 Dec 02, 2009 08:25 AM
Rant Mega Motor Customer Service and Repair xwingnut Power Systems 6 Sep 17, 2007 09:41 PM