Gray Beard

My Feedback: (-1)

I used to build VW engines for racing and sand buggy's plus my own auto engines for street rods so I knew something about engines. Then a long long time ago I bought my first four stroke glow engine, the OS 70fs. I go it at a club auction from a friend so I knew the history of the engine. It ran great until I flew the plane through a tree then it just wouldn't run right at all. I sent it into Towers OS service for repair. They told me they would run it up first to see what they thought was wrong. I got a call from them telling me it was run lean and needed a complete rebuild? The cost was $28.00 cheaper then a new engine so I had them send it back. They sent it back in pieces, that turned out to be a good thing. I took it to a local shop that rebuilt model engines and they saw no signs of a lean run at all? At that point I bought a little book called OS Model 4/Strokes by Graham C. Rice sold through RCM. It shows and tells you how to assemble the engines. Piece of cake but the engine still didn't run correctly. When I sent the engine in I told how it went through a tree and I thought the needle valve was bent or something in the carb was off. I just ordered a complete needle valve assembly, installed it and the engine ran perfectly again. I used it in several planes and I had it in a bipe and sold the plane complete, still kicking myself in the butt.
From then on I have been given several four strokes and if they run then fine, if not I rebuild them. I have only bought one YS new and no OS engines, sense then I have no idea how many YS and OS I have rebuilt for myself and others. The hardest part in any of them is a valve job, those little keepers are hell to get back in.
I was a huge fan of the OS pumpers but OS/Tower won't sell you a regulator diaphragm and there pumps are designed as a replacement part so you can't rebuild them. YS you can get every part required for a complete rebuild and I like them a bunch better then OS.
People can't seem to understand how they work and can't keep there hands off the regulator screw, when they get fed up trying to get them to run they tend to give them to me as a gift. These are the older models and most of them are the FZ so they are about the perfect sport engine.
I have been using rcbearings.com for years and so far have only gotten one bad bearing from them. I just started using Bowman rings too for both gas and glow engines and they fit better then the stock rings.
Most the guys I fly with have gone over to gas so I don't get very many four strokes to rebuild these days but I love rebuilding them. I won't work on a Magnum and I'm not a big fan of Saito but I will work on them.
Anyway, I felt OS service was a total rip off and they can't do anything I can't but they won't sell me the regulator diaphragms, those two screws and spring must be beyond us mortals to replace or something so I no longer fool with there pumpers at all. It's been a long time sense I have had to buy a new glow engine, OS makes a good one but I refer people to YS if they are local and I can teach them how to tune them. They aren't really much different but they seem to boggle some minds??

izzy-israel-73

Thanx Gray I have also got a 91 fs pumped still in the box not sure what plane I will be putting it in

izzy-israel-73

I have read a few threads about the YS's and people do seem to have probs tuning them never had one to try out myself

Gray Beard

My Feedback: (-1)

Don't get me wrong about the OS engines, I really like them and have gotten some very long use out of the pumpers. They don't like to be out of use though, the castor can really gum up the pump and diaphragm. My problem with them is they don't have a pump that is rebuild-able. OS doesn't sell a diaphragm for the pump or regulator so they can be rebuilt, I don't care for that.
I have just had way better luck with the YS engines but my advanced instructor was there to teach me about them and the do and don't of the engine. They aren't for everyone and the older models are a balancing act to tune. Not hard but they can be a problem for some people. The biggest problem I see is new users can't seem to keep there hands off the big brass screw on the regulator. It's an air bleed carb and the low end adjusts backwards to other engines. Just simple things but people seem to have a problem with them?
Having someone around to teach you how things work makes it a bunch easier.
We have a great engine forum here on RCU with factory support, the OS and YS forums are a huge help. Bill Baxter is there for you in the OS forum. He has helped me out with some strange problems I have had. If you have a problem then just ask Bax, he has seen it all hundreds of times. Now with the new smaller gas engines from China I don't get to work on glow engines very often these days but I have so many of them I haven't gone completely to gas. If it calls for an engine over 1.20 then I go gas. I still have a couple of the OS 91s and a bunch of the YS 120s and 110s not in use.
I just did a rebuild/repair on my favorite YS 110, first flight I crashed the plane and the cylinder broke where the header screws into. I can either have it welded or just buy a new cylinder. The parts are easy to come by.

izzy-israel-73

The 91FS being my first four stroke was all new to me I love the note they give out but it can be hard to find were it is at it's peak rpm, I flew the plane this week for it's maiden used a APC 15x4 she sat in the high seven's on the taco but still was running rich take off was easy only needed some trim in the elevator, landed gracefully love the sound of the prop wash as she comes in to land did about ten touch and goes I was hooked on that prop noise sounded like a real plane coming in lol hope to fly her again on Christmas Day if weather permits have purchased a 91FS 11P engine brand new price was to good to say no to was thinking about putting in the extra 300s 60 size plane but not sure wether just to stick to the 61FX I will see what happens when I get to that project soon

izzy-israel-73

what rpm's were you getting from a 15x4 BigTim?