OS FS Surpass II bearing question
 

I am in the process of replacing the bearings on my OS engine. Having removed both bearings, I see that the rear one is shielded on both sides and the front one is shielded on one side. What is the recommended procedure with rear bearings? The new one that I have is shielded on both sides. Do I need to remove both shields or should I use it as is since the OS also used a shielded rear bearing? The replacement front bearing has rubber shields on both sides and the manufacturer recommends that they both stay on..
Matt

hey Matt I was a complete noob when it comes to engine rebuilding even though I own over a dozen engines mostly 4 strokes since COVID I have been on a engine rebuilding tear its funny RCU has really quieted up since I first joined usually there would be a bunch of posts related to this subject..

many of the 4st engines I have were used and I really had no idea what I was doing except how to adjust the valves, I would recommend looking up https://www.youtube.com/channel/UCjm...m794jkGxutejcg the author is David McIntire he has pretty much stopped posting about engines but has left his videos for posterity, hugely informative on Bearing installation, Carb adjustment, and allot of valuable information on glow engines in general like performance RPM numbers etc.

what I have gathered and how I have been currently rebuilding my engines is with the front Bearings I leave the shield facing the prop intact, and open the shield facing the rear of the engine on all my 3 current builds.
for the main rear bearings I have both shields removed, as I understand it its for lubrication, for the cam Bearings I leave them fully shielded as they are very small on a 4 stroke engine, this was recommended by David,some have said leave the shields on the front bearings of the larger OS120, but I haven't seen any leakage at all so far in my test runs.

so far so good for my rebuilding adventure, I bench ran the 2 OS 91's I had replaced all 4 bearings, on one I did replace the rod and piston pin because they were obviously worn, I got a easy 9K+ on the top end and a smooth 1800+- on the idle for both, neither needed carb work but I did give them a thorough cleaning.
I just ran engine #3 on my test stand a couple of hours ago, I rebuilt a very used OS 120SE non pumped 4 stroke, it also needed a new rod and I got a new pin for it even though it probably didn't need it for right about 30$ new on ebay.
my run last night was pretty bad, it was running really hot and fuel starved,so I went strait for the carb carefully pulled it apart, carbs are actually pretty simple, and cleaned all the parts in my sonic cleaner, love my sonic cleaner for cleaning engine parts it works unreal.
I have a small basket for the tiny stuff, the carb needed a new barb on the fuel intake the old one was clogged, and I had a extra needle valve so I went for that also, after using Davids carb reset technique and a couple of small adjustments 9200-1750 RPM range with great transition.

I just got my Bearings for 2 more Pumped OS 120 4 strokes one of which I have torn down in the mail, I will have a nice pile of fresh engines soon some of which I paid less than 100$ for and have been stocking up on small replacement parts our club finally opened up with some restrictions so I am ready for some air time.

Hello,
Thanks for posting a reply. I was beginning to wonder perhaps interest in glow engines may be completely gone and I am really glad to see that it is not.

I bought my replacement bearings from Boca. They're supposedly stainless steel. The were both shielded except that the front one is rubber shielded and the rear one is all metallic. In corresponding with Boca they suggested that I could just install the front one as it was but remove the shield on one side of the rear bearing (facing the front of the motor) and this is what I ended up doing. It went back together relatively easy and of course along the way I cleaned up the motor as well. I did not touch the cam bearings. I wanted to but did not remove the valves as the idea of working with tiny springs did not bode well. Anyway I ran the motor and did not see a performance change which was bad as lack of performance (~ 8800 RPM, 14x6 prop) was the primary reason as to why I had replaced the bearings. Finally I replaced all the fuel lines, .., etc and this did it. It now reaches 9300 RPM which is close to where it was when new (~ 9500 rpm). The fuel that I have is old and that may be a factor too. Considering the fact that the motor is 20 years old, all seem to be in relative order for now.

I ended up watching some of David's YouTube videos. It is too bad the he decided to quit. He might have thought that the era of glow engines was coming to an end to why bother. At the end of the season, I may remove the valves and clean the seats. In some of the videos David shows the procedure but he, too, struggles at times.

Matt

when I pulled my engines apart I decided not to completely disassemble the head and just put it into the sonic cleaner as a unit it seemed to clean it just fine without removing the springs etc.I did blow it out with air and lube it generously with 3in1 oil right after drying to prevent rust, Dawn soap in my cleaner really works well on the dirt and oil I also scrub the parts with a little plastic brush between rounds just to loosen up the grime, removing the cam bearings is easy I bought my bearings off ebay from a guy in AZ there also stainless from the USA,and pretty inexpensive BTW, he gave me a great tip on a home made puller from a screw I ground down and butterfly nut works like a charm, I tried the wax method for pulling the cam bearings and frankly it sucks,this little screw device was the ticket.
I will post a pic this afternoon with a couple of tips I have learned through trial and error on proper placement etc.
I may not of had the best performance due to old fuel as well,I did notice the 2 engines I replaced the rods on were a little lower RPM so it could be with some break in they will come up a bit, its what I had on hand so I used it the new needle and overall carb cleaning did wonders for the performance for sure.

Hi Bigtim,
I would love to learn how you made the bearing puller.

Another thing that I noticed in cleaning the engine was that the cam followers were sticky in their housings. Likewise I used a sonic cleaner with soft bristles to clean them. I have never used 3 in 1 oil as I do not know its make up. I know Dave in his videos uses them. In putting the engine back together, I just used after run oil.

Matt

https://cimg5.ibsrv.net/gimg/www.rcu...da0031a0a.jpeg
https://cimg7.ibsrv.net/gimg/www.rcu...06fb982a0.jpeg

cbr10006zu2 is the ebay seller that turned me onto making this little tool and if you need inexpensive quality bearings check him out with every purchase he includes instructions for making this little gem.

in the second photo I use this screw its about a 2" long Allen head screw, I put a old needle for scale, I used a dremmel cut off wheel to trim the head off leaving enough of it to slip under the bearing in the engine case, then I trim just a little extra off of the screw shaft so it gets more bite that was my mod to the tool, too much and the head bends, my first one broke off because I trimmed too much metal trying to get too much grip, so you need to be conscious of that,I got one set out but the second engine it failed on me more on that later.

then I reduced the top with a sanding wheel so it just barely fits in the hole of the bearing, I also ground a little spot on the end of the screw so I could grip it with my mini vice grips without destroying the threads see the first photo.

so a note on the how too's, I made some mistakes at first:
after getting your tool into the hole use a toothpick or like me take a small round dowel like in the photo and sharpen the end with a knife real sharp like a toothpick, this is critical because you need to wedge the sharp end into the hole to secure the puller to one side firmly this is critical.
mistake #1 I didn't use a sharp enough stick because I didn't have any toothpicks and the tool kept slipping out when I tightened the butterfly nut,when I switched to the sharpened stick and really wedged it into the hole past where the head was, poof worked like a charm, I also clipped the stick off right where the fender washer comes in contact with the case so as you tighten the nut down it keeps pressure on the stick.
mistake #2 when I tightened the nut the screw would eventually spin and when I grabbed it with some pliers I destroyed the threads on tool #1 and had a heck of a time getting the nut off after extracting the bearing hence the spot at the top cleaned of threads, now the nut spins off easy as can be, I would suggest putting the nut on the screw and then grinding off the threads then spin it off and your good.
lastly for the cover bearing I used a short 10mm socket as a extension, it fits on the outside of the cover, and the bearing pops clear through the hole, same thing with the stick clip it where the washer contacts the socket and crank once you get the vice grips locked on to the end and the nut is tight you will need a wrench or pliers to turn the nut as it gets tight you need to adjust the socket when its looser but as it tightens up the cover stays put.

several videos I have watched sort of gloss over the cam bearings but without question every set I have pulled 4 now have been rough and stiff, it seems that that area gets less oil than the piston rod area and there such a pain to get out that most just change the crank bearings and thats it, I have had to use my heat gun but not always so I will be changing them every time I do a bearing swap.

3 in 1 is just another inexpensive rust preventative oil, I don't even use after run oil per say if I don't have that I use Marvel Mystery Oil it works great for freeing up stuck engines and is way cheaper most everyone swears by it.

I'm no expert on these engines but my method is once I get the engine apart ie;head off,pushrods and tubes out,I open up the cam cover and with a Allen wrench push the closest one out then I turn the engine over while pushing the follower down so the cam moves it to its highest point the cam should slip out, I have had to grab it with some needle nosed pliers but in most cases it will come right out then again push it out with the Allen after cleaning I use a liberal amount of oil when I reassemble the engine, my sorting trey organized kaos all parts go into there compartment or a plastic bag
https://cimg3.ibsrv.net/gimg/www.rcu...b1dd49680.jpeg

Thanks for the pictures and the accompanying text. Have you ever replaced a piston ring on an older engine and seen a performance improvement afterwards?

yes, its easy but you need to be careful when you remove the old ring and replace it so you don't damage the piston, and you also need to do a break in run just like you would for a brand new engine to seat the ring in the cylinder.

when I was rebuilding dirtbikes, when I was much younger we had to hone the cylinder when we did a ring job, but for these motors its not necessary just a rich break in and your good to go.

as for performance not much in RPM's they generally go 9-10K on the top end and idle at 1,800 on the low, but when you have more compression it does seem t give you more power at the prop, these OS engines will run on 5-15% nitro fuel with 18-20% oil I got a deal on some 15% and they run a little better but not that much.

one thing I have noticed my OS 91 surpass engines seem to get higher RPM's than these 120's if your getting decent compression your ring is probably OK, if after adjusting the valves and knowing the head is in good shape,my test is to blow into the intake and exhaust ports while the head is off the engine while opening and closing the valves after cleaning, they should close up tight, once everything is set correctly and your mushing through the compression stroke the ring is probably worn for me a good stiff bump at the top of the compression stroke tells me the ring is good.

one thing I did notice when I put this last 120 together with it all oiled up the compression was really soft before the first run on my engine stand after a tank of fuel it had some real pop to it, it also took a few spins with the electric starter to get running at first, now it has a nice tight flip on the compression stroke so I am guessing some of that assembly oil cleared out and the ring seated back into its old grove, on these 120's the piston only goes in 1 way so unless you twist the sleeve around it should be ok,

David talks about using the old mark on the sleeve to line up the access hole on the case, this latest pumper I have ripped apart doesn't have that staining but it has other issues I need to sort through like this pump issue being out of adjustment and I am getting no help from OS or the forums

so here is some work I had wanted to do to the carb but didn't have the parts on hand before I did my after build runs, I also wanted to see if the engine would run without having to mess with the carb, first the 120 SE has a O ring at the carb/intake manifold junction and a tiny O ring at the fuel mixture screw you would think no big deal but I found on my older engine the mating surface had actually flattened and the carb was pretty loose when I pulled the mounting screws it literally fell off the motor.

when I pulled the carb apart that rubber O ring was pretty hard and had a flattened smashed surface, it also didn't pop back into its groove when I reassembled the carb the first time I had to massage it back into it's old position which took some doing, this is a potential area for air to leak, it didn't feel like it was making a proper seal at all, this can affect fuel draw from the tank as well as the engine can run erratically like with any engine was doing at first and to a lesser degree as I began to work my way through this carb learning as I go.

another area was the mixture adjustment screw its the one at the throttle lever on these older Surpass engines, mine was really easy to turn and even seemed a little bit loose, my other engines the adjustment screw felt allot stiffer and when turning them the screw stayed put this one was just too easy to rotate.

well when I was digging through my endless stuff from 3 years ago, I came across a bag of additional OS parts, and low and behold I had a set of O rings for the mixture screw, I had purchased them thinking the were for the needle valve but they didn't fit, so they just got tossed into a bin of parts,so I ordered a proper carb O ring off ebay that just got here the other day

pulling the barrel out is easy loosen the screw that keeps it in the housing and it drops out, there is a spring in the housing that you need to keep a eye out for so it doesn't get lost, the O ring on the mixture screw was really hard, the rubber was old, stiff, and had dried out, another area for potential leaking air into the carb, another reason for why my engine was a bit sloppy to adjust.

the mixture screw goes forward through the barrel which is a little bit of a pain, when putting it back together, the screw needs to be dropped into the barrel threads first, and with a pointy object, I used a pair of pointed scissors to hold it in place, I just screwed it back in after replacing the O ring, I immediately could tell the difference the screw was snug and smooth to operate.

I then popped in the new manifold connection O ring the softer rubber just slid right into the grove at the carb body, when I went to put the carb back on the engine the connection was nice and snug I could tell the seal was not going to leak at all and I am expecting allot better performance from jus replacing a couple of rubber parts.


https://cimg3.ibsrv.net/gimg/www.rcu...854d924fd.jpeg
https://cimg1.ibsrv.net/gimg/www.rcu...e12e4dc3f.jpeg
https://cimg2.ibsrv.net/gimg/www.rcu...2dc47d2c2.jpeg

The 3 rd pic is how I adjust the carb after disassembly I just blow into it and set it up for flow David actually has a full video on it and so far it works like a charm

End result with a parts list when I finish with a engine if I am not going to mount it right away, I use a large plastic bag to wrap it up as air tight as possible to prevent corrosion and put it in a box with a label this one is going to be put in a mustang.
time to start on this next one.

https://cimg6.ibsrv.net/gimg/www.rcu...42c61c017.jpeg
https://cimg8.ibsrv.net/gimg/www.rcu...55b88cbfa.jpeg

Bigtim,
Again thanks for all the details and pics. I only went as far as removing the barrel on the carb as wells as the regulator's components (I have a pumped engine) when I cleaned the carb.
The so called mixture control valve is accessible once the carb barrel is out but I did not know how to take it out on my 91 engine. It either needed a special tool or perhaps a small needle nose pliers would have done it. It is awesome that you managed to remove it and replaced the O-ring. BTW when I Iook at the exploded parts for the mixture control on a 91 engine I see two O-rings for this part. In your pic you show only one. Does the part on OS 120 need only one O-ring?

for this engine the mixture screw only had one slot for the O ring this was the first time I had ever pulled this screw out of a carb on any of my 91's or these 120's, to get it out I just used the tiny screw driver in the photo to unscrew it until the mixture screw fell out, it wont back out it has to go forward through the barrel.

I used to get so paranoid about messing with the carbs and the adjustment screws after I got a engine running right but I am getting way more confident the more I mess with these little engines and watching allot of videos helps I wish there was more info on the pump mechanisms,I did search through some older posts some from 2002 and found some info on these older pumps, there used to be a guy Bill Baxter(Bax) that ran this OS forum but he doesn't seem to be responding here any more and no one has filled his shoes kind of a bummer because he had a ton of info to share.

I have some ideas on first verifying if these pumps even work, and then I need t work out a gauge to set it at optimum range some sort of a specific gravity vacuum gauge, or a pressure gauge to meter maximum flow, or draw, my guess is pressure.

I wish I had more information on the tool used and any PSI readings I could expect to see, but I guess this is all part of the learning curve on these older engines, I can build allot of stuff in my shop if I had a example of what to do even if a tool is not available.

OK now I see that we're talking about two different things. You have removed the mixture screw that controls the mixture at idle. If I follow you, you're saying that if I were to remove the barrel and keep turning in the mixture screw, it will eventually fall out. It is funny that my exploded diagram of the carb does not even show this screw!

yes exactly if that little O ring is loose the carb will leak air and it makes it less sensitive to adjustment, I think one of the main things with these engines is making sure everything is tight and sealed really everywhere at the engine anywhere oil can leak, get messy,and gum things up, and with the carb, any little air leaks makes adjusting the low and high speed sloppy these little parts are not terribly expensive it seems as though age and the alcohol in the fuels drys these rubber parts out so they don't seal well.

I am attaching a diagram of my carb. Coming to think of it I think I had it right before. The part that you've removed in your engine is the part that I've circled in red. In my case this screw apparently has two O-rings. In your previous note you had mentioned that once you removed the barrel, there was a spring that you had to watch out for. There is no spring that I can see in the diagram for my carb. Anyway I am going to order the O-rings for the needle valve and the mixture screw and see whether they do anything or not. I thought I had overcome my erratic engine behavior but this afternoon when I went flying, it started to misbehave. Rats!

https://cimg3.ibsrv.net/gimg/www.rcu...1b6302b8d9.jpg

thats probably why they include 2 O rings in the package they are the same size as the Surpass 1 your carb just required 2 rings, mine being the older version only had the one on the mixture screw, the real rub is why not make the needle valve and the mixture screw O rings the same size, I tried to use the Mixture rings on my needle and it was so loose it wouldn't work,even though the part was smaller than the needle.
part of the reason I went with a new needle was because the old one was so loose in the housing I was sure air was leaking into the carb,I guess I need to order needle valve O rings as well.
I just got a new computer so I was lagging a bit on my response.

On this specific engine all three O-rings have different part numbers so I think this means they're different. Each part number comes with two O-rings so you end up with a spare I guess. Where do you buy your OS engine parts from? I buy mine from Tower hobbies as there are hardly any hobby stores left in my area.

On a side note this afternoon I almost bought a used Edge540 that came with all the servos and an OS120 engine like yours. At the end I decided not to primarily because I just did not want another project on my hands.

I get most of my parts off of ebay I do buy from towerhobbies also, but I found several sellers with better prices than tower and there new parts as if they came from OS, tower also has a ebay distributor called omnimodels they do allot of there discontinued sales and also have the same stock as tower just not there supersaver program, most of the sellers on ebay also sell at quite a bit cheaper than the distributors, I just search for bargains and do a bit of selling myself .
there is also several bearing guys that have good quality bearings at really good prices, these engines I have found do need maintenance and parts do go bad especially the rubber ones and bearings, I still haven't put together my latest engine because I am working on this P-51 Mustang project, but I will probably put it together tomorrow afternoon, I'm still a bit bugged about the lack of support on the forums concerning my pump issue, but I think I can sort it out if I can get the pump cleaned up and working .

on a side note I just scored another 120 new in box with all the tools instructions etc. for a song, seems like some people are getting tired of fuel and going electric, I just love the fact that I have a internal combustion engine in my planes

Nowadays I hardly see anyone fly anything but electric. Like you I still like my glow engines and in particular the sound of a 4-stroke. Unfortunately glow fuel is also becoming hard to find and because of this, I won't be acquiring any new glow engines in future. Congrats with the purchase of the new 120 engine.

I looked for the O-rings on Ebay. With shipping they're either the same price or more expensive than Tower's. This may be a temporary situation as Tower's shipping charges are $1.99 for the three sets of O-rings.

I usually combo up parts together if I can find them from 1 seller, most of the engines I have been rebuilding are Surpass 1's, some of the parts Tower doesn't even carry any more,which is a bit of a bummer, if I am buying more than 1 item I usually request a shipping quote and the little parts are so small it doesn't add anything to a single item shipping charge, I just ordered 2 extra needle assembly's and a couple of muffler pressure nipples and the shiping was 4$ had I purchased them separately it would have been over 10$, I definitely have a couple of glow engines I want to get rid of especially the 2 strokes I want to get more into gas engines and I have 1 electric foam plane just to screw around with.

Yesterday I ordered the O-rings from Tower. They had them in stock and shipping was 1.99 for all. Regarding the O-rings installation, is there a trick in mounting them or do they easily snap in place?