Engines - general questions.

[jrman]

Try phoning JE rather than just looking on their website, they can also supply gasket paper from which you can cut your own. Model Fixings should be able to supply all the screws/bolts that you need. They also supply bearings.

[Denis Watkins]

http://www.modelfixings.co.uk/OS%204%20Stroke%20Aero.htm

Just replace all your screws Tom, with socket cap heads

Gaskets are on eBay

And bearings from modelfixings.com or bearing shop

The bearings are not made by OS, but just bought in

Many parts on the 48 FS are the same

Slot your damaged screws carefully with a dremel cutting disc, and tap them carefully to loosen

Edited By Denis Watkins on 27/11/2017 20:53:44

[Steve Hargreaves - Moderator]

Bearings you can get from Simply Bearings.....measure the od, the id & the thickness & pop them in here..

To get the screws out may not be easy.....you need to get some way of turning them. I presume they were probably cross head screws to begin with. Do you have a suitably sized screw driver? Support the engine & gently tap the screw driver into the head of the screw to try & form a suitable sized recess that will take the torque. A short blast of heat from, say, a small blowtorch can help expand the aluminium around the thread & make it a little easier to turn.

When (if?) you get the screws out then measure them (od & length) & modelfixings will supply some nice new cap screws as replacements. I would guess the thread will be 2.5mm or 3mm...

Modelfixings also offer engine bearings...see here....they list a 40FS but check your bearings first to make sure they are the correct size...

Good luck....

[Tom Major]

Steve, you're right, they all were cross head screws. I have all tools needed to disassemble the engine, I am just stuck with them screws. I tried few penetrating sprays and tapping to start with, but to no effect. Forgot however about heat. If it did work with bearings, I am hoping it will be enough for screws too .

Jrman
thanks for reminder about gasket paper, used that for motorcycles, but wouldn't think it could be used for model engines as well. Sometimes obvious things are not so obvious :D.
Will give JE the call, they might have few other bits I could use but have not seen on their website...

Denis
All good pointers, option with dremel and then application of heat sounds quite promissing.

Appreciate your time and effort to reply gents, thank you.

[Martin Harris - Moderator]

I assume you've checked that you're using the correct screwdrivers - it never ceases to amaze me how many people are unaware that there are several types of crosshead forms (e.g. Philips, Posidriv, JIC) and only the correct driver should be used for each type. This is the usual cause of damaged heads.

There are various tried and tested ways to shift damaged fasteners (cutting slots for flat blade screwdrivers, hammering while turning, drilling off heads for example). There is a product called Screw Grab (hard particles held in a greasy substance) which is surprisingly effective at getting a screwdriver to grip a damaged head - good on rounded hex sockets too.

[Tom Major]

Martin,

I always do, but in this case there is no tool that would fit those heads as they are long gone. I got it in that state and never really cared, but now attempt to run it would just cause massive damage - saw all kinds of dirt in the carb, from sawdust to metal particles.

I'm gonna try few of those ways soon.

Cheers.

[Bert]

If you mount the engine on a wooden block you will be able to drill the heads off the bolts (assuming you have access to a pillar drill or similar) then, after removing the part that the bolts secured you will have some protruding bits to get hold of to unscrew the rest of of what’s left of the bolts.

Bert

[Tom Major]

Just packed all my tools for today. Operation was successful and patient survived . 9 out of 12 screws were damaged even more during removal, but all came out nicely. Slotted them first with rotary tool, then applied some heat to the crankcase around them and removed with flat screwdriver. Exhaust however was removed by tapping small T bit into rounded heads.

I can't remember the details from taking apart other FP engine, but will anyone be able to confirm that crankshaft just slides out easily? I expected I will have to knock it out fr some reason...


Also had a quick look at model fixings website and it looks like they have all I want and much more.

Will be great to hear that little engine running after over 5 years. Once again thank you all for help .

PS. Nice to see some members still hang around here .

[Peter Miller]

The crankshaft will just slide out of the FP engine. The prop driver could be tight on the taper of the shaft but a sharp tap will free that. I forget if it is a shallow taper or not.

I tend to use Just Bearings for bearings but mainly because I always for get that Modelfixings does bearings. I have bought bearing for old Enya four strokes from them in the past,

[Tom Major]

Thank you for information Peter, and for pointer to just bearings too. The more sources the better .

I am expecting test stand and few props to arrive before the weekend, if all goes to plan my rig will be ready and engines will run .

[Nigel R]

Worth checking the thread isn't M2.3, IIRC OS used that on a few engines.

 

Another source for bearings if the above don't come up trumps.

 

https://www.bocabearings.com

 

I ordered a set for a 70FS some while ago, good price, delivery quite rapid - the usual 'no connection just satisfied customer'.

Edited By Nigel R on 28/11/2017 14:07:49

[Tom Major]

Good point Nigel, will check before I place the order.

Thank you for another source and feedback on them.

[Engine Doctor]

Hello Tom . You mention a OS 40 FS and an FP . What engine are you restoring or are you restoring an FS and an FP ? No bearings in an FP is a plain bearing two stroke and the 40 FS is a four stroke. The crank will just slide out of an FP and the prop driver is a "D" section slide on fit. Be careful not to loose the thin thrust washer that fits between the prop driver and Shaft to stop the driver wearing away on the crankcase. If any parts are stiff the heat will always soften the castor thats holding them .

[Tom Major]

Engine Doctor

Engine in need of restoration is .40FS. 10FP was the one with most screws damaged.

I'm glad you mentioned thrust washers, have few in box with spares and wondered what these were for .

I was well chuffed when I got little FP apart yesterday. Piston and liner are near perfect, looks like this engine had very little use and still has plenty of life left in it. .40FS has quite a lot of carbon build up inside, half of the piston, exhaust and exhaust port and even conrod was black. I'll have to have a look on ebay, maybe I'll find new parts, but if not, compression was still good and I'm sure it will run for a while .

[Martin Dance 1]

Another source of bearings that I have used is SMB bearings who are in Carterton Oxon. The lady that answers the phone is brilliant and well used to us modellers and skateboarders looking for bearings. By the way at around about the time the 40 fs was made OS quite often used a mixture of metric and imperial bearings on their engines, measure your old bearings in both inches and mm and it should be apparent which type has been used.

[Tom Major]

Another amazing tip, thank you Martin.

[Tom Major]

I have another question.

Just finished measuring all screws for .10FP. Here is what I came up with:

2x 2.4x23
4x 2.4x10
5x 2.4x6
2x 3.3x5.

but the closest dimensions I found were

MF-SC57 M2.5x20 Steel Cap Screws
MF-SC51 M2.5x6 Steel Cap Screws
MF-SC52 M2.5x8 Steel Cap Screws
MF-SC27 M3.5 x 8 Cap Screws

Do the sizes selected in order seem to be correct? I suspect my Vernier gauge is not exactly reliable...

The last two 3.5x8 are supposed to hold the carb in place, couldn't find 5mm though. Will find way round it, as long as I have something to work with I guess

[Denis Watkins]

Woe Tom

Your 2.4

Will be 2mm or 2.5mm

And your 3.3

Will be 3mm or 3.5mm

Get a new vernier

Your order does look likely to fit the OS

Yes, you can cut down bolts with slitting disc or your way

 

Edited By Denis Watkins on 28/11/2017 20:25:17

[Tom Major]

Yeah, this Vernier should have been binned long time ago....

Thanks for input Denis, will find out soon if order is correct

[Engine Doctor]

The 40 FS is nice engine ,very economical and quieter than modern more powerful engines ; ideal for gently flying models. The carbon can be removed with Betterware oven cleaner or carbon remover or similar but do check for suitability for use on aluminium as some are extremely aggressive and can damage the metal. Failing that elbow grease works well Dremel tools wire brushes can remove most of the carbon after an overnight soak in cellulose thinners. Valves will need a light re seating/ grinding . I use a grinding past thinned with a drop of paraffin on the valve as it helps the grinding paste to work better and a short length of fuel tubing pushed onto the valve stem to turn and grind them. It only needs a very thin contact line for a good seal . When removing valve collets put the head in a large polythene bag  incase the slip and fly off ! Make sure piston ring is free in its groove. Carbon builds up and holds it in causing lower compression and uneaten wear on ring. Remove it and clean the groove thoroughly . Good luck with restoration.

PS I hate this spell checker thing two edits and it keeps changing entire words ! Arrrgh !

Edited By Engine Doctor on 29/11/2017 10:10:59

Edited By Engine Doctor on 29/11/2017 10:13:36

[Tom Major]

I think I will go for elbow grease. It does work wonders and shouldn't consume as much time as my Golden Bee did - took me 3 days to get rid of that golden anodising, but it was worth it - prior to polishing engine was all scratched etc, now it's just Silver Bee .

I managed to remove carbon from piston ring groove already, now it's only piston and conrod left (well maybe few other bits too). Ring itself is in good shape and looks like will hold up for much longer.

I will need to find a way of removing the collets, tried once and failed. I remember using socket on valves from GPZ500S engine and that worked amazingly well, just need to find socket small enough...

Thanks a lot for good advice, I'm sure it will make whole process much easier.

[Martin Harris - Moderator]

Unless you have bolts (part threaded) as opposed to machine screws, where you can measure the shank, measuring the thread major diameter (which is what you measure across the thread) will always be less than the nominal thread size - so don't bin your verniers yet!

If you consult this chart you can check the thread pitch to confirm the size - measure the distance covered by 10 threads (theoretically from trough to crest but you'll need good eyes - measuring more threads is better and improves accuracy at the expense of simple maths) and divide the result by 10.

[Tom Major]

Amazing tip, thank you Martin.

[onetenor]

Try Wheelspin Models for Spares.

[Engine Doctor]

Hello Tom . Valve collets are not usually a problem as the springs are not very strong. I cut a piece of hard balsa that fits into the cylinder head and touches the valves, this holds the valves in their seatings when you compress the spring . The head is then put on top of this and a good press on the valve spring disc usually releases the collets. Don't forget to do this with all the bits and your hands inside a plastic bag as the tiny collets are very hard to find on a workshop floor and probably very hard to source new ones .