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Engines - general questions.

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Tom Major29/11/2017 22:58:42
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94 forum posts
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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 Harris29/11/2017 23:18:49
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8798 forum posts
215 photos

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 Major29/11/2017 23:34:10
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94 forum posts
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Amazing tip, thank you Martin.

onetenor29/11/2017 23:55:17
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1900 forum posts

Try Wheelspin Models for Spares.

Engine Doctor30/11/2017 11:32:19
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2296 forum posts
27 photos

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 .

Tom Major30/11/2017 21:11:03
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94 forum posts
22 photos

Once again thank you Doctor for very valuable advice.

I have received ordered screws for .10FP today so I thought it might be good idea to try them. All screws are perfect fit, so since I had engine out, I gave it a little clean with polishing paste.

image.jpeg

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Sadly I was unable to remove all blemishes, but it already looks much better. Now all components are drying out and once they did, I can reasemble most of the engine - set of gaskets still didn't arrive, neither did prop, so I'm guessing I will manage more during weekend. Now I only have backplate to clean/polish, but don't want to touch it in case ordered gaskets don't match.

onetenor30/11/2017 22:40:05
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1900 forum posts

Isn't it more usual to measure threads to the inch?

Tom Solvol do an aluminium polish now.

Martin Harris30/11/2017 22:51:06
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8798 forum posts
215 photos
Posted by onetenor on 30/11/2017 22:40:05:

Isn't it more usual to measure threads to the inch?

It's the convention...for imperial sizes.

Metric threads are specified by pitch.

Tom Major01/12/2017 01:01:00
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94 forum posts
22 photos

Speaking of threads... does anyone know what is thread size on the crankshaft? Disaster happened as it turned out I don't have prop nut for .10FP...

Now little engine is back in one piece. I managed to salvage backplate gasket, but still need to wait for head gasket, hope new set arrives tomorrow.

image.jpeg

All moving parts are oiled and engine turns over smooth like never before. Despite bolts being only tightened by hand and lack of head gasket, I can hear very nice popping sound, of course followed by air leak. This one should run sweet once I finish it, in the meantine I can get back to .40FS and also got 3 Cox engines to test

Edited By Tom Major on 01/12/2017 01:03:04

Peter Miller01/12/2017 08:38:39
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10166 forum posts
1192 photos
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Not sure what size of prop thread, I think it is 5 mm but I do have an OS 10 FSR which I could let you have the prop nut off if you want It is a bit low on compression but does run.

PM me if you need it

Edited By Peter Miller on 01/12/2017 08:39:09

Denis Watkins01/12/2017 08:44:41
3877 forum posts
59 photos

You are right

It is M5 guys

Tom Major01/12/2017 18:56:25
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94 forum posts
22 photos

I just finished looking for any matching nut, found one of same diameter, but no joy with pitch frown. I'll message you shortly Peter.

Gaskets arrived today, new head gasket is so much thicker than old one - that is like tinfoil.

Steve Hargreaves - Moderator01/12/2017 20:52:50
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6720 forum posts
189 photos

M5 is quite a common size Tom.....a local engineering supplies company will sort you out....even a trip to Halfords might elicit an M5 nut or two...

Tom Major01/12/2017 22:49:04
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94 forum posts
22 photos

I know it is quite common Steve, I was surprised I don't have even one fitting... There is not many specialist shops in my huge city, but I will try to visit Wilko if I finish work early enough - they should have various sizes in stock.

TartanMac01/12/2017 23:07:07
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250 forum posts
157 photos

Looks like a nice project you have here and that is a nice 10FP. I used a pen style magnet to get the collets out my four stroke engines I just pushed down on the retainer to expose the collets then use the magnet. I got it off ebay around £1.20 that includes delivery. If you don't already know you should be careful pulling the valves out. Over time the top of the valve gets wider with the rocker arm hitting it. What I do is get some wet and dry push the valve with your finger into its seat so it does not rotate in the head once you have the spring and collets and retainer off. Go round the top edge above the collet gap with your wet and dry be careful not to put a curve on the edge where the collet top edge sits. Then clean the debris off with a paper towel and put some oils on it then clean it again make sure no metal is still on the stem then gently push the top of the valve stem down to the guide and see if there is resistance. If so sand a little more then repeat. you don't want any resistance really and be careful cleaning and make sure everything is off the valve and the top of the guide.

I did this with my Laser V twin build and after rebuild there was no oil coming up between the guide and valve. My Enya has worn guides from just years of use and it kills the engine I am getting oil over flowing the rocker area and a big power loss. I replaced the ring new ceramic bearings recut the valves cutting through small pitting on the edge of them and they seal great. But when you push down when the springs are on they have a notch feeling. They move side ways and don't seat straight away so at high rpm the valve is not really sitting on the seat. it only makes 1.1hp with a 16x6 and 1.4 with a top flite 14x8 all because of the guides. Just something to watch out for.

Tom Major02/12/2017 22:52:11
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94 forum posts
22 photos

Some really amazing advice coming in, thank you.

Didn't touch FS as I got back from work not long ago, but spent few minutes with Testors McCoy .049 that only came in post today - cylinder was pinching the piston a bit, on closer inspection I have noticed tiny chip/dent, most likely caused by careless cylinder removal. I have used thin file to get rid of it and surprisingly piston moves up and down freely, fair compression still present, looks like it might be a runner 😀. It's a shame that not many of these little engines remain complete, I have another one with cracked crankcase and both are missing starter spring. I am hoping I will be able to get at least one running, just need to order 1/2a prop to test it.

Also finished .10FP, there wasn't much to do, just put new head gasket in and tightened the bolts. Here is a shot of two gaskets for comparison. What difference £1.29 can make...

New and old head gaskets

I checked once again few nuts that I could use on the crankshaft and am not sure if it really is common M5 - none fit...

 

 

 

 

 

Edited By Tom Major on 02/12/2017 23:20:17

TartanMac02/12/2017 23:36:42
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250 forum posts
157 photos

I bought a domed nut for my 15LA it was M5. If you check the Just engines website under spares for O.S 10LA it has the nut under M5 and the spinner nut. fits 10fp la and 15LA. Should be the same. You could phone them check the thread.

Martin Harris02/12/2017 23:57:15
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8798 forum posts
215 photos

OS list the thread size of the 10 FP as M5 in my handbook. The 15 FP has an unusual 7/32-32 UNF thread (@ 5.5mm) - could they have beefed up later 10 FP crankshafts?

Dig out that iffy vernier and measure the shaft diameter behind the thread, measure the distance covered by 10 threads and if the results aren't 5.0 mm (+- very little) and 8mm then you don't have a standard M5 coarse thread. Let us know the results if they don't confirm the expected 5mm thread dimensions and we can help identify the thread.

Edited By Martin Harris on 03/12/2017 00:15:26

Tom Major03/12/2017 13:27:40
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94 forum posts
22 photos

Measurement was bang on 5mm on the shaft and about 7.6mm over 10 threads. Went to Wilko and just grabbed pack of M5 bolts with nuts and washers. What an amazing fit !. Of course they are madde of cheese, but for the time being will do just fine . Now to finish test rig and .10FP can have its final run before another cleaning and storage.

In other news, package with Cox props that I ordered over a week ago most likely went missing in post. Can't have everything I guess...

Thank you all for advice.

onetenor03/12/2017 15:18:24
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1900 forum posts

If nuts really are soft use two as locknuts..Actually I have always found Wilco's fastenings to be good quality. What makes you suggest that they may be otherwise ?

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