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Thread sizes for Amco .87

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onetenor04/12/2017 21:14:48
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1900 forum posts

Hi all. Can anyone tell me the thread sizes on Amco .87cc Mk 1 for Crankshaft nose and Comp screw.Also what type of solder was used to attach transfer passage and induction tube to the cylinder .No guesses please. .Need to know for sure..O/T John

Engine Doctor06/12/2017 17:32:53
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2317 forum posts
28 photos

The transfer port can be soldered with normal soft solder 60/40 or 50/50  lead / tin should do it . A decent flux will help , something like Fluxite paste will help it to flow. Most of the old side port engines had soldered transfer and inlet ports. Can't help with rank thread but I might know a man who can . I think he still has an Amco 87 I'll ask him at the weekend . The online sites only seem to list the MK 11 Amco 87.

brokenenglish06/12/2017 18:14:48
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464 forum posts
29 photos

Sorry John, I'll go against your instructions and comment anyway!

I'm not an engineer or even a doctor, but I do have a lot of old engines.

I have no way of identifying a thread, but I checked the Amco propnut/spinner thread against a few other engines, and it's the same thread as the Allbon Dart, DC Dart, ED Baby and Mills 75. So it can't be an unusual thread.

I checked the Amco engine test (AM August '48), but Sparey doesn't mention thread sizes. However, in view of the above, I think it's extremely likely to be 5 BA.

Edit: When posting, I noticed you wanted the compression screw thread as well. I checked and it's the same as the crankshaft. The propnut screws onto the comp screw perfectly! How's that for useless knowledge!

Edited By brokenenglish on 06/12/2017 18:36:28

PatMc06/12/2017 19:42:23
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4223 forum posts
521 photos

The Dart shaft is 4BA.

thomas oliver 106/12/2017 20:20:46
93 forum posts
23 photos

AMCO 0,87cc threads are both 4BA - measured from my engine. T.O

Denis Watkins06/12/2017 20:56:12
3914 forum posts
61 photos

John OT, the current 60/40 solder is better than anything from the past

Prepare both surfaces and apply extra flux if you have it

Cut off enough solder from the reel to encircle the joint, and apply it to the joint

Play a pencil flame around the cylinder and tube, not the solder directly

When the cylinder reaches about 180° the solder will flow and play the heat continually tube and cylinder

To encourage a full circle of shiny flow, then take the flame away,

Do not continue to cook it for good luck

The joint will have been made everywhere that the area was clean and fluxed

onetenor06/12/2017 21:36:10
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1900 forum posts
Posted by brokenenglish on 06/12/2017 18:14:48:

Sorry John, I'll go against your instructions and comment anyway!

I'm not an engineer or even a doctor, but I do have a lot of old engines.

I have no way of identifying a thread, but I checked the Amco propnut/spinner thread against a few other engines, and it's the same thread as the Allbon Dart, DC Dart, ED Baby and Mills 75. So it can't be an unusual thread.

I checked the Amco engine test (AM August '48), but Sparey doesn't mention thread sizes. However, in view of the above, I think it's extremely likely to be 5 BA.

Edit: When posting, I noticed you wanted the compression screw thread as well. I checked and it's the same as the crankshaft. The propnut screws onto the comp screw perfectly! How's that for useless knowledge!

Edited By brokenenglish on 06/12/2017 18:36:28

Seems good to me thanks I'll check it out. I have some 5 BA nuts.

onetenor06/12/2017 21:40:55
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1900 forum posts
Posted by Denis Watkins on 06/12/2017 20:56:12:

John OT, the current 60/40 solder is better than anything from the past

Prepare both surfaces and apply extra flux if you have it

Cut off enough solder from the reel to encircle the joint, and apply it to the joint

Play a pencil flame around the cylinder and tube, not the solder directly

When the cylinder reaches about 180° the solder will flow and play the heat continually tube and cylinder

To encourage a full circle of shiny flow, then take the flame away,

Do not continue to cook it for good luck

The joint will have been made everywhere that the area was clean and fluxed

Thanks I did know how to solder just need to know type. but no harm in a reminder is there

brokenenglish07/12/2017 07:09:07
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464 forum posts
29 photos
Posted by onetenor on 06/12/2017 21:36:10:
Posted by brokenenglish on 06/12/2017 18:14:48:

Sorry John, I'll go against your instructions and comment anyway!

I'm not an engineer or even a doctor, but I do have a lot of old engines.

I have no way of identifying a thread, but I checked the Amco propnut/spinner thread against a few other engines, and it's the same thread as the Allbon Dart, DC Dart, ED Baby and Mills 75. So it can't be an unusual thread.

I checked the Amco engine test (AM August '48), but Sparey doesn't mention thread sizes. However, in view of the above, I think it's extremely likely to be 5 BA.

Edit: When posting, I noticed you wanted the compression screw thread as well. I checked and it's the same as the crankshaft. The propnut screws onto the comp screw perfectly! How's that for useless knowledge!

Edited By brokenenglish on 06/12/2017 18:36:28

Seems good to me thanks I'll check it out. I have some 5 BA nuts.

John, in one of the above posts, T.O. is certain that they're 4 BA and, in view of my non-engineering non-expertise, I should think he's probably right!

And thanks to Denis for the bit of soldering experience that many of us lack!

Edited By brokenenglish on 07/12/2017 07:10:03

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