G3 oil pump guide pin screw/body

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
SPRIDDLER
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Re: G3 oil pump guide pin screw/body

Post by SPRIDDLER »

The thread peaks at the end of the holder seem to be a bit worn/flattened/blunted and not as 'sharp' as the first few turns. Perhaps that's what is causing it to become stiff and prevent it going fully 'home'? (Just a thought).
I'd get new one.
Holder. Oil pump pin.JPG
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clive
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Re: G3 oil pump guide pin screw/body

Post by clive »

Well spotted Sprids (bet you weren't looking on my phone!) . Damage to the holder thread suggests damage to the thread in the crankcase too. So thats a new holder and a tap.
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tippi11
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Re: G3 oil pump guide pin screw/body

Post by tippi11 »

Thank you!
It is really hard to inspect the thread in the crankcase by doing the flashlight/mirror trick - one can clearly see the first few turns (bottom side of crankcase) but it is almost impossible to check the upper turns (oil pump side), apart from there is no obvious blocking.
Saying this, I will go for the tap way.
As you know inch threads are not too common over here in Germany and I have to find a dealer selling the correct tap. I understand that I need a tap for 3/8" UNF (F for fine?), is that all for specifiying the thread, or anything else like TPI (turns per inch?)?
Regards, Peter
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Expat
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Re: G3 oil pump guide pin screw/body

Post by Expat »

3/8 inch x 24 TPI UNF is the suggested thread spec. F does denote fine, whereas in the case of UNC, C denotes coarse.
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Dixter
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Re: G3 oil pump guide pin screw/body

Post by Dixter »

I'd strongly encourage you to carefully check the thread pitch, once you receive your new guide screw. 3/8-26 CEI is far more likely on a fastener produced in Ole Blighty in the 40s & 50s than what we Yanks used in Detroit, and would call 3/8ths National Fine. (24 TPI).

Tracy Tools in Torquay will sell you a 3/8 cycle thread (26 TPI), Plug tap, for £3.

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SPRIDDLER
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Re: G3 oil pump guide pin screw/body

Post by SPRIDDLER »

clive wrote:Well spotted Sprids (bet you weren't looking on my phone!)
Correct Clive, I was listening on my laptop.
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Mick D
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Re: G3 oil pump guide pin screw/body

Post by Mick D »

Hi

Having just scaled the image I think Dixter is correct - 3/8" x 26 TPI (BSC / CEI) :oops:

Regards Mick
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Expat
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Re: G3 oil pump guide pin screw/body

Post by Expat »

I'll get me coat then :oops:
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alanengineer
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Re: G3 oil pump guide pin screw/body

Post by alanengineer »

Talking out my arse again, but cei in aluminium. I know what the bolt in the photo looks like, but does it look like what it should look like. What thread is specified?
Andy51
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Re: G3 oil pump guide pin screw/body

Post by Andy51 »

AMC normal thread in alloy/cast iron is BSF - 20tpi for 3/8 in - easy to distinguish from CEI thread @ 26tpi. It won't be UNF (24tpi) as AMC never to my knowledge used that thread form. BSF is whitworth thread form (55 deg angle) but UNF is 60 deg thread angle; the two are not interchangeable. Andy
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