1948 Sq4 basket job - help!

[paul.jameson]

AX1280 went to Fred Deeley in Vancouver on 23.8.48 but not with any of the engines mentioned. Its gearbox was a G49G48 if that helps you with the gearbox quest. I don't want to post the engine number publicly but it was in the CJ 76_ series.

[RayBlack]

Thanks for clarifying Paul. It was a bit of a long shot to expect matching numbers, but at least I have confirmation of the '48 frame and I can pick the best of the three crankcases to build the bike. We still haven't gone through all the gearboxes yet, but I'm sure with all the information received so far I will be able to come up with a serviceable unit.
Whilst you have your number checking hat on could you possibly check the two '39 frames previously mentioned (AX491; AX532) against crank cases DE181? There may be another project in the making...

[paul.jameson]

DE181 went out in a rigid frame - which is a lot lighter than the plunger, less maintenance, etc, etc..........................

[RayBlack]

Thanks again Paul. It was another long shot.

[RayBlack]

Moving along to the speedometer: the parts book lists a 100mph chronometric instrument that sits in the tank top panel (part number 5202-47). Does anyone have the Smiths ID number, or a photo of an original unit? I have never actually seen a 100mph chronometric speedometer and all of the images of '48 Sq4s I have found online have 120mph chronometric in the tank.

[RayBlack]

Hmmm... looks like I struck out on finding someone who could clarify the speedometer issue. Either that or people have lost interest in my post ... .

Anyhoo: I have decided on using a BA gearbox from 1950 Mk 1 (G106 M49). I will also get a slightly later one for spares (G106 M51). I understand both these boxes will have (should have??) the updated speedo drive. So, back to speedos: does anyone know if the 1950/51 top yoke mounted speedometer will fit the tank panel of the 1948 model?

[Roger Gwynn]

Yes if you change the bezel for the correct type and replace the trip cable. Speedo numbers are a bit of a black art, consult a good speedo guy Chronometric Services in Nottingham is recommended, he will take yours in, repair or restore or swap the bits to make it correct for your machine.
A little known company has lots of info that you may find useful https://draganfly.co.uk/product-categor ... nd-cables/

[RayBlack]

Thanks Roger. I have actually started (belatedly I must admit) to do a search of the AOMCC documents and also the Draganfly site info pages to see if I can get the information I need before asking Club members. Without doing that the list of questions associated with the previous post would have been much longer...

[RayBlack]

I am now getting to the point where I am starting to think about doing a prebuild with all the parts I have accumulated for my 1948 Sq4 project so I can identify what I have got, not got, and what I have got, but which is either wrong, questionable, or not useable. I have a set of barrels (with only one broken fin ) that are marked '+30' that likely need boring. I also have a set of new low compression pistons that are marked as 'semi finished' and 2.650. I have not come across semi finished pistons before - any advice regarding their use would be welcome.