BSA 420cc Model G

Somehow ended up with a new project!
Appears to be in good order, no history on it other than it's been in a container for 20 years, nothing prior to that.
Research to commence but believe it's mid 50's but ask for any information on the drive peg type pulley, any clue as to what it might have driven?

Alan

Looks interesting, no idea with regard to the the three pin drive pulley though, hopefully somebody will be able to help.

Just wondered, do you find these engines or do they find you!

No doubt it will look like new, within a week or two, enjoy the journey.

Neil.

Brilliant, another air-cooled engine...

Those slots in the drive look slightly wider at one end, as if they worn. I'm thinking another set of pins went in the slots on the other half, maybe a cush drive with rubber in-between?

I like the cush driver idea. Maybe it was originally part of of a pump or generator  set.
Nothing like it in any of the manuals I have.

Neil a bit of each I think! Not experienced a BSA before and a friend had this one surplus!
Doesn't seem to be much info on the web but luckily I don't think it will be needing much (fingers crossed!)
I think you might be right with the doughnut type drive, it makes sense as with no radial loading on the crank that would go towards explaining the lack of wear in the main bearings.
Bit of an external clean up today making it a bit presentable.
Drained the oil (seen worse) and discovered a filter as part of the drain plug. This engine has an oil pump drawing oil through the filter with a pressure relief valve before the oil is supplied to the mains, big end and camshaft!
Very nifty.

Alan

This any use?
https://www.greenmachinesurplus.com/bsa-model-afe-and-g-power-unit-instruction-manual-1679-p.asp

Thanks for the link, I have a service manual but it only covers up to 'E' models not sure what the differences to the G are.
Not sure what happened to the governor cover but it has undergone quite a neat repair. Flywheel came off nicely but the pegged drive put up quite a fight, had to drill out the grubscrew and with applied heat then an impact wrench on a hub puller it eventually came off.
Quite large crank journals I thought and yes the exhaust will require some work!

Alan

Bit more on the BSA today, mainly stripped now for evaluation. All looks very usable except the big end shells!
Crank journals are almost looking like new but big end shells appear to have suffered contamination or just breaking up? although sump looks pretty gummy.
Standard size shells are Vandervell items marked 1426M on a standard 1.375 ccrankpin, hoping I can find a set (any recommendations on supplier?)
All oil seals just broke up upon removal but should be readily available.
It looks like the repaired governor housing was the result of the flyweights coming adrift with damage also to the main housing.
Continuing with the clean up and assessment tomorrow.

Alan

Should have included the contaminated big end!

Eventually found a replacement shell bearing and it turns out it's the same one as used on an Aerial Square Four. Problem was find a supplier willing to sell one rather than a set of four!
Had cylinder barrel immersed in jenolite for 36 hours, came out looking well, washed it in hot water and a quick mask up whilst still hot. Out with the high temp paint and once finished it fell off the wooden board it was on onto the freshly cut lawn - didn't improve it's looks!
Parts appear difficult so cut one of the most awkward gaskets it have come across. Will also need to cut the exhaust valve seat as it is quite pitted and didn't want to keep grinding away at it.
Took the main cowling to our local electroplaters for rust removal process, however I was advised it wouldn't be tackled for 8-10 weeks! Plan B.
Onwards and upwards.

Alan

Re rusty cowl...
https://ukengineforum.forumotion.com/t8394-rust-removal-using-citric-acid?highlight=rust

Thanks might give the old citric a go although I think once the rust is removed there won't be much left!

I have no welding skills or equipment but, once cleaned back to bare metal, I managed a decent looking bodge with glass fibre bandage on the inside and epoxy on the outside.
That said, a visit to your local tinsmith might be in order. Good luck

https://www.ebay.co.uk/itm/255541869525?hash=item3b7f7b7bd5:g:guwAAOSwFOhicol0

Thanks Matt, I'd missed that, amazing how these things pop up!

Alan

Won the BSA spares booklet! Found out that the 'G' model has a deeper sump.
The exhaust on the engine had seen better days and I was considering using an empty gas bottle as a replacement but then chose the retain what was usable and replace the (heavily!) corroded end section. End was dawn off externally and removed exposing the inner pipe which was cut off leaving it as long as possible.
4 inch disc of material was formed over a scrap lump of steel and chucked in the lathe for indexing the 40 hole positions and boring the large hole in the middle.
Brazed together with a cover disc over the centre pipe, took loads more time than I planned but at least it still looks original (almost!)

Alan

Nice job on the silencer

^ Wot 'e said.

Always nice to save something that someone else might just chuck in the scrap bin, isn't that pretty much what our hobby is all about?

Your right, we get immense satisfaction saving something that 'most' folk would just chuck away without a second thought.
Painted it today!

Alan

Alanengine wrote:Your right, we get immense satisfaction saving something that 'most' folk would just chuck away without a second thought.
Painted it today!

Alan

Even if it costs 10x the amount a replacement would there is no price for satisfaction

Gradually been assembling the BSA, will be re using the solid aluminium head gasket and have annealed it ready.
Bought some gasket material to making manifold gaskets, the type that consists of an insulator sandwiched between aluminium outer skins. Found it a bit of a pig to cut holes in, no doubt fine using a flypress with the correct punch and die!
Made reasonably respectable ones using a hole punch (hammer type) for the smaller holes and the larger ones I ground to size using a small drum sander in my Dremel.

Alan

More gasket! Today I used a stepped cutter with the gasket material against a piece of wood, worked well although still finished off with the drum sander.

Alan

Took the BSA casing for media blasting and yes, it came back full of holes! Lower section of case was quite badly corroded so decided some metal surgery was required. Wanted to tackle this before it started to flash rust.
Cut the sheet metal with a Nibblex cutter attachment for an electric drill which worked really well and no distortion.
Tacked the larger curved section in first before a multitude of tack welds to make the joint more or less complete. The section that clears the flywheel was flanged to fit the case radius which caused it to go banana shaped and required cuts to relieve the tension and would be welded up later.
The flange for the inner radius didn't cause a similar problem.
All in all a worthwhile repair despite taking up most of the day, just got to make and fit new mounting brackets.




Alan (Thanks Paul for assisting me with this post!)

Started to put some paint and stopper onto the engine casing and for the first time noticed a very faint stamping on the top!
1964! - thought it was earlier than that although not been able to take out much about these engines at all.

Alan

Good old AJH. God bless 'em for helping us date aircooleds