Hello
I’m new to WM20 forum.

I’ve just bought my first British bike, it’s a 1947 XM20 girder front. I’ve had plenty of good years on Japanese bikes and ten years or so riding Harleys.

No jump on, press a button and go here!!!!!!!!!!!!!

My plan is to make it stop and go mechanically that’s all, I like the 65 years of keeping it on the road look.
It hasn’t run or been on the road for years so it’s a bit of a project, I haven’t even tried kicking her yet. For now I’m checking her over, not that I know much about motorcycles mechanics, but what I don’t know I can surely find on the forum. The old & new posts are a great way to educate yourself...

So the tank off along with some other bits & bobs, I’ve got some issues with the wiring but hopefully none too troublesome. The tank doesn’t look to have had petrol in it for years so it’s got the usual crusty bits of rust inside. The carb was bunged up so that will need a strip down and clean, new jets and gaskets to order. I’m thinking for now doing a chemical clean or 12v battery, washing soda/electrolysis way to remove the rust.
I’ve removed the fuel taps can someone let me know the thread size so I can bung the tank for cleaning?

I plenty more questions to ask before I kick my M20 to life again

DC

email (option): damian153@hotmail.co.uk

Hi Damian..and welcome to the forum. Your M20 should theoretically have the WD pattern tank..ie..A 'flip up' filler cap and twin taps..BSA tanks used a screw in adapter which was fitted to the tank after being machined to suit the tap thread to be used. So, if you have removed the taps only and left the adapter in the tank (you will see it has a hexagonal shape with a tapped hole in the middle that takes the tap), the hole in the middle will be either 1/8" B.S.P. or 1/4" B.S.P. (British Standard Pipe). Confusingly these threads are not the size stated...a 1/8" B.S.P. thread has an outside diameter of .383"( approx. 3/8")..1/4" is .518"(approx. 1/2") and 3/8" is .656"(approx 5/8").
So, measure the thread on the taps you have removed to see if they are 1/8" or 1/4" B.S.P.
If you have removed the adapter from the tank as well this has a 3/8" B.S.P. thread on the outside.
Just to add further confusion motorcycle pipe thread is parallel along its length whereas plumbing pipe thread is tapered..something you need to be aware of. Therefore plumbing fittings won't screw all the way into a motorcycle pipe thread but can be used to temporarily blank holes (as long as the entire thread does not need to be protected).
Plumbing thread...BSPT (T denoting tapered)
Motorcycle threads...BSPP (P denoting parallel)....Ian

email (option): ian@wright52.plus.com

Boy's a dear! Ian did you eat the whole book?
This is the most comperhensive reply I've ever got from any forum!
Sign me up, here I stay!!!
Tank is as discribed, flip up filler cap & twin tap.
I've removed the adapters and the taps as one part. I can now go either way depending on the size of bolts i find.

Oh
By the way, I'm a Northern Ireland owner.

email (option): damian153@hotmail.co.uk

I think Ian WROTE the book. He was about 3 years old at the time.

email (option): jonny.rudge@verizon.net

Hi Damian..I have a Harley, other BSAs and an interest in other bikes...Consequently I've been on a few forums..Frankly, you won't find another one as friendly and informative on the subject matter as this one. You might find it addictive as you get into it...There are some contributors from your 'neck of the woods' as well...Ian

email (option): ian@wright52.plus.com

I could be here all night asking question after question.
So here goes another one before I nod off.

I'm not sure of the sequence I should take these job on?

Oils engine/gear box.
Replacement, draining flushing, refil and grades HELP??

As I plan ahead my weekend jobs.

email (option): damian153@hotmail.co.uk

Engine, Gearbox, and Chaincase oils are all easily removed – just look for the drain plugs at the bottom. It would be better to get everything warmed up first by taking your bike for a spin but it sounds like you’d rather not ride it before doing basic maintenance, so I’d suggest swapping the oils now and doing it again (maybe flushing beforehand) after 50-100 miles of running. It doesn’t take a lot of oil so the expense isn’t so bad! Oh, and clean the engine oil filter too - in petrol, letting it dry thoroughly afterwards.

The engine takes 5 pints Imperial, less if the existing oil is thick and cold so won’t drain properly. If in doubt, fill to about an inch below the top of the return standpipe in the oil tank. Originally the oil was straight (mono-grade, not multi-grade) of 50 weight for Summer and 30 weight for Winter, so a plain 40W oil might suit you, although some people do use 20W50 multi-grade and personally I don’t see why not. The important thing is to avoid modern synthetic oils and (again usually modern) oils with lots of detergents. Several major manufacturers (Castrol, Millers, …) sell suitable “old fashioned” oils, often listed as Classic. To be safe, take the sparkplug out (and ground it) then spend a few minutes kicking the engine over until you see the new oil returning through the standpipe in the top of the tank.

The chaincase takes the same oil as the engine. I can’t lay my hands on the quantity required (probably less than a pint) but there is a level plug as well as the drain plug, so remove it and pour oil in via the large chain inspection cover at the top until it overflows through the level plug. Top Tip: do up the drain plug first - we’ve all been there!

The gearbox takes 1 pint Imperial, with the same caveats as for engine. The filler cap is at the rear and the general idea is that you fill up until the oil reaches the bottom of the filler cap thread, assuming the bike is level. I’m less sure about the specification of gearbox oil (opinions seem to vary) but originally it was pretty much the same as engine oil although maybe a bit thicker and I wouldn’t be against using one of the classic oils referred to above, remembering the 2 rules: no synthetics and (in this case preferably rather than essentially) no detergents. I’m sure someone will put me right.



ChrisJ

hi damian and welcome...

theres a few irish based and ex pat members on here so where abouts are you ?

email (option): chris.astinbarker@btinternet.com

Thanks ChrisJ for the oils info,
everything explained for a green boy like me to understand.

Oils added to my weekend shopping list

I just need to find a few hours in the garage

Life's good!!

DC

email (option): damian153@hotmail.co.uk

Hello ChrisB
For those of you who know the North I live in Lurgan and for those of you that don't,
i live in Co Armagh about a mile from Lough Neagh

The doors always open, if anyone wants to call round

DC

email (option): damian153@hotmail.co.uk

Weekend job

Thanks for everyone’s help so far!!!!!!!!!!!

I’m planning to change the engine, gearbox & chaincase oils over the weekend. My reason for changing all the oils is at once is I’ve no idea when this job was done last.

Before I add the new oils are there anything else I should remove, clean, change or inspect before adding the new oils.

An ongoing list of routine maintains jobs I need to do before I kick her too life again.

DC

It may be too late now, in which case I apologise for the omission, but you should also remove and clean the oil strainer plate in the sump (4 nuts to remove the sump plate) when draining engine oil. Other than that, oil cables, pivots and everything else that moves and grease your nipples (stop sniggering at the back, Jenkins!).

ChrisJ
It's never too late for advice, I always say
"there's always the next time"

The truth is I never got to even see her today, too many other things took preference.

Your advice has been noted, i take it there's more than two nipples on this girl.

This forum has become an addiction!!!

email (option): damian153@hotmail.co.uk