Hello
My M20 came with an Amal 928 concentric carby, it seems to run ok and idles nice and slow just ticking over.It has an alloy spacer about 50mm.
Would a 626 be more suitable.
Mark

email (option): mhadfield35@yahoo.com.au

If the bike runs well, you might as well leave it like it is.

A new pre-monobloc is quite expensive (I know as I bought one a few months ago).

My old pre-monobloc was very, very tired. Whereas you have a carb that seems to be fully functional.

If it was me, I would change it when I could justify the expense i.e. not get my wife into the decision making process.

email (option): sacombsashtrees@hotmail.com

A 626 will not run any better but it will use less fuel.
The 928 allowed my M20 to rev a bit higher and I got about 10 kph top speed ( eventually ) out of it but I lost about 3 to 4 MPG.
It moved peak power up the rev range a bit and probably added another 500 rpm or so to the top where side valves are the least effective and the most thirsty.
So on long strait sections of level freeway it would just pull 110kph, till a sparrow farted in front of me.
FWIWI have a nice new 262 premier waiting to go on because I felt my bike ran best with the 626.

email (option): bsansw1@tpg.com.au

Pull 110,you pull more than that

email (option): mhadfield35@yahoo.com.au

be careful that the concentric carb doesn't leak into the magneto when tickled I had mag trouble got it renovated then the same thing happened again and found out that it was petrol leaking into the mag from tickling the concentric carb very expensive

email (option): roger.beck@node6.com

Petrol leaking into the mag is very expensive if the bike goes up in flames!

email (option): sacombsashtrees@hotmail.com

Well Pull is probably being a little generous.
Could get up to was more like it.
Bike was geared up at both the primary & secondary.
The members who mostly rode A 65's & unit B's had a bad habit of leaving too late so we ended up doing way too many k's of expressway which is hard work & very little fun.
Did Torkey to Albury on the Hume in company with 5 others , just keeping up with the highway traffic on the flat ( 110 )and getting worse fuel economy than the A65F running original off road gearing my tank is 3.5 Gallons his is 2 & I ran out of fuel before he did.
More than 1 person on this list who has been passed by me at an All British or BSA National.
I bought the B2 to watch the flowers grow while I ride past.

email (option): bsansw1@tpg.com.au

Just a case of moving it back far enough.
The spacers on mine add up to just under 2"
Thus there is little space for the air filter and the only one that fits is a firebird pill box ( Spitfire too I think ) and then you have to assemble it on the carb as there is not enough space to get it on in one piece.
The concentric is a much better carb than the type 27 and it will go better with one on. I have been running concentrics since 1998 and ended up giving the old type 27's to a member for his B31.
Then all my bikes are for riding, not looking at and think nothing of doing 600km trips.
In fact we are plotting a 1600 km trip down to the SA BSA National which we need to do in under 24 Hrs to qualify for an Iron Butt award.

email (option): bsansw1@tpg.com.au

Hello Trev
Sounds like your a real knowlegable fella. You wouldnt know where i can get a pair of rear mudguard stays for a plunger m20.

email (option): mhadfield35@yahoo.com.au

Well Bill Green motorcycles would be a good start as he is the only M20 specialist in the country.
Cob Smith is usually good at dredging up obsecure bike parts.
B series are not exactly the same but can be made to fit if you need something to get you on the road.
If you are handy to Bulli that AMCA monstrosity is on in 2 weeks.
Cob will be there not sure how many others are going to attend.
Most of the clubs I have spoken to are boycotting the event as there is nothing happening of any worth to historic motorcycling in Australia.
I thought they were going to set up a full branch of the AMCA which would be handy particularly for owners of obscure USA motorcycles, but it s just a money grubbing exercise to hold an annual show and misrepresented to the clubs I am associated with the the nth degree.

email (option): bsansw1@tpg.com.au