Back to the mighty TM 40

Bernhard · Oct 20, 2020

baz said:
It could well have been mate
I bought the bike in Dagenham!!

Ann Summers sell a lot of bikes in Dagenham. Don't ask what they sell at the back of the shop !

baz · Oct 20, 2020

Derek Wilson said:
I am a total newby to the single carb world on a Commando - I have always run twin Amal's. But the bike I am restoring currently requires some carb work and I am open to exploring options.

Just curious on the sizing - why 40 mm? Why not 38 or 42?

Principle reason I ask is it seems (where I am), 38mm are substantially less expensive.

The reason I chose 40mm was because it was going to replace the 40mm lake (widow maker) injector on my drouin but as that has never reached fruition I thought I'd try it on a normally aspirated commando
There are more than enough posts about single carb set ups
But if you just want a sweet running commando go for the single 34mm VM IMHO

Schwany · Oct 20, 2020

Since you are only using the two outer mounting bolts, did you fill and blend the center bolt holes out in the intake? Those mounting hole pockets inside the manifold are probably a big reason for why the twin carburetor versus single carburetor debate exists. Flow

baz · Oct 20, 2020

Schwany said:
Since you are only using the two outer mounting bolts, did you fill and blend the center bolt holes out in the intake? Those mounting hole pockets inside the manifold are probably a big reason for why the twin carburetor versus single carburetor debate exists. Flow

The centre holes are plugged and the join between the elbows has been blended to form a small steeple in between the inlets

FastFred · Oct 20, 2020

What will it do Moster

baz said:
The centre holes are plugged and the join between the elbows has been blended to form a small steeple in between the inlets

What will it do Mister with that 40mm carb? Have you had it flat out on any private roads?

Fast Eddie · Oct 20, 2020

baz said:
Ha ha it's not professional at all I'm afraid
Just two mild steel elbows welded together
I just thought I'd try it to see if it'd work,I was just a bit taken back with the results
I painted it silver so as not to shock people too much ,plus it stops people telling me that steel is not the right material to use etc etc

Would never have guessed!

Nice work Baz.

baz · Oct 20, 2020

FastFred said:
What will it do Moster
What will it do Mister with that 40mm carb? Have you had it flat out on any private roads?

I've not had it flat out in top gear it'd never pull it anyway because I have slightly overgeared the bike
But it's easy to rev beyond 7000 rpm in the lower gears
The other day I sat between 80 and 90 on a private road for about 25 miles
I'm guessing it'd do just over a 100 mph flat out ,I'll have to try it and report back

cliffa · Oct 21, 2020

baz said:
Ha ha it's not professional at all I'm afraid
Just two mild steel elbows welded together
I just thought I'd try it to see if it'd work,I was just a bit taken back with the results
I painted it silver so as not to shock people too much ,plus it stops people telling me that steel is not the right material to use etc etcBut it lo

Did you do the welding baz?

Any chance of a picture or two of the carb mounted please?

Cheers,

cliffa.

baz · Oct 21, 2020

cliffa said:
Did you do the welding baz?

Any chance of a picture or two of the carb mounted please?

Cheers,

cliffa.

Yeah it's just two elbows welded together
I'll take a photo later
Cheers

baz · Oct 21, 2020

I just took 2 welding elbows, welded them together
Made a flange to fit the head
And a spigot for the carb

cliffa · Oct 21, 2020

baz said:
I just took 2 welding elbows, welded them together
Made a flange to fit the head
And a spigot for the carb

I'll say it again, nice job and great welding from what I can see around the stub tube

baz · Oct 21, 2020

cliffa said:
I'll say it again, nice job and great welding from what I can see around the stub tube

Thank you
But I've been doing it for 44 years and I'm at best average
I can remember looking at the stuff the BOC blokes could do when I was at college
Razor blades butt welded together etc etc amazing stuff

Schwany · Oct 21, 2020

baz said:
The centre holes are plugged and the join between the elbows has been blended to form a small steeple in between the inlets

I misinterpreted, oops. I thought you were modifying one of the retail single intake manifolds and welding your larger spigot mount on top. The typical retail single intake manifolds with the two center bolt holes in the manifold are not what I would ever consider a performance product. Yours is a improvement over the 4 bolt setup as long as it doesn't leak, and apparently it doesn't. Well done

baz · Oct 21, 2020

cliffa said:
Did you do the welding baz?

Any chance of a picture or two of the carb mounted please?

Cheers,

cliffa.

Is this ok?

baz · Oct 21, 2020

Schwany said:
I misinterpreted, oops. I thought you were modifying one of the retail single intake manifolds and welding your larger spigot mount on top. The typical retail single intake manifolds with the two center bolt holes in the manifold are not what I would ever consider a performance product. Yours is a improvement over the 4 bolt setup as long as it doesn't leak, and apparently it doesn't. Well done

Most of the single carb kits I have seen these days have done away with the two centre screws so I can't claim any credit there
Cheers

cliffa · Oct 21, 2020

baz said:
Is this ok?

Perfect thanks baz. Removing the gusset really does leave a lot more room for experimentation doesn't it.

baz · Oct 21, 2020

cliffa said:
Perfect thanks baz. Removing the gusset really does leave a lot more room for experimentation doesn't it.

I'm wondering what carb/carbs were on the bike before I bought it?
The frame was also chrome plated!! It had CMA mag wheels fitted
It was about 70% of a bike
I re worked it doing away with all the stuff that I didn't like on previous commando's I'd owned
There's no attempt at gasflow on this manifold,I just thought I'd try it and I was surprised by the results
I dare say a longer more Y shaped manifold would work better?
Cheers

Back to the mighty TM 40

Bernhard

baz

Schwany

baz

FastFred

Fast Eddie

baz

cliffa

baz

baz

Attachments

cliffa

baz

Schwany

baz

Attachments

baz

cliffa

baz

Similar threads