Premiers vs TM40-6 (HS40)

I have spent the last couple of day settings up and tuning the twin Amal Premier 32mm, (300/301). After dealing with idle and running up issues, I now have them running perfectly.

I removed them and found a clear lube (maybe faucet grease) in the pilot jet when unscrewed from the opposite side if the air screw. I am sure this is for the oring in but they must have put a little too much in there. This would be a good thing to check before install.

I also validated the float height. This part was dead on.

I reinstalled and adjusted them and took it for another run and a plug chop. The color was great on the plug and idle remained stable throughout the run during some stop and go traffic. The power delivery was very good down low, great in the middle and OK up top. I have considered going up in the main jet to 230 or 240 but the plug chop indicates that all is well here.

This top end performance is relative for I am comparing it to the single TM40-6 (HS40). I believe that the single Tm40-6 has better all-around performance particularly in the upper range, then the twin Amal 32 Premiers on my particular machine, JS stage 1 with BSA lifter kit, a converted/modified RH1 and 1 ½” extended (tuned) exhaust.

That being said, these are really the best Amals I have used and dialing them in and running them are everything that people say they are.
I realize that some shit fly will but I have little pride and no reason to lie.

I was looking for other result and if that were the case this report would dictate that. I am performance oriented with my machine and if these Premiers would have given an advantage, I wouldn't be heading out to the garage to put the Tm40 back. On that you can rely!

Great to hear they are working well for you.

How quick is the bike to start now?

Mine is 1/2 kick from stone cold or full hot.

I'll have to check mine for the grease.

bwolfie said:

Great to hear they are working well for you.

How quick is the bike to start now?

Mine is 1/2 kick from stone cold or full hot.

I'll have to check mine for the grease.

Click to expand...

They were a 1 kick situation.
FWIW, The TM40-6 is back on already. What an awesome carb.

The single 40 seems like a much better idea than all the 32 and 34's I have seen used.

Just using basic math, each 32mm carb has an area of 804 sq mm, for a total area of 1608 sq mm

a single 34mm carb has an area of 908 sq mm.

the single 40mm has an area of 1257 sq mm.

A single 46mm carb (1662 sq mm.) would give comparable intake area as the dual 32's.

I am sure there are calculations out there to find the optimal sizes.

http://www.mathsisfun.com/geometry/circle-area.html

Yes, I'm sure there must be a limit when relating venture and atomization characteristics. It could be that the flat side carbs offer an advantage in this regard, I'm sure.

+1
Good objective review. I was so keen for the single Tm36-68 pumper carb option on my bike. I just couldn't come to cutting the gusset to fit it.
When I eventually get my featherbed project that I'm still looking for I will definately re-explore these big mik options but for the time being I will run these JS34's for a while and see how they go.

It is no surprise that the 40 mm carb makes good power.

The most power I ever got on my 880 street bike [before fuel injection] was with a 44 mm Keihin carb from a "big twin" on a thoroughly reworked and ported manifold. It was not a CV carb but it had a very nice wide powerband. Jim

Dkt26 said:

+1
I was so keen for the single Tm36-68 pumper carb option on my bike. I just couldn't come to cutting the gusset to fit it.

Click to expand...

I hear you. This was the biggest part of the gamble. Since then, this action has been totally justified, in my mind anyways. After this recent comparison, my resolve in this regard has been deepened.

I am resistant to jump on the soap box and shout the praises for it is a little radical. Yet when I feel called upon to give doubt its benefit, my doubt disolves. I feel strong that I can recommend this set up, just not officially.

Until someone else decide to do this, I can't explain the pop that this unit adds. My best example is the difference in normally aspirated vs fuel injection. Comnoz, please forgive the comparison for I haven't a clue what fuel injection is like on a Norton. All I know is that the difference is BIG.

PV, what kind of manifold do you use with that 40? Where do you get it? How much did you have to cut the gusset? Pic?
Jaydee

jaydee75 said:

PV, what kind of manifold do you use with that 40? Where do you get it? How much did you have to cut the gusset? Pic?
Jaydee

Click to expand...

Manifold from Rocky Point.
http://www.rockypointcycle.com/p-norton ... -2535.html

I went up an 1" and across 3 1/2" under the grommet for the wile loom. My real regret is that I didn't do a neater job, but I will clean it up maybe next wu=inter fro a frame re-paint. This also require re drilling the side cover bracket and relocating the hole for the Dzus connecter.

Having done a quick search on ebay for Mikuni TM40s it would appear that there are two types of TM40s, one with a single throttle cable coming out the top and one with the side mounted pus/pull arrangem (as fitted to your bike). Looking at your picture I would think the model with the single cable exiting at the top would go on without any clearance issues. Or are they two completely different carb types?
One thing that I do like about all the modern carbs is the absence of the mess made by the ticklers on Mk1 Concentric Amals. I wonder if Amal make a Premier version of the Mk 1.5 Concentric, as they just run an enrichener. I must email them and ask.

pvisseriii said:

Dkt26 said:

+1
I was so keen for the single Tm36-68 pumper carb option on my bike. I just couldn't come to cutting the gusset to fit it.

Click to expand...

I hear you. This was the biggest part of the gamble. Since then, this action has been totally justified, in my mind anyways. After this recent comparison, my resolve in this regard has been deepened.

I am resistant to jump on the soap box and shout the praises for it is a little radical. Yet when I feel called upon to give doubt its benefit, my doubt disolves. I feel strong that I can recommend this set up, just not officially.

Until someone else decide to do this, I can't explain the pop that this unit adds. My best example is the difference in normally aspirated vs fuel injection. Comnoz, please forgive the comparison for I haven't a clue what fuel injection is like on a Norton. All I know is that the difference is BIG.

Click to expand...

If I still had my old combat which wasn't matching numbers I would strongly consider the cut. I'm hopeful a featherbed commando will have enough clearance to go all out!!!

bsaboss said:

Having done a quick search on ebay for Mikuni TM40s it would appear that there are two types of TM40s, one with a single throttle cable coming out the top and one with the side mounted pus/pull arrangem (as fitted to your bike). Looking at your picture I would think the model with the single cable exiting at the top would go on without any clearance issues. Or are they two completely different carb types?
One thing that I do like about all the modern carbs is the absence of the mess made by the ticklers on Mk1 Concentric Amals. I wonder if Amal make a Premier version of the Mk 1.5 Concentric, as they just run an enrichener. I must email them and ask.

Click to expand...

The issue for me with the tm36-68 was the height of the carb and the size of the 36mm manifold. A VM36 only just fits. Just!
I think these two factors will be only increased with the 40mm flatslide. PV will be able to explain it much better than me.
I think I've already posted pics in a thread here titled TM36-68. I will have to check but if not I'm happy to show how much the flatslide pumper doesn't fit standard.

I already have a 36mm Mikuni. Is that the same manifold as the TM40?

Snakepit said:

I already have a 36mm Mikuni. Is that the same manifold as the TM40?

Click to expand...

Yes.
Just an FYI,
Main Jet 180
Pilot 17.5
9DJY-04 needle.
These needles go in an odd order as in 01,03, 04, and 02 being the richer.

568 Type Needle Jet 568-y-8.
These needle jet used to go up just to Y-8 but I see them now up to Z-6.

I have found all this stuff and more at Jets R Us and the carb I got at Niche.
http://www.nichecycle.com/ncs/index.php ... -pump.html

pvisseriii said:

Snakepit said:

I already have a 36mm Mikuni. Is that the same manifold as the TM40?

Click to expand...

Yes.
Just an FYI,
Main Jet 180
Pilot 17.5
9DJY-04 needle.
These needles go in an odd order as in 01,03, 04, and 02 being the richer.

568 Type Needle Jet 568-y-8.
These needle jet used to go up just to Y-8 but I see them now up to Z-6.

I have found all this stuff and more at Jets R Us and the carb I got at Niche.
http://www.nichecycle.com/ncs/index.php ... -pump.html

Click to expand...

Have you compared the 36 to the 40mm? What about slide cutaway?

Are you talking about the 36"VM"?

There is no comparison. The 38vm was my first single carb conversion 4 years ago and have been through at least a 1/2 dozen different carb situation since then.

If you are speaking of the TM36 flat slide pumper, which I doubt, then it should be good. Even the TM34 flat side is a good setup (and fits) and a favorite of many with good all around performance and excellent economy.

I like the 40, considering it. What is your starting drill? Will the pumper prime enough, or do you pull the enrichener?
Jaydee

Comparing two smaller carbs to one bigger one isn't as easy as just the total bore area.

I would think that two PROPERLY SET UP small carbs would out-perform a single larger one, as the flow is more direct and precisely metered to each port; the flow from a single bigger carb is not only indirect and turbulent, but more fuel AND air than either cylinder needs on it's own.

...prepared to be educated...

pvisseriii said:

Are you talking about the 36"VM"?

There is no comparison. The 38vm was my first single carb conversion 4 years ago and have been through at least a 1/2 dozen different carb situation since then.

If you are speaking of the TM36 flat slide pumper, which I doubt, then it should be good. Even the TM34 flat side is a good setup (and fits) and a favorite of many with good all around performance and excellent economy.

Click to expand...

I have the VM36 right now. In what areas do you see an improvement?