[Bullet Whisperer]

All is explained in the video regarding all the tuning work, which was done last year, but there were no performance cams available from Hitchcocks until recently, when the owner bought a set and brought them and the bike to me a few days ago, so I could add the finishing touch. I have to say, the result went better than I was expecting!
B.W.

https://youtu.be/64TVt7jTsns

[Softlysoftlycatcheemonkey]

...this is the moment I've been waiting for...does ASBO 44 have a Power Commander installed and if so is the rev extend activated, or do you think the stock ecu only limits the fueling rev limit but not the spark ( meaning replacing the fuel injection with a carb removes the rev limit restriction a bit )?...DON'T WAIT FOR THE TRANSLATION!!...

[Bullet Whisperer]

...this is the moment I've been waiting for...does ASBO 44 have a Power Commander installed and if so is the rev extend activated, or do you think the stock ecu only limits the fueling rev limit but not the spark ( meaning replacing the fuel injection with a carb removes the rev limit restriction a bit )?...DON'T WAIT FOR THE TRANSLATION!!...

I am pretty sure the bike was standard apart from the silencer when I first worked on it and made all the other changes apart from the cams. When the injector etc were removed, a few connections were unplugged and the engine management light is now lit all the time, but I don't think any of the engine management system has ever been changed. I don't think these machines have rev limiters, I think between their standard state of tune, cam timings, valve springs etc, they just run out of steam and hit a wall just before 5,000 rpm. This one was pulling hard at 7,000 rpm in third gear, during that last overtake.
 B.W.

[Taurim]

Pulling hard at 7K RPM 
Did you think retarding the inlet performance cam is a must have ?

...this is the moment I've been waiting for...does ASBO 44 have a Power Commander installed and if so is the rev extend activated, or do you think the stock ecu only limits the fueling rev limit but not the spark ( meaning replacing the fuel injection with a carb removes the rev limit restriction a bit )?...DON'T WAIT FOR THE TRANSLATION!!...

If the engine revs up to 7K RPM we have the answer ! As you probably know Rev Xtend is limited to 6.5K RPM (That's the config I have on mine) and it won't accelerate past 6.5K so it's most probably a fuel cut only. By the way it does strange things past 5.5 K RPM : if you turn off the throttle then back on : nothing ! You have to wait for the revs to drop below 5.5K then you can re-accelerate. (at least on my Euro 4 535).

Maybe I will have to install a carb sooner or later 

[Warwick]

Uber nice bike!!!!

[Bullet Whisperer]

Pulling hard at 7K RPM 
Did you think retarding the inlet performance cam is a must have ?

Maybe I will have to install a carb sooner or later 

In the case of the machines I have tuned, retarding the inlet cam timing helps get the inlet valve and piston crown back to a safer distance from each other after the barrel has been shortened a little, but a happy side effect, both with these machines and many Bullets I have tuned, is the increase in rpm and power at higher rpm, with a small loss of bottom end 'Thump'.
 As far as carb conversions go, they would be a must for me - the settings on this one are different to the out of the box settings by Hitchcocks, with a 240 main jet and 107 needle jet in the MK1 Concentric 32 mm carb, but it is so easy to make changes to the fueling, if required.
 B.W.

[Taurim]

Thanks for your answer Paul ! I keep your settings just in case I need it one day 

At the moment my engine is disassembled (gearbox main bearing failure) and I'm waiting to get my crankshaft back after a disassembly to install H's improved conrod and a balancing.
So I'm still scratching my head to find if I should install the intake cam retarded by one tooth or not... Your ASBO 44 convinced me to dot it 

[Softlysoftlycatcheemonkey]

    Thank you for posting your findings; it's a very generous way to run a business. I've been waiting for better/more minds to chime in, but before the bread turns stale I'd have several things I'd like to know. ( I'll probably leave it to one question per post so you don't have to sort through too-much-novice-at-once. ) With the alterations you've made to ASBO 44 do you think the stock ignition timing is good enough for running beyond what was the rev limit?

[Bullet Whisperer]

    Thank you for posting your findings; it's a very generous way to run a business. I've been waiting for better/more minds to chime in, but before the bread turns stale I'd have several things I'd like to know. ( I'll probably leave it to one question per post so you don't have to sort through too-much-novice-at-once. ) With the alterations you've made to ASBO 44 do you think the stock ignition timing is good enough for running beyond what was the rev limit?

Thank you for your interest in this. The best way I can answer that is to say this machine performed well in excess of my expectations and I certainly didn't feel the need to question the ignition timing, advance curve, or any other related areas. There are a couple of other 'Asbo' 535 GT machines which are very similar and also run performance cams timed to my specs, but this is the only one currently running with a head I modified slightly too, as well as my usual modifications and performance cams timed to my specs. Another machine is up to this spec with the head mods, but last I heard of it was still running standard cams, with the inlet retarded and I would expect that to probably go as well as this machine if / when fitted with performance cams timed to my specs.
 I think there has been a lot of 'over thinking' where the tuning of these machines is concerned and most of what is required to make these machines fly is already present and correct and just in need of some modifications, such as combustion chamber tidying around the valves, shortening the barrels as required and a little porting work. Bolt on stuff which I would consider 'must have' items would include decent valves and springs, performance cams, carburettor conversion and a decent exhaust system.
 I have no idea what Asbo 44 could do in terms of top speed, but I am sure it could get into three figures with no trouble and there are no flat spots, although the engine likes to be at north of 3,000 rpm in the higher gears and really wakes up at around 4,000 rpm, pulling strongly to 7,000 rpm, according to what I saw on the rev counter. All the other Asbo GT's have been able to reach 6,000 - 6,500 rpm with no problems, which is also well above standard.
 B.W.

[Bullet Whisperer]

Just noticed, and it seems it is too late to edit my mistake now, but I called this thread 'Tuned 535 GT Asbo 44 Black Mountain road rest', when I obviously meant road TEST! And on 01 April, too  It was no joke and the 7,000 RPM and everything else it did were all real, I promise!
Must concentrate harder when posting in future, I just got carried away in all the excitement!

B.W.

[Softlysoftlycatcheemonkey]

    No harm done; you're state is highlighted at the 51:44 mark in your recording. In a day or so I'll sort myself and next ask about carbs ( Amal mk1...mk2...32mm...34mm ). I hope you and your family was well for Easter.

[Softlysoftlycatcheemonkey]

and I think "rest." is also an abbreviation for restoration so there is some leeway.

[Bullet Whisperer]

    No harm done; you're state is highlighted at the 51:44 mark in your recording. In a day or so I'll sort myself and next ask about carbs ( Amal mk1...mk2...32mm...34mm ). I hope you and your family was well for Easter.

Thanks - I just took a look and it is at the 50.40 - 50.45 mark in my video where the tacho needle goes out of sight in 3rd gear as I overtake two cars and exceed 7,000 RPM while doing so.
 B.W.

[Softlysoftlycatcheemonkey]

    In various postings you've mentioned that if you owned a Continental gt 535 you'd prefer installing an Amal 34mm mk2 ( over other brands ). After the success of ASBO 44 with it's 32mm mk1 do you think though that 32mms might be sufficient, or would the smaller bore be too restrictive overall compared? ( My bike is currently held at bay for "covid delayed" warranty work, but when I've had it I'd put in 4,500 miles of errands and short tours limited so far by the stock seat. Beside fancying a better seat I'll probably fabricate an airbox to fill the space occupied by the battery, utility box, mudflap and current airbox, and add a foreward facing air intake with filter; all this just because my mind wanders. When I carb convert I'll have to account for this change in addition to those you've mentioned performing and the header/muffler. )

[Bullet Whisperer]

    In various postings you've mentioned that if you owned a Continental gt 535 you'd prefer installing an Amal 34mm mk2 ( over other brands ). After the success of ASBO 44 with it's 32mm mk1 do you think though that 32mms might be sufficient, or would the smaller bore be too restrictive overall compared? ( My bike is currently held at bay for "covid delayed" warranty work, but when I've had it I'd put in 4,500 miles of errands and short tours limited so far by the stock seat. Beside fancying a better seat I'll probably fabricate an airbox to fill the space occupied by the battery, utility box, mudflap and current airbox, and add a foreward facing air intake with filter; all this just because my mind wanders. When I carb convert I'll have to account for this change in addition to those you've mentioned performing and the header/muffler. )

Going by the Electra X I tuned for Hitchcocks in 2008, where increases in carb sizes from 32 - 34 - 36 mm also increased the power in corresponding steps, from small to full throttle openings as proven on a dyno, I would be tempted to fit either a 34, or maybe even a 36 mm carb on a 535 GT ported to suit [the Electra X porting had to be left as standard btw], as I am sure Asbo 44 still had a lot to give that would be reigned in by the 32 mm carb currently fitted.
B.W.

[Softlysoftlycatcheemonkey]

    For a motorcycle that is usable in town/traffic do 34-36mm carbs still work well? Though the increased top end would offer security for traveling at ( American ) interstate highway riding speeds, would they make too severe a trade-off at slow speeds/need to be in a relatively higher rev range to accelerate than a 32mm?
    Also, would this have much importance for a non-track bike?: since the rev range has been extended upwards on this should one consider blanking-off the choke? Youtube channel for Canadian Paul Brodie mentions that for a race bike Amal mk2 carbs bleed fuel into the carb "above 8,000 rpm due to vibration" and Continental gt 535's happen to vibrate from the cradle. His explanation is at the 5:47 mark and the alteration is at 10:17 https://www.youtube.com/watch?v=pXcKuuD1jyA
   And as with all-too-many examples of this and a few other models that you've presented I'll opt for a good output fuel tap with reserve to make up for the increased need.

[Softlysoftlycatcheemonkey]

...Amal mk2 chokesbleed fuel into the carb "above 8,000 rpm due to vibration"...

[Adrian II]

Do the bigger carbs still work well in town/traffic? Here's one of Bullet Whisperer's test ride videos with a 500 RE Fury fitted with a 38mm Amal Mk2. It appears to chug around the back lanes quite happily as well as going for higher speeds on more open roads.

https://www.youtube.com/watch?v=p-Q11n9D4A8

I've used 36mm carbs on different AVL Bullets and a big head Bullet, they're still fine in traffic and in town too.

Not sure the 8,000 rpm is a figure that even an ASBO CGT535 would need to worry about.

A.

[Bullet Whisperer]

On a 500 Electra X I tuned in 2008 for Hitchcocks as a basis for a tuning kit, I tested 32, 34 and 36 mm carbs on the dyno, one after the other, on the same day. Each increase in size gave an overall increase in power, throughout the rev range, with no porting work done to the head, as requested due to the proposed kit having to be of the 'bolt on' variety.
Our own RE 500 'Big Head' racer runs on methanol and wears a 38 mm MK2 Amal carb, fitted with a rather rare twin float, float chamber and while running on the dyno, we have sometimes had issues at certain higher RPM's, where the floats have been overcome by vibrations, causing the carb to flood, although it is difficult to know for sure if this happens while out on the track. We have had some random, strange fueling issues with this machine on occasion, so perhaps it can rear its head during a race from time to time.
I don't think Asbo 44 would need to ever go much past 7,000 RPM to give its best - I was both surprised and pleased to see it get to 7,000 RPM while still pulling well!
B.W.

[jez]

I've got an Asbo 535, just as this one sans headwork. It does 85 in 4th and 5th as it came to me overgeared. Rather like it like that as it lopes along at Motorway speeds.
 There doesn't seem enough frame height to fit anything bigger than a MK1 32mm Concentric. The original injector throttle body is 36 though, and another has commented he lost about 4mph at the top end with the change. Still worth changing to the carb though for ease of jetting. I've recorded 88 mpg without even thinking abou it. Honestly i was shocked. My Nuovo Falcone does about 58 at much lower speeds.
 I think a MK2 34 would fit.  Amal do not sell MK2 bodies. One can get all the parts. but I probably would not fit one until Paul had done the headwork. I have a MK2 34 body I picked up at a show.

[Taurim]

The original injector throttle body is 36 though

34  34.5mm to be exact.

Believe me, I rebored mine to 36 with a weber 36 carburetor flap.

On top is the standard 34(.5) TB. At the bottom is my modified 36 TB.



Not tested as the engine block is not back in the bike yet 

[gizzo]

Still waiting?

[jez]

Thanks for that. I'e seen 36 so many times I took it as read. Should have known better.  MK2 seems an even better fit now. A MK2 Amal is a pretty short carb.
As a matter of interest, what is the inlet port diameter?

[Adrian II]

If the larger Amal Mk2 carbs are not currently available new, PHF36 Dell'Ortos with the accelerator pump still are! I wouldn't advise the PHM38 (think BMW R90S) as they're probably slightly too bulky. The dreaded Mikunis are still available too, of course.

A.

[Taurim]

Still waiting?

Saturday the block was reassembled and almost ready... at last !

Thanks for that. I'e seen 36 so many times I took it as read. Should have known better.  MK2 seems an even better fit now. A MK2 Amal is a pretty short carb.
As a matter of interest, what is the inlet port diameter?

When not ported I think it is 32mm or maybe even less. It is smaller than the tube with the injector and the gasket !



After some work it is 36 mm on the whole intake tract

[jez]

Thanks for the port size. As to Dell Orto: I doubt they'd fit in the space. Larger Mikunis wouldn't. There's little point putting a bigger carb on before the head work, if the port size is around 32. I don't know if Paul reamed that out.  I'm not sure if I'd want mine to rev to 7000. A surprising number of bits fell off at 6.5......

[Taurim]

With the previous incarnation of my engine 4.5K was the RPM at which everything fell off... Quite annoying if you ask me !

The new one will have a correctly balanced crankshaft with a different balance factor. It may help 

[Softlysoftlycatcheemonkey]

"There's little point putting a bigger carb on before the head work, if the port size is around 32. I don't know if Paul reamed that out."
https://m.youtube.com/watch?v=FyTY1hQoec4
   It seemed like Mr. Henshaw smoothed and extended what was a hard transition between the rubber manifold and the intake port, and didn't open the whole intake port through to the valve to the circumference. He'll probably see these comments and clarify.

[Adrian II]

Thanks for the port size. As to Dell Orto: I doubt they'd fit in the space. Larger Mikunis wouldn't. There's little point putting a bigger carb on before the head work, if the port size is around 32. I don't know if Paul reamed that out.  I'm not sure if I'd want mine to rev to 7000. A surprising number of bits fell off at 6.5......

The size of the PHF range of Dell'Orto carbs is reasonably compact, the same casting is used for 30, 32, 34 and 36mm carbs. The jump point to a bigger casting is with the 38mm when it goes up to the PHM range. In comparison, IIRC the Mikuni VMs as well as the Amal Mk2 Concentrics jump to the bigger castings with the 36mm as well as the 38mm versions.

I'll see if I can get you some pictures, but the PHFs are 114.5mm in total height from float bowl drain plug to to top of the rubber boot over the base of throttle cable. For tight locations under fuel tanks you can get 90° ferrules to point the cable away from the underside of the tank.

A.

[Richard230]

I used to own a 1985 BMW R80 that I modified with an R90 top end and a couple of R90S Dell'Orto carbs. I thought the Dell'Orto carbs worked well, but what I really hated about those carbs were their throttle slide springs. Those things must have been about a foot long and when you took the slides out, the springs would leap 10' across my garage. When trying to reinstall them it was like trying to compress a Slinky. It were almost impossible to reinstall the springs. They were just too long to refit into the throttle slide body. What I finally did was to cut the springs in half, which made the springs a lot easier to install and the throttle a lot easier to turn.

[jez]

The most relevant measurement would be from the centre point to the top. The MK2s are spigot mounted as  the Hitchcocks Mikuni kit [which requires a different air filter assembly, if I remember correctly].

[Adrian II]

Just had a measure up on a PHF34. from the centreline on the horizontal bore to the top of the screw-in throttle cable adjuster (without rubber boot) is 85mm as accurately as I can measure it. These have a 44mm mounting stub but you can get one-piece plate flange mountings for these with the 60mm hole spacing - I believe this hasn't changed from the AVL models, some Indian home market UCE bikes are carb fitted, and the flange for one of these fits my Electra-X head.

Any help?

A.

[jez]

 The Amal MK2 is 6cm. The 38 Mikuni is about the same as the DellOrto. I don't have the cable adjuster for it so it could be at least another 15mm depending... I've already allowed a bit for that.
My Amal has a recessed  double diameter spigot set into the top cap so adjustment could be at the throttle; that takes a bunch of height out

[Adrian II]

Yes, I found the Amal carb dimensions here, page 10 for the different Mk2 ranges. Not having an accelerator pump does save you a bit of height. Shame the full range of Mk2s is not currently available. Worn casting dies have stopped production of the 2000 series, I was given to understand.

https://triumph3ta.nl/Downloads/Amal%20Concentric%20&%20Mark%202%20Carburetor%20Technical%20Manual.pdf

A.

[gizzo]

I used to own a 1985 BMW R80 that I modified with an R90 top end and a couple of R90S Dell'Orto carbs. I thought the Dell'Orto carbs worked well, but what I really hated about those carbs were their throttle slide springs. Those things must have been about a foot long and when you took the slides out, the springs would leap 10' across my garage. When trying to reinstall them it was like trying to compress a Slinky. It were almost impossible to reinstall the springs. They were just too long to refit into the throttle slide body. What I finally did was to cut the springs in half, which made the springs a lot easier to install and the throttle a lot easier to turn.

Tell me more...Did the slides return to closed on their own when you let go the throttle?

I'm in the same boat with my Ducati. I want to take it on a road trip in a few months but I know the heavy throttle is going to make me take Another Bike. I did consider cutting down the springs but don't know whether they will be able to close the throttle. Am also loath to go ruining something I'll have to replace if it doesn't work out. Thanks.

[Adrian II]

You can actually get three different strengths of throttle spring for the Dell'Orto PHM, strong (9389), medium (8532) and weak (8550).

https://www.dellorto.co.uk/product-category/dellorto-motorcycle-carburettors-parts/carburettor-parts/phm-parts/

A.

[gizzo]

Thanks Adrian. I've just had a look at Gowanloch's website, they have the slide springs for only like $5! I've emailed them to see if they have the light ones. Will buy some key blanks while I'm there  .

Should've looked into it years ago. Maybe they also have a solution to the stupid heavy clutch...

[Richard230]

Tell me more...Did the slides return to closed on their own when you let go the throttle?

I'm in the same boat with my Ducati. I want to take it on a road trip in a few months but I know the heavy throttle is going to make me take Another Bike. I did consider cutting down the springs but don't know whether they will be able to close the throttle. Am also loath to go ruining something I'll have to replace if it doesn't work out. Thanks.

I don't know what strength springs came with the R90 Dell'Orto carbs. But when I cut them in half the throttle closed just fine and the throttle still was more stiff than Japanese bike carbs of the time (1987).

[gizzo]

I don't know what strength springs came with the R90 Dell'Orto carbs. But when I cut them in half the throttle closed just fine and the throttle still was more stiff than Japanese bike carbs of the time (1987).

That's good to hear. Thanks. I've emailed my Ducati place so I'll wait and see what they can tell me.

The Japanese bikes back then probably had CV carbs, right? For all their faults, the throttle is super light (actually I think they're ok carbs and easy to live with)

[Bullet Whisperer]

"There's little point putting a bigger carb on before the head work, if the port size is around 32. I don't know if Paul reamed that out."
https://m.youtube.com/watch?v=FyTY1hQoec4
   It seemed like Mr. Henshaw smoothed and extended what was a hard transition between the rubber manifold and the intake port, and didn't open the whole intake port through to the valve to the circumference. He'll probably see these comments and clarify.

Sorry, I only just came back to this, but basically I just removed any lumps and bumps from the ports, but I opened out the entrance of the inlet port so a 34 mm carb could be fitted in the future, if required. Other work included tidying up the combustion chamber areas around the back of the valves and the edges of the squish bands, as well as shortening the barrel a little and retarding the performance inlet cam's timing. Upgraded valves, springs and caps from Hitchcocks were also fitted. I am confident this machine would see the other side of 100 mph with relative ease, even as it is, with the 32 mm Amal MK1 carb.

[Softlysoftlycatcheemonkey]

    Hopefully Mr. Henshaw will reply to this ( as he pointed out many times that more can be turned from the half formed clay of the GT ) and a further tweak can be suggested from his observations: I'm in the process of acquiring a carburetor from a manufacturer that sounds like Ramalr and has a stock bore somewhere between 35 and 37mm ( jinx, jinx, jinx ) that comes with a "300 main jet, 25 pilot jet, and 3 throttle" and wonder if these are a good starting point for tuning the carb following your recommended head work, "shortening the barrel a little and retarding the performance inlet cam's timing. Upgraded valves, springs and caps from Hitchcocks"? The carb doesn't come in "complete conversion" kit form like those from Hitchcock's and needs to be sorted somewhat before tuning would even begin. I'll continue then using the stock airbox and filter to protect, with a velocity stack extending into the airbox ( can't hurt ) as championed elsewhere on this forum. Will give a wde-band O2 sensor and gauge a try for final tuning as I don't have the experience to go by feel yet. Any input to point me in the right directon would be welcome. Thank you. ( I'm sorry I've run out of steam and have to get some sleep ).

[Softlysoftlycatcheemonkey]

   If I'm hoping for unconfused advice I should probably clarify and enhance the information about the carb I'm looking at buying ( jinx, jinx, jinx ); it is a set of stock Amal Mk2 36mm smoothbores part#s 2036/312T and 313T ( righthand/lefthand ), and being stock they don't have throttle adjusting screws installed and the appropriate holes drilled in the bodies. There are avenues to getting other Amal standard 36mm bores, but these smoothbores are unused, assembled, and can have the needed jets, slide, and needle installed at no charge ( I think ). And, if needed and possible, I may install throttle adjusters. I have no plans to take the bike any faster than highway speeds and understand tuning these carbs can be tricky, but I'm still interested. They still come with a 300 main jet, a 25 pilot jet, and a 3 throttle slide. If you don't think well of the smoothbores I may revert to the standard model before porting the head, "shortening the barrel a little and retarding the performance inlet cam's timing" then adding "upgraded valves, springs and caps from Hitchcocks". I haven't heard of an experienced Royal Enfield mechanic near me ( Johnson City, TN ) so that may leave me to save some probable grief and buy an Ace clubman head from Guaire. Again any input is welcome.

[Softlysoftlycatcheemonkey]

...and mailing the current head off to Performance Classics would be even more interesting.

[Adrian II]

The smoothbores are racing carbs, hence no throttle stop for idling, though if you're very patient and precise with your throttle cable adjusters you might get the engine to tick over, as they at least still have the idler circuit and pilot jets. Or you could just get used to having to blip the throttle when at a standstill.

The non-racing version of the 36mm Mk2 is part of the Amal 2000 range, currently out of production, so you would be looking at NOS or a good used example if you can find one.

A.

[Softlysoftlycatcheemonkey]

    Thank you for the response. Are there any advantages to using this smoothbore carb over the standard model as I'll be using it on a road going Continental gt 535 and not for race? The few mentions of them that I've found say that the smoothbore is usable but very sensitive to needle, slide, and jetting changes, and is also very peaky when using a straight velocity stack as opposed to one with a short/wide bell mouth. Also, and this is where Mr. Henshaw's hands-on experience would be welcome, are the stock intetnals ( jets, etc. ) good enough to begin tuning with the previously mentioned engine upgrades or would change need to be made at the outset? Thank you for your time.

[Adrian II]

Using a smoothbore Mk2 on a road bike shouldn't be too traumatic, people have been riding BSA Gold Stars, Velocette Thruxtons and the odd Royal Enfield Fury around on Amal GP carbs well enough, and as I mentioned earlier, your only difficulty will be getting the engine to tick over/idle at a standstill, though with very careful cable adjustment you might manage it. Any advantage of the smoothbore would be at higher-end throttle openings, if your riding conditions and local law enforcement permit!

Otherwise it's just an Amal carb, and the usual rules of tuning apply.

https://www.amalcarb.co.uk/downloadfiles/amal/mk2_fitting_tuning_instructions.pdf

A.

[Softlysoftlycatcheemonkey]

    Again, thanks for the reassurances. My next concern about buying an Amal Mk2 36mm type would be for clearance under the motor mounting plate points: the plates themselves can be redone to work around a ( 32mm Mk1 ) carb body as shown by Hitchcock's, and that Mk1 carb mounted will clear the space given ( with no mention of issues by Mr. Henshaw during his multiple installs ), but the Mk2 36mm is a few mm taller from it's intake bore center and 1 1/2+cm longer from it's slide bore center, and looks like it may/maynot fit. Measurements of the Amal carb bodies are from the "Amal Concentric & Mark 2 Carburetor Technical Manual.PDF" ( https://www.scribd.com/document/359030354/Amal-Concentric-Mark-2-Carburetor-Technical-Manual-pdf ) and views afforded by Mr. Henshaw's work ( https://m.youtube.com/watch?v=d4RRMA-r3wY ). Hands-on guesstimate would be a plus, though. A stubby Dellorto rubber manifold might do it, but more thermal seperation from the head would be nice. An aluminium stub correcting for any degrees off center-line into the intake port and rubber boot joining to the carb may be water under a bridge too far away and long ago.

[Adrian II]

I don't know if this will help, but here is a CGT535 I saw three years ago, the owner (I presume) has fitted a Mikuni carburettor conversion, I'm guessing it's a VM34, the VM36 & 38 use a larger size carb body.



If you're planning to fit a larger carb I won't say it's impossible, but it might well need a re-worked head steady to provide more clearance.

You will note this conversion needs a one-piece flange rubber manifold thingy, a separate alloy flange and connector hose will usually move the carburettor back to somewhere where it won't fit. The Amal Mk2s and Mikuni VMs often have the same size stubs, so I'm guessing the smooth bore 36mm Mk2 will have a 43mm stub, That being so, you'll need a one-piece rubber manifold to take a 43mm stub with 60mm stud-hole centres. Does such a thing exist?  Yes. (It's meant for 38mm carbs too.)

https://www.ebay.co.uk/itm/360763627336?hash=item53ff301748:g:3JoAAOSwBP9UW93S

A.