Mikuni conversion

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Wolfman

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Hi guys. Finally gonna get my ole Norton road worthy. Thinking about going to a single carb via one of the Mikuni kits. Problem is I see them listed in 3 sizes 34,36,&38mm. All say they are for my 1973 750 Comando. Which one is the best for my occasional week end rider? Also going to go with TriSpark & electronic regulator but have been told they are not compatable with my bike.

Thanks Guys
Mikuni conversion
 
Others may offer more expert advice, but I believe the single 34mm is what you will want. I can't imagine who would say
that your bike is not compatible with a TriSpark ignition and an electronic regulator (e.g. Podtronics and others).
These are all great aftermarket improvements for driveability and reliability. Others will offer more both good and bad
stories. The archives of this forum will offer you multitudes of threads on each of the three items you mention.

I am an old man week end rider and have all three of what you mention, albeit I have upgraded my charging system to
3 phase and thus have the Podtonics regular for a 3 phase.

This forum has amongst it's contributors, RACERS, PURISTS and RECREATONAL RIDERS. Each have viewpoints which are valid.
 
"I am an old man week end rider and have all three of what you mention, albeit I have upgraded my charging system to
3 phase and thus have the Podtonics regular for a 3 phase."
Sorry I misspoke. It was regulator only they said was not compatable. Sounds like this may be what they meant. I will look into this 3 phase thing.
 
Ok there are many many threads on this but basically if you want an easy to live with commando fit the VM 34
Trispark ignition failures are a common theme on here and I don't know enough to comment about them
I only know Boyer and that gave great service for many years until it failed but now I use an antique Lucas Rita that's 40 plus years old
I have a podtronic regulator that works well
 
Wolfman said:
"I am an old man week end rider and have all three of what you mention, albeit I have upgraded my charging system to
3 phase and thus have the Podtonics regular for a 3 phase."
Sorry I misspoke. It was regulator only they said was not compatable. Sounds like this may be what they meant. I will look into this 3 phase thing.
Click to expand...
3-phase regulator/rectifier is only needed if you are changing the stock 2-phase alternator to a 3-phase type (has three wires coming out of it instead of two)...which gives better output at lower revs which of course is desirable esp if doing alot of around town work. That said I'm running around town some 75-90% of my riding on the original 2-phase with stock rectifier and stock zener diode regulator.
No reason for it being "incompatible" with our bikes. Even the positive ground is irrelevant here because the reg/rec's can be hooked up either way. Check out Podtronics, Sparx, Lucas and Tampanium makes at your fav Norton parts source.
 
Wolfman said:
"I am an old man week end rider and have all three of what you mention, albeit I have upgraded my charging system to
3 phase and thus have the Podtonics regular for a 3 phase."
Sorry I misspoke. It was regulator only they said was not compatable. Sounds like this may be what they meant. I will look into this 3 phase thing.
Click to expand...
You can use a 3 phase regulator with a single phase alternator
Just connect to 2 of the 3 yellow wires
 
My ‘72 Roadster has VM 34 mikuni , Boyer mk4 EI and a Podtronics R/R , has been trouble free for many years .... once you start bringing things up to spec , it hard to stop ... would recommend you upgrade front brake as well as making sure both your brakes will stop your old bike .... have some fun with it and enjoy getting your bike back on road, where it belongs ....
 
tri spark has an unusually high failure rate and i have had three fail on my bike along with numerous others on other bikes i know of, so IMHO the trispark is a no go. a pazon sure fire is ok on a single mik. but my go to now is a boyer micro digital as it has idle stabilization where the pazon does not.. as to the carb size the 34 is the one to use on a week end rider. the twin amal premiers are ok but the single mik is a set and forget carb setup.
 
I’m a bit of a mix. After my first TriSpark packed it in less than 1000 miles the at no cost replacement has been doing fine. Prior I had a Lucas RITA that was bullet proof for years until it wasn’t. Not sure of the cost comparison between a single Mik VM34 and new Amal Premiers, but the Mikuni is probably a safer option. Not my choice though as it requires some modification to air cleaner and relocating the ignition switch bracket. I’m still using the original type alternator, rectifier and zener with no problems at all. Since my ‘72 750 has no electric start I use whatever cheap Pb/acid 12N9-4B I can get.
 
My Norton came to me with a vm34. It is simple, starts first kick (pazon surefire) and works well for a 40 year old carb. That said, I never knew my bike with twin Amals, so I bought a set. Waiting for the right moment to MAYBE make a switch. If you want a simple, reliable set up, go with a Mikuni. Can't speak to the Amals but I like twin carbs. You can always switch back!
 
I plan to put a Mikuni on my 1973 Norton Commando around the same time I plan to put four Amal Concentrics on my 2019 Kawasaki Z900RS Cafe... :rolleyes:



Sorry for the unhelpful sarcasm. I'm a big "anti-fan" of Miks on Nortons (and "fixes" for wet-sumping).:mad: Sometimes it gets the better of me.;)

I've had great luck with my TriSpark, purchased new shortly after they came out and it's been completely trouble free since I installed it 10 years ago.

Podtronics works fine but it doesn't work any better than the OEM rectifier/Zeners. The originals were working perfectly; I only replaced them with a Pod because...well, at the moment, I can't remember WHY I did that but I must have thought it was a good idea at the time.o_O
 
Oh...now I remember! :)

I installed the Pod when I installed the Alton Estart because the bike had the Lucas 180W three-phase system and the Alton alternator is 150W single phase.
 
MexicoMike said:
I plan to put a Mikuni on my 1973 Norton Commando around the same time I plan to put four Amal Concentrics on my 2019 Kawasaki Z900RS Cafe... :rolleyes:



Sorry for the unhelpful sarcasm. I'm a big "anti-fan" of Miks on Nortons (and "fixes" for wet-sumping).:mad: Sometimes it gets the better of me.;)

I've had great luck with my TriSpark, purchased new shortly after they came out and it's been completely trouble free since I installed it 10 years ago.

Podtronics works fine but it doesn't work any better than the OEM rectifier/Zeners. The originals were working perfectly; I only replaced them with a Pod because...well, at the moment, I can't remember WHY I did that but I must have thought it was a good idea at the time.o_O
Click to expand...
A local bloke to me had a cb750 big bore with 4 Amal mk 1 concentrics back in the 70s it certainly went well
 
baz said:
A local bloke to me had a cb750 big bore with 4 Amal mk 1 concentrics back in the 70s it certainly went well
Click to expand...

Not quite the same but close: through the 80s and well into the 90s Amal smoothbores would be found on many big 4 cyl Japanese race bikes and tuned specials.
 
16K miles on a Tri Spark and no issues, including many days riding with temps in the high 30's.
As for a carb, single or twin they all work well, apart from original Amals which many were beyond worn out when originally fitted.
 
my advice is to ALWAYS have a spare stator if you insist on one. my first failure was going down the road and it started to run bad than quit. the second one I shut it off and on the restart it run bad so I stopped and put on the spare stator, than on the third one it was running perfect, shut it off and it would not restart 10 minutes later so again on went the spare. after the morning ride I promptly sold it and am DONE with them. my experience has been repeated by over half a dozen guy's i personally know. next you will ask about the rest of the ignition system. I have a twin output 4.6 ohm coil and others run stock coils and different wires and caps BUT every one has failed regardless of the rest of the system so as I stated it has too high of a failure rate for me to trust one ever again and you can buy as good of an ignition for less money and a far better reliability history. good luck with your POS and carry a spare unless you have recovery insurance.
Madnorton said:
16K miles on a Tri Spark and no issues, including many days riding with temps in the high 30's.
As for a carb, single or twin they all work well, apart from original Amals which many were beyond worn out when originally fitted.
Click to expand...
 
Both my Norton's have had Tri Sparks since 07 and 08 never a problem, maybe they were better back then?
 
It’s a strange ole situation for sure. If I’d suffered Bills failure rate I’d be EXACTLY the same as he is with regards to Tri Spark.

But I’ve fitted 5 so far. Still got 3 of the bikes and the 2 I sold are still running fine with the Tri Sparks. So I’m one of those that’s in the ‘I’m a fan’ camp.

Hope it stays this way cos if I change camps I’ve 3 bikes to change!
 
I went through four of them but I perservered and my current one is trouble free. When I go on long runs, I carry a spare. Within ten minutes I can have it changed over and be on my way. I'm a believer. I guess it's like running a pair of Amals. You screw around a lot before you get it right.
 
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