Mikuni Questions

Got a chance at a Mikuni VM34 for sale locally for a good price. Not sure what to look/lookout for. Here's a pic from the ad:



Can this be made to work with stock HamCan air filter setup I already have the single hole style for the single Amal 932 my bike came with. Will I need a new manifold or will the 2into1 I have already fit if I get the correct rubber adaptor? What about throttle/choke cable (I have a single for each now, no spitters).

Thanks!

You have your choke lever already in place why clutter up your bars ... take the top off and have a look at jets and check for scoring on sides ... the photo looks like it fairly new ... no idea bout hamcan , I like the uni-filter or a K&N ... not sure on your manifold .... I obviously use one forget letters or word on it now will check if someone else doesn’t respond .... have no experience with the Amals ... bike came to me with the single Mikuni....glad it did

Thx...I see, the Miku has a in-situ choke lever...no need for the cable driven assembly. Like it. Reason for keeping HamCan....other than being frugal with expenses, is that I'd like to get the bike insured under the "Collector" class, which means it can only have certain changes from OEM....carbs can be changed to period correct/similar sized units...but losing the airbox to a modern foam/open gauze type might be an issue.

I have mine registered as vintage vehicle ... had to provide written mechanical fitness form signed by certified bike tech. local guy had no problem filling out form .... suppose each Province has different rules .... I would check out the details ....

This Mikuni looks very old, I've not ever seen this design of slide height adjuster, but it could be an accessory, but the fuel barb leads me to believe that your carb is over 12 years old, all the ones I have seen are brass. It also looks like your float bowel has 2 gaskets and a metal spacer between them, I could be wrong. Nothing wrong with an old carb, but they do wear and gunk-up. Don't be pennywise and Pound foolish...

Anyway, it can still be a keeper, be good for you to strip it and make a record of the calibrated parts: Main jet, Idle (pilot) jet, needle, needle jet, slide cutaway and air correction jet. Before you spend money be sure that slide is not galled, fits smoothly, and that the idle (pilot) passages are clear, both air and fuel

The single hole Ham-can you have can easily be made to work, simply mount it and the carb, slide the fuel filler neck hose back trace the larger hole for it, then cut out and pretty up the edges.

I sell all the calibrated parts you would need for a 750 or 850 Norton, including the rubber adapter and throttle cable. I also have the fuel filler neck hose in the correct ID to fit the Mikuni, that you can use to locate the hole for the Ham-can. If you want the choke to be active on your handlebar I have all the parts for that as well.

https://www.rgmnorton.co.uk/buy/commando-air-filter-front-plate-for-one-carb_1668.htm
for a single inlet hamcan

Tornado said:

Got a chance at a Mikuni VM34 for sale locally for a good price. Not sure what to look/lookout for. Here's a pic from the ad:
snipped

Can this be made to work with stock HamCan air filter setup I already have the single hole style for the single Amal 932 my bike came with. Will I need a new manifold or will the 2into1 I have already fit if I get the correct rubber adaptor? What about throttle/choke cable (I have a single for each now, no spitters).

Thanks!

Click to expand...

Nice looking VM 34. You need to question the seller what this came off of. Mikuni has a vast range of needles & needle jets. If you are lucky, it came off of another Brit bike like a Triumph. If so, then your chances are good that it will work, as is, with maybe just a main jet change. However, if it came off of a Jap bike [other than a Yamaha XS650] you will need to know the correct parts to install for your Norton. Otherwise, you could spend weeks and a lot of money trying to sort it out. You need someone on this list who has one of these VM34s, to tell you what the jets are in his carb. Just like an Amal, check the slide and bore for wear.

I have hope this came off a Commando...seller also had a glass Roadster tank for sale a week ago....

I think there might be a pressed-in brass ring in the top of the needle jet, if you have trouble jetting it. Also the common Mikuni needles for the 34mm carb are 6F (rich) and 6D (lean) They are all the same size on the parallel part of the needle - the F and D refer to the taper which operates above 1/3 throttle.

Seller has told me it came in a box of spares with some Norton Commandos they recently acquired. Sent more pics:

You gotta buy a manifold, gaskets, bolts, a rubber mount, strip it, re jet it and fix anything that you find broken or U/S.

So, it’s gotta be pretty bloody cheap to make it better value than one of the brand new, readily jetted, off the shelf kits readily supplied !

Manifold you will need...

https://www.ebay.ca/itm/Norton-Comm...ash=item2843e81851:g:YTQAAOSw4nhZ6tXv&vxp=mtr

Full kit

https://www.ebay.ca/itm/Norton-Comm...ash=item28199be2e4:g:YFkAAOSw9eVXUNV3&vxp=mtr

Tornado said:

View attachment 4378

Click to expand...

"32" should make it a VM32.

If 32 leave it and get a proper sized one ...

Your carb is a 32mm VM, it's old and it will need plenty of support parts 1) manifold (w/screws and gaskets). 2) adapter. 3) throttle cable. 4) air filter and may need a full set of calibrated parts which can cost up to $60 USD. E-Bay is full of this stuff if you have the time to sift through the chaff to find the wheat and then to hope that all these orphans integrate well.


Or.


You can purchase a "system" that is guaranteed to put your carb issues behind you, or give you a 100% refund if you are not completely satisfied. www.rockypointcycle.com/p-norton12_mikuni_kits-2380.html. The same kit for a MkIII differs only if you still have the OE twist grip/switch gear.

Craig said:

If 32 leave it and get a proper sized one ...

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If it were a 34 I'd still leave it , this is my opinion of course
Everybody and their dog has an opinion on this single verses twin carb plus what size etc etc option
If there's nothing wrong with your single amal concentric 32 just stick with it they are easy to set up and great mpg just don't have the performance just like the vm34
Don't know about the US but in the UK there are often complete single vm 34 kits including manifold for sale on eBay , might be worth looking on there cheers

Thx all. Seems this one's a throwback. Will keep working with the Amal 932 single for the next while.

Doc. Dave who I ride with has ‘72 Commando non-Combat , he runs with single Amal , not sure on size but I have yet to wait on him , starts and idles fine since he mounted the Tri-spark .... funny thing is he rides same Ducati as I do too ,we met through local Duc Club ECDC .... also I have no knowledge of Amal carbs , I once tried a pair of VM32 Mikuni on my bike while performance may have increased not sure I noticed, I do remember burning more gas though and mounting and setup was a pain in the arse .... still happy with the single vm ....

I see I'm late to reply. Odds are, that carb came off of an older Triumph. Either as a single on a Tiger, or one of two on a Bonneville. As suggested by others, pass this one by. A single 34 or 36 would work. I've run both Mikuni & Amal [Mk 1 & Mk 2]. They all work great when set up correctly. Down side of the Mk 1 Concentric was rapid slide/body wear. Back in the day, I could buy brand new Concentric bodies from KK Cycle Supply [defunct] at a good price. Anyone sell new bodies in the USA now? As Craig mentioned, the downside [in my experience] of Mikunis was reduced fuel economy & they tend to run rich on the choke. The Mk 2 Concentrics only downside, was it's price compared to the other two. They would also run rich on choke, until you swap out the #50 choke [same style as idle] jet for a #35. Once you do that, they are the best choice in my opinion. There is a used pair for sale on eBay right now.

https://www.ebay.com/itm/Norton-Com...e=STRK:MEBIDX:IT&_trksid=p2055119.m1438.l2649

The great thing about the Mk 2 is that it uses the same jets as the Mk 1. Make her an offer.

You might want to simply keep using the single Mk 1, till you can afford to buy a set of the new Mk 1 Premiers. That would keep the machine looking stock.

Charlie

PS There is a vendor on Amazon selling brand new Mikuni VM38 for about $96, shipping included. I just bought one for an old Sportster. Jetting is set up for the 900/1000 Sportster, so it should be close for an 850. Let me know if you want more info.

There's a complete single 34 mikuni VM and manifold on eBay UK ,
I thought there would be one along soon!
So if you want to make your commando run sweet but slow it's only £30 at the moment, cheers