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Single carb conversion to Mikuni VM36

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MikuniOz eBay c£250, Allen's Performance UK £397 for what is apparently the same thing, a kit of all the necessary parts, both include carriage. How does that work ???? Am I missing something???

I'm in the market for a single carb conversion but only at a sensible price.

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The existing Amal carb bodies and slides appear worn and I'm no expert carb whisperer where two carbs are involved. If I need to dig deep in the pocket I thought I'd make it simpler and by most accounts better. I'm quite happy tweeking a single Mikuni but twin Amals seem to be an  unnecessary complication. Twin Amals might have been the best option in 1974 but maybe there's a better bang for my buck nearly fifty years later ? V

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In strict truth, probably both — but are they both worn past using? When I first got my current Fastback the slides rattled like anything, and were clearly knackered when removed for inspection.

However, there wasn't any evident wear in the carb bodies; replacing with Burlen's hard anodised slides eliminated the rattle and provided very smooth operation.

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My '74 Commando had a single Mikuni when I bought it. The only problem I have with it is it's really hard to start cold, i.e. multiple kicks. However once it's starts and warms up it runs fine.

 

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I converted my 850 Roadster to single Mikuni about 10 years ago and have never looked back! I bought the bike nearly 30 years ago with a single Amal on it, which was OK, but the rate of wear in slides was a joke. I spent a lot of time and money on exotic combinations of bores and slides  before a pal suggested the Mikuni.

Now the bike starts first time every time, even after a winter layup. (Assuming new petrol in the tank)

It needs the choke when cold and no twist grip at all (very important) and then it's away. When hot no choke is required.

It may not be as fast accelerating as a twin carb set up, but I don't notice the difference and rarely drag race with anyone else so equipped - so no problem.

What I do notice is a supremely dependable tickover in all circumstances. 50 miles of motorway running at 70 +, drop down the exit ramp to the roundabout and the bike will sit there at tickover as long as you want. I have never had that confidence on any Amal set up - I always felt the need to keep it going on the twist grip. No problem at all with the Mikuni - very important with only a kick start and a duff knee in modern traffic!

I bought my kit from Allens who provided an excellent service.

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I've always run Amals and still perform the over-the-shoulder 'lifesaver' that I was taught in the 1970s...Must be a bit of a traditionalist, I suppose :-)

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Ok, thanks to all contributers, I think the majority verdict is that the Mikuni is a good idea if you need to change the set up you already have and if you're not stuck on origanality. But for me I need to justify the extra £125 to buy the kit from the UK supplier rather than have the very same thing sent all the way from Australia. I really can't understand how that works, it's bonkers,  if I go for it my pound notes will be sent to the antipodean supplier sad though that is.

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Include the import duty and VAT that will be slapped on it when it gets here?

 

When I bought my Mikuni some 20 years ago from Rocky Point in the USA I was required to pay substantial duty. I have been very pleased with the carb but I would say that the main benefit over a single concentric is longevity. This may not matter if the bike is only doing a few thousand miles a year.

When, after 90,000 miles, I decided that some limited refurbishment was necessary Allens provided an excellent service. 

Rocky Point also offers an adaption to enable handlebar choke control which makes life much easier.

I have a 34mm Mikuni (the spell checker just changed this to Bikini!). There has previously been some debate on whether to use 36 or 34.

 

 

 

I hadn't considered the customs/import duty issue but having researched it it appears I would be charged 20% which means about another £50. Perhaps Brexit will help !!

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Will it have the correct jets etc?

There are Post office handling charges as well as VAT, so take care you do all the sums...

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I think we can all draw our own conclusions about my original question, I have!  Meanwhile I have changed tack and have just bought two NOS Amal slides for £24, nothing fancy, plain aluminium, I can't see me wearing them out and I will have to practice my Carb Whispering. 

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I was going to suggest you refurb the Amals seeing everything was in place but that wasn,t your original question.

If your slides were worn it would be a good idea to renew the needles and needle jets as a set to go with the new slides. Got mine direct from Burlen, £35 delivered for my Premiers which had around 12,000 miles from new and they run beautifully again.

Instant EFI type throttle response and great pickup to redline puts the dynojetted/refurbed CV carbs on my Yamaha FJ to shame, although the Commando has nowhere near the outright grunt of the Velvet Sledgehammer to be fair...

I remove the K&N and use the old (perspex) rod method in the carb throats to synch and a mirror to check they both reach full throttle at the same time, then tune 1000rpm idle speed by tach and mixture by ear. Trispark set to a standard 28° advance keeps the idle boringly steady.

A major part of carb whispering is having good bits to work with and getting the basics right like no air leaks, float levels, good cables etc.

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I coverted my 850 to a single Amal Concentric carburettor many years ago. The first thing I noticed was the machine used a lot less fuel. The Concentric carburettor certainly has its drawbacks but for all that it works quite well. You could fit a 'premier' Amal which is superior to the original 'pot metal' fitment.' You will lose a bit of performance from the pick up and the top end with a single carburettor, but who rags their Commando through the gears and rides at 90 miles an hour plus anyway.

I do....

My Mk3 came with a mikuni and i then bought and fitted an SU carb conversion (one of the ones from Phoenix) She regularly gets thrashed and will top the ton given a clear road, The big benefit over the twin amal setup is economy. Ride like a granny and you can see upto 90mpg. Ride it like you stole it 65 -70 mpg.    

 

 

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