Best S.R. /RGS NEW carb option?

[Joolstacho]

Well, Concentric? Monobloc? Mikuni?
If money wasn't a problem, which would you choose?
My Super Rocket is about 9:1, pretty well RGS spec. I've had a worn 930 Concentric (I hate them!), and a semi-worn 389 Monobloc on it, but I've never been quite happy with them.
I've decided that it's about time I treated it and bought a new carb for it... But which one? Mechanically the bike's pretty good, (I even had the Maggie reco'd).

I'm thinking of fitting an SRM Electric leg conversion, so I want to be confident everything else is spot on.
I built the bike up from parts, over many years, and it's, well, sort of 90% there. It needs tyres, details like better levers. I've fitted the nice TLS front brake, it has Koni shocks, Lots of the right stuff. But the Carb (and air cleaner) is next.

(Or I could just go out and buy a new Interceptor... probably a better option, but Jacko reckons the 'street cred' of the beezer will trump the Enfield any day, hahaha).
Actually I'm more concerned that my dikky spine will hang in there rather than street cred points!

Sorry I'm sure there are many posts on this subject, but anyway... What think ye...

[Rex]

I thoroughly recommend a new Amal Premier, but apparently you don't like Concs for some reason..

[Joolstacho]

Rex, I've been through x3 Concentrics. (on the SR and my Velo) In spite of very careful flange tightening and correct insulation gaskets every one of them has distorted.
Each one of them has worn the slide in no time. Tell me the Premier is a LOT better in quality, and I'll consider it.
I've run Mikunis in all sorts of applications, with no wear or distortion problems. We know the crap 'pot-metal' Amal used to use.
The bike originally would have used a 389 Monobloc. I'm leaning in that direction, but maybe a Mikuni would be a better option.

[Rex]

The Premiers use a hard anodised slide and have a removable external pilot jet. I'm happy with the few that I'm using (one on the Star Twin) and wouldn't use anything else on anything British.
Even after all these years some swear by Miks while others still swear at them so the jury would still appear to be out. At least with Amals they're easily tunable, parts are readily available, specs are known and they look in-period, and that means a lot to me.
(I don't recall ever having a distorted flange or body on the original Concs though)

[a101960]

I run a 389 on mine that I bought from Surrey Cycles. It was fitted with a chrome plated side. The idea being that this would reduce slide wear and in practice it has proved to have been borne out. There is no detectable wear the slide is still unmarked and is s good fit in the body. I do believe the chrome slide option is exclusive to Surrey Cycles, but I am not absolutely certain about that.

[RDfella]

If money wasn't a problem, which would you choose?

A monobloc. After my experience with Mikunis, wouldn't fit one if someone gave me one plus £500. They're actually very well made - just try and tune them. Don't like concentrics a lot, as they seem cheap and less robust when compared with monoblocs.

[chaterlea25]

Hi Jools,
I have a Mikuni on my SR for 20 years
and probably about 30 k miles
It runs great and I have had no issues with it
John

[Black Sheep]

Have had a 389 on mine for 40+ years. No problems.

[CheeserBeezer]

I use Mikunis on anything non-standard. I find the build quality of the Mikuni superb. The main issue with tuning a Mikuni is the wide range of needle jets. Unlike Amal, changing a needle jet doesn't make a lot of difference due to the very fine increments, so the needle jet is for fine tuning once you're in the correct range. On one of my bikes which I sold a couple of years a ago using a Mikuni was the only way I could stop it pinking.

[Kickaha]

If money wasn't a problem, which would you choose?

A monobloc. After my experience with Mikunis, wouldn't fit one if someone gave me one plus £500. They're actually very well made - just try and tune them.

Did you buy one for your application or just buy the carb an start from scratch?  if you do the latter then putting it on a dyno so you can see the afr is the best way forward or you can *** about for days changing things between rides to get it right

[chaterlea25]

Hi All,
Originally I bought a kit for my SR as it was the first bike that I put a Mikuni on.. it came with a couple of pilot and main jets ,
I found it easy to tune, 1/2 steps on the needle can be done with a 3mm washer 1/2mm thick.
I have fitted Miks to quite a few more bikes over the years successfully...
There are masses of needle jets and needles listed but only a few available. Spares are also pricey

John

[RDfella]

Did you buy one for your application or just buy the carb an start from scratch?  if you do the latter then putting it on a dyno so you can see the afr is the best way forward or you can *** about for days changing things between rides to get it right

Sadly no such item as 'my application' so bought a pair (new) to match as near as possible. After several months changing jets (at considerable expense as changing one means you have to change the others because they compliment each other) including delays each time as they only seem to be available from USA, I binned them and bought a pair of Concentric MK2 (Monoblocs unfortunately don't stretch to 34mm).
If one has access to a dyno (which I don't) and possess a full set of jets (maybe a grand's worth?) and have several days to spare, no doubt a Mik would end up nicely tuned. Twas only after I bought mine that I learned from the internet of the grief people have trying to set them up. Too many variables. If I recall correctly, something like 300 different combos of needle / needle jet. BTW, the needles aren't a taper, as with Amals, but a collection of ten steps of different diameter, and not in any order. For example, a needle could be rich at each end and lean in the middle. A veritable nightmare. The carbs are very well made (though you need a special tool to get the float out to access the valve) but not much use if you can't tune them. From what I learnt, you can get a bike running reasonably OK on them but with starting a real problem or vice - versa - but not both.

[berger]

RDfella i bought a mikuni jetted for the A7 but had problems starting it, i messed about and fell out with it then bought a repro amal and have had no problems. the mikuni was sold at a great loss of £££'s to a chap who was fitting it onto a 250 single, i hope he had a better result than i got with it.

[berger]

i tried photos but it didn't work so here is the next try. o dear it's now in the wrong bit it should be in the pistons bit about cols stubby kicker. never mind here is a kwaker nakker or suzi kicker fitted to a steel block on the gearbox shaft, works very well and a lot easier to start things off with more length  i went to the pub so maybe that's why it's in the wrong bit. will kind admin send it over to the imd   { In Many Directions,, RDfella    ]  piston bit thread cheers

[Joolstacho]

That's a very interesting kickstarter mod Berger, more leverage would be useful. It there any conversion to the actual kickstart quadrant/shaft?.
Possibly one of the Goldie more forward set KS quadrants might help - to give more rotation.
I was looking at my extensive collection of wrong carbs yesterday, (hahaha), - maybe I could use my monobloc - if I could get an unworn 389 body (the retailers don't seem to sell new bodies).
Actually my 389 isn't TOO bad apart from the graunched top ring screw thread - (the jubilee clip around it isn't very impressive!) It has a worn Concentric at the mo'.
A new 389 would cost summat like A$600 ! Ouch!
There's a half-decent Mikuni there too, -I'd need to make a flange adaptor. Not such a big problem. Food for thought.