keihan, mikuni, or Amal

Does anyone have experience with the linked keihan 35 mm carb set?
Is it really well spent money and a noticable gain in performance and responsiveness as everybody that wants to supply me is saying?
Or.. would i be better off buying the mikuni VM set. [cheaper]
Or..would it be better to have 32 mm amals redone or replaced.[ much cheaper].

I don't want to use a single carb set up and gas consumption isn't my main concern since I use several bikes next to the Norton.
What do you guys think?

I am riding a very healthy 73 MK1a 850

Willem.

If it ain't broke...

..."fix it", till YOU are.

If you mean the Keihin 35mm FCRs (e.g., like CNW sells), I can assure you they are awesome. Great power, smooth, easy to adjust (rejet - and they typically need it), easy starting, you name it.

And incredibly expensive.

If you get a set, let me know and I'll send you my jetting changes - they took a LONG time to dial in and perhaps may be of value to you.

For what it's worth, I got a set from Kenny Dreer that are dialed in for an 880 with Megacycle 560 cam; I'm going to have a look at the hardware and I'll post what they've got, to "compare notes"

I prefer reworked AMALs with a chrome plated brass slide, which seems to extend their useful life some ten-fold. Moreover, AMALs are easy to tune, provide excellent performance and provide a great base for an air filter. Lastly, nothing beats the look of an AMAL, in my mind.

I hadda go look up my own post to remember them (although I'm sure I've got them in my log at home). Here they are. These took the FCRs from 35 MPG and black plugs to ~50+ MPG and tan plugs, with great starting and performance:

140 main jets (came with 152s)

Needle clip in #2 slot (from top; there are seven slots; the needle clips came in #5 slot I believe)

Stock pilot jets

Slow air screw out two turns (were originally out one turn)

Slow fuel screw out 5/6 turn (Right side was originally about 2/3 turn out. Left was originally 1.5 turns out)

Suffice it to say, the original settings were way rich on all counts - conservative, I guess, but not optimal.

Willem....why the Keihans? trying to break Norton land speed records?
I am happy with my single Mikuni conversion. A friend of mine owns a '73 850 Commando with the AMAL set up and I am faster off the line (ok, he's a but older than me, so his reflexes are a bit slower than mine), I have more top end (ok, his vision gets blurry at higher speeds, must me age related) and I get better gas mileage (I am just cheaper than him, I guess)
BUT...if you read between the lines...it says, I would like very much to have a Keihan set up, but that goes back to me being too cheap.
C74 aka Eric

Willem...I mentioned I am quite cheap, but if we can get a deal on two sets of Keihans...I might be interested.
C74 aka Eric

Willem
The Mark I Amal carburetors are excellent on a Commando when they are “brand new!” They pull in all throttle openings and suit the bike well. The Amal Mk I Concentric is a dinosaur in simplicity compared to the Mikuni or the Keihan but like I said when Amals are new its tuff to beat in price/performance. But alas they are prone to rapid ware…again especially on a Commando. 5000k is the norm for worn out Slides&Bores. When they are worn out they give the owner all sorts of grief. This is due to the similar pot metal material used in the main body and the slide. Installing larger slides does alleviate the symptoms for a brief period, but it still does not address the root problem. Many Owners have cursed and shook their fists, frustrated with the Amals and switched to single Mikuni or other carburetors. You are probably here at this crossroad!
If you rebuild your Amal concentric carbs there are people to do this. Bruce Chessell in Canada will re-bore your main bodies and sleeve your slides with bronze inserts for approximately $65 US a piece… http://www.tritonmachining.ca/ also in the USA… http://www.amalsleeve.com/ who will rebuild Amals… your choice. I, who have used Bruce Chessell am happy with his work. I am not sure where you Hale from but this is a good start if you wish to remain stock.
If you go this direction you should invest in a piece of glass or granite surface plate and ensure the float bowl to main body contact area is dead flat using wet/dry sand paper. Also the Main body to carburetor spacer…ensure this is flat because if this is distorted by too much torque applied to the stud/nut fixing this warps the body and causes the slide to stick. Only enough torque to make a good seal and no more… use a new nyloc- nut to hold it in this position the O-ring will do the sealing. Viton Tipped Needles are next…if yours are just the white plastic units then you probably have seen your amals dribble gas when you shut off your engine and forget to cut off your tank petcocks. Biff these in the garbage bin and go for the Vitons. Now check your float height @ 0.80” below the float bowl chamber rim. Don’t bend the plastic on the float it will only return by memory to its original. Heat the float bowl in boiling water and move the brass insert up or down to achieve this 0.080” gap. There is oodles of info for the Amal in Jerry’s website @ the top and on other sites. I personally have replaced my needles and needle jets because these tend to ware with the original slides. If the needles have a frosty look on their surface bank on the jets and needles to be out of round. Replace!
These are options for you …it all revolves around money…get your pocket book out! I think there is even a fuel injection set up coming up for the Commando real soon. CNW I think.
The sky is the limit. :roll:
CNN

willem said:

Does anyone have experience with the linked keihan 35 mm carb set?
Is it really well spent money and a noticable gain in performance and responsiveness as everybody that wants to supply me is saying?
Or.. would i be better off buying the mikuni VM set. [cheaper]
Or..would it be better to have 32 mm amals redone or replaced.[ much cheaper].

Click to expand...

As the earlier replies confirm the answer to all of the above is undoubtedly yes.
For me i don't like the look of the Mikuni's, my sesleeved Amals wore out again and i was sick of balancing them and was fortunate at the time to be able to afford to splash out on the Keihins. But then i have a mate who runs a single Mikuni and thinks i'm a nutter for wasting all that money. We're both right.

:lol: :lol: :lol:

Ya know people are always giving me grief about hopping up a Norton. I have heard "just go buy a 600 cc crotch rocket if you want to go fast. Well I have an FJ. Great bike under all that dust. But my hot rod Norton doesn't have any dust on it. Come to think of it I better go put the battery tender back on my FJ. Don't want to have to buy a new battery again next time I want to ride it. Jim

Heck,

I hot rodded a CJ (Chinese 1939 BMW copy) so I'm not going to pick on folks who hop up a Norton. It sure is expensive now to get a Norton horsepower though.
After all this stuff is a hobby for most of us, and whatever strikes your personal fancy is fair game.

panic said:

Hmmm...
Tough question.

FCR = $500.00 per horsepower added.
Oh, wait - $550.00 after all the rejetting (if your time is worth zero).
Yes, you should definitely do that.

But, a carburetor is a primarily a fashion statement, isn't it? Because all the cool kids will laugh at you if you buy one they think is dorky?

What to do?

Buy replica GP carburetors, about twice as expensive, don't start, don't idle, no info available, hard to get spares.
But it'll get those nods of approval from the wankers.

Click to expand...

The premise being that the FCRs are good for 2 HP? I haven't dyno'd my bike, but methinks the difference is greater. I didn't buy them as a fashion statement. And I don't know why the price would go up by $100 based on purchase of two $5 main jets.

Perhaps you could make your generalizations a bit more sweeping....

What you get over most 35mm carbs with the FCR's is the ability to meter the fuel precisly at low speeds as well as getting the performance advantage of big carbs at higher speeds. With the common round slide carb you will find that installing carbs that large will make slow running pretty touchy. FCR's have a well designed slide and venturi that works well at low speeds as well as high. With the linked throttles they are pretty much set them and forget them.
Lot's of people like the single Mic. setups. They do give good throttle responce at low speeds and are dependable. They also loose to twin carbs when the engine speed exceeds 4000 rpm. Actually it's not the single carb that hurts the power but the poorly designed manifolds that are used. I have done a lot of work on the dyno trying to makle a single setup make power and still fit on a Commando. I have succeeded using a large throttle body and injection. I am not yet sure how this is going to relate to a carb but I will find out. Jim

comnoz said:

... I have heard "just go buy a 600 cc crotch rocket if you want to go fast... Jim

Click to expand...

Big difference in going fast, and going fast with 'Style'. :wink:

Most of us here get it. 8)

For this thicky here, what's FCR? sorry!