Twin carbs or not. (2011)

Hi , according to victory , you could try those settings for a 750 cdo:
pilot:20/25
slide:2.5
needle jet2,P4
needle:6DH2
main:220
air jet::1.0
give us feedback ,please......i am sure they could work well!

"That's kinda like saying "Man up and surf the Internet with a 2400 baud fax modem"."

A real man would use a 300 baud modem!

I intended my "man up" remark to be humorous - sorry you didn't take it that way. As has been noted a bajillion times, it's all a matter of personal opinion. I PERSONALLY would not run anything but the oem Amals on my Commando. But I don't care at all what kind of fuel-metering system that anybody else uses. I will say, as I have before, that a properly set up pair of Amals will idle smoothly at 600 RPM and provide all the air/fuel that a Commando can use. I have a good friend who runs a single Mikuni and loves it. But he will tell you that the bike runs out of power if you start pushing it around the "ton." The Amals don't.

I'm sure the flatsides (had em on one of my Ducatis) work great but FOR ME in this application - a stock 850 motor - I don't see any reason to change and I'd be really surprised if a dyno plot showed any power difference between flat slides and a pair of Amals on a stock engine with no other changes.

mike996 said:

"I intended my "man up" remark to be humorous - sorry you didn't take it that way.

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It's cool, I was laughing.

Jeeezuss, I didn't mean to start a bloody war !! Thank you all, it's now clear as mud. No really... I get it. They all work, it's just a matter of the experience each individual has had with what Carby. I've used Miks on... XL250 Honda, 550 CCM, 500TT Yam, XS650 Yam, plus many 2 Strokes, all for very good results. The reason, Because I just happen to have a Mikuni dealer close by that is very helpfull. Unfortunately we ( Australians ) have to pay through the nose for ANYTHING related to " Classic Bikes" and it will be the manifolds that are the telling $$$ factor. Any way, it's now gone to the bottom of the list since she tried to kill herself and we'll see what I can pick up on... FOR SALE, while I wait for parts to arrive etc. etc. for the rebiuld...Thanks guys ( and girls if there is any ). AC.

After reading this thread. I have decided to (man up) and buy some NEW Amals for my Norton. I want to keep the look of the stock filter and plenty of people have told me the same thing about Amals...If they are set up properly...yada yada.

So, My Commando is running great as it is...First kick start, tons of tourqe and accelerates like lightining. But The idle is less than dependable. I have done all of the cleaning and adjusting many times, but the fact is my bores are loose. Instead of re sleeving the 40 year old carbs, I want to buy a new set and start fresh.

my question, who sells 930 69/68 at a nice price besides Amal themselves.
Thanks, tyler

Get the Amals made by Burlen Fuel System, that's real important if you want a better quality carb. I had a bad experience with NOS Amals and Burlen took them back and provide a new pair. There is a noticable difference in the new metal casting and material quality and the fastners etc' are stainless steel. Worked fine straight out of the box, but I did check the float levels first. PS - I run a single 34VM Mikuni on my 850, but the Burlen Amals went on to a mate's 850 as he prefers the original equipment look. Personally, I think the price at the moment is pretty good value if you order them from Burlen direct in the UK.
Mick

Mk 1 / 900 series from RGM England... 96.00 pound.
Mk 1 / 900 series from Andover Norton... 86.52 pound.
Aussie-- American exchange rate is about the same at the moment but to English pounds is + 40% I think... Ish.
I would be looking to Burlen or checking on where the others come from.

As my recent 750 Commando purchase came with a single Amal, yes that's right, I wanted to go back to dual Amals. Just last week received my pretty new 932's shipped directly from Burlen to NY. Shipped US price $300. Now for spring.

I've been using an single sleeved 32mm amal with the stock air filter set up for about 8 years and love it. I use that set up because it looks stock and I got sick of fiddling with keeping two carbs in sync all of the time. There is no maintaining the silly balance or sync with one carb and I find there is absolutely no difference between one and two carbs performance wise up to the 70-80 mph I ride the bike. I am currently setting up the stock air filter to accommodate one single amal on my recent commando purchase as well. Using one or two carbs, amal or mikuni is a personal choice; there is no right or wrong answer, but your choice should be based on what you plan on doing with the bike not what everyone else is doing. If you are lucky enough to afford racing a different set up is going to be necessary. If you are running the bike hard over 90-100 mph regularly on the street chances are you're gonna have other problems and not carb related, but if your riding your 40 year old bike like the average person on the street one carb is fine. Refusing to man up in Illinois. :lol:

In common with some other OE parts for older bikes, Amal carbs are 40 years out of date and are made using worn out machine tools, and very poor quality materials which results in rapid wear. However sleeving them does provide a service life comparable to more modern carbs, and obviously the OE appearance is retained.

From the perspective of performance though the modern carb is by far the better choice, unless of course you are the type of rider who would prefer to fit late 1960's tyres (if still available) to retain a more authentic appearance. Its certainly worth looking at the flat slide carb kits from JLC in the US, as these seem to work extremely well on Brit twins, and are very reasonably priced.

ML said:

Get the Amals made by Burlen Fuel System, that's real important if you want a better quality carb. I had a bad experience with NOS Amals and Burlen took them back and provide a new pair. There is a noticable difference in the new metal casting and material quality and the fastners etc' are stainless steel. Worked fine straight out of the box, but I did check the float levels first. PS - I run a single 34VM Mikuni on my 850, but the Burlen Amals went on to a mate's 850 as he prefers the original equipment look. Personally, I think the price at the moment is pretty good value if you order them from Burlen direct in the UK.
Mick

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- burlen doesn't make the carbs themselfs but farms them out - I know beciuase they were having problems getting carb bodies a while ago from their manafacturing source because of pourus castings (their explanation not mine)

while they may have "tighter" quality controls than the originals the same inherent problems exist - some people are fans of those problems other not

New 900 Series Amal carbs are cast from new tooling and machined on modern CNC machines. Castings come from a variety of different foundries and always did. The castings remain zinc alloy forv now but with a passivated finish - a form of anodising which improves wear qualities and resistance to corrosion. Jets are now made from manganese bronze rather than brass, needles are nickel silver, O rings are Viton - all materials that do not react to ethanol. Slides can be zinc alloy, hard anodised forged alloy or ground hard chrome. Needle valves are now Viton tipped alloy rather than brass, which improves the operation of the float chamber. Floats are now solid ethanol resistant foam and adjustable for level. Speak to the Amal guys at shows or ring the technical help line and you will find there is a constant programme of development and improvement going on.

Carbonfibre said:

In common with some other OE parts for older bikes, Amal carbs are 40 years out of date and are made using worn out machine tools, and very poor quality materials which results in rapid wear. However sleeving them does provide a service life comparable to more modern carbs, and obviously the OE appearance is retained.

From the perspective of performance though the modern carb is by far the better choice, unless of course you are the type of rider who would prefer to fit late 1960's tyres (if still available) to retain a more authentic appearance. Its certainly worth looking at the flat slide carb kits from JLC in the US, as these seem to work extremely well on Brit twins, and are very reasonably priced.

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I also love my K81's on both commando's

I must be just lucky, twin AMALs, with 28k on them and still working fine. Maybe if my engine was tuned to an inch of it's capability, maybe I would look for something that could meter the fuel better, though mine maybe worn they keep it ticking over nicely, and deliver the fuel well - yes I do ride it like I stole it, if it breaks - fix it is my motto.

I never noticed that there was a problem with air filters or splaying on the twin Mikunis with my MK II and MK III. The MK III has a single K&N with some fabricated rubber snorkels, They have been on there since about 1981. The MK II has Unis, and has had since by brother bought it from HPI in about 1979. It is on its second set, ans the first disintegrated over the decades. I never considered this was a problem at all, until reading threads about it here. I intend to replace the 32s on the MK III with new 34s I already have. Although the MK II has more cam, compression and porting, I think it can still be used as a baseline for carb set-up pretty easily.

I run two 34mm Mk2 Amals with methanol fuel, but I use Mikuni 6D needles. The motor is on standard compression, but the methanol still works well. On a race bike, wear is not a problem and you don't have air cleaners. With a road bike on petrol, air cleaners are essential because of the fire risk - but they richen the mixture. Even with methanol, the slightest bit too rich will slow the bike - with petrol the effect is twice as bad. I have always used twin carbs, but I doubt a single carb would make the bike slower, even at 100 MPH. - What WILL make it slower is jetting slightly too rich. But with a road bike, you probably need to do that. And another thing - the configuration of the exhaust system can have a big effect on carburation. If you are looking for power, you need to set your ignition advance, the cam timing and the exhaust system, then jet to them. If you change anything including the fuel type, re-jet to suit.

The advantage of using a single carb, is it is much easier to get right. So a bike with a single carb can be faster than one which has twin carbs where you are playing with two sets of jets. My bike is on methanol. Half a thou of an inch too big in the needle jet is the difference between fast and slow. Petrol is twice as bad.. Most of the reason race bikes are faster on methanol, is it hides-up the tuning errors. But if you get your bike jetted right when using petrol, the changes in the weather might have much more effect. So with a road bike, I would always run slightly rich and go slower.