New Amals Replace Mikuni - What a difference!

Fast Eddie · Jun 16, 2014

Phil, if you're talking to Jim Comstock... and the conversation is about building a Rocket Racer... and you're also talking about carbs... then he must have mentioned the FCR35s...!?

No bike can be called a Rocket Racer with a single carb! Next step from a single carb is to run it on Diesel...

Being mildly serious, I ran a 36mm Mikuni and it pulled nicely up to 5k, after that it tapered of quickly and badly.

My advice is A) talk to Jim about the FCRs and then B) talk to Matt about ordring a set !!

phil yates · Jun 16, 2014

Fast Eddie said:
Phil, if you're talking to Jim Comstock... and the conversation is about building a Rocket Racer... and you're also talking about carbs... then he must have mentioned the FCR35s...!?

No bike can be called a Rocket Racer with a single carb! Next step from a single carb is to run it on Diesel...

Being mildly serious, I ran a 36mm Mikuni and it pulled nicely up to 5k, after that it tapered of quickly and badly.

My advice is A) talk to Jim about the FCRs and then B) talk to Matt about ordring a set !!

Thanks Eddie
Jim is most helpful, I'll ask him about the FCR's. I joked about selling my house for this project, but now thinking it wasn't a joke at all!! I guess living permanently in the Mitto won't be so bad, at least the bikes can stay permanently parked out front. Forget the diesel, I think kerosene might be my cheaper option.

Thanks eddie, I'll let you know how it pans out.

Phil

Nater_Potater · Jun 17, 2014

Bonwit said:
Phil, yes, I notice an improvement in acceleration with the Amals. The other surprise is how well the bike idles, A nice slow lope, even after a short warmup. I never had that with the Mikuni. I'm sure it's because they're new, but hopefully the anodized slides will wear better than the old Amals. As for the throttle pull, it's very light. . . almost too light for my taste. It's become obvious to me that you just cannot compare these new Amals with a set of 40 year old originals.

By the way, I did sell the Mikuni kit, and the new owner is thrilled with it (which I'm glad of). To each his own.

Best

I'm the new owner, and still diggin' it! :mrgreen: It might be my altitude (2400 ft), but the lower circuits were running a bit "fat". I dropped the pilot from 40 to 32.5, and changed the 2.5 slide for a 3.0; made a noticeable difference in how "crisp" the throttle response is, and the needle is still right in the middle slot. I'm running a fully stock motor with old Dunstall mutes, for reference. As for the throttle pull, the single is so-o-o much lighter than the original twin Anals (sic) that it can be difficult operating the turn indicator without making the bike jump around. I'm getting better with practice.
Nathan

P.S. Bonwit, I'm still waiting for you to send me the skirt that's supposed to be supplied with every Mikuni sold. Should I just get a new one from the factory?
P.P.S. Phil, what's this "Mitto" you're talking about living in? If this keeps up, I may find myself needing to free up some cash.

phil yates · Jun 17, 2014

Nater_Potater said:
Bonwit said:

Phil, yes, I notice an improvement in acceleration with the Amals. The other surprise is how well the bike idles, A nice slow lope, even after a short warmup. I never had that with the Mikuni. I'm sure it's because they're new, but hopefully the anodized slides will wear better than the old Amals. As for the throttle pull, it's very light. . . almost too light for my taste. It's become obvious to me that you just cannot compare these new Amals with a set of 40 year old originals.

By the way, I did sell the Mikuni kit, and the new owner is thrilled with it (which I'm glad of). To each his own.

Best

Click to expand...

I'm the new owner, and still diggin' it! :mrgreen: It might be my altitude (2400 ft), but the lower circuits were running a bit "fat". I dropped the pilot from 40 to 32.5, and changed the 2.5 slide for a 3.0; made a noticeable difference in how "crisp" the throttle response is, and the needle is still right in the middle slot. I'm running a fully stock motor with old Dunstall mutes, for reference. As for the throttle pull, the single is so-o-o much lighter than the original twin Anals (sic) that it can be difficult operating the turn indicator without making the bike jump around. I'm getting better with practice.
Nathan

P.S. Bonwit, I'm still waiting for you to send me the skirt that's supposed to be supplied with every Mikuni sold. Should I just get a new one from the factory?
P.P.S. Phil, what's this "Mitto" you're talking about living in? If this keeps up, I may find myself needing to free up some cash.

I'm selling the house to pay for all the Norton projects, so will be renting a room at the Mitto pub. It's all that bloody hobot's fault!

The 34mm VM Mikuni won't be leaving the Fastback, but twin FDC's are coming for the Rocket Racer. Like you, I've been and am extremely happy with the single Mikuni, second one I've had. I will admit, Jim and Matt have given such good information and help, especially Jim, I generally go with his advice. Not that he tells or even suggests what I should do, but always has the answer on any question I ask him.

Just a tip, when operating the turn indicator, pull hard on the brake lever at the same time, it offsets blipping of the throttle and causing the bike to jump around. You just go over the handlebars instead.

Phil

Nater_Potater · Jun 17, 2014

Fast Eddie said:
Phil, if you're talking to Jim Comstock... and the conversation is about building a Rocket Racer... and you're also talking about carbs... then he must have mentioned the FCR35s...!?

No bike can be called a Rocket Racer with a single carb! Next step from a single carb is to run it on Diesel...

Being mildly serious, I ran a 36mm Mikuni and it pulled nicely up to 5k, after that it tapered of quickly and badly.

My advice is A) talk to Jim about the FCRs and then B) talk to Matt about ordring a set !!

Hm-m-m; is that a Single Mikuni I see on the winning bike there? http://i1219.photobucket.com/albums/dd4 ... 0_9742.jpg

1up3down · Jun 17, 2014

hard to tell but yes it could be a single carb

not surprising as without a front fender and knobbies it looks to be dirt tracker

in that case a single carb makes some sense as maximum rpm horsepower is not called upon so much that a twin carb set up would provide

Nater_Potater · Jun 17, 2014

1up3down said:
hard to tell but yes it could be a single carb

not surprising as without a front fender and knobbies it looks to be dirt tracker

in that case a single carb makes some sense as maximum rpm horsepower is not called upon so much that a twin carb set up would provide

It is, in fact, a single carb. nortons-the-dirt-t19629.html Keep in mind that, for me at least, the usable power band that a flat-tracker produces is closer to what I look for from a street bike, rather than a drag racer. Thus, pure horsepower numbers don't matter as much. But, that's just me rambling...
Nathan

pete.v · Jun 17, 2014

1up3down said:
in that case a single carb makes some sense as maximum rpm horsepower is not called upon so much that a twin carb set up would provide

Now your talking. Give it to me down and dirty, baby. Any body can go fast. How "quick" you get there is the tricky part.

McBob · Nov 4, 2016

dave M said:
The other thing I have found is to screw on the metal locating rings for the boots with the flange facing forward, it seems somewhat counter- intuitive but gives a few mm extra clearance and every bit helps in this tight environment.

That's what I did . Works great.

concours · Nov 4, 2016

McBob said:
dave M said:

The other thing I have found is to screw on the metal locating rings for the boots with the flange facing forward, it seems somewhat counter- intuitive but gives a few mm extra clearance and every bit helps in this tight environment.

Click to expand...

That's what I did . Works great.

Hi Bob, welcome. Mine were backwards when I got the bike.

RoadScholar · Nov 5, 2016

I have ridden and built Nortons configured with both twin Amals and single Mikunis, both have their place. You want fast (an extremely relative term) you go with the Amals, you want simple easy to tune with a majority of 1 kick starts, you go with the Mikuni, almost analogous to a car equipped with standard transmission versus and automatic...

Changing out the air filter element or just adding it initially is a piece of cake (I'm not kidding!)

You will need an assistant.

De-fasten the two 1/4-28s that hold the ham can together. Have the assistant use the tabs on the forward most ham can plate and pull them uniformly forward while you simply remove the air filter element with its' surround. Once the element/surround is back in place the assistant can relax the forward plate, add the 2, 1/4-28s and you are done; you may have to straighten out one or both rubber connectors and a shot of WD or silicone spray may be useful, but the entire procedure shouldn't take more than 3-5 minutes.

seattle##gs · Nov 5, 2016

for carburetor removal I usually replace the two 5/16 studs with allen bolts, usually the button head type. Then buy a ball end allen to fit, screwdriver style, and the problem becomes easier. This means you do not have to take off the manifolds. I have also taken a ballend driver, cut it off and welded on a small cross piece to make it a T-handle. It just barely fits in the very cramped space. Also, buy 8 allen head BS2 screws for the carb tops and float bowl and again buy the matching ball end driver...makes that job much easier and cuts down frustration. The ball end drivers are about $5 apiece and thats for good quality. Harbor freight probably sells the whole kit for $5. Cheap and hardly noticeable modifications...and lots of bang for the buck.

When I hear people say that dual Amals way out perform a single Mikuni my first thought is that the Mikuni was poorly jetted. Both set ups will make the Norton run very well. I prefer the looks of dual Amals and the ham can air cleaner, and it can run very well if new carbs and the float levels are set correctly. I have set the float levels on many Amals and about %80 have low float levels, EVEN BRAND NEW Amals. So I check this first. Solve this problem first before twiddling with the air screws and it will respond better to the air mixture screws . It will start easier and idle lower and smoother.

Personally, I like the single Mikuni for the simplicity and it makes it so much easier to work in that area. And it really smoothes out the vibration.

N0rt0nelectr@ · Nov 6, 2016

DogT said:
I don't bother trying to fit that ham can back on with the carbs in the way, I just take the time to put the carbs on after the ham can. To me it's worth the bother.

Dave

I have found that if you install the air cleaner assembly with the carbs off, install the boots and then the left carburetor and then the right it is easier. Doing the left first makes it easier to get around the ignition switch mount. Yes it is a pain but a whole lot easier than trying to put the boots on after the carbs are fitted.

John in Texas

Danno · Nov 6, 2016

RoadScholar said:
I have ridden and built Nortons configured with both twin Amals and single Mikunis, both have their place. You want fast (an extremely relative term) you go with the Amals, you want simple easy to tune with a majority of 1 kick starts, you go with the Mikuni, almost analogous to a car equipped with standard transmission versus and automatic...

I get 1-kick starts with dual Amals. 2 if they flood. Get rid of the points and substitute EI. Much more germane to easy starts.

Danno · Nov 6, 2016

RoadScholar said:
I have ridden and built Nortons configured with both twin Amals and single Mikunis, both have their place. You want fast (an extremely relative term) you go with the Amals, you want simple easy to tune with a majority of 1 kick starts, you go with the Mikuni, almost analogous to a car equipped with standard transmission versus and automatic...

I get 1-kick starts with dual Amals. 2 if they flood. Get rid of the points and substitute EI. Much more germane to easy starts.