Pros and cons of different carbs? Keihin vs Mikuni vs Amals?

Well said, I agree. I have the wrong model (850 mk3), wrong carb (single), wrong tyres (TT100s), wrong drive sprocket (23T), wrong shocks (Hagon).... Absolutely love my bike! :)

But, I wouldn't have bought it without knowing there's the knowledge, friendly advice and help I need on here. It's already helped me keep it running on several occasions.
 
Ok Guys,
A report back from Page 5 post #84:
I completed a 777. 8 mile rally run with a stock 73 850 on my 74 Interstate. (Engine change) The bike was loaded up with camping gear. Tank bag (Magnetic) tail case and two sidebags with sleeping bag and other stuff under a spider web holder (net).

11.2 gallons Imp used or consumed, 68.02 miles per Imp gallon average as per fuel receipts.
Not bad for a Twin Mk1 Amal design that was introduced in 1967/68
Cheers,
Tom
 
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Fast Eddie said:
Thats exactly what an Amal Smoothbore looks like inside.

The supposed benefit from modern carbs is a) better quality design, manufacture and materials and b) better and more tune-able jetting inputs.

At WOT there should be little or no difference between any true version of a smoothbore if all other aspects are equal, cos it’s basically a pipe !

I‘ve run CRs on a big triple and they’re great carbs. Obviously Keihin superseded them with the FCRs, I kinda doubt they did that for fun, so obviously Keihin believe them to be a better instrument.
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No doubt that flat slides are a higher performance carb through the midrange. They give better throttle response. But space restraints leave us few choices.and 35mm is a bit much for a 750 street bike.
 
MexicoMike said:
TOTALLY concur with FastEd! I did so many dyno/track tests where testing demonstrated that the butt dyno is literally worse than useless for exactly the reasons Ed mentioned. I say worse than useless'' because it will often tell you the opposite of reality. If it was simply "useless" it wouldn't tell you anything at all...which is better! ;)

OTOH, any sort of test that can reliably determine results is useful - the hill dyno is a good example, time in seconds to accelerate from X RPM to Y RPM in (usually) a higher gear, etc, etc.
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So if I took my butt dyno tuned bike and ran it up a doctor's hill, it would mean something here? I seriously doubt that. Only way it would mean anything here is if Glen rode it. ;)

Nortons only go what? 120 miles an hour or so unless a lot of parts and the gearing is changed. Hard as it is for folks here to believe, I can tell when a motor is running efficiently and when it is not. I can feel the changes I make to timing (if it is off too far) carburetion, and exhaust length and restriction or lack thereof. I would think any reasonably good tuner could.

I personally don't need a slip of paper off a dyno to confirm anything. I do understand the value of it to the people that want to see one, but what the heck good would it do me? A slip of paper wouldn't make my bike go any faster than it does. It's quick enough to kill me. Far as I know it has no fall off in power nor show any of the other worse than useless issues the parroted phrases about dyno testing always bring up anywhere on the internet. I tune all those issues out of my engines be it 4 or 2 wheels and don't quit tuning until I do. What else have I got to do?

BTW, I reached the same conclusion about what tune works well on my 750 Norton engine with 35mm FCRs using my butt dyno that FF reached with a dyno. I don't see the logic as to why my butt dyno results are considered useless by the prolific posters, if the results are the same. Doesn't matter one way or the other in the grand scheme of things. It's just ponderous.

Anywho, if anyone wants to bring their 750 Norton to Seattle and show me how much difference a dyno tune can make over a butt tune, Bring it!! I'd like to see how slow and over carbureted my bike is. ;)
 
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Schwany said:
So if I took my butt dyno tuned bike and ran it up a doctor's hill, it would mean something here? I seriously doubt that. Only way it would mean anything here is if Glen rode it. ;)

Nortons only go what? 120 miles an hour or so unless a lot of parts and the gearing is changed. Hard as it is for folks here to believe, I can tell when a motor is running efficiently and when it is not. I can feel the changes I make to timing (if it is off too far) carburetion, and exhaust length and restriction or lack thereof. I would think any reasonably good tuner could.

I personally don't need a slip of paper off a dyno to confirm anything. I do understand the value of it to the people that want to see one, but what the heck good would it do me? A slip of paper wouldn't make my bike go any faster than it does. It's quick enough to kill me. Far as I know it has no fall off in power nor show any of the other worse than useless issues the parroted phrases about dyno testing always bring up anywhere on the internet. I tune all those issues out of my engines be it 4 or 2 wheels and don't quit tuning until I do. What else have I got to do?

BTW, I reached the same conclusion about what tune works well on my 750 Norton engine with 35mm FCRs using my butt dyno that FF reached with a dyno. I don't see the logic as to why my butt dyno results are considered useless by the prolific posters, if the results are the same. Doesn't matter one way or the other in the grand scheme of things. It's just ponderous.

Anywho, if anyone wants to bring their 750 Norton to Seattle and show me how much difference a dyno tune can make over a butt tune, Bring it!! I'd like to see how slow and over carbureted my bike is.
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Not quite so sure why you seem to have taken things personally, no one is, or was having a go at your Norton, or what you’ve done to it.

But the fact remains, a Dyno is still widely recognised as the best way to ascertain incremental changes in tune.

Why is the slip of paper important? Simply becasue it tells you what’s going on, it’s not just a number, that wouldn’t be very helpful, it shows you power and torque curves and AF ratio at each point along the curve. So you can think about the changes made, and next change, and so on... IF you want to!

But no one said they should be compulsory, seriously, chill out and enjoy your ride !
 
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Fast Eddie said:
Not quite so sure why you seem to have taken things personally, no one is, or was having a go at your Norton, or what you’ve done to it.

But the fact remains, a Dyno is still widely recognised as the best way to ascertain incremental changes in tune. Why is the slip of paper important? Simply becasue it tells you what’s going on, so you can think about the next change, and so on. If you want to!

But no one said they should be compulsory, seriously, chill out and enjoy your ride !
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Compulsory to prove any claims that carburetors other than Amals work better came up a while ago.

Not taking it personally though. I'm saying with far too many words I believe is definitely possible to tune a Norton with enough experience and a butt dyno to make it pleasurable to ride.

If I could get on a Dyno for free, I'd do it. That's personal for sure.

I'm not crapping on people that use a dyno. I've heard this discussion many times on hot rods forums. It's always implied that the people that tune without a dyno don't do a good job. There was a time when dyno tuning and the internet did not exist for the common man. Had to learn things. I wasn't that good at tuning back then. Took a very long time to get my head around it. I guess that's not chill enough and too personal. Oh well can't please everybody.
 
Schwany said:
Compulsory to prove any claims that carburetors other than Amals work better came up a while ago.
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Well, actually, I think the context of that remark was aimed at someone who was making very specific and bold claims… and who also sells them. And so the question was asked IF these claims had been proven. No mention of being compulsory. And no insinuation that the claims were wrong either, just wanting to know if they’d been proven.

I’d like to know. I am very happy with my FCRs, but I do sometimes wonder what / if benefits they really give over similarly sized Amal's or others.

You‘re right, dynos haven’t been around forever, but actually they have been around for an awful long time! But even today, for the top lads, dyno tuning is not the finished article. It’s only a baseline and the fine tuning is done at the track.
 
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robs ss said:
Yes - but if your butt dyno tells you things are good, then they actually are, despite what other precision instruments may measure.
Most of us aren't in this for absolute horsepower - we're here for the fun!
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Got to keep yer butt happy!
 
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