What is the deal with Keihin carbs? (2011)

Are you sure your carbs are the problem, I would say not likely.

If you prime, it will start, if the ignition is correct.

Which ignition, which plugs, which leads, which plug caps, which coils ?.

well... if i may chime in on the quality of materials in the amal carbs, just let me say at the outset that i can't wait to get rid of mine

as i was on my way home from the INOA rally, my bike decided to swallow its tongue... literally

i was riding along... bike was running fine when all of a sudden there was a bang (i think) and a horrendous loss of power and continued sounds of unhappiness coming from my motor

i pulled the plugs to find the porcelain smashed on one and it covered in alluminum splatter... i though i had holed a piston, so called for a rescue... when i got it home, i found this

it wasn't a holed piston, the skirt had fallen off one of my slides



further teardown revealed lots of splatter in the combustion chamber (notice the broken porcelain of the plug on the left )



there wasn't a whole lot left of the skirt material in the cylinder (if you are wondering, the pistons are at different levels in the barrels because of the offset crank)



pulling the valves revealed where the rest of the skirt was



so.. what do i think of amal carbs? well... they were $2.00 carbs when Triumph/bsa commissioned amal to make them originally and the are still a $2.00 carb today.... as burlin reps will tell you... they are still made to the "high?" standards they were made to in the 60s...

i have a friend who owns the local british bike repair shop... and as he said... while not a common occurance...this is not an unusual occurance in a norton either.... frankly... once is enough for me, so my amals WILL be replaced.... i don't want to see this problem again... i can't wait to get rid of mine

Carbonfibre said:

The "unbeatable" Amals mentioned here must be made out of something other than the lead/zinc pot metal that is used more commonly? Like it or not making precision parts using materials which are totally unsuitable, results in rapid wear and in the case of a carb reduced levels of performance.

This is the reason why its so popular to get Amal carbs lined, which while it does improve things considerably is not comparable to using properly made carbs, which are fit for purpose and do not need to be lined to overcome problems with wear.

Bikes will very often still run with badly worn carbs, but performance will be greatly reduced, and the effects of replacing them with new carbs will be even more noticeable.

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Mr carbonfibre (i hate that new age stuff , good on modern bikes but not on ours but ...)
Just out of curiousity , how many miles have you ever ridden , with these crappy amals?
i had my slides always bushed with bronze sleeves by Mr Bratby , and for what he is asking to have them done , one can have them sleeved 100 times before you get to the price of one fcr . But believe me that will not be necessary as the sleeves last a looooooong time (i have never worn a set out )
ps dell'ortos and weber are an option too but again i found no gain in them , even on the track ( stil have the set up for the weber , in case one would have a go at it )

as for the broken off bits, this is a sad sight but could it be the slides had been abused in the past ? (dropped etc)
an engine of mine once swallowed a needle but i did not blame the needle , just myself for not using a new clip

leia said:

well... if i may chime in on the quality of materials in the amal carbs, just let me say at the outset that i can't wait to get rid of mine

as i was on my way home from the INOA rally, my bike decided to swallow its tongue... literally

i was riding along... bike was running fine when all of a sudden there was a bang (i think) and a horrendous loss of power and continued sounds of unhappiness coming from my motor

i pulled the plugs to find the porcelain smashed on one and it covered in alluminum splatter... i though i had holed a piston, so called for a rescue... when i got it home, i found this

it wasn't a holed piston, the skirt had fallen off one of my slides

further teardown revealed lots of splatter in the combustion chamber (notice the broken porcelain of the plug on the left )

there wasn't a whole lot left of the skirt material in the cylinder (if you are wondering, the pistons are at different levels in the barrels because of the offset crank)

pulling the valves revealed where the rest of the skirt was

so.. what do i think of amal carbs? well... they were $2.00 carbs when Triumph/bsa commissioned amal to make them originally and the are still a $2.00 carb today.... as burlin reps will tell you... they are still made to the "high?" standards they were made to in the 60s...

i have a friend who owns the local british bike repair shop... and as he said... while not a common occurance...this is not an unusual occurance in a norton either.... frankly... once is enough for me, so my amals WILL be replaced.... i don't want to see this problem again... i can't wait to get rid of mine

Click to expand...

Hey Leia, sorry to hear of your troubles. Spoke with Rick the other day about my experience with the PWK flats he installed last year and expressed how great they are. I've since moved from the 30's to Jim Schmidts 32mm kit (manifolds, cables, norton needles etc...) and the performance is great. Idles like a stone and plenty of power up top. Maybe you should give them a try?

lynxnsu said:

[... how many miles have you ever ridden , with these crappy amals?...as for the broken off bits, this is a sad sight but could it be the slides had been abused in the past ? (dropped etc)...an engine of mine once swallowed a needle but i did not blame the needle , just myself for not using a new clip

Click to expand...

Ah, logic.

I'm guessing several thousand times more miles have been covered with Amals working quite well than will ever be covered with all other brands, new and old, put together.

As with the high incidence of Boyer EI failures, I'm fairly certain it has more to do with the sheer number of installed units, miles covered over the many years, and non-electrically-inclined "fixxers", than anything else.

Hi, any idea about the dual VM Mikuni setup ??? I imagine the curved and tortuous manifold won't help gas flow ??

Wow, got some folks a little heated it looks like, but in a good way.

FIrst of all thanks for all the replies and information. Since I have seen enough people talking about how old and running good their amals are I am going to see about replacing all the internals (Needles, jets, slides, etc). I spoke with a gentleman at Bikes and Bits in Columbia, TN who I have purchased some parts from before and he has a few amal parts and he thought my main jet at 260 was a bit big. He also told me the idle should be relatively smooth and not moving 100-200 rpms while sitting there. I am going home to verify the sizes of everything since I wrote the information from each carb when I pulled them apart and cleaned them recently.

I have read all the replies on the forum about not using the zinc slides but to use the newer coated slides. I think for the price and being able to order everything from Amal I will stick with original.

Hopefully I can order everything soon and get the motor running smooth and then go from there. Right now I can get all the parts for less than $100 so that puts me having the bike going better sooner than waiting to get the excess funds to buy a PWK or some other carb!

Josh Cox said:

Are you sure your carbs are the problem, I would say not likely.

If you prime, it will start, if the ignition is correct.

Which ignition, which plugs, which leads, which plug caps, which coils ?.

Click to expand...

The problem with accelerator pumps is that every time the throttle is turned, it pisses a bit more in the inlet tract. Mine were getting just too much fuel and the plugs turned soothy very fast. It was hard to start because of the clipons and lack of a center stand, I just could not get a good kick to get it to go. I straigtened the accelerator pump linkage to get less gas per throttle movement and that helped the most. When it has started, it runs great with the FCRs, but then again my Commando runs great with the PWKs for half as much.

Jean

leia said:

well... if i may chime in on the quality of materials in the amal carbs, just let me say at the outset that i can't wait to get rid of mine

as i was on my way home from the INOA rally, my bike decided to swallow its tongue... literally

i was riding along... bike was running fine when all of a sudden there was a bang (i think) and a horrendous loss of power and continued sounds of unhappiness coming from my motor

i pulled the plugs to find the porcelain smashed on one and it covered in alluminum splatter... i though i had holed a piston, so called for a rescue... when i got it home, i found this

it wasn't a holed piston, the skirt had fallen off one of my slides

so.. what do i think of amal carbs? well... they were $2.00 carbs when Triumph/bsa commissioned amal to make them originally and the are still a $2.00 carb today.... as burlin reps will tell you... they are still made to the "high?" standards they were made to in the 60s...

i have a friend who owns the local british bike repair shop... and as he said... while not a common occurance...this is not an unusual occurance in a norton either.... frankly... once is enough for me, so my amals WILL be replaced.... i don't want to see this problem again... i can't wait to get rid of mine

Click to expand...

:shock: Yikes, did you make it home like that :?:

Jean

warpedscout said:

...I have read all the replies on the forum about not using the zinc slides but to use the newer coated slides. I think for the price and being able to order everything from Amal I will stick with original. Hopefully I can order everything soon and get the motor running smooth and then go from there. Right now I can get all the parts for less than $100 so that puts me having the bike going better sooner than waiting to get the excess funds to buy a PWK or some other carb!

Click to expand...

The bike will run better with new slides, but remember that the carb bores are still worn and will not be the BEST solution. Sometimes, pretty good is good enough; other times, not so much. Your worn carb bores will wear out your new slides relatively quickly; you may want to budget having the carbs sleeved AND new slides.

grandpaul said:

warpedscout said:

...I have read all the replies on the forum about not using the zinc slides but to use the newer coated slides. I think for the price and being able to order everything from Amal I will stick with original. Hopefully I can order everything soon and get the motor running smooth and then go from there. Right now I can get all the parts for less than $100 so that puts me having the bike going better sooner than waiting to get the excess funds to buy a PWK or some other carb!

Click to expand...

The bike will run better with new slides, but remember that the carb bores are still worn and will not be the BEST solution. Sometimes, pretty good is good enough; other times, not so much. Your worn carb bores will wear out your new slides relatively quickly; you may want to budget having the carbs sleeved AND new slides.

Click to expand...

Who does boring in the US and also do you buy your amal parts from someone in the US? Most of the prices I saw on Amal were much lower than the prices I have found on this side of the pond.

Mr carbonfibre (i hate that new age stuff , good on modern bikes but not on ours but ...)
Just out of curiousity , how many miles have you ever ridden , with these crappy amals?
i had my slides always bushed with bronze sleeves by Mr Bratby , and for what he is asking to have them done , one can have them sleeved 100 times before you get to the price of one fcr . But believe me that will not be necessary as the sleeves last a looooooong time (i have never worn a set out )
ps dell'ortos and weber are an option too but again i found no gain in them , even on the track ( stil have the set up for the weber , in case one would have a go at it )

as for the broken off bits, this is a sad sight but could it be the slides had been abused in the past ? (dropped etc)
an engine of mine once swallowed a needle but i did not blame the needle , just myself for not using a new clip[/quote]

I for one feel that swapping very poor quality OE parts for more modern ones that are properly made out of the correct materials, and result in increased performance and reliability, is well worth looking at. OKO 32mm carbs are available here in the UK for around £50, and will fit straight onto the Norton intake manifold using a pair of flange mount to spigot adapters. These are ideal for the Norton and will provide better performance and use less fuel.

leia said:

well... if i may chime in on the quality of materials in the amal carbs, just let me say at the outset that i can't wait to get rid of mine

as i was on my way home from the INOA rally, my bike decided to swallow its tongue... literally

i was riding along... bike was running fine when all of a sudden there was a bang (i think) and a horrendous loss of power and continued sounds of unhappiness coming from my motor

i pulled the plugs to find the porcelain smashed on one and it covered in alluminum splatter... i though i had holed a piston, so called for a rescue... when i got it home, i found this

it wasn't a holed piston, the skirt had fallen off one of my slides



further teardown revealed lots of splatter in the combustion chamber (notice the broken porcelain of the plug on the left )



there wasn't a whole lot left of the skirt material in the cylinder (if you are wondering, the pistons are at different levels in the barrels because of the offset crank)



pulling the valves revealed where the rest of the skirt was



so.. what do i think of amal carbs? well... they were $2.00 carbs when Triumph/bsa commissioned amal to make them originally and the are still a $2.00 carb today.... as burlin reps will tell you... they are still made to the "high?" standards they were made to in the 60s...

i have a friend who owns the local british bike repair shop... and as he said... while not a common occurance...this is not an unusual occurance in a norton either.... frankly... once is enough for me, so my amals WILL be replaced.... i don't want to see this problem again... i can't wait to get rid of mine

Click to expand...

Pretty common problem on Amal carbs, and occurs due to the half moon wear ridge that tends to form on the lower part of the pot metal slide, creating a weak area, which often cracks along the half moon wear ridge, and the broken off part often gets sucked into the motor.

Never ever seen this happen on any other make of carb, but then again not seen any other carbs made out of lead/zinc pot metal, which is totally unfit for purpose.

Actually a very uncommon occurence with Amal carbs, most commonly encountered on badly worn slides in 2 stroke scramblers.

The Mazac zinc alloy from which Concentrics are made is the same material from which various models of Mikuni, Hollies , SU's , Zeniths, Kleins, Bing, and Dellorto carbs are also made. It's probably the most common and appropriate material found in carb construction over the last 100 years. It will have been chosen because it produces high precision, non-porous castings which are easy to machine accurately and offer superior strength to weight ratios and so thinner sections than required with other alloys.

Back in the day slides were cheap and easily available service items which were replaced regularly before excessive wear developed.

ebsbury said:

Actually a very uncommon occurence with Amal carbs, most commonly encountered on badly worn slides in 2 stroke scramblers.

The Mazac zinc alloy from which Concentrics are made is the same material from which various models of Mikuni, Hollies , SU's , Zeniths, Kleins, Bing, and Dellorto carbs are also made. It's probably the most common and appropriate material found in carb construction over the last 100 years. It will have been chosen because it produces high precision, non-porous castings which are easy to machine accurately and offer superior strength to weight ratios and so thinner sections than required with other alloys.

Back in the day slides were cheap and easily available service items which were replaced regularly before excessive wear developed.

Click to expand...

Do I detect someone who sells Amal carbs perhaps?

Amal are in fact the only modern day carbs being made using lead/zinc pot metal, with the use of high lead content intended to provide some degree of friction reduction between the moving parts. That Amal are the only commonly available modern day pot metal carbs, is easily verified by their rather obvious problems related to rapid wear, which is often dealt with by lining and fitting a slide not made from pot metal.

Amal are just about the worst carbs currently on the market in terms of rapid wear, and Taiwanese OKO carbs (copy of the Keihin PWK series) which are about a 1/4 of the price, will vastly improve any bike fitted with Amal as OE, and provide far better performance, reliability, improved gas mileage, as well as outlasting the Amal . Only reason I can see to fit a part that doesn't work very well and wears out fast, is to retain original looks, and obviously this is quite important to some of those who ride older bikes.

oh... and don't forget the ritual bloodletting required before starting ... and the dribble of fuel down the float bowl and inevitably dripping onto the motor and the resultant staining... not to mention the stinky fingers you are left with

yup... amal... the epitomy of modern scientific carburetor development....

There's nothing wrong with Amal using zinc for the bodies of the carbs, Amal's error was in ALSO using it for the slides.
Similar metals vs dissimilar metals.

The pre-Concentric carbs, the Monobloc Amals, used hard chrome plated brass slides and they worked beautifully in concert with their dissimilar metal zinc bodies.

Through the 60's, 70's and 80's most carbureted Japanese motorcycles came with zinc bodied carbs but with slides of chrome plated brass or anodied aluminum. Those carbs, typically, didn't wear out. The Brit bike zinc slided Amal carbs did wear out, almost instantly.

Sleeved Amals are a great thing. So are Jim's carbs.

Grandpaul, your point on Boyers is well taken but their selling of a Triumph advance curve in a product that they held out as appropriate for Nortons for 25 years is unforgivable.

Might as well get in on this,
Marinatlis, I love Mikuni carbs, have seen them on many diffrerent bikes, they work well and are easily tuned, provided you
know a bit about carburation. However, twin Miks are not the most perfect fit on a Commando, because of the size of the
carbs them selves. The manifolds need to be splayed so the carbs don't touch, and with the extra length of the adaptors, there is very little
room for large air cleaners. On a Cafe' racer style where the removal of the original airfilter backing plate is not a concern to looks, then go for it.
Ask aound, severel guys here will vouch for them. Remember, Mikunis were the choice of thousands when it was notticed that the Amals weren't
of such great quality. If I wasn't concerned about the loss of the backing plate, my bike would have had Mikuni carbs on it the day I bought it.
Jims kit is a genuine "bolt on remedy for the Amal problem" if you don't mind customizing your Norton just a little.
As GP states,.. There's lots more Amals and Boyers around, probably more than the rest put together,
so there's going to be more problems aired. People generally only complain when there is a problem.
I guess when there is thousands of all the rest out there we will here more stories of faillures.
Warpedscout, I recently bought a pair of good second hand Amals, they are only slightly worn.
My bike starts easily hot or cold, goes like a proverbial cut cat, but I am NEVER sure that it is going to idle when I pull up at the lights.
Today it idles sweatly at 1200 revs, tomorrow it struggles to idle at 500, the next day it idles at 1500 revs. It's a pain in the arse.
The remedy would be new slides and a resleeve.
The Bushmans idle conversion is great. If you'r handy you can check and clean you idle passages in half an hour.
No musical instuments necessary.
I am currently running # 30 pilot jets in my Combat. They are too rich, however if I go down to # 25, with the slides bouncing around as they do,
I get spit back and flat spots as I try to putter around at low revs. It's only because of the wear in the slides and bodies. A slightly less cuttaway would help.
Do I spend more money on resleeves, or new Amals, do I change the look of my Norton with Japanese carbs......
Time and finances will tell.
AC.

One other thing about the Keihin Flat Slides. They are so compact they look like a single. I have the race version fitted to the VR880 by Kenny Dreer. The bike always starts, idles easily and runs like a scalded cat when you twist the throttle. I am not sure how much effort went in to setup but I can say once they are set up they are an amazing carb that out performs just about everything else out there IMHO.

leia said:

... not to mention the stinky fingers you are left with...

Click to expand...

Hey, it turns hot dogs into "haute cuisine" :mrgreen:

Jean