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Re: replacing Mikunis with Amal, BSA lightning [Re: bodine031] #744783
08/07/18 6:48 pm
08/07/18 6:48 pm
Joined: Nov 2013
Posts: 295
Bristol England
R
redrooster Offline OP
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redrooster  Offline OP
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R

Joined: Nov 2013
Posts: 295
Bristol England
Hi Bodine,

So your clip is on 3, but your bike is way different.
Clip is on 4, cutaway 2 1/2, pilot jet 30 screw 1 1/2 out and still looking lean.

I have decided to look at this in another way, I will keep the Mik's , mount them properly as the advise I have had.
Then start on the jetting

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Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #744799
08/07/18 8:19 pm
08/07/18 8:19 pm
Joined: Sep 2004
Posts: 1,020
Farnham, Surrey, UK
gunner Online content
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gunner  Online Content
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Joined: Sep 2004
Posts: 1,020
Farnham, Surrey, UK
Hi Redrooster,

I have a 68 A65 Firebird fitted with AMAL 930 carbs (not the Premier version). I purchased these carbs from Burlen about 6 years ago when I was completing the rebuild of my bike. So far these carbs have performed well although my annual mileage is limited due to parenting commitments. I deliberately omitted the choke slides from both carbs as I felt this was a useless design and I can easily start the bike just using the ticklers, even in the UK winter. My feeling is that the standard AMAL Concentric is a good carb when new but it does have some drawbacks as already noted. Part of the problem is that it was not a high quality design when new and when combined with poor maintenance over several decades a bad reputation arises. I have no doubt the new Premier carb is better and more durable than the original AMAL Concentric, however I think we should show some respect (as Trevor suggests) to all the millions of Concentrics which have kept BSA's, Nortons, Triumphs etc. running for all these years.

For what its worth, I'm running a single Mikuni 34 on my 750 Norton. It runs great and starts virtually first kick helped by the choke lever/enrichment circuit. I'm also using a JRC carb on my B44 also with a choke lever/enrichment circuit. Agreed that these carbs may look slightly odd on a British bike, but they do have a plus side.

I would keep the Mikuni;s and just get them jetted right. Maybe you can find a rolling road nearby and get them dialled in spot on.


1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #744807
08/07/18 8:49 pm
08/07/18 8:49 pm
Joined: Dec 2013
Posts: 4,987
ohio, usa
kevin roberts Offline

DOPE
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ohio, usa
Originally Posted by redrooster
Can anyone post a picture of how they have mounted there Mik's on a brit bike twin ?


[Linked Image][Linked Image][Linked Image][Linked Image][Linked Image][Linked Image][Linked Image][Linked Image][Linked Image][Linked Image][Linked Image]

maybe there's something useful here? i've run 32mm and now 34mm mikunis on my morgo commuter for almost 40 years, and also use the same mounts for the keihin FCRs inb my LSR machine.

spigots are available for bothe the screw-in and bolt-on carburetor manifolds.

side covers on an OIF are always an issue. i used to use 1976 honda CB360 covers, which are a perfect fit. now i just don't run any. on a dry frame, carb extensions bump into the oil tank, but short mikunis shouldn't be a problem.


every day you do not take a chance is a day of your life that you will never get back.
Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #744809
08/07/18 9:01 pm
08/07/18 9:01 pm
Joined: Dec 2017
Posts: 32
Athens Greece
Konstantinos Offline
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Athens Greece
Hi Redrooster,
I thought that you have a stock bike with modified engine but it' s modified at all
So no problem to keep VM because unfortunately they are much reliable than Amals
Just be sure to have right jets and good quality rubber manifolds
VM have old classic look.
My first reply was for Kevin with keihins.
Here in my country most of my friends have on their british bikes single VM because it' s more easy to fix it
But friends with old dual Concentrics are faster so if you have dual VM are better at all.
I hear that old Concentrics are much better than new and I have experience with my T140 when It was with stock head
And AMAL MKII 30mm with made in England bodies never had problems for many miles but when I modified to eight
valve and fitted New 36 mm AMAL MKII made in Spain after of 15.000 km the slides were bordeline.
So keep Mikunis I have the same opinion with gunner.


Re: replacing Mikunis with Amal, BSA lightning [Re: kevin roberts] #744816
08/07/18 9:42 pm
08/07/18 9:42 pm
Joined: Dec 2017
Posts: 211
England
F
ferretjuggler Offline
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F

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Posts: 211
England
Originally Posted by kevin roberts
Originally Posted by redrooster
Can anyone post a picture of how they have mounted there Mik's on a brit bike twin ?


[Linked Image][Linked Image][Linked Image][Linked Image][Linked Image][Linked Image][Linked Image][Linked Image][Linked Image][Linked Image][Linked Image]

maybe there's something useful here? i've run 32mm and now 34mm mikunis on my morgo commuter for almost 40 years, and also use the same mounts for the keihin FCRs inb my LSR machine.

spigots are available for bothe the screw-in and bolt-on carburetor manifolds.

side covers on an OIF are always an issue. i used to use 1976 honda CB360 covers, which are a perfect fit. now i just don't run any. on a dry frame, carb extensions bump into the oil tank, but short mikunis shouldn't be a problem.

Just out of interest what sort of gas milage are you getting with twin 34mm Mikuni VMs ?
I've got no experience of them on a Triumph, but I swapped the 34mm Mikuni CV carbs on my XS650 for a pair of 34mm Mikuni VM slide type.
Turned it from a tame little kitten into a ferocious snarling beast - with no other mods.
But fuel economy went from 50+ mpg (imperial gallons) to the low 30s

Re: replacing Mikunis with Amal, BSA lightning [Re: Konstantinos] #744817
08/07/18 10:10 pm
08/07/18 10:10 pm
Joined: Dec 2013
Posts: 4,987
ohio, usa
kevin roberts Offline

DOPE
kevin roberts  Offline

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Posts: 4,987
ohio, usa
Originally Posted by Konstantinos
I wanted to have a pair of keihins on my T140 eight valve to see how it runs on the road.
I am very sure that works great.
And I am sure that your bike is flying with them but they are not looking good on classic Brit bike like the box section swingarm on my featherbed trident works great but not looking good to be honest
I think the reason is what you want from your bike.
If you want performance you need modern goodies.
If you want classic look have to stuck with stock parts.


i'm sorry, konstantinos, i missed this post of yours.

yes, what you change on the machine you ride is completely a function of what you want from it. if complete originality is the most important thing, then you must use original-style carbs. but you must also do without electronic ignition, modern tires, brighter lights, updated charging systems, and so on. most people compromise somewhere in the middle.

i use the keihins for a race machine. they would work very well on a street bike with a fabricated airbox, but i have used mikunis on the street for decades and they work well for me. i also have some Concentrics, and they work too, but when they wear out i usually replace them with mikunis.


every day you do not take a chance is a day of your life that you will never get back.
Re: replacing Mikunis with Amal, BSA lightning [Re: ferretjuggler] #744820
08/07/18 10:17 pm
08/07/18 10:17 pm
Joined: Dec 2013
Posts: 4,987
ohio, usa
kevin roberts Offline

DOPE
kevin roberts  Offline

DOPE

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Posts: 4,987
ohio, usa
Originally Posted by ferretjuggler

Just out of interest what sort of gas milage are you getting with twin 34mm Mikuni VMs ?
I've got no experience of them on a Triumph, but I swapped the 34mm Mikuni CV carbs on my XS650 for a pair of 34mm Mikuni VM slide type.
Turned it from a tame little kitten into a ferocious snarling beast - with no other mods.
But fuel economy went from 50+ mpg (imperial gallons) to the low 30s



boy, i don't know. i never measure it. 35 years ago my machine was an unmodified 650 with Concentrics, and got 43 mpg, US gallons. then i installed 32mm VM mikunis with no changes and highway mileage went to 55 mpg. then i had the head worked on and installed a 750 kit and the mileage went down to 42 again.

i broke one one of the 32s trying to get a float needle out and replaced them with VM34s. the 34s are more compatible with the original headwork and the bike is quite comfortable on the street. i've never measured the fuel mileage, but i'm running 21/47 gearing on it too, so that would have an effect. i tend to keep the rpms higher than i did with 19/47, so i probably get poorer fuel economy.

the 35mm keihin FCRs get about 7.2 mpg on my race 650, but that's not really comparable.


every day you do not take a chance is a day of your life that you will never get back.
Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #744853
08/08/18 3:31 am
08/08/18 3:31 am
Joined: Aug 2001
Posts: 4,757
Owego, NY, USA
Mark Z Online content
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Mark Z  Online Content
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Joined: Aug 2001
Posts: 4,757
Owego, NY, USA
Originally Posted by redrooster
Hi Mark,
Judging by your photo I am being plank thick and will be looking at doing this set up.
Mik's are 30mm.
Bodine, idles highest at 2 turns out so have set a/m to 11/2. Everything I have read says no less than 11/2 so have been reluctant to go to 1. So I changed pilot jet from 25 to 30. This did not seem to change idle so left it at 1 1/2 out Is this the wrong approach ?


Ok. FWIW, my filters are Uni foam (sold in a sheet), soaked with Uni filter oil, over 3/16" wire mesh, all held on with hose clamps. Because of the small surface area, the foam needs to be cleaned (with gasoline) and re-oiled regularly. Triumphs and OIF BSAs offer more options for air cleaners, as shown in Kevin's photos, but on a dry frame BSA, there is only about 1/2" clearance between the carb mouths and the frame.

If it idles highest at 2 turns out, then that would seem to be the correct setting, no? Out = leaner, In = richer, so if you really want it at 1 1/2, I think you're going the wrong way with the pilot jet. (They do make a 22.5 pilot jet.)

When you get it where you think you want it, a good test of the idle mixture is this: Start and warm up the engine so it can be re-started without enrichening. Put in new plugs and re-start the engine. Let it idle for a few minutes without touching the throttle. Shut it down and look at the plugs.

Always let the head cool for about 10 minutes before removing the plugs, and always use the anti-seize lubricant that's made for spark plugs on the threads.




Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: replacing Mikunis with Amal, BSA lightning [Re: Mark Z] #744876
08/08/18 9:19 am
08/08/18 9:19 am
Joined: Nov 2013
Posts: 295
Bristol England
R
redrooster Offline OP
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redrooster  Offline OP
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R

Joined: Nov 2013
Posts: 295
Bristol England
Hi Mark,
Ok, I changed the 25 for a 30 to make it richer and have made it leaner ?, I have 20 it my box I should try this.

Hi Ferret,

I see the aluminium adaptors on your photos that bolt straight on to the head, this is what I think I need but can,t seem to find them supplied by anyone here.will look harder.

Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #744877
08/08/18 9:47 am
08/08/18 9:47 am
Joined: Aug 2001
Posts: 4,601
argyll. scotland, uk
gavin eisler Offline
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gavin eisler  Offline
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Posts: 4,601
argyll. scotland, uk
"Ok, I changed the 25 for a 30 to make it richer and have made it leaner ?, I have 20 it my box I should try this."

No .

When you put in the 30 the jet passes more fuel so the screw ends up at 2 turns for the correct balance, more fuel needs more air, the screw controls the air flow. try the 22.5 if you must have correct balance at 1.5 turns out.


Last edited by gavin eisler; 08/08/18 9:48 am.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: replacing Mikunis with Amal, BSA lightning [Re: gavin eisler] #744882
08/08/18 11:35 am
08/08/18 11:35 am
Joined: Nov 2013
Posts: 295
Bristol England
R
redrooster Offline OP
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redrooster  Offline OP
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R

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Bristol England
Ok got it, happy where I am now with the 30

Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #744918
08/08/18 7:11 pm
08/08/18 7:11 pm
Joined: Nov 2013
Posts: 295
Bristol England
R
redrooster Offline OP
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redrooster  Offline OP
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R

Joined: Nov 2013
Posts: 295
Bristol England
Hi all,
Your photos and advice is really appreciated, I am going to put this into practice and will let you know how it turns out.

Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #744928
08/08/18 9:03 pm
08/08/18 9:03 pm
Joined: Aug 2015
Posts: 1,356
Bolton Lancs UK
A
Andy Higham Offline
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Andy Higham  Offline
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A

Joined: Aug 2015
Posts: 1,356
Bolton Lancs UK
Look at plate manifolds in the lower half of This page, they take up less space than the adaptor/rubber sleeve arrangement


BSA B31 500 "Stargazer"
Greeves 200 "Blue Meanie"
Greeves 350
Greeves 360
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500 sprint/LSR bike "Deofol"
Jawa 500 "Llareggub"
Aprilia RSV Mille "Lo Stregone"
'35 & '36 OK Supreme
Kawasaki ZZR1400 "Kuro no senshi"
Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #744930
08/08/18 9:08 pm
08/08/18 9:08 pm
Joined: Aug 2015
Posts: 1,356
Bolton Lancs UK
A
Andy Higham Offline
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A

Joined: Aug 2015
Posts: 1,356
Bolton Lancs UK
On a B31 engine
[Linked Image]20170125_170939 by Sigma Projects, on Flickr
On a DBD type engine
[Linked Image]20180609_152238 by Sigma Projects, on Flickr


BSA B31 500 "Stargazer"
Greeves 200 "Blue Meanie"
Greeves 350
Greeves 360
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500 sprint/LSR bike "Deofol"
Jawa 500 "Llareggub"
Aprilia RSV Mille "Lo Stregone"
'35 & '36 OK Supreme
Kawasaki ZZR1400 "Kuro no senshi"
Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #744945
08/09/18 1:24 am
08/09/18 1:24 am
Joined: Aug 2001
Posts: 4,757
Owego, NY, USA
Mark Z Online content
BritBike Forum member
Mark Z  Online Content
BritBike Forum member

Joined: Aug 2001
Posts: 4,757
Owego, NY, USA
Originally Posted by redrooster
Hi Mark,
Ok, I changed the 25 for a 30 to make it richer and have made it leaner ?, I have 20 it my box I should try this.


What Gavin said. I didn't explain it very well. Right, if you're happy with two turns out on the air screw, then leave in the 25 jet. If you want the air screw in farther (richer), then you want a smaller pilot jet to compensate.

Originally Posted by redrooster
Hi Ferret,I see the aluminium adaptors on your photos that bolt straight on to the head, this is what I think I need but can,t seem to find them supplied by anyone here.will look harder.


This may not help you over there, but I got my Mikuni kit from M.A.P. Cycle in Florida, which kit included the manifold adapters.



Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: replacing Mikunis with Amal, BSA lightning [Re: Mark Z] #749968
09/21/18 10:25 am
09/21/18 10:25 am
Joined: Nov 2013
Posts: 295
Bristol England
R
redrooster Offline OP
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redrooster  Offline OP
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R

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Posts: 295
Bristol England
[Linked Image]


Hi all,
Thanks for help this is what I ended up with

Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #750141
09/23/18 12:58 am
09/23/18 12:58 am
Joined: Aug 2001
Posts: 4,757
Owego, NY, USA
Mark Z Online content
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Mark Z  Online Content
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Joined: Aug 2001
Posts: 4,757
Owego, NY, USA
RR, I don't know how well it will show up in this picture, but if you want to get some rudimentary filtering, you may want to try something like this:

[Linked Image]

"Filters" are 3/16" square galvanized wire mesh covered with oil-soaked Uni foam, all held on with hose clamps. Because of the small surface area, they need to be periodically cleaned (with gasoline) and re-oiled, but it's better than nothing.

Also, I have only about 1/8" between the two spigot mount clamps, and it looks like you have about 1/4". You may be able to gain a bit of clearance by cutting the coupler and/or the manifold adapter a bit shorter.



Last edited by Mark Z; 09/23/18 1:05 am. Reason: screwed up the picture the first time

Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #750299
09/24/18 2:55 pm
09/24/18 2:55 pm
Joined: Nov 2013
Posts: 295
Bristol England
R
redrooster Offline OP
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redrooster  Offline OP
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R

Joined: Nov 2013
Posts: 295
Bristol England
Hi Mark
Thanks, yes will do something like this.

Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #753138
10/17/18 4:46 pm
10/17/18 4:46 pm
Joined: Nov 2013
Posts: 295
Bristol England
R
redrooster Offline OP
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R

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Posts: 295
Bristol England
[Linked Image]

Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #753139
10/17/18 4:52 pm
10/17/18 4:52 pm
Joined: Nov 2013
Posts: 295
Bristol England
R
redrooster Offline OP
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Bristol England
Hi Mark and everyone,
Advice is really appreciated, Bike is running beautiful

and it goes on and on and on

Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #753322
10/19/18 3:04 am
10/19/18 3:04 am
Joined: Aug 2001
Posts: 4,757
Owego, NY, USA
Mark Z Online content
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Mark Z  Online Content
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Joined: Aug 2001
Posts: 4,757
Owego, NY, USA
RR, I like your air filters better than mine! What are they? Did you make them, or are they "store-bought"? Held on with set screws?



Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #756510
11/18/18 9:08 pm
11/18/18 9:08 pm
Joined: Nov 2013
Posts: 295
Bristol England
R
redrooster Offline OP
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R

Joined: Nov 2013
Posts: 295
Bristol England
Hi Mark, been away for a bit, Air filters are velocity stacks bought from a US website, they came with wire mesh gauze filter but have fitted the foam over. they are secured with 3 grub screws, Will try to find where I got them from.

Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #757548
11/29/18 9:03 pm
11/29/18 9:03 pm
Joined: Nov 2013
Posts: 295
Bristol England
R
redrooster Offline OP
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redrooster  Offline OP
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R

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Bristol England
Hi Mark,
Just remembered, they are from Dime City Cycles 'polished aluminium shorty velocity stacks'

Re: replacing Mikunis with Amal, BSA lightning [Re: redrooster] #757574
11/30/18 1:22 am
11/30/18 1:22 am
Joined: Aug 2001
Posts: 4,757
Owego, NY, USA
Mark Z Online content
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Mark Z  Online Content
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Posts: 4,757
Owego, NY, USA
Red, got your PM, thanks! I'll check out Dime City!

Ok, got 'em bookmarked. One more question, if you don't mind: How do you keep the foam in place?





Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: replacing Mikunis with Amal, BSA lightning [Re: Mark Z] #758007
12/03/18 9:17 pm
12/03/18 9:17 pm
Joined: Nov 2013
Posts: 295
Bristol England
R
redrooster Offline OP
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redrooster  Offline OP
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R

Joined: Nov 2013
Posts: 295
Bristol England
Hi Mark,
Just cut the foam slightly larger than the metal gauze supplied and fit in front of the gauze,when the stack is pushed onto the carb it is held in position along with the gauze.,
Bit fiddly but probably 1/2 hour job. Cut well oversize first then trim.

Last edited by redrooster; 12/06/18 7:47 pm.
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