BritBike Forum logo
BritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorThe Bonneville ShopBritBike Sponsor
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
ShoutChat Box
Comment Guidelines: Do post respectful and insightful comments.
Buy BritBike staff a coffee
Buy BritBike's staff a coffeeStill here since 1996 serving BritBike enthusiasts..
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
Member Spotlight
glastrywhippet
glastrywhippet
co.down n.ireland
Posts: 52
Joined: May 2007
Show All Member Profiles 
Newest Members
Mark Chapman, JacksMacnLE, Argos parts, Mr. Bean, rudi
10864 Registered Users
Top Posters(30 Days)
franko 167
DavidP 69
reverb 59
NickL 53
Popular Topics(Views)
1,019,866 mail-order LSR
a word from..
Forum Statistics
Forums34
Topics67,804
Posts680,446
Members10,864
Most Online14,755
May 5th, 2019
Who's Online Now
66 registered members (1958superrocket), 719 guests, and 894 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 4 of 8 1 2 3 4 5 6 7 8
Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #351738 01/06/11 9:49 pm
Joined: Jan 2011
Posts: 2
P
plumridge Offline
BritBike Forum member
Offline
BritBike Forum member
P
Joined: Jan 2011
Posts: 2
I was interested in the comment about needing to change the slides for leaner jobbies on the A65. I have been having problems with over-rich running in the transition stage from idle circuit through the cutaway phase to the needle jet range since rebuilding my TR6R with standard compression pistons so I can run it on pump gas (instead of 100 octane race fuel). As we know our pump gas now doesn't have lead in it and the additives used instead run cooler and leaner. It runs great at idle and from about 1/2 throttle on right to the stop. Plug readings at these throttle settings back this up, but that transition phase has got me stumped. Looking at the other issues raised on this thread, I have made a nice little jig to mount the float bowl in the vice to set the float level by measuring to the gas level (.170" - .240" as per AMAL's information), am using a stayup float (they should have introduced this years ago!), and also found I needed to add an extra groove to the (new plus new needle jet) needle to lean that off even more. Has anyone else found this? On the subject of float levels, I note that only Hitchcocks web page about this states the float level as being measured thus including the gasket. The AMAL information makes no mention of the gasket being part of the equation. What's the correct answer? Also does anyone have an actual figure for the best float level for these carbs (say within a +/- .010" tolerance)? The range given by AMAL is quite large and you would expect quite a variation in mixture strength across it. A couple of points worth noting with regard to using the float edge below the top of the bowl method to set the level is that the actual gas level resulting in the bowl will vary slightly with the manufacturing variations in the weight of the floats and with variances in fuel specific gravity in different countries/regions. Agreed, variations may be small and possibly insignificant - comments?

Support Your #1 BritBike Forum!

Check out British motorcycles for sale:
British Motorcycles on e-Bay UK
British motorcycles on e-Bay North America
Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #351758 01/06/11 11:53 pm
Joined: Mar 2005
Posts: 10,250
J
John Healy Offline
BritBike Forum member
Offline
BritBike Forum member
J
Joined: Mar 2005
Posts: 10,250
Comments:
At idle to 1/2 throttle (actually 1/3rd if you want to be picky) you are in the: pilot jet, slide cutaway and needle jet diameter (straight portion above the taper) stages of this carburetor.

With time:
-The pilot jet tends to block up with stuff. This equates to leaner running. So we can rule this out!
-The slide tends to wear in the body. Again this equates to leaner running. So we can rule this out! Of course you can effect this in a positive manner by changing cutaways.
-The needle going up and down in the needle jet will wear it oversize. This equates to richer running.

So before you tear your hair out and spend money answer these questions:

So with the above in mind have you replaced your needle jets? If you have replaced your needle jets did you have them measured or measure them yourself? As little a .0005" can make a difference. This can be from wear or improper manufacture.

Comment: Because the straight diameter of the needle (.0985" did you measure this??) does not come clear of the needle jet orifice until approx. 1/3 throttle making another groove to lower it will do nothing below 1/3rd throttle. It will above that, but that is not where you are telling us your problem is.

Comment: Have you had the body sleeved? If you did, what's the slides clearance in the body. To have the standard jetting work you need at least .0035" and a bit more is better. Less clearance increases the signal (manifold vacuum) on the fuel circuits at low throttle openings.

Comment: Do you have all the right kit installed:
Straight spray tube?
4 stroke - cross drilled needle jet for the model carb. you are using? Needle jets for MKII and MKI are different.
Do you have the correct 2 ring needle 622/124 if this is a MKI Concentric?

As far as the float, set it up using the Triumph Service Bulletin measuring the top edge of the float at .060" to .080".

Don't assume that new parts are correct EVEN IF THEY ARE STAMPED AMAL. There are a lot of after market AMAL parts that are not on specification. Not that AMAL has never made a mistake they try real hard to get things right. They are also now putting their parts in AMAL bags which should give the punter more confidence in what they are getting.
This should get you started.


Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #351764 01/07/11 12:27 am
Joined: Jan 2011
Posts: 2
P
plumridge Offline
BritBike Forum member
Offline
BritBike Forum member
P
Joined: Jan 2011
Posts: 2
Thanks John that was a quick reply! You must be constantly sitting at your pc waiting for people like me to come up with problems!

Anyway, to clarify some of these points:

I recently replaced both needle and needle jet. No I did not measure either, just assumed (wrongly as it happens) that they would be correct. Actually I noted later that the AMAL website warns against fake parts too. I note that the needle jet does not have AMAL stamped on it so maybe this is a clue to my issues after all? Forgot to mention in the first post, I have increased the cross drilled hole from .035" to .039" as recomended by some other blurb I read on this, but it didn't seem to make any difference.

No I have not had the body sleeved, but some time ago I made a steel slug to reshape the body back to round without removing metal from it so the slide won't stick. I am also VERY careful about tightening the flange nuts so I don't distort the flange and recreate the problem. With all this in mind I think we can assume that the time produced wear in the body will be giving us at least the .0035" clearance necessary even with new slides fitted (again I have not measured things yet to be 100% sure).

When I first struck the problem after fitting the standard compression pistons, I found that the carb was still set up as per 1968 manufacturing specs so that's when I updated it with the cross drilled needle jet, it's matching 2 ring needle, and the longer main jet holder. The spray tube is straight cut across the top too. I was aware that Notrton and Tridents have angle cut spray tubes to richen things up a bit. I wonder if with the current additives in the fuel whether they might benefit now from leaner spray tubes? But that is another debate altogether!

I now have some parts coming from AMAL direct so I'll see how these change things. Will update the forum when I've tried them.

Thanks again

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #394056 09/11/11 9:46 pm
Joined: Aug 2007
Posts: 51
Britbiker1234 Offline
BritBike Forum member
Offline
BritBike Forum member
Joined: Aug 2007
Posts: 51
Hello, basic question on Mk2 AMAL's. Does the pilot contribute to fuel delivery over the full range of throttle position (as with a Mikuni VM) or is it limited to the first 1/4 or so? From my limited experience with the Mk2 I don't believe it does, however would like to understand for sure in order to make some adjustments to previously established settings for main jet & pilot. Many thanks.

Re: Tuning Your AMAL Carburetor [Re: Britbiker1234] #394360 09/14/11 12:40 am
Joined: Jul 2009
Posts: 3,518
P
Pete R - R.I.P. Offline
In Remembrance
Offline
In Remembrance
P
Joined: Jul 2009
Posts: 3,518
The pilot jet would still flow some amount of fuel,even at full throttle.It would only flow about 1/3 as much as it did at low throttle openings,because there's less vacuum on the idle ports.

You'd have about 20 times as much air,or more, going through the carburettor at full throttle.The percentage of fuel supplied through the pilot jet wouldn't be much;probably less than 2% at full throttle.

You could notice the effect of a blocked pilot jet at 1/2 throttle.I doubt that you'd notice any small changes in pilot jet size,or other idle adjustments.

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #394412 09/14/11 11:51 am
Joined: Aug 2007
Posts: 51
Britbiker1234 Offline
BritBike Forum member
Offline
BritBike Forum member
Joined: Aug 2007
Posts: 51
Thanks Pete. I know the Mikuni's do and have witnessed the effects on fueling on the dyno but haven't had enough time testing the AMAL's to understand them. That'll put my mind at rest for this Saturdays race meeting before I can get back to the Dyno to test again. Cheers

Re: Tuning Your AMAL Carburetor [Re: PoorBoy] #398822 10/14/11 3:45 pm
Joined: Dec 2010
Posts: 14
B
Brose Offline
BritBike Forum member
Offline
BritBike Forum member
B
Joined: Dec 2010
Posts: 14
I have a newer AMAL 930 with idle jet sealed inside it has a plug on the under side approx 3/8" dia) where the passage should be. I bought this carb new a couple years ago and installed on a 68 TR6. It ran great for a little while and when I went to start it again it is verty stuborne and will not start without continued priming. Once warm it seems to run ok. The bike will only run when the air screw is turned almost completley in. I have put the carb in cannec cleaner and blew on each orface with canned cleaner and everything seems clear. Anybody any ideas?

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #399287 10/17/11 5:58 am
Joined: Sep 2011
Posts: 17
J
johnmc Offline
BritBike Forum member
Offline
BritBike Forum member
J
Joined: Sep 2011
Posts: 17
i have the same problem with my bsa .i drilled out the blank side to find there was no pilot jet and can,t figure out where the fuel supply comes from lol

Re: Tuning Your AMAL Carburetor [Re: johnmc] #399355 10/17/11 5:19 pm
Joined: Dec 2010
Posts: 14
B
Brose Offline
BritBike Forum member
Offline
BritBike Forum member
B
Joined: Dec 2010
Posts: 14
I'm sure someone will know what the problem is. If I find out the problem I'll let you know. Did you drill out the blank side opposite the air screw?

Re: Tuning Your AMAL Carburetor [Re: johnmc] #399356 10/17/11 5:22 pm
Joined: Dec 2010
Posts: 14
B
Brose Offline
BritBike Forum member
Offline
BritBike Forum member
B
Joined: Dec 2010
Posts: 14
Forgot to mention, been to NSW and love Australia

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #399378 10/17/11 6:30 pm
Joined: Dec 2006
Posts: 4,104
B
btour Offline
BritBike Forum member
Offline
BritBike Forum member
B
Joined: Dec 2006
Posts: 4,104
Hi Brose,

Did you read this whole thread first before you asked the question?

I am sure it must be posted in here somewhere. You must use a #78 drill bit, and tweedle it carefully in through the hole where the pilot/air screw goes. This will clean the pilot/idle jet properly, which you should do anyway and frequently.

Next if that does not correct the problem, then look for an air leak, by spraying some carb cleaner or WD 40 around the appropriate culprits and see if the idle changes. You might be sucking air if you have to screw the PA air in all the way.

And you should have the appropriate oring in between carb and manifold, not the one that comes with AMAL kits.

Next be aware that the blends or high volatile an low V elements gets off this time of year. And the high volatiles that you need for starting, evaporate off quite quickly. S if gas is old then start with fresh.

Of course all carb stuff should be done after all the mechanical stuff like timing, valve lash etc. are spot on.

HTH
Bob ISoBe



Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #399380 10/17/11 6:34 pm
Joined: Dec 2006
Posts: 4,104
B
btour Offline
BritBike Forum member
Offline
BritBike Forum member
B
Joined: Dec 2006
Posts: 4,104
PS, you can use the search function to search for "carb tuning" on this forum and the Triumph forum and use John Healy as the poster in the search and you will find a ton of valuable information.

Keep submitting the query until the search function works. Pay attention the time range in the search. By default it is set to one day only. Why? I do not know. It should be three years by default.



Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
Re: Tuning Your AMAL Carburetor [Re: btour] #399540 10/18/11 3:56 pm
Joined: Dec 2010
Posts: 14
B
Brose Offline
BritBike Forum member
Offline
BritBike Forum member
B
Joined: Dec 2010
Posts: 14
Bob
Thanks for your help. I'll try cleaning the air jet screw hole again. I have used canned carb cleaner with a straw/stem squirted into the hole and the cleaner gets through but, maybe no enough? I have even changed heads and manifolds on this bike thinking possibily a valve or head leakage of some kind.
A PWK works fine. Valves and timming is correct.
Thanks again.

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #399627 10/19/11 12:16 am
Joined: Dec 2006
Posts: 4,104
B
btour Offline
BritBike Forum member
Offline
BritBike Forum member
B
Joined: Dec 2006
Posts: 4,104
Hi Brose,

No amount of compressed air, nor carb cleaner, nor a wire will clean that pilot jet. It is not a hole, it is a jet. That is what John always says. You need to find and purchase a #78 drill bit and fit a plastic or brass or other sort of extension to hold it, and then carefully locate the orifice and gently turn it into the jet. I have not done it myself yet, but I do have a pile of those drill bits. They are very fine and easily broken.

Get some and do it. You will be amazed at the results. There is an overlap with the pilot circuit in the carb and the rest of the circuits. The pilot circuit is like a carb within a carb, so when you clean it properly, the results will effect more than just the idle.

Cheapest tune up possible as John always says. Get one or two and do it. Post haste.

Most likely is your problem will go away, unless as I mentioned, you have an air leak.


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
Re: Tuning Your AMAL Carburetor [Re: btour] #399712 10/19/11 3:17 pm
Joined: Dec 2010
Posts: 14
B
Brose Offline
BritBike Forum member
Offline
BritBike Forum member
B
Joined: Dec 2010
Posts: 14
Bob
Thanks again. I will order those bit's today and give it a try.

Re: Tuning Your AMAL Carburetor [Re: btour] #401569 10/31/11 11:26 pm
Joined: Dec 2010
Posts: 14
B
Brose Offline
BritBike Forum member
Offline
BritBike Forum member
B
Joined: Dec 2010
Posts: 14
Bob
Using the fine drill bit in the air jet hole seems to have worked. Thank's again for your help.

Re: Tuning Your AMAL Carburetor [Re: johnmc] #401570 10/31/11 11:31 pm
Joined: Dec 2010
Posts: 14
B
Brose Offline
BritBike Forum member
Offline
BritBike Forum member
B
Joined: Dec 2010
Posts: 14
I don't know if you read Bob's answer to the carb problem or not. If not, get a #78 drill bit and use a needle vise or something simular to hold it and gently clean out the air pilot jet hole deep in the carb. It seems to have worked for me.
G'day mate

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #401892 11/03/11 11:24 am
Joined: Oct 2011
Posts: 7
M
Michel Peys Offline
BritBike Forum member
Offline
BritBike Forum member
M
Joined: Oct 2011
Posts: 7
Probably because my English is not 100% and my little belgian brain didn't run on full capacity I must have misunderstood this thread. I drilled the idle jet with a 1mm drill in stead of the #78 diam. Which -now I realize- is too large and will result in a to rich idle mixture. Can I still install a new jet or did I screw up my 930 carburetor completely?
AMAL says that those screw-able idle jets are actually for 2-stroke engines thus unusable for my BSA A65L oif.

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #401900 11/03/11 12:55 pm
Joined: Mar 2005
Posts: 10,250
J
John Healy Offline
BritBike Forum member
Offline
BritBike Forum member
J
Joined: Mar 2005
Posts: 10,250
Michel:
You didn't do the carburetor any favors.
I would start by screwing in a removable pilot jet (two stroke) and see how it goes.

You have little to loose at this point!
John


Re: Tuning Your AMAL Carburetor [Re: John Healy] #402051 11/04/11 3:57 pm
Joined: Oct 2011
Posts: 7
M
Michel Peys Offline
BritBike Forum member
Offline
BritBike Forum member
M
Joined: Oct 2011
Posts: 7
Thought so. My order from AMAL is on its way. I'll keep you updated.

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #402492 11/07/11 4:10 pm
Joined: Oct 2011
Posts: 7
M
Michel Peys Offline
BritBike Forum member
Offline
BritBike Forum member
M
Joined: Oct 2011
Posts: 7
OK, today I received the idle jet (25cc) and installed it in its proper place.
Started the bike and although the petrol is getting old I could more or less manage to get it at a good idling rev. But when I opened throttle a bit to fast the engine stalled (I assume this is the term for it. It acts like to much air is getting in thus no petrol to keep it running). I suppose this is because of the K&N filters? Does this mean that I should raise the needle and install a larger needle jet?

wow it was so nice to make an illegal test ride :-)

Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #402498 11/07/11 4:56 pm
Joined: Mar 2005
Posts: 10,250
J
John Healy Offline
BritBike Forum member
Offline
BritBike Forum member
J
Joined: Mar 2005
Posts: 10,250
Quote
Does this mean that I should raise the needle and install a larger needle jet?


No, raising the needle would change the mixture from approx 1/3rd throttle while increasing the size of the main jet would change the mixture from approx. 3/4 to Full throttle.

Your problem is in the area which is influenced by the size of the pilot jet (including adjustment of the pilot air screw), slide cutaway and the size of the needle jet itself.

Removing the K&N filters should make it worse.


Re: Tuning Your AMAL Carburetor [Re: John Healy] #402520 11/07/11 6:38 pm
Joined: Oct 2011
Posts: 7
M
Michel Peys Offline
BritBike Forum member
Offline
BritBike Forum member
M
Joined: Oct 2011
Posts: 7
So should I install a 30cc for example and raise the needle size or rather lower? I noticed I have a 3 cutaway slide..should I also raise it? Or better go 1 at a time to control costs and to understand what's happening during changes?

Re: Monoblock float level [Re: Morgan aka Admin] #405795 11/27/11 3:04 am
Joined: Dec 2007
Posts: 164
darbone85737 Offline
BritBike Forum member
Offline
BritBike Forum member
Joined: Dec 2007
Posts: 164
There is a ton of informstion here re: Concentrics. I have a question re: monoblocks.

I have a persistant rich running condition with the 389 monoblock carb on my CB 34. I believe the cause us too hight a level of fuel in teh floar bowl aas it can not be cured different jetting or needle position changes. I also find evidence of fuel on top of the jet block in the slide chamber. I've also replaced the shutoff needle with a new viton tipped piece and cleaned the seat well.

Is there an adjustment to the float bowl level in a monoblock?


Tucson, AZ
1955 BSA Gold Star clubman
1958 BSA A10 Super Rocket
Re: Tuning Your AMAL Carburetor [Re: Morgan aka Admin] #412201 01/07/12 7:51 pm
Joined: Sep 2006
Posts: 164
marinatlas Offline
BritBike Forum member
Offline
BritBike Forum member
Joined: Sep 2006
Posts: 164
Hi, why the Monobloc main jet are bigger in size than the Concentric, for example for a Norton Atlas with twin Monobloc 389 and 689 it should be anything between 350 and 420!!!

Page 4 of 8 1 2 3 4 5 6 7 8

Moderated by  Alan_nc 

Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | DVD- Manuals & Parts books
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
Powered by UBB.threads™ PHP Forum Software 7.7.3