Hi guys,
I got my bsa A50 1969 running and now is time for some adjustments :)
I have new amal 626/300 and after few attempts I have following settings:
Main jet 170
Needle jet 107
Pilot bush
Needle on midle ring
I have problem that when is engine hot and I rev it, close throttle and rev it immediately again It shoots into carburator sometimes (if it is cold it shoots more often).
Spark plugs are dry, but little bit black.
I would change pilot jet, but there is only bush in this carb...
Idle is ok, mixture is set hopefully correctly...
I'd have to check my Amal carb settings to be accurate with what it should have. But what I can say is your needle jet is too big and your main jet too small.
Is your carb the original one or a replacement?
In the carb there is a little brass tube (spray tube) at the bottom of the carb throat. Is it flat or is it slanted towards the engine?
On the needle, there is the clips which the needle clip, clips onto and then there are some identification marks in the form of rings. Does this have 1,2,3 or 4 fine rings above the clip slots.
Also, what is likely causing your spitting back is if the pilot circuit is blocked. There will be 2 holes under the slide. These both need to be clear for good transition between the idle carburettor and the main carburettor
Hi Allan,
You were right...
It is new Amal 626/300:
https://www.britishbikebits.com/626-300-premier-amal-mk1-concentric-carburettor
I returned back to needle jet 106 and I have tried main jet 190 and it seems that it stoped spitting back and it goes much more better.
There is still a litle gap if I quickly open throttle from idle so maybe I will go for main jet 200.
If I check spark plugs they are dry, but nearly completely black.
I use NGK B7ES - do you thing that could help usage of hotter spark plugs?
Which spark plugs do you recommend?
I
Another question - When I bought it there was mounted a carb 926 (I suppose that it is for 650) and I used air filter box (I made reductor for 626).
Am I right if I say that filterbox are the same for 650 and 500 and only difference is in front plate where is different diameter for carburator?
Thank you
Zdenek
Hiya
The main jet only has effect from about half throttle onwards, you could actually remove the main jet and ride the bike at lower speeds and not even notice it's missing. Well till at least you go beyond half throttle.
Do you know what slide number you have fitted? I'm guessing it's a number 3? It should have a 3.5. The number is written on the underside of the slide. However before you take the carb off to check. Ensure that when you set your idle mixture - ON A HOT ENGINE. So do a good 20 miles riding before you consider making any adjustment. You want the idle
Mixture screw to be turned out enough so the engine revs its fastest - which indicates the correct mixture. Then turn it back a touch until you hear it just start to slow by the tiniest amount. Then slow the diagonal slide adjusting screw to slow down the tick over speed.
Then crack the throttle open. Is the engine hesitant/slow to take revs? Or does it want to stall so the engine almost dies.
Slow to rev is too rich a slide. Wanting to stall is too lean.
Hi Allan,
Thanks a lot for your advice.
I set the mixture screw as you described, but I will double check for to be sure.
I believe that it will be the main jet - it's happen only if I quickly open throttle from idle to more than half. Then engine want to stall... As I can see in manual there should be mainjet 200. Don't know why I thought that should be 190...
I will check slide number, but I believe that it is 3...
What is affected by slide number?
Thanks
Zdenek
Hi Zdenek,
You could try an NGK B6ES. It should stay a bit cleaner.
Dave.
Thanks Dave, I will try....
Quote from: DAVE BRADY on 25 Apr, 2024, 08:09
Hi Zdenek,
You could try an NGK B6ES. It should stay a bit cleaner.
Dave.
You could, but you risk detonation if the cylinder temps get above the self cleaning temperature of the plug. Basically it becomes a glow plug.
Correct the fuel mixture, fit some new N4C plugs and go from there.
Fuel mileage is a good indication that the slide is too rich. Since we spend most of our time riding I. That throttle range(1/8-3/8 opening). If your seeing around 60mpg your not going to be far off the mark.
@Dave. If you decide to put your 750 back to 840 then I pretty much have optimised my carb settings with the 28mm.
Hi,
The B6ES seems to cope better with the ethanol fuels and performed better when we went to a USA rally. I have run them in my A65 and not had a problem but cleaner plugs.
I would agree that a problem may arise if maxing the performance but is that likely?
Dave.