A10 "start you bastard"

[raindodger]

Here goes with my 2 penn'orth. I, too, had sooty plugs on my A10, nothing seemed to cure it, I weakened the mixture until it would hardly pull the proverbial rice pudding skin.  The plugs were still sooty, so in desperation, I tried a different approach.  I had always suspected that this modern fuel that we are forced to use does not burn as hot as good old leaded petrol.  So I decided to fit plugs 1 heat range softer, set carbs back to standardand run the bike very carefully, over several days, gradually increasing the speed.  Result no soot, plugs are grey/brown and the bike runs really well.
Might be worth a try!
Raindodger.

[a101960]

I had always suspected that this modern fuel that we are forced to use does not burn as hot as good old leaded petrol.

I do not know if that is the case, but it could well be. I did read somewhere that modern fuel has a different flame path and therefore tends to burn faster and that this can cause pinking because it burns hotter. it really is a big problem. I have tried hotter plugs and the soot level was marginally reduced, but the engine pinked even more. I have also read that modern fuel is formulated to burn rich in order to protect the cat units which do not like a lean burn. How true this I don't know.

John

[nagrod]

Thanks for all the replies! What I have learned so far is that I need to get this bike on the road and check plugs then before making big decisions about changes to be made. Right now ease of starting is my main concern and I seem to have achieved that. Fresh fuel is important, and modern fuels may not allow "reading" of plugs like I used to do in the past. And I need to properly determine Road Rocket or Super Rocket.
I have a question about needle size. If I'm interpreting the Amal site correctly the Amal 389 monobloc takes a D or D2 needle, but I don't see anything about a size (John had mentioned a .106 needle). How do I determine what size I've got and if it's suspect, what size do I order? Thought I'd try here before e-mailing Amal.

Again Thanks

Rick D

[a101960]

Rick, The "D" indicates that the needle is for a 389 monobloc carb. Sorry I do not know the significance of the "D2" marking.   .106 is the needle size and that is what you need for what ever size 389 you might have.
Just to clarify the model that you have the 389/47 is the USA Super Rocket specification carb. So looks like your bike is indeed a Super Rocket.

John

[bikerjohndavies]

Hi Rick, I have a 62 export SR with the 389/47 monoblock fitted. I have left it configured as standard. 389/047  Bore = 1 5/32"  Pilot = 25  Slide = 3  Main jet = 290  Needle jet = 0.106  Needle position 2. She starts and runs perfectly at these settings. The needle jet is the jet that the needle moves in and out of when the slide goes up and down and will have .106 stamped on it. If you unscrew the jet holder block from the bottom of the carb the main jet is screwed into the bottom of the block and the needle jet is screwed into the top. If you look at the exploded diagram in A101960 posting back up the page the needle jet is part 21.

As a note the 389/47 carb used on the export models was set up to run with the standard A10 air filter whilst the UK model 389/46 was set to run without an air filter which is why it has a larger 420 main jet.

[brackenfel]

Hi Rick,
Welcome to the Forum...  Glad you have got the bike running.. You may find once you get used to it again you may well not need the electric start..
When I first had my Velocette I couldn't start it (and I was 15 years younger then!) .. After 3 months of cussing, swearing and giving it the same name as you have yours things clicked.. Now I start it first kick....

As others have said modern plugs are simply cr*p... Oddly it seems to affect twins more than singles , for me anyway.. I've had NEW NGK plugs in both the A10 and the Laverda and almost immediately had weird non-starting episodes - both traced to a plug that had experienced sudden death..

I'm going to get some Champions at the next Shepton Jumble...

Cheers,

Adrian

[nagrod]

Again, many thanks to all who replied. I am having much better luck in starting it these days. Not perfect but much better! My next step is to replace all the jets on general principal and probably the needle. I want to see if I can find a stamp on it somewhere as to size, Burlen seems to say there should be one. The thing that worries me about the richness, besides possibly fouling plugs, is the possibility of a rich mixture affecting cylinder wall lubrication, so I intend to keep after it. I did send an e-mail to Amal (Burlen)and I am including it here along with the questions I asked them:

"Question: I have a Monobloc 389/47 on a 1960 BSA Super Rocket A10. I am trying to determine if I have the correct needle. I am currently running a 270 main jet, a 25 pilot jet, and a 106 needle jet. The needle is presently in the second notch down from the top. I am trying to troubleshoot sooty plugs in this bike which is presently not on the road but capable of running. I see on your web site that both D and D2 needles are available for this carb. How do I determine what I have, and what is the difference between the D and D2 needles? Thanks for your attention R Dorgan NY, USA

Vehicle Details: 1960 BSA Super Rocket, 650cc A10 engine"


Reply:  Dear Sir,

 

The needle stamped D is the standard 4 stroke needle for a 389 Monobloc. The D2 is a richer needle, so not be of use if you are getting sooty plugs.

 

Depending on the age of the carb, some of the jets may have started to wear letting more fuel through.

 

Also if the bike you have has been modified in any way i.e. pattern exhaust or high compression cams this will affect the mixture

 

Kind Regards,

[a101960]

The needle stamped D is the standard 4 stroke needle for a 389 Monobloc. The D2 is a richer needle, so not be of use if you are getting sooty plugs.

Well, I never knew that. I personally would not put to much faith in what what you are seeing (sooty plugs) until you can do a proper pug chop. You can fiddle around blindly going up up alleys that go nowhere. To properly assess your mixture you need to put the engine under load. You need to ride hard on a slight gradient, pull in the clutch and kill the motor simultaneously.  Then examine the plugs to see what they look like. If you go for a good ride on open roads you will see a more representative insight into combustion characteristics, but I doubt you will resolve this problem unless you get the engine up to proper running temperature, and see what is happening under real road riding conditions.

John

[brackenfel]

Hi Rick & John,
I never knew that either... I recently bought a needle for my A10 but just ordered a "106" from the Amal (Burlen) website so I've no idea which one I have! Bike isn't back together yet either so I'll bear this in mind when it is..

Agree with John about reading plugs..
As an aside (and quoting the Velo again, sorry) years ago I bought a Concentric for the Viper & fitted it.. Ran better than the Monobloc but the plugs always looked a bit rich.. Recently checked it and found the slide to be a 3 instead of the 3 1/2 often recommended.. So when I bought the needle mentioned above I also bought a slide....
To start with the plug looked the same but after some time when I checked it it was nicely brown in the centre. The bike only feels marginally better but I'm getting quite a bit more mpg..!!

keep at it, you'll get there !!

Adrian.

[redbeeza]

I've been following this thread with interest because I am in a similar position to Rick (3 year rebuild and just about to try and get the thing running well on the road). I hope that it will help me get my SR sorted when I can start working on it again in November, and that I won't need to ask all the same questions to you guys!

All the stuff about the spark plugs is new to me and I've been noting it all down. Likewise the carb settings. Would I be right in assuming that your SR's/RGS's have the 'big valve head' and 357 cam like mine?

Also if the bike you have has been modified in any way i.e. pattern exhaust or high compression cams this will affect the mixture

I have a siamesed exhaust system with a pattern Goldie 'silencer', which is just a straight through pipe with a bit of muffling surrounding it. How will this set-up affect the carb settings? And how would a 'high compression (high lift?) cam affect carb settings?

Cheers,
Terry

[chaterlea25]

Hi All,
Heres my 2 cent opinion, firstly starting and running the bikes in the garage or just running around the garden will lead to all sorts of "mystery problems"
You need to get the bike on the road or onto some private place where you can drive the bike properly and get it up to full running temp
The original carb settings are now only a rough guide due to the crap now sold as petrol/gas
modern "petrol" has a different specific gravity which affects the float height and therefore the mixture
Its well discussed here the many and various attempts to cure "pinking" with modern unleaded
Retarding the ignition and or richening the mixture help (probably depending on where you live as the fuel varies so much from place to place.
The first rule of setting up any carb is to ensure correct float height, get this right and everything else will fall into line!!!
On a monobloc this isnt the easiest adjustment!!! adding shims under the float jet piece will raise the level
or machine a bit away from the underside of the piece to lower the level
Unless you have one of the old floats with the brass piece to tweak,
An old bottom nut can be drilled and a little hollow stub soldered in to take a piece of clear plastic tube brought up the side of the carb to check against the mark on the body!!!!

HTH
John O R