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1965 BSA C15 not running right #334256
09/19/10 9:53 am
09/19/10 9:53 am
Joined: Sep 2010
Posts: 3
australia
O
ozmick Offline OP
BritBike Forum member
ozmick  Offline OP
BritBike Forum member
O
Joined: Sep 2010
Posts: 3
australia
Hi everyone

Recently bought a 1965 C15 with side points and I am having issues with getting in running.

It has an AMAL 600 Concentric carb fitted (the 1965 C15 so far as I know should have been mono bloc.

Anyway on tickover its ok. But a ride round the block and after a few minutes the engine cuts out and will not start again. Until I push it back around the block and back into the garage. I can then get it going on the emergency ignition side first and then on the main switch.

The plug is covered in soot so its running rich, and I wonder if the correct main jet was used when the 600 was fitted. The ammeter also does not seem to show a charge, although i make sure the battery is charged up when I take it out.

I presume I will have to take the carb apart but any ideas would be welcome!

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Re: 1965 BSA C15 not running right [Re: ozmick] #334263
09/19/10 11:08 am
09/19/10 11:08 am
Joined: May 2004
Posts: 3,569
Sydney Australia
B
BSA_WM20 Online content
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BSA_WM20  Online Content
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B
Joined: May 2004
Posts: 3,569
Sydney Australia
If I were to start typing all of the possible things it could be and you read them all you would be too old to ride by the time you finished reading.
Firstly go to [url=www.jba.bc.ca/Bushmans%20Carb%20Tuning.html]www.jba.bc.ca/Bushmans%20Carb%20Tuning.html[/url]Bushmans Concentric pages, and read it all TWICE taking particular notice of the jet chart showing which jet dose what where.

Next start your bike and adjust the idle air screw.
If you can turn it more than 1/2 turn in either direction without drastically changing the idle speed then you idle jet is blocked, follow Bushman's instruction on how to clean it.

600 series comes in 3 sizes. The next two numbers are the size of the carb in mm what are they ?
When you pull the carb apart to clean it there will be a number in the underside of the slide should be between 1 to 4 including 1/2's
Tell us and we will tell you what size jets and slide should be in there. And even then this is just the starting point but at least you will be in the right state.
Go and buy a complete new set including the needle and slide the whole lot is about $ 50.00 and they are items that should be replaced regularly in any case.
DO NOT BUY THEN OFF THE CHEAPEST eBay SELLEr YOU CAN FIND.
Get them form a reliable retailer such as the ones that advertise on this list or as you are in OZ. Modac, Trojan, Eades ,Classic Style, Mike's Classic parts, Motorcicclio ( others on this list will give you a few more choices )
They should come in a blister pack or in a box or labeled bag if they are genuine quality parts.
Do you have an air filter attached, is the element new ? If not then buy a new one of them as well ( another $ 20.00 ).

The reason why it starts on emergency position is that every last milli amp that the bike can produce goes directly into the coil, producing a much bigger, higher energy spark packet.
Because this is AC directly from the alternator it will not occur at the exact correct time but it will be a lot bigger so if a plug is fouled or your fuel is bad or ( as inteneded originally ) your battery is flat, the bike will start and run to about 1/4 revs before the inaccurate timing becomes a problem.

The fact that it will only start in that position is meaning less in this context other than telling us that the engine has big tuneing problems
are the

Last edited by BSA_WM20; 09/19/10 11:12 am.

Bike Beesa
Trevor
Re: 1965 BSA C15 not running right [Re: BSA_WM20] #334359
09/19/10 11:44 pm
09/19/10 11:44 pm
Joined: Sep 2010
Posts: 3
australia
O
ozmick Offline OP
BritBike Forum member
ozmick  Offline OP
BritBike Forum member
O
Joined: Sep 2010
Posts: 3
australia
Yes you are right BSA_WM20 about all the things that can go wrong! Thanks for the info and I will read Bushmans site and spend some time making sure I understand what is required

Re: 1965 BSA C15 not running right [Re: ozmick] #334370
09/20/10 1:34 am
09/20/10 1:34 am
Joined: Mar 2010
Posts: 63
Tucson, AZ, USA
C
CafeLoco Offline
BritBike Forum member
CafeLoco  Offline
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Joined: Mar 2010
Posts: 63
Tucson, AZ, USA
Dear OZ;
My newly rebuilt, though modified 65' C-15 Star was a bummer to tune from scratch. I mentioned in a recent reply my initial starting/run-in problems after the rebuild, including a nasty backfire. I installed a 'new' AMAL Concentric 626 carb. initially fitted with a 190 main jet. I also ordered a 180 and 170. The 190 was far too rich, the 180 now fitted is a smidge less rich, and suspect the 170 will do fine. I'm running an open magaphone exhaust and unrestricted velocity stack. It's tricky business, but the critical balance between the air jet and throttle adjustment are crucial, assuming all else is in good order. I'd start with the air mixture screw two turns out.
Best- Jeff

I'll also suggest you get the Rupert Ratio (Dave Smith) Unit Single Engine manual, the bible on tuning, rebuilding the C-15, B-40, B-25, B-44 and B-50.

Re: 1965 BSA C15 not running right [Re: CafeLoco] #334479
09/21/10 12:38 am
09/21/10 12:38 am
Joined: Sep 2010
Posts: 3
australia
O
ozmick Offline OP
BritBike Forum member
ozmick  Offline OP
BritBike Forum member
O
Joined: Sep 2010
Posts: 3
australia
Thanks Cafeloco.

I was going to ask about jet sizes so that is good info. I wanted to make sure I had all the information before I started taking things apart!

I have got Rupert Ratio (Dave Smith) Unit Single Engine manual so its getting plenty of use


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