Hi all , I have had my 61 C15 for some years now but have never been able to use it as it is such an unreliable starter. I overhauled the head with new guides and valves with no improvement, this winter I converted to 12volt and fitted Boyer electronic ignition with a new coil and battery plus HT lead and plug, still no better I have renewed the needle and jets and tried the needle in alternative positions with no improvement, if it ever does start I can ride it round the block and it seems fine but the next time you want to use it , back to non starting . It always wets the plug and only by changing to a dry spare can you sometimes fire it up. It has an Amal concentric Mk 1 600 series carb do you think replacing the carb could be the answer or any other thoughts would be very welcome as I cannot believe a C15 can be this frustrating but don't know anyone else with a similar bike to compare notes with.
Hi,
C15s can be a bit temperamental and timing and carb accuracy are important. As you have eliminated the electrics/points then if the timing is spot on then it comes down to the carb. The needle position and jets are less about starting and more about running once started. The pilot 'circuit' could well have a blockage that is making the mixture too rich. I would suggest re-checking the ignition timing and making sure the carb is clean paying particular attention to the tiny fuel and air ways of the pilot. An aerosol carb cleaner and an airline help here as the pressure may dislodge and blockage. Pocking bits of wire through could cause damage so should be avoided. If you have a manual it should have the sequence for setting up the carb.
Although the Concentric was not originally fitted to C15s there should be no problem once set up properly.
Hopefully some one with such a set up will come on and give you the settings that they are using.
Dave.
Many thanks Dave I can swing the timing till it is kicking back from being too advanced to too retarded with no success but when it is running I can set it to run nice and evenly with no backfiring and performing well, but next time you try and restart it, no luck. Will take the carb off and blow through the drillings with an air line , it does have a cable operated slide in the throttle valve which I leave off pulling it on makes no difference to starting. Thanks again for your help.
Hi,
If you are removing the choke block off the cable access hole in the carb. top otherwise air will be drawn through messing with the settings.
Dave.
Just a longshot but you say "pulling the choke on makes no difference". Does the choke not pull for off on the amal? ie wondering if you are leaving it on?
Check your battery voltage and its charging. Boyer will need good voltage.
Hi thanks all for the advice, at the moment I have a brand new fully charged 12v battery, certainly when it was 6v and on points the battery had to be fully charged if you had any hope of it starting. The choke operation has always puzzled me but I have tried it in all positions, at the moment the operating lever is fully anticlockwise which I assume puts the slide at the bottom and moving it clockwise lifts the slide against the spring, it does not start in either position but to clarify what is the correct position for starting and running and is there any advantage in taking the mechanism out and blanking the hole off. Many thanks again.
yes , anti clockwise is choke on (ie blocking air intake) clockwise (pulling on the cable) choke off. If you are wetting your plug you probably don't need choke.. just plenty tickle. I have never had a british bike that needed choke. Always just tickled them. the other thing with these unit singles is kicking technique. get it over compression and a little more. then sharp prod on the kickstart. Good luck..
I've been there: not being able to take a bike out in case it won't start to come back.
Just a couple of thoughts.
I have a B40 that I had rebored. Before, it used to start with choke and now it won't start unless it has no choke. Why, I don't know. My A50 will not start hot or cold unless it has full choke and no throttle. As soon as it fires I turn the choke off. Each bike has its own starting routine. It might even be a matter of not tickling the carb.
I'm not convinced from your description whether your choke is on or off. With the cable adjusted correctly, when you turn to full choke you should hear a clink as the slide closes in the carb and there'll be a little slack in the cable. When the cable is under tension, the choke is off.
My A50 also has Boyer which I feel can be temperamental if the electrics aren't just so. Make sure there are good earths. Check that the cable connections are sound (crimping can give poor connections) and preferably run cables direct rather than using the frame as earth.
Hi,
Not much I can add really other than confirm the choke is off when under tension. I know it doesn't help but my 61 C15 almost starts as soon as my weight is on the kickstart. I found 2 things that would counter that:- Having the switch in the Emergency position and not Run. It would do nothing for several kicks then emit a loud backfire. A bad battery connection was the other.
Have you got a solid sate relay/rectifier as electronic ignition does not tolerate over voltage i.e. when you close the throttle? If not is your rectifier ok, got good earth etc?
I don't have a choke but have the Amal Monobloc, flood the carb, feel for compression, slip the clutch to get the kickstart horizontal and then go for it. Thankfully always goes 1st or second kick, hot or cold.
Good luck
Hi many thanks everyone for so many useful comments , I bought the BB power box with the electronic ignition and when running charging appears fine but lots of advice to follow on carb which I will try, starting after a few kicks would be a dream !!! Thanks again,