Misfire problem at medium speed

Will need to check the auto-advance at some point soon to see if that is what is causing the misfire problem. It felt like one of the centrifugal arms (behind the points plate) is a bit loose - perhaps one of the springs has broken or come off?


There is a good video on YouTube of how the auto-advance mechanism works.

Burnt-out connector

As usual, click any image to zoom in.

Last night, Mark rode the bike to the Antrobus Arms for the Thursday night meet-up. It was charging perfectly but he complained of a slight misfire when the revs began to build in each gear. Changing up a gear lowered the revs and the engine reverted to running smoothly.

On the way back, the ammeter showed a discharge even on sidelights and would occasionally go wild for a second or two.

I took the saddle off this morning to be greeted by a roasted connector on the Bridge Rectifier.  Now that all the earths have been sorted the full 8 to 10 Amps of alternator current is testing any poor connections.  Well, it found one. Last night before setting off the connector looked mint but obviously the spade type connector was corroded, hence destructive heat was generated, thereby destroying the connector.

I cleaned the rectifier terminal, cut off fried connector and temporarily connected lead from alternator to rectifier. Voila! Charging again.

I read something very interesting last night from one of BSA's Service Sheet where it states that "if running the bike in Emergency Mode for too long the battery will charge to a point that the bike will MISFIRE!" What I am saying is that battery conditions affect the timing to the extent that misfiring occurs with resulting poor performance.

Trip down memory lane

We found some photos tonight from when I lived in the Isle of Man - these photos would be from 1963.

As usual, click any image to zoom in.

		The old bike leaning against a wall belonged to an old boy that used it to get to work on. I passed this machine every day (parked up) as I travelled to work at Keigs the Photographers.
The guy hanging off the pier (Peel harbour) looking into the water for his mate's magneto cover, which I actually witnessed shooting off his bike like a bullet, spotted the cover and was directing his mate to where it sank. Yes, his mate removed his boots and socks and waded out to retrieve the cover. The things we do for our bikes eh.
		The young lad sitting on his bike resting his feet on my bike lived just down the road from my grandparents' house. His bike was a 350cc Velocette Venom (same model of bike as his father's).
Here he is again - shame I can't remember my old mate's name!
		Ah - there she is.
Percy during his lunch hour, faithfully guarding my old bicycle that I traded in for the C15 above! I never looked back (except for that time when I heard the siren and saw blue flashing lights)

Speedo cable info

As usual, click any image to zoom in.



I found a page on the Classic Motorcycles website that gives details about speedometer and tacho cable lengths.

Well worth a viewing if you need to replace your cable.

Bullet connectors

As usual, click any image to zoom in.





I also picked up a couple of packs of insulated bullet and bules for the points wiring and any other rotten connections I come across.

New bridge rectifier parts

As usual, click an image to zoom in.

Weather has been terrible today so didn't do any work on the bike. Took 'er indoors for a meal instead at lunchtime - ordered a steak dish and a fish dish. The waiter asked if we wanted the head and tail left on, so I looked at her before answering, "Yes, please - she looks like she could eat a whole cow."

After that I popped into Maplin to get some parts for a new bridge rectifier. It's encased in a solid metal body which bolts to the bike's frame so any heat dissipation won't be a problem. It was really cheap and a great alternative to some rectifiers on offer.  Check this link for a crazy price!

More news on the charging fault

As usual, click any image to zoom in.

The first picture shows bridge rectifier, which measures fine but the next two pictures reveal a non-existent earth before I scraped the paint away to reveal bare metal:

The fourth photo (on the left) shows a non-soldered connection on the lead leading off to the points contact.


The connector in this last picture on the right then goes into a snap connector, the other end of which had another lead (connecting into it and coming from the  ignition coil), hanging on by a single rusted strand of wire.  As soon as I touched the wire it just dropped out of the snap connector:


We were lucky that Mark was able to ride the bike as far as Antrobus on Thursday night to get to the BSA meet-up, never mind back home. Still - that'll be why I drove in my car and met him there instead. Just in case, you know, 'cos there was no way *I* was going to be the one stuck riding down the country lanes with only a side light to illuminate the carriageway. Ha - I burnt him off big time in my trusty Reliant Robin.

I will solder a length of 14mm wire to each earth point just to make sure.  I've tested the alternator stator for AC output with my AVO meter.  No problems there. When everything is connected I will measure the battery voltage when the engine is running  to make sure the charging circuit is functioning efficiently.

New speedo cable

As usual, click any image to zoom in.

The speedo needle wobbled, and there was an unpleasant crunch from the back wheel every so often while riding the bike. Turns out that one of the notches on the back wheel hub was cracked.

Mark came over last weekend and helped me cut out two new notches to sit a new speedo gearbox onto. We did this very carefully by hand with a metal file - making sure no filings went down into the bearings.

Tedious but looks good. You can see the original and damaged cutouts at approximately 9 o'clock and 3 o'clock in this photo, and the new ones at top and bottom of the shot.


When we came to fit a new speedo cable it would not connect to the speedo - turns out that there are two types of speedo (chronometric and magnetic) and that we had the wrong type. We're impatiently waiting for the new one to turn up!

Heavy clutch lever

As usual, click any image to zoom in.





The clutch lever was VERY heavy and difficult to use without breaking a sweat or resorting to a can of spinach for every gear change.

Mark (his blog) came over to help me take the clutch apart. Turns out some dipstick had put spring cups in that were several millimetres too short which meant that the springs were highly compressed even before you pulled the lever in.














New cups and springs later and the clutch is lighter than a long-distance runner on a diet. Result!

Will check the wiring loom on the bike at the weekend for bad earths.  Headlamp bulbs blowing on this early sixties bike suggests that the accumulator is intermittently being disconnected from the charging circuit.  This was a common problem on bikes in my day and I remember my father telling me that a poor connection on the battery resulted  in bulbs blowing.

Bulbs keep blowing

The front headlight blew twice and the ammeter was showing a poor charging rate while riding the bike.

After looking at the wiring diagram it became clear that some of the links were broken inside the light switch.

Will check the wiring on the bike at the weekend paying particular attention to all the earth connections. It is obvious the stator and rotor are operating to spec as they producing sufficient power to blow headlamp bulbs with consummate ease. I suspect the accumulator is being intermittently disconnected from the charging circuit caused by a bad earth. Crude system by BSA to use the bulbs to regulate the circuit.