C15 Breakdown, Hot Engine

[Sticky]

Hi All
Well, been the owner of a BSA C15 for 2 weeks and broke down twice 
Been on the longest ride today, the symptoms being quite clattery, losing power, then slowing down and stopping.  After 15 mins I managed to get it started again, travelled 4 miles before it happened again.  Engine very hot and oil smoking.  So any ideas.  Why is it getting so hot? and what is the clattering.  Sounds metallic but wondered could it be pinking and there is a problem with the timing.  Or could it be valve adjustment?  Any suggestion greatly appreciated.
Pete

[Spaceman]

It's best to give the bike a thorough check out covering:

1. Tappets - check inlet and exhaust clearances

2. Contact breaker points - check condition (not burned away) and gap (15 thou)

3. Ignition timing - check fully advanced it is 7.1 mm or 33.5 degree BTDC

4. Carburation - check carb flange is flat and O-ring is ok - check jet sizes and if no air filter fitted increase main jet by 10

The problems could be caused by a retarded ignition timing or a very weak mixture. Check spark plug colour after a run - sooty means too rich and no deposits or no colour means too weak. The engines can be a bit clattery at the best of times but can be made worse by incorrectly adjusted tappet clearances.

[Sticky]

Thanks for that
Tappets fine
Spark plug dry but black
Will check points
Timing is beyond my expertise so may have to take it to my local garage.


What I don't understand it's fine for 10 miles or so but then loses power and dies.

[AdrianS]

I would also check the coil and possibly change the condenser if it is breaking down when hot.

[Mike Farmer]

 

Guess a check on the oil return would be a good direction/

Mike

[Spaceman]

Thanks for that
Tappets fine
Spark plug dry but black
Will check points
Timing is beyond my expertise so may have to take it to my local garage.


What I don't understand it's fine for 10 miles or so but then loses power and dies.

The ignition timing is fairly easy to check with a pencil inserted into the spark plug hole (don't insert too far and risk the piston snapping it in half). With bike on centre stand and in gear, rotate the engine by turning the back wheel until the pencil shows you are at top dead centre (TDC) which be when you have max projection of the pencil out of spark plug hole. Mark pencil at lip of spark plug hole to indicate TDC position.

To check ignition timing, you need to be at TDC on the compression stroke rather than the exhaust stroke with the former indicated when both valves are closed (adjusters will both have slack at this point). Rotate the engine backwards until the pencil has dropped a couple of cm. Then insert a bit of aluminium foil or 1 thou feeler gauge between the contact breaker points. Once done, slowly rotate the engine and back wheel forward until you find the point at which the foil/feeler gauge will just slide free of the points which marks the point at which the points begin to open and the spark is generated. This should occur just before the TDC mark but only just - in fact, just 0.2 mm before TDC.

This is checking the fully retarded ignition setting but is probably good enough to show if the timing is ok or way out. The best way of checking the timing is fully advanced which should occur 7.1 mm before TDC. However, to do this test you have to rotate the contact breaker cam fully CCW while doing the test which unfortunately requires 3 hands or extra ingenuity!

Once you've checked the ignition timing, the next step would be to check out the carb and fuel supply.

[cdsdorset]

Sounds like the piston us nipping up in the bore.

[Sticky]

Thanks for all the suggestions, yes, oil is returning. Spaceman, I will do that, many thanks for the explanantion.  Sorry, not sure what "nipping up the bore" means.

CONTROVERSIAL STATEMENT AHEAD. DO NOT READ IF EASILY OFFENEDED 
Ive always like old, classic vehicles and bought this to dabble with, with the intention of possibly getting a twin in the future.  But so far experience has not been all positive.  Good job I still have a couple of reliable Jap bikes I can still get out and ride.

[cdsdorset]

You are getting a light seizure of the engine. Often occurs nowadays as many run the mixture too rich and causes "bore wash" where the oil which would be on thd cylinder wall gets washed off by the rich mixture. Can you get your hands on a cheap flexicam to put down the plughole. Have a look at the sides of the cylinder for signs of alloy on the walks.
Where are you based.

[AdrianS]

Thanks for all the suggestions, yes, oil is returning. Spaceman, I will do that, many thanks for the explanantion.  Sorry, not sure what "nipping up the bore" means.

CONTROVERSIAL STATEMENT AHEAD. DO NOT READ IF EASILY OFFENEDED 
Ive always like old, classic vehicles and bought this to dabble with, with the intention of possibly getting a twin in the future.  But so far experience has not been all positive.  Good job I still have a couple of reliable Jap bikes I can still get out and ride.

You are right about Jap bikes. They were far more advanced than anything we had to offer. I have 3 BSA bikes as that's what I had as a student in the 70's. If you keep British bikes, you have to accept their problems. I don't blame anyone for jumping ship to have a bike that works, doesn't leak oil and you can use. Have you seen the price of Jap classics!

[Sticky]

Cheers CDS....makes sense.  Im in Malton, North Yorks.
Adrian.....quite agree but nothing looks or sounds like a BSA twin, to me.  But if Im going to spend more times mending it than riding it then I may have to reconsider my plans.  It's ok if you are a dab hand at engineering but I'm not sure they are a good option for the average DIY er.  But that's why I bought this.  Cut my teeth, and see how I get on with one.

[DAVE BRADY]

Hi Sticky,

Stick with it and keep asking questions.  There quite a few reliable C15s about.  In fact at a BSAOC event over the last couple of days one attendee had ridden from the NE to an event near Selby and would be riding it back home.  A female rider used to ride her C15 all over Europe to BSAOC events.
It can be done and you can do it.

Dave.

[Sticky]

CDS, how can I weaken the mixture then?  Is it one of the screws on the carb

[Sticky]

Cheers Dave, this did ride fine and I had a lovely ride until after 1/2h it lost power and came to a stop.  Its a nice change to my other bike....Suzuki B King...Hayabusa powered naked. 

[Mike Farmer]

 

Its all relative. I've just read a book called "Gasoline Gypsy" its about a girl who rode a Beesa Babe(125cc) 12000 miles from Vancouver all down the west coast of USofA into and across Mexico then back into Us and up the east coast to New York. Carrying All her supplies, camping gear and an Airedale dog in a box on the back. Yep she had some problems along the way but the bike basically kept going.

I have had several Jappers and with one exception OK except Honda 400cc twin almost new late 60's I think 9000 miles on the clock----siezed solid. A fault in all of them.

My best ever was BMW 75/5 750 twin Lovely alround bike---Normal Beemer gear change???

Brit bikes??? do them or have them "done" properly and they are fine. Pay particular attention to the gaskets and don't accept even the first little dribble of oil---sort it straight away cos it wont go away on its own and it will generally get worse.

If it sounds like bag of nails--do it now---its no good saying "yeah I know, but its always sounded like that"

End of yap

Mike