Author Topic: C11 Problem  (Read 1211 times)

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Offline stev60

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C11 Problem
« on: January 18, 2019, 10:22:28 pm »
My trusty C11 came to a halt a week ago luckily close to home, I have checked timing, checked condenser, replaced coil, the reading was a bit low but it was probably ok. There is spark at the plug.New plug. Carb is new concentric, stripped it down cleaned it with carb cleaner, blown out the tiny holes no sign of ant crap in it, filters clean. The only response is to fart back out the carb, like its a timing issue, but points are opening exactly where they should.The only thing I can think of is possibly valve timing  any ideas
Steve

Offline Ginge

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Re: C11 Problem
« Reply #1 on: January 19, 2019, 12:39:22 am »
Did it die suddenly and cleanly or start faltering, coughing and gradually went into decline until it expired?

Suddenly would be electrical maybe.

Not suddenly might be fuel related or something mechanical.

Has the distributor twisted itself around in the port that it sits in?  Is the gear still on the end of the distributor shaft?  There's a roll pin that holds it on that can shear.

Something earthing the high tension lead or feed to coil?

Crook switch?

I'll fly up...
Ginge.

Offline stev60

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Re: C11 Problem
« Reply #2 on: January 19, 2019, 06:42:46 am »
A quick death, but the timing is ok as far as points to piston, I will pull the distributor   out to check its all been redone not long ago, it seems to me to be a timing isssue, ive been through the obvious, on kick it blasts back through the carb as mentioned, instead of flying up ride The C , then we will both be in need of rescue

Offline Owen

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Re: C11 Problem
« Reply #3 on: January 19, 2019, 07:34:23 am »
Have you tried another plug?
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Offline wooders81

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Re: C11 Problem
« Reply #4 on: January 19, 2019, 07:43:14 am »
My C12 stopped with a bang, turned out to be a bent pushrod, have you checked compressions and if valves are opening?
Rebel without a clue! Oxfordshire lad

Offline timsdad

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Re: C11 Problem
« Reply #5 on: January 19, 2019, 08:49:05 am »
You need to go back to basics, Steve, and check that the Suck, Squeeze, Spark/Bang, Blow is all happening at the right time, that compression is good, valve clearances are there (sounds suspiciously like a tight inlet tappet) and that fuel is getting through. Turn it over slowly, with the plug out, and watch the valves opening and closing, and then the points breaking so you're sure all timings are correct.

If the bike won't start then, after several goes, the plug should get wet and need changing. If not, it needs more tickling.


Lots of bikes, on here, have just stopped - but it's usually something different to everyone else's!


Ray
Just a motorcyclist.

Offline Ginge

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Re: C11 Problem
« Reply #6 on: January 19, 2019, 10:07:49 am »
I'd ride the C to Wellington no worries Steve.

Ray might be right I reckon.  Inlet valve is sticking open for some reason. 

A bit of carbon in the valve seat from rich running or oil burning, or tapper clearance.

Pull the rocker cap off. 
Ginge.

Offline ianinglis

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Re: C11 Problem
« Reply #7 on: January 19, 2019, 02:31:54 pm »
i agree with ginge and ray - sounds like the inlet valve is not sealing for one reason or another

burnt valve and / or seat?
tight valve guide?

take the lid off and make sure everything is moving as it should and check that you have decent compression etc etc


ian
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Offline Owen

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Re: C11 Problem
« Reply #8 on: January 19, 2019, 02:42:18 pm »
But surely that would be notible by the lack of compression?
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Offline timsdad

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Re: C11 Problem
« Reply #9 on: January 19, 2019, 04:33:56 pm »
He didn't actually say it still had good compression, Owen, - just asked for ideas of what it could be. After all the checks mentioned, spitting back sounds to me the likelihood of the inlet valve allowing a flame-back to the carb, which could indicate a tight tappet due to valves bedding in after a recent strip-down or tappets set incorrectly for a ramped cam.

We have to start somewhere!


Ray
Just a motorcyclist.

Offline Owen

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Re: C11 Problem
« Reply #10 on: January 19, 2019, 04:49:32 pm »
Yes as they say a picture (or more precisely being there) is much easier than guestimating.
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Offline stev60

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Re: C11 Problem
« Reply #11 on: January 19, 2019, 06:39:00 pm »
Thanks for the great response, I ran out of time yesterday but rocker cover will be coming off today, the motor had been done up before I bought it , but it has done a lot of miles since then. I havent checked compression but it feels good always been hard to kick over, i will do that first. The plug is new and ive tested it with a multimeter. By the way the bike stopped its a mechanical top end problem, I know the previous owner had a valve nip up when it was running in, but im not to sure about him, why would you go to the expense of reboring a motor new piston etc and not look in the oil tank there was no filter and full of sludge when I got it >:(

Offline stev60

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Re: C11 Problem
« Reply #12 on: January 19, 2019, 06:42:03 pm »
It always had noisy tappets the setting was for the later cam, but I was never sure which cam it had is there a way of telling

Offline stev60

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Re: C11 Problem
« Reply #13 on: January 19, 2019, 08:30:57 pm »
It would appear the exhaust cam rocker has gone awol, the push rod was not moving, when I pulled it out and  looking with a torch could see nothing to move it, although a little hard to see never the less its a bit of an operation, can these break

Offline camman3

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Re: C11 Problem
« Reply #14 on: January 19, 2019, 09:25:42 pm »
Anything can break....or at least, I claim my wife can break anything ???...although it is unusual for the cam follower rocker to break , and more common for valve rocker to crack as there is more stress on them.
Are you certain that the push rod has not jumped out of rocker cup? you'll need to pull camshaft cover off to be certain.
Graham
1957 C12
In sunny (sometimes) Christchurch, Dorset, UK