CCM 404 DS starting problem

[Richard Simpson Mark II]

Well, it's carb cleaning time tomorrow...

[Tonibe63]

There's a good spark. Stuck a new plug in there to be sure.

Cams are in the right position at TDC. All checked against the Clymer manual.

There's an occasional bang from the exhaust, with and without Easy Start, but nothing to suggest the engine is firing properly.

Ignition timing is 'non adjustable' on this bike...but I suppose I could check the trigger is in the right place.

I will do as you suggest and take another look at the carb.

If that's OK, then its head off and check the valve seats etc.

Ignition timing is not adjustable BUT if the woodruff key has sheared the flywheel can rotate a few degrees on the end of crank so the ignition trigger is not correctly timed with the valves. On my mates 404 the flywheel nut was tight and it did not rattle or appear to be loose but it had slipped.
If the plug is wet with petrol and the plug sparks then it can only be the timing.

[Hugh]

Greetings Richard,

Do you have anyway of conducting a cylinder leakage test, ie lock engine at top dead centre compression with both valves closed, apply air pressure through the spark plug hole and look/smell/listen for air escaping past valves out through the carburettor or silencer, piston - bore through oil filler or breather, coolant or oil gallery via head gasket failure or crack, before ripping the head off? Naturally there will be some slight leakage but hopefully not too much.

I note that the valve clearances and valve timing are correct but as Toni has recently suggested have you checked the ignition timing? I have known flywheel keyways to fail in the past and so the ignition timing slips. This might be why you are getting the occasional bang in the exhaust, unburnt fuel collecting and then suddenly ignited by a spark.

Does your bike have a vacuum activated petrol tap? I have come across age related cracking of flex pipe failure on Triumphs causing similar problems, was a swine to track down but so obvious when found.

The little drops of moisture do n't really look like the problem but blocked jets/drillings in the carb could be contributing. Sonic cleaning is really good in my experience although it does take time.

TTFN

Hugh.

PS the two attached files might be of use to somebody.

cylinder leakage test.pdf

(1.09 MiB) Downloaded 99 times

compression test.pdf

(67.53 KiB) Downloaded 102 times

[Fried Egg Sandwich]

It's a DRZ engine. If it's had a replacement alternator stator fitted check that the pickup wires have not been fitted incorrectly in the stator (swap them round at the connector end not on the stator) I've had that in an expensive German made replacement and a cheaper Chinese one. The blue and green cables needed swapping around at the connector end and everything was then fine.
It had a healthy spark even with the wires wrong, so faked me out for ages.

[GFJ1]

Another possibility that i know has happened on a bike i now own; have you pulled the flywheel off and checked the stator? Some bolts worked loose which over time wore through the stator windings causing the bike to stop running.

[Richard Simpson Mark II]

Thanks folks...job is taking a bit longer because the back of the bike has to come off to access the carb, so I'm taking the opportunity to clean it all up, grease the suspension etc.

[garyboy]

thanks for updating us Richard



Brexit pales into insignificance
a welcome distraction, and an edge of u seat interest





amazing how none of us. me included. well especially me. are able to fix our own bikes ..

yet seem to know instinctively what is the exact problem with other bikers bikes

[Richard Simpson Mark II]

Will the CCM run before the end of October?

Who will finish first...me, or Mrs May?

Stay tuned!

[herman]

"Who will finish first...me, or Mrs May?" thats a picture for the mind bleach

[Richard Simpson Mark II]

I won...it runs!

Must have been the carb...just seems very strange that the problem should present in the way it did...carb woes are usually caused by inactivity.

I started it before it was fully back together and can can confirm that it is very loud on a open header pipe!


Thanks to everyone for suggestions, help and support!