Adventure Bike Rider Forum

I agree Tramp...but there's a really good spark. If the s/s cutout switch is activated than it kills the starter as well as the spark.

I'm beginning to think that what I thought was 'causation' (taking the tank off) was just coincidence.

A mate stopped his 404 to refuel during a rally and when he restarted it the bike fired, stopped and wouldn't restart. The cause was a sheared woodruff key on the flywheel which meant the ignition timing was out. Worth testing when the flywheel sensor triggers the ecu to spark using a multimeter.

Have you sorted it Richard just out of interest what was it?

As the loom is so short its common for the plugs around the headstock to pull apart I found until I fixed it on mine. Worth a look just in case as even plugged together if you pulled the wires either side of the plug it would separate just enough to cut out

Bike still in shed...waiting for a wet weekend.

Step-grandchildren, dogs, garden, and work (IAA truck show in Germany, 2000 exhibitors!) all keeping me away from it.

I have a too hard pile as well.

Right then...

Vegetable garden cleared, hedges laid, trees felled and all commercial work done until the middle of the week.

I returned to the CCM...fresh fuel, charged battery, and it started first press of the button....NOT!

Pulled the rocker cover off...valves were all timed correctly and clearances in spec.

Dismantled the back of the bike and pulled the carb...all looks OK. Looked down inlet port...no bird nest or anything else to be seen.

Round to the front...pulled the exhaust an looked up the exhaust port. All black and sooty, like you'd expect, but there are funny yellow stains coming from around where the valve stems go up into the top of the head....and, there's water. I think it's water rather than coolant, and the coolant level in the rads appears to be where it always is.

It's a swine to get to just to look, never mind photograph...but I've done my best
You can see at around the 8 o'clock position

Any ideas...collective wisdom of the forum?

I'd guess that the yellow marks are some sort of oxidation from standing. In theory the only thing that can leak passed the exhaust valve or guide is oil and even if a waterway was cracked it wouldn't matter because the fuel/air mixture has already fired. The exhaust gas temperature when it's running will be 1,000's of degrees which would just vaporize any moisture.

First off I would check for a spark.
If the plug sparks then spray some easystart through the air filter to see if it fires.
If it doesn't fire on easystart then look at the ignition timing, the valves may be timed correct to each other but if the flywheel has slipped the ignition timing will be wrong and won't fire.
If it does fire on easystart you know everything is good inside the cylinder regarding valve/ignition timing so the problem must be before the inlet valves so carb/air filter. First place to look is the pilot jet/emulsion tube recess in the bottom of the float bowl, when left unused the lacquer in the petrol can seperate and go hard in the emulsion tube chamber.

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.

if the exhaust port is black and sooty, could the mixture be too rich?

got to be the carb, surely?

choke not working or stuck?

air inlet to mixture blocked?
check mixture screw?
vacuum pipe loose?

rubber diaphragm above main jet perforated?
float needle sealer washer leaking giving flooding to float chamber?
check float height?
pilot jet still gummed up .. try a new one? .. or clean ?

clean petrol tank several times? fit in line filter?
clean out petrol lines?