V50mk2 only running on one side

My V50 is only running on the left hand cylinder. It has a good spark and the fuel is getting through. The plug gets wet and there is also oil collecting inside the cylinder head. The compression is about the same on both sides, I have had the rings off and the gaps are within tolerance and it is not smoking. There is no oil collecting above the piston. I have also tried fitting a replacement head but the symptoms are the same. The pushrods are the same length. I don’t think it’s to do with the carbs, the slides are opening at the same time and I have also tried fitting another carb, swapping the cables over etc. The finger of suspicion is now with the cams, I have measured the height of the valves when at tdc and compared to the good side they are a couple of thou shorter when open. Is this normal? If not what are the chances of both cams wearing at once? Is there anything else that could be going on down there? I’ve never had the bottom end apart so am not familiar with anything below piston level. Any advice welcome as I am running out of options.

2 thou variation on cams won’t make any difference. “The plug is wet” - suggests no spark on that side. Or, is flooding, far too rich - check choke plunger is sealing properly. Float height? Float sticking?

Not sure if they will be long enough but Have you tried swapping the plug leads over? To see if the fault changes sides.

Has it always done this or something that has just happened? Did you do anything to the bike that may have affected something?

Are you sure the ignition timing is correct? Try checking it with a stick down the plug and seeing when the spark occurs.

Could it be the electronic ignition? It’s usually the last to be looked at because it’s expensive but going through everything else will cost more in the long run. c.f. my experience a few years ago with the electronic ignition on my Targa - should be on the forum. Good Luck!

Mk II means Bosch ignition units under side panels. Did you swap them? Then, have you had a look under plastic front cover? Pickup points are hidden there, to make sure they’re right you will need to remove both stator and rotor (special bolt needed). But before you start, check pickup wiring too.

You seem to have done a lot of investigation on the mechanical side but don’t mention ignition. Points already mentioned here that are pertinent -

. Was it running OK before this suddenly happened?
. The ign side on the mk II is all separate for each pot. Try swapping things over a bit at a time.

Do not mess with the ign timing, do not do any more mechanical work looking for this.

No more posts for OP since that first one. :astonished:

Fixed it and has been out happily riding ever since.

Got same problem. What was it you fixed?