I think my lemans 2 is increasing pinking under load and is also beginning to run a little rough feeling like it is firing one side better then the other. has been running well though I suspect a little lean. I am generally filling with super unleaded. To make it richer in general motoring do I need to alter the main jet? Am I right in thinking there is no adjustment to the mixture above tickover? The plugs are evenly a mid to dark brown colour. Â it also labours when pulling away at low revs
Out of interest have you had the valves recut? If you haven’t I would strongly advise that you do.
As for pinking in my experience that’s mainly down to the timing being out. Get it sorted though or you could wind up, like I once did, with a large bill for a new pair of pistons. The land between the rings fractured under the duress of the pinking.
If you have a decent dyno service near you then ask how much they charge to set up your bike. You may be pleasantly surprised with what they can do. My local is Dynotech & they’re very, very good.Â
Simple things first, have you checked ignition timing. I assume it’s got twin contact breakers. These do go out of tune and need to be checked and if necessary readjusted occasionally. The LM’s are a bit advanced anyway being 8 degrees BTDC at idle (fully retarded) which is a mite excessive IMO, a bit too far and unpleasant vibration ensues and possibly pinking as you describe.
If you still have the bog standard jet sizes then no shouldn’t be necessary. UNLESS jets are getting partially blocked. There is no sharp division between jets etc. in a carb, but a wide amount of overlap, so in fact idle mixture screw can still have an effect possibly beyond half throttle.
Retarding the ignition timing a bit will most likely help with the slow speed starts.
Will have the tank off tonight and distributor cover off. Am planning to fit my new electronic ignition purchased a few months ago and go from there. Didn’t do it earlier based on the don’t fix what ain’t broke philosophy. Have a few friends locally if I get stuck.
