Triumph Repair: auto advance timing, auto advance timing, crank case

Question
what would one do if they have removed the auto advance timing without marking the oreagi of said piece on the crank case cover in order to replace with boyer micro 3 ignition and re-set timing.For 1969,650bsa. thanks jeremy

Answer
Hi Jeremy,
I am not familiar with that ignition system. However total timing is what is critical. Too far advance and you are in danger of detonation which WILL destroy your engine in very short time. Too far retarded will loose horse power and can overheat the engine.

Any time any modification to an engine is made, a new timing is most likely needed.

Low RPM detonation can be heard as "Pinging" sometimes mislabeled as "Valve Rattle" This is often the result of low octane fuel and/or too far advance ignition timing. High RPM detonation is usually not heard so it is most dangerous to the engine.

How to find this ideal timing that is advanced enough to get horse power and not be in danger of damaging the engine is sometimes difficult. The ideal method is with a dyno, but most people don't have access to a dyno. Even though I worked in a BSA dealership I don't remember what the total timing was on most 650 BSAs. I would guess around 42 degrees would be a safe starting point. If you live in a hilly terrain you may be able to find a long straight hill and use it as your dyno. I use to race a 500cc Triumph in AMA flat track and a 650 Tri in TT and raced a 250cc Honda in road racing and I used a straight road as my dyno but that is dangerous and I wouldn't advise you to do what I did when I was young and indestructible. A steep hill would work fine and the speed will be much lower and you can use 3rd gear. The method is to set the timing at a starting point (like 42 deg.) and make a full throttle run and read the tach. Then advance the timing by about 5 deg. and make another run. If you get a higher RPM advance by another 5 deg. If you get the same or lower retard by 5 deg. The point that you get the same RPM or lower you need to retard by 5 deg and consider that as max.

That's about the best I can tell you.
Howard

My 500 tri could handle 42 to 45 deg and my 250 Honda handled 60 deg. Keep in mind that the out side temperature, the grade of fuel and your fuel mixture have bearing on how far advanced you can use. I liked to use one jet size richer than what was just right on the street. Also be sure you use a "Cold" heat range spark plug to make the test runs.