At present the advance an retard lever and plate at the points end move freely and to their full range but the engine speed doesn't change. After I refitted the Magneto ( tested and good consistent spark) I set the piston 11mm BTDC on the compression stroke, both valves were closed and tappets moving freely. I set the points closed and ready to open all set with full advance ( cable on left loose advance).The bike starts and just about hangs on to idle, open the throttle and it does feel like the timing isn't quite right. Have I missed something? I'm about to go through the process once again but the advance and retard not changing the engine speed is something I need to understand first. Any advice would really be appreciated.
Does your advance/retard cable attach to the magneto on the side next to the cylinder or the opposite side? If it is next to the cylinder the ignition is fully advanced with the cable tight, if it's on the opposite side then the ignition is full advanced when the cable is loose. Apologies if you already know that.
Hi, the cable is on the points end of the Mag and on the left ( engine side ). It's definitely slack advanced. It should be the other way for a war bike but its obviously had a post war Mag fitted. When it was previously running advanced was 100 percent lever forwards.
Yes, you are correct, I just rethought that and slack cable is full advance. Sorry for talking rubbish. The only other thing I can think of is checking the contact breaker gap is between .012"and .015". I usually set to 13 thou.
Not talking rubbish at all and so appreciate your comments. I set the points to the manual which I'm sure is wider than you suggest so I will definitely give that a try. Thank you again.
Hate to be guilty of stating the obvious but you have checked the timing after tightening the pinion nut havent 't you. In my experience tightening the nut almost always results in the timing giong off and having to do the whole thing again. It's pretty hit and miss for me, sometimes I get it first time, other times it can drive me mad for an hour!
this is the definitive article on the subject. http://wdbsa.nl/ignition_timing.htm
good luck solving the problem.
Yes, I tapped the pinion in gently, wound the nut on slowly finger tight and then it won't move, I also had my hand on the points to feel if it moves and further to that I marked the points just to be sure. I really was as meticulous as I could be, that's why I'm stuck. Thank you though!!
I would invest in a Stroboscopic Timing Light.
Then you could paint a mark on the cush drive and the crankcase with Tipp- Ex or some such, run the engine, and advance the ignition and see if the ignition is actually advancing. If it is, you could then use a protractor to mark perhaps 35 or 40 degrees on the cush drive and accurately mark TDC, making sure your Degree mark is BTDC and not ATDC.
I hope you are rechecking the timing after you have fully tightened the drive pinion nut, and turning the engine in the correct direction of rotation?
I wonder if the brass extension on the end of the armature is worn, allowing the points carrier to move? Is your armature coming apart?
Are you using a fag paper to establish the exact opening of the points, and ensuring that you turn the engine forwards when coming up to points opening, to take up the backlash?
It may be that you have very low compression and a weak spark.
Let us know how you get on.