BMW Einzylinder-Forum
TERMINE und FORUMSTECHNIK => International discussion forum in english language => Thema gestartet von: hotfoot am 10 Dezember 2011, 17:28:00
I fitted another engine, complete with ignition system, to an R25, and wondered why it would not start. I eventually reversed the advance/ retard mechanism so that the cam fitted the flyweights 180 degrees around, and away she went. Obviously, someone had fitted the two parts and springs the wrong way round. Can anyone say what the position of the cam should be in relation to the locating pin on the flyweights? I ask because I think I have the same problem with another bike, my original bike has been sold, and I did not keep a note. It would certainly beat the fiddly job of trial and error!
Hey Footi,
I can`t give you the degrees....but you don't need them too.
The breaker should (all nearly!) open when the piston are on TDC (?)....on working TDC (TDC: I mean the point when the piston is on the top)..working TDC= the valves don't move....if it is wrong....the breaker opens at the "Überschneidungs-OT"...the "wrong" TDC....where the valves are working.
Understand it? If not....because of my english....ask again!
Rolf
If the points open at TDC, that's too late. The points should open at the "S-mark" (not sure what it is on the singles) which is nominally 4-6 degrees before TDC. The governor and the weights open the points even more degrees before TDC as the RPM goes up. There is an RPM where the full advance point is reached...the weights reach the extent of their throw and don't advance anymore. On the /7 twin, the full advance point is around 30 degrees before TDC.
Kurt
Kurt...he should not make a ignition set up ;D....he wants to know if his flyweights are on the right position (and NOT 180° on the wrong place)
The answer seems to be to align the high point on the cam with the peg on the flyweights, and then connect the springs.
Hello hotfood,
as the crankshaft with its flywheel notch is turning 2 times
when the camshaft is doin 1 turn there is a 0° and 180° position
all 2 crankshaft turns. Ignition is fired 2 times every camshaft turn.
Thomas