Triumph Rat Motorcycle Forums banner
1 - 3 of 3 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter · #1 ·
Anyone able to help me when common sense fails... trying to get my 67' bonneville running and having a problem getting the spark right... Common sense tells me the points need to be closed until the valves have received gas and ready for a spark.. problem I've having is actually getting the points closed and figuring exactly when they need to open.. The cam is an oval that basically opens twice a revolution...there is a mark on the cam that looks like a guide to indicate proper place to fire...As far as closing.. they never seem to fully close when not on the cam's oval peak...I've moved the base with the little screw and even shaved the plastic contact piece.. If i shave it anymore it won't touch the cam at all. Also how many time should one cylinder fire in a rotation??? Always when the valve is closed?? Sorry for the description of the problem, but any help would be appreciated...
 

·
Registered
Joined
·
54 Posts
There are timing marks on the assembly at the end of the crankshaft, the first step is to figure out how to read them (I think your bike is a bit different from my mid-70s vintage in the way all that works, but mine has a pointer and the alternator has scribes in it). You want the points to be just beginning to open (the plastic sweep is JUST making contact with the cam) at full advance when the scribe closest to TDC is aligned with the static reference in the case. I found the notch in the cam to be useful for putting a screwdriver blade in to force the cam to full advance.

You have three basic adjustments on the points-- the rough adjustment, which allows you to rotate the whole assembly a few degrees, and then the fine adjustments for each point (where you loosen the point's holding screws slightly, and then twist the adjustment cam). The gap adjustment affects ONLY the grounded, static contact on each point (the one that is not attached to the sweep with the big spring and wire and all). There are notches in the end of each of their assemblies that you can use to pry them back and forth when their retaining screws are loosened. They do not have an "adjustment screw", so what you may be doing is moving the fine-adjustment for the point rather than adjusting the gap. These might be a bit sticky from just not being moved in a long time, and you might want to just slightly loosen all the screws in the points assembly and make sure the parts are moving freely.

The sequence I generally use is:

1) Set points' gaps
2) Set each point's fine adjustment cam to the middle of its travel
3) Set the crank to the appropriate timing mark
4) Set the rough adjustment for the first point so the sweep on the closed point is just making contact with the cam lobe with the cam fully advanced and tighten down the screws (I may fine-adjust the first one if it's slightly off after I've tightened the points assembly down after the rough adjustment, but that's usually not necessary).
5) Rotate the crank a full revolution, back to the timing mark, adjust the second point using its fine adjustment.

You shouldn't have to shave the sweeps at all. I think your gaps are probably wrong and you just need to get more aggressive at moving the gap assemblies. If the gaps are correct when the points are open but they just never close and the sweeps always stay in contact with the cam, you may have a worn-out or improperly modified cam, since it has to allow enough travel for properly-gapped points to close.

Each cylinder should fire once per complete rotation of the camshaft, when both valves on the cylinder are closed (only intake valves are closed on the exhaust stroke).

Scott
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #3 ·
thanks scott

Thanks so much for your reply!!! It was very informative...I'll do those steps and see what happens....Again thanks you for your help it is very appreciated...
 
1 - 3 of 3 Posts
Top