Motorcycle Repair: timing, emery paper, maximum gap

Question
I have a honda 1970 750four the timing needs to be set but not sure on the settings if you could help i would appreciate it  

Answer
Melanie... some helpful files are on the www.sohc4.us site.
There is more to it than just turning a few screws....

There are a number of factors to be considered when adjusting the timing on a points/condenser ignition system.

Here's a photo of your bikes ignition plate under the chrome cover on the left end of the crankshaft...
http://cyclexchange.net/index%20pics/WEB%20points%20cover.JPG
The little round guys are the condensers....

1. Condition of the point faces and wear on the rubbing blocks that open and close the points.
2. Condition of the condensers.. weak ones cause excessive arcing that causes excessive pitting on the point faces.
3. Condition of the mechanical spark advancer, behind the point plate. Sticking mechanisms will cause improper timing.

Cleaning the point faces with a point file or some kind of emery paper... maybe 400 grit or a fingernail file. Point faces must be clean and free of grit when you are finished cleaning the surfaces.

Point gap settings (maximum gap) are .012"-.016" (factory settings), best checked with an automotive dwell meter when running, so both sides match closely. Once gaps are set correctly, the point opening occurs at the 1-4 F and 2-3 F (firing)marks at idle speeds.

Checking the spark advancer before you begin to set the points will ensure correct spark advance at higher engine speeds. If point cam does not move smoothly from retard to advance and come back to rest the springs may be stretched and/or the point cam needs lubrication inside, between the cam and the mechanism shaft. Be sure to lightly lubricate the point cam surface with "point grease" available at auto parts stores or Harley Dealers!

If you get the point gaps close, then you can use an automotive timing light (engine running) to check the spark timing at idle and at full advance. Match both sets (1-4 and 2-3) to each other and you should be good to go.

Many owner's of older bikes will opt for a DYNA ignition system, which is electronically operated and once it is set properly, there is no further need for maintenance other than the spark advancer.

Bill Silver