Timing 1936 Model 18

The difference between 38 and 42 is too small to matter. If it were mine i'd set it at 3 /4 btdc and mark a paint line at 5/8. You can then easily retard from the more advanced setting but if it is set a bit retarded you cannot do anything about it on the road. With the big long stroke single cylinder the piston drop is good enough.

Are you sure you are timing at full advance?

It should be a brisk performer!

Regarding valve timing... Both of the settings you describe are symmetrical so they amount to the same thing. Good luck!t

Hi John,

Getting the timing spot-on is dependant on the compression ratio and the fuel you are using. There have been a couple of threads on timing pre war engines over the last 2 or 3 months so sorry if I am repeating myself. If your mag is the original it will betight wire advance. So to set the timing it is best to use a degree disc, but you can measure it through the plug hole if you can get an exact measurement. With a disc you will need to remove the primary chain cover and fit the disc between the engine sprocket and its nut. Find TDC through the plug hole and fix a pointer next to the discso it readszero degrees. Make sure you are on the firing stroke by checking both valves are closed. Next pull the advance/retard lever back as far as possible and make sure it stays tight. Turn the engine backwards at least 45 degrees then turn the mag anti-clockwise (viewed from the points end) so the points are just opening (a cigarette paper is the norm to measure this) and then drift the mag sprocket home. This should hold tight while you tighten the nut. If you measure the advance through the plug hole 45 degrees equals 5/8ths inch. AsDavid says you can go more and adjust the lever for best results.

While you have the disc set up you can check the valve timing. With open valves this is quite easy as you can put a feeler gauge between valve and tappet and get an accurate reading. You will find it difficult to get the timing exact because of the design but a couple of degrees either way will be O.K. You should be looking for around 25/25 degrees overlap and a general rule of thumb is the smaller the overlap (20/20) the more flexible low speed running will be, and a larger overlap (30/30) will give better top end performance. With standard cams anything outside of these the engine willstruggle. After setting all the above fit a new plug as an old one can fail under compression. Let us know how you get on.

Regards, Richard.

If you decide to check the ignition timing via the plug hole, John, make sure you use a measuring device thin enough to go in nearly vertically as the plug hole is at about 50deg to the horizontal which will affect your measurement. 5/8" at 50deg is about 15/32" vertically.

Conversely 5/8"vertically is about 13/16" at 50deg.

Clear as mud!

George

To be sure you're on the compression TDC the pushrods should both be free to rotate. Also, if you put your thumb over the plug hole & rotate the engine forwards you'll feel the compression.