Cam timing looking at back of engine of the Saito 90T which is similar to the present day 100T (note the 90TS is a different engine)

Right cylinder top dead center. Cam dot goes towards crankshaft.

Do not turn engine crankshaft!

left cam dot goes towards crankshaft also

The book says to turn crankshaft 180 degrees to top dead center on the left cylinder to set left cam but this leaves the timing of the left cylinder 90 degrees off.

Check your cam timing by observing the overlap period being centered at the alternate TDC position 360 degrees from the TDC compression stroke for each cylinder. At this point one valve will be closing and the other opening but they will both be open exactly the same amount.

The desired result will have two cylinder firing 180 degrees apart and then a coast period of 540 degrees

The 90TS is similar to the 60T with a single cam. They are timed by putting the crankshaft gear mark towards to mark on the case with the accessory cover off the rear of the engine. Then the mark on the cam gear goes towards a mark on the case also.

Here is the present day twin manual. Use the 100T for explanation of the older 90T

http://www.horizonhobby.com/ProdInfo...oke_Manual.pdf