63 40hp bigtwin timing

[tich]

According to the manual that I have for my 63 40hp bigtwin it states that in order to check the timing I will require special tool 378966. This lool appears to sit on the shaft arcing over the armature plate and lines up between two marks on the side of the plate if the timing is correct.<br />Assuming that it may be a little difficult to obtain the tool, is there a way in which I can check the timing without it?<br /><br />Regards<br />Tich

 

[Paul Moir]

Re: 63 40hp bigtwin timing

There are two ways. If you look further along the manual it'll say somewhere that you can gap the points to open .020" (0.75mm) maximum. I don't find that this is deadly accurate, so I follow by checking the timing with a timing light. Most people just set the point's gap though.<br /><br />See the two marks on the breaker plate that tool 378966 points between? Now look at the flywheel. There'll be two marks on it near the bottom, 180° apart. These pointers will appear between the two breaker plate marks when the timing is set perfect and shot with a timing light. One mark is for the top plug and the other is for the bottom.<br /><br />You can also use the flywheel like tool 378966, since the marks on it are in the same position as the marks on the flywheel.<br /><br />

 

[Chinewalker]

Re: 63 40hp bigtwin timing

Those old OMC 2-cylinder mags are VERY forgiving. If you gap the points at .020 with the fiber rider of the points aligned with the crankshaft keyway, you should be good to go. It is possible to tweak things a bit more using a timing light, etc., but it rarely results in any improvement in engine performance if all else is in good shape. There is generally so much slop in the mag plates and linkages, that going through the trouble of timing it beyond gapping the points isn't worth it....<br /><br />- Scott

 

[CATransplant]

Re: 63 40hp bigtwin timing

What Paul and Chinewalker said. Just be careful with setting the points and you'll be fine. More critical is the linc and synch routine. Now, that's worth checking, and no special tools are required, just a piece of wire to wiggle when the throttle begins to move.

 

[tich]

Re: 63 40hp bigtwin timing

Thank you Gents.<br />With ref to the "linc and sync" routine that you mentioned CAT. What is the reason for it and,quite simply, how is it done? <br />Tich

 

[CATransplant]

Re: 63 40hp bigtwin timing

Hah! Excellent question. The procedure for it is laid out in the service manual, and I'm not going to repeat it here, since it's quite long and is illustrated.<br /><br />Basically, it's to get the throttle linked up in the right place with the armature plate that controls engine timing.<br /><br />It's not all that hard to do, but it's pretty difficult to describe just in words. Bottom line is that you should try your engine out after setting the points. As long as you haven't removed the armature plate, it should still be at the same place it was.<br /><br />If the engine runs well throughout its RPM range, you can forget about the procedure. If not, or if you want to do it just for grins, you'll need the manual.

 

[Paul Moir]

Re: 63 40hp bigtwin timing

Ah, a picture's worth a 1000 words when it comes to link&sync. This will be helpful to people with Seloc manuals too:<br />

<br />What you want happening is the throttle shaft on the carb to just begin to move when the pointer on the manifold is lined up with the mark on the mag plate's cam. To adjust it, you loosen the indicated screw and turn the little plastic insert seen in the second picture. Like CATransplant said, you can exagerate the movement of the carb's throttle shaft by attaching a stiff piece of wire to it.

 

[tich]

Re: 63 40hp bigtwin timing

Cheers Chaps!<br />Think Ill run the engine first and see what the outcome is. <br />Many thanks<br />Tich