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Discussion Starter · #1 ·
hi - yesterday, I helped my girlfriend change out her points oil seal on her cb350 - she was having the same symptoms as me (oil leaking into, then out of the points housing) and replacing that seal did the trick for me. of course, replacing that seal involves knocking your valve tappet clearance and timing (and point gap??) out of whack. so after we got the seal replaced and reassembled everything, we started doing a tune-up. while doing this, I found such similarity (in a bad way) to my tune-up that I want to reach out for some help here. I'll start with what I know....

point gap has a range of .3mm-.4mm - timing is set by adjusting both the point gap and the orientation of the points baseplate (with a range of maybe 30 degrees or so). I heard a tip from a local cb350 owner that you can use the points baseplate to get the timing on both sides as close as possible, then mess with the point gap until you get the timing right, as long as those are within the tolerance range (.3mm-.4mm) - here's what I've found ....

on both her bike (1970 cb350 - pretty much entirely stock) and mine (built from a '72 and a '73 cb350 with pretty much everything questionable about it) I had to turn the points baseplate as far counter clockwise as it would go to get the timing even close. with that baseplate oriented straight up, timing is very early on both sides and turning it counter clockwise seemed to move it later but then I would hit a point where I could turn it no further and then use point gap dial in the last bit. with the point gap, I keep finding that I'm very close to the lower end of the tolerance (.3mm) - in fact, the only way I could get the timing correct on the right side was to put the point gap closer to .25mm. on the left side, the gap is just over .3mm.

my concern is that I've got these two ranges (baseplate orientation and point gap) and that I've got both of them pushed completely to their extreme values (and one even outside of the acceptable range). what am I missing? I would assume that the baseplate orientation and the point gap would be (based on the law of averages) somewhere near
their median values in most cases, but I've found that with both of these bikes I need to set these to an extreme. given that the constant here is me, I have to assume that it's me and not the bikes.

in the end, the bike doesn't appear to be leaking oil and was drivable .... to a point - after she drove for about 4 miles the bike starting backfiring and stalling. I'm going to go take a look at it now and see if something moved out of place due to vibration (or heat). if anyone has any advice, I'd love to hear it.

thanks
 

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Discussion Starter · #4 ·
This guide looks very helpful - thank you

How can I tell if my spark advancer sleeve is 180 degrees flipped? There's a notch in it and on the thing it mounts to, but they don't line up .....
 

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superwesman said:
How can I tell if my spark advancer sleeve is 180 degrees flipped? There's a notch in it and on the thing it mounts to, but they don't line up .....
If you know you're on compression stroke, the advancer lobe should be somewhere in the area of the point "foot". If it's way off, maybe it's 180 out. Try rotating 180 and see if that does it.

If the gaps and plate rotation are at extremes, then something's goofy - try new points, first of all.

The procedure at my web site goes into things to try when it don't work....
 
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