Topic: 1979 CB650 Spark Advancer Locating Pin Diameter

[Joewago]

Hey yall. Rebuilding a 79 CB650. Pulled the spark advancer out of the parts tub the other day and found the locating pin sheared off ... Genuinely no idea how it could have happened. I have the means to drill out the remains of the original pin and install a new one, but does anyone have one laying around that they could measure the pin diameter? Kind of an oddly specific thing to have lying on a shelf but it's worth a shot. I can fudge it by the diameter of the locating hole but if I can get something more precise I'd appreciate it.

[onepieceatatime]

I am sure that I have one, but am not sure when I will make it to my garage to measure.

[DaveBarbier]

Could have been from someone using the little bolt under the ignition cover to turn the motor instead of the left side rotor bolt.

I think I have one too and can check Saturday.

You could see if any drill bit shanks fit nicely in the crank hole. It’s by no means a precision fit, normally it has quite a bit of slop so you don’t have to go nuts. And from what I remember those pins are pressed in the advancer. You might be able to tap the broken off piece out and measure that.

[Joewago]

The funny thing is I don't remember it being broken when I pulled it off... I must have been the one who snapped it lol, probably by trying to turn the crank like you said. But either way, I'll try tapping out the remains in the meantime. Thanks for finding that out for me!

[DaveBarbier]

Ok, I was under the impression you could get at it from the other side. Looking at mine you can’t. Unless I’m looking at the wrong pin.

This is it, right?



I’m getting .118” or 3mm. It sticks out about .102” or 2.6mm.

Hope that helps.

[Nicklopic]

The pin is 3mm in diameter. I have one on the shelf off my 80' and the pin is clean all good so it should be accurate lol

[DaveBarbier]

The pin is 3mm in diameter. I have one on the shelf off my 80' and the pin is clean all good so it should be accurate lol

Ohhh, beat you by 60 seconds, haha!

[scottly]

I've got one that also has a 3mm pin, but I don't know what year it's from. It's stamped 426 and TEC. I don't really have a use for it, so would let it go for cheap if you want it, Joe. Make 3 more posts so you can send/receive PMs.

[Joewago]

3mm it is! Thanks for your guys' help. If I really screw this one up Scottly, I'll probably take you up on that. I made a quick eBay search yesterday and the ones I saw were naaaaasty. But I'm gunna finally get to try the Haas mill in the lab in my college for something it's wildly overqualified for lol. And yeah, I've been lurking on here and the CB650 forums for a grip, I bought this bike almost three years ago, abused it a while, then took it all apart and never put it back together... Being jealous of all the riders that are cropping up in the warmer weather is a hell of a motivator. I'll probably make a project log post sometime.