Topic: Spark advancers - how are they heat treated?

[turkey2143]

Does anyone know how these were heat treated from the factory? I'm trying to have one drilled out to 8.5mm (the diameter of the shaft on a CB650) in order to fit my 550/650 hybrid (http://forums.sohc4.net/index.php?topic=40414.0), and it might make me happy to know that I won't have to spend $100 on a carbide drill bit to chuck onto a lathe.

Or if that's too tough of a question for the community, has anyone ever drilled one out with a cobalt drill bit? Paulages would be the obvious gentleman to ask, but I'm going to wait a bit before I PM him.

I had originally drilled it out to 8.75mm (my machinist had a carbide bit on hand), but that was too much slop between the crankshaft's right-hand side stud and my spark advancer. This caused my timing to be wayyyy too advanced and I'm surprised I made it 1600 miles on my build.

Thoughts, bantering, insults; it's all good.

[crazypj]

Mount a dremel  or die grinder in toolpost with small grinding burr.
 Even if you use a few stones them it will be a lot cheaper than 100 dollar bit

[KingCustomCycles.com]

They can't be too tough, those ears break off in a heartbeat if you wrench on the big nut..........

[turkey2143]

That's kind of what I thought, until I read this: http://www.motorcycleproject.com/motorcycle/text/sohcign.html

"Its hardened steel design completely eliminates the need for lubrication that was the..."

I don't want to make a machinist angry by breaking his drill bits.

[KingCustomCycles.com]

Whole article sounds like a load of crap with a few kernels of good advice hidden in it.  Others may disagree.  I will go drill a busted unit with a stock bit and tell you how it goes...........ttyl

[KingCustomCycles.com]

OK, no drill bit I own will touch it.  I have no idea on the Rockwell but a premium bit will be in order.

[turkey2143]

Thanks for checking

[754]

 Shim the first one. Carbide drill should be way under a hundred bux.. You could bore it with a carbide tool boring bar. but its probaly a bit deep..

[754]

 Turn down a rethread the stud.. or build a custom one..

[dave500]

while your at it find true tdc and calibrate your advancer,heres the slack you can find,this is at true positive stop tdc,you can be a couple of degrees out either way with all of these units,dial it if your fussy.


i havent got the centre bolt in,,this is the backlash in this unit for one and ive even seen slightly worse,so where you lock it up is a gamble if your not on true tdc.