Topic: HELP. CB750K Spark Advancer Locator Pin Replacement

[Dolomite]

Mechanic called yesterday saying when he was taking apart the starter assembly he noticed the locator pin was missing from the advance assembly. When I was in there last it was to replace the advance stud that had snapped when timing the DynaS, but I swear the pin was there when I reassembled. That was weeks ago so needless to say it's most likely lost to the cosmic winds.

Has anyone had any luck with finding a replacement?l, possibly from another bike that fits it? Or creating one from something like a roll pin? Or i was thinking about finding the base of a drill bit that fits the hole and cutting it to size? Any ideas or if anyone has had to solve this in the past and can offer some insight that would be great.

I've even gone as far as to message the people selling used ones on ebay to see if they come with the locator pin and just buying a new assembly for the pin. But none of the ones I've found come with it. Again, any help is greatly appreciated.

[BenelliSEI]

I found a metric drill bit with a shank size that fit snugly. Cut off a length, with a Dremel grinding wheel (SAFETY GLASSES FOR SURE). Loctite holds it nicely to the advancer. Still working fine....

[Dolomite]

Do you happen to recall what size bit you used?

[HondaMan]

Mechanic called yesterday saying when he was taking apart the starter assembly he noticed the locator pin was missing from the advance assembly. When I was in there last it was to replace the advance stud that had snapped when timing the DynaS, but I swear the pin was there when I reassembled. That was weeks ago so needless to say it's most likely lost to the cosmic winds.

Has anyone had any luck with finding a replacement?l, possibly from another bike that fits it? Or creating one from something like a roll pin? Or i was thinking about finding the base of a drill bit that fits the hole and cutting it to size? Any ideas or if anyone has had to solve this in the past and can offer some insight that would be great.

I've even gone as far as to message the people selling used ones on ebay to see if they come with the locator pin and just buying a new assembly for the pin. But none of the ones I've found come with it. Again, any help is greatly appreciated.

It is easier to just get another spark advancer. They are often available on eBay, among other places. Any of the CB750 advancers will work, although the full advance angle on the earlier engines (K0, K1) was longer than the later ones.

[Dolomite]

All of the advancers I have found on eBay, I have contacted the sellers and they do not include the locator pin.

[seanbarney41]

?...Am I misunderstanding something here?  The pin should be permanently cast or machined in place if I am not mistaken...If yours is missing than it is broken.  And if used parts on ebay don't have it, than they are broken also.

[Dolomite]

The pin is not machined in. It is pressed in, but not tightly. It needs to be removed in order to change it over to a new spark advance shaft or for an electronic ignition

[slikwilli420]

The pin is not machined in. It is pressed in, but not tightly. It needs to be removed in order to change it over to a new spark advance shaft or for an electronic ignition

Never removed mine and im running a dyna. The advance will cease to work without it.

[flybox1]

two of the 4 advancers i have, had a removable pin.  just fab a new one.  ID the holes and mic the depths.  easy.

[scottly]

The pin is not machined in. It is pressed in, but not tightly. It needs to be removed in order to change it over to a new spark advance shaft or for an electronic ignition

Which pin are you referring to, the one that indexes the advancer base to the crankshaft, or the one in the side of the advancer shaft on some of the 750s that retained the point cam? The pin on the side did indeed have to be removed on those bikes to fit Dyna as well as other electronic ignitions that use the stock advance base/shaft. None of those require removal of the pin that locates the base relative to the crankshaft. If this is the pin that's missing, it should be 4mm, although I've seen pins that were only 3mm on some models. 

[Deltarider]

What advancer is it about? Hitachi? TEC? Are they 100% the same?

[HondaMan]

What advancer is it about? Hitachi? TEC? Are they 100% the same?

There are 3 different advance angles (K0 had the most degrees of advance), and half a dozen different spring rates. The ones numbered "AD125-00" (some have different "-nn" numbers) are the most generic type. They Hitachi ones have the fastest advance (weakest springs) after they are heat-annealed. The TEC versions are probably the most common. The locator pin on the backplate comes in 2 sizes (large and slightly smaller diameter), and the hole in the crankshaft is always the large size. Well, almost always...I still remember that uber-special 750 (that was really 700cc) at Mannheim Honda in 1970 that had lots of odd parts, including a spark advancer with a setscrew thru the plate, into the crank's hole...and it was sold as a standard 750, no one knew it was special until it sucked a valve in a street race against a Dodge Hemi one fine summer's day...