Topic: troubles mounting RC distributor drive

[cbr954]

I am trying to mount a RC distributor to my 970cc motor.  The drive is supposed to use the existing ignition stud that is threaded into the crankshaft using an extended nut.  My problem...I tried it on two different crankshafts and the stud is about 1/4" to short to engage in the extended nut that came with the drive.  The drive is seating up tight against the flat of the crankshaft. Could someone measure how far the stud extends out from the flat face of the crankshaft for me?  I want to see if by some chance the studs I have maybe had been shortened at some time.  If not I will have to look into having a longer stud machined.

[scottly]

On a K7, the stud sticks out 1.815". Just for the record, the sohc650 stud is about .300" longer, and larger diameter, about 8mm, where the stock advancer fits over it.

[cbr954]

Thank you for measuring, I appreciate it.  Mine are both around 1.795" so pretty close to yours and not enough to make a difference.  I might look into finding one for the 650 and have it turned down in diameter as it would be to big to fit in the drive but the length would be just about right.  Now I am kind of wondering how this was ever mounted...something doesn't seem right.  I will have to keep digging.

[scottly]

Does the RC drive have the locating pin that fits into the hole in the end of the crank like the stock advancer? How about some pics of the parts involved?

[cbr954]

Yes it has the locating pin.  It fits in place of the stock advancer.  The extended nut fits on the end of the drive and fits inside to thread onto the advance stud, but it doesn't reach.

[scottly]

Are there threads all the way to the bottom of the nut?

[cbr954]

Yes it is threaded the whole way through and full length.

[scottly]

How deep into the drive does the ID of the counter bore for the nut go? In other words, if the sleeve part of the nut was .250" longer, would it fit into the drive without bottoming out?

[cbr954]

yes I did measure it and there would be room for a longer nut....about .210" longer.  I am just puzzled as to why things are not right.

[scottly]

Any chance the end of the nut had sheared off? What is the OD?

[cbr954]

Nut does not appear to be sheared off, it looks like a factory machined surface.  OD is .390"

[754]

Make sure that pin is not sticking out too far..may have fit one motor but not the next.
 Making the nut is fairly easy if you have Hex stock and a lathe.

[cbr954]

I agree making a nut would be an easy solution if I had a lathe.  Trying to find a machine shop that will bother with this small part is the challenge.

[cbr954]

Little bit of an update.  I have started getting further into getting the distributor installed.  For the heck of it I put the drive on the stock stud making sure it is seated all the way onto the crankshaft.  Then I attempted to install the distributor housing...the housing wont seat against the engine case.  I then removed the drive and again installed the distributor housing..it seated!  So... for what ever reason this drive is too long by about a 1/4" which is the same amount that the advancer bolt is too short.  So today for the heck of it an after my dad lent me his 1974 bone stock cb750 I attempted to install it on his bike...same result.  So the drive itself is too long.  Now...does anyone have a drive laying around that they could take some measurements off of so I have something to compare mine too and see what is out of spec?  If I can get some measurements I will look into having it turned down shorter.