Topic: cb750 crankshaft bolt

[Z0wner]

Hey guys. I posted this (http://forums.sohc4.net/index.php?topic=53027.0) thread not too long ago.
In the process of removing my alternator rotor I stripped the crankshaft bolt and the crankshaft... I'm having a heck of a time finding the thread / pitch for the bolt. Does anyone know what the size is?

When I measured the bolt, I got 12 mm with 28 threads per inch, but that does not help because those tap and die will cost me $300... So, I'm hoping I measured wrong...

[HavocTurbo]

Sounds to me like you have the metric diameter and the SAE pitch...

If the bolt is salvageable take it to a local machine shop and see what they say. Otherwise get yourself a metric thread pitch gauge and give it another go.

I'll see if I can find anything in the parts books.

[754]

First off, you only need a tap, just get a new bolt.

Didya kick the "mechanic" in the nutz yet , that "helped" you out

If you have a calculator, divide 1000 by 28.. should be in the neighbor hood of 36 or so.. then divide that by .03937.. that will give you the metric pitch.

 Soon someone will come up with proper measurement. OIff the top of my headI am thinking it is a 16mm thread or so.

 KBC has a large quantity of odd pitch taps in metric, probably under 100 bux, probably your cheapest out.

 make sure you grease the tap, and dont send any buddies to the "mechanic"

[HavocTurbo]

lol suuuuure stick in some math.

Good advice on the "mechanic".  

[MRieck]

First off, you only need a tap, just get a new bolt.

Didya kick the "mechanic" in the nutz yet , that "helped" you out

If you have a calculator, divide 1000 by 28.. should be in the neighbor hood of 36 or so.. then divide that by .03937.. that will give you the metric pitch.

 Soon someone will come up with proper measurement. OIff the top of my headI am thinking it is a 16mm thread or so.

 KBC has a large quantity of odd pitch taps in metric, probably under 100 bux, probably your cheapest out.

 make sure you grease the tap, and dont send any buddies to the "mechanic"

That's funny.

[754]

Sometimes machine shops have oddball taps or maybe a hi-perf sportscar shop will have the tap you need.

I am guessing you just buggered the first few threads,  I think that they are fairly long, sometime you can just relieve the  first few bad ones, and you are in business.

 Good luck, dont rush, it will happen.

 Sounds like the pitch is maybe .75

 When pulling the rotor with the right tool, these threads are not touched..

[Z0wner]

All right, guys. Thanks for the quick responses... man this forum is awesome.

Got a hold of some proper measuring tools.

looks to be 12 mm x 1.00 pitch, which is something cheap and easy to find!
Threw on the 28 thread/in standard size for kicks, and it is close...but starts shifting over after 10 threads or so.

Yeah, didn't kick him in the nuts...but wish I would have... even though he'd probably never need them.

[754]

1.0 should be extremely close to the 25 TPI guage..