'77 front caliper question

[stou]

The front caliper on my '77 CB750k7 as the bleeder bolt broken. I tried to removed with a bolt extractor it but it is like welded in the caliper. I have 2 questions.

1- Someone know the size of the bolt and the thread pitch? In order to rethread the hole in thecaliper.

2- When I bought the bike, the guy give me 2 boxes of used parts and a second engine. I found what it look like a '75 caliper in the boxes. From what I see, it look in good shape and it look like it can be a bolt-on replacement for the damaged one. What do you think?

The '77 caliper on the right and the probably '75 on the left

 

[Dave]

1- You'll need a replacement bleeder valve, tap the hole to fit it.

2- If you have the "complete" caliper and it fits on, sure.

 

[stou]

A regular replacement bleeder valve will not work. The bleeder was so stuck that I had to drill the bottom part too. So I have ordered a repair bleeder valve like this:

I'll see if it's good enough. If not, I'll used the '75 caliper.

Thanks!

 

[amc49]

You can actually re-drill for a slightly larger bleed screw that is just big enough to cut good solid threads with tap and then re-drill the lower angle carefully using a new drill bit. The casting material is soft enough that tightening the new bleeder slightly over tight will cut you a new seat that does not leak.

The picced part can work but takes quite a bit of material out.