Topic: RE: 1975 CB750 crank case dowls how many?

[chewbacca5000]

So what should have been an easy fix repairing a head with a broken plug has turned into a full engine rebuilt after ruining my upper case trying to drill out a broken stud.

Now I am rebuilding the whole mess.  I need to know how many crankcase dowls there?  It appears there is two crankcase dowls according to

http://www.cmsnl.com/honda-cb750k6-four-usa_model14380/partslist/E14.html#results

Looking for confirmation. Yes I know this is a K6 diagram, but the engine I a building is a K6.  I believe the other was a supersport F1 as it had the 392 head.

Thanks in advance!

[Davez134]

I wish I could give you a 100% for sure answer, but my experience is only with k2. I know on the K2 cases there are 2 dowels, along with that large oil collar in the front, and looking at the link to CMSNL diagram you posted it looks to be the same deal as far as dowels go. I don't see anywhere else they could or would go except right behind outer crank bearings.

[chewbacca5000]

I wish I could give you a 100% for sure answer, but my experience is only with k2. I know on the K2 cases there are 2 dowels, along with that large oil collar in the front, and looking at the link to CMSNL diagram you posted it looks to be the same deal as far as dowels go. I don't see anywhere else they could or would go except right behind outer crank bearings.

Thanks Dave,

Just wanted to make sure as I had smashed a dowl and was not sure where it went.  It was a cylinder dowl so I am good there.

One more question do you put 3-Bond / Hondabond on both case halves?  Also, this stuff is drying very, very fast in a few minutes.  I thought I had 15 minute work time on this stuff?  It is a couple years don't know if that makes a difference.  Applied a nice thin coat with a brush.

[Davez134]

Just one side, and yeah gotta work somewhat quick


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[chewbacca5000]

Just one side, and yeah gotta work somewhat quick


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Thanks!  Any tips for laying the bottom case down?  Start with front or back.  What is the easiest.

[Davez134]

Sorry was out for a while at a local vintage bike night, almost melted

I tried to go as "straight down" as possible, but I believe I started more with the front. Keep an eye on position of the shift forks and don't force anything.


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[PeWe]

2 dowels in my K6 case
I had 22mm long dowels in mine between case and cylinder, front outer. Yamiya750 say 18mm, 22 mm between cyl and head which is not possible in my engine. Important to have good lenght in both mating surfaces as long as not bottom out.
http://www.yamiya750.com/index.php?main_page=index&cPath=21_249_54&sort=20a&page=2

EDIT: Or Between the cases?
The holes that need a metal pipe (various names) between and into mating surfaces is visble when the holes for them are specially made. Between cases, case-cylinder, cylinder-head, cam holders-head, engine covers....
I find 3 between cases.