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1967 CB450K0 Black Bomber Rebuild - By Royhall
Laverda Dave:
Looking superb Roy. A great read of a rebuild, keep the commentary and photos coming.
We'll done to Ash for coming to the rescue with the barrels to keep the build going.
This is such a great forum with members helping each other out, great stuff 👏.
JamesH:
Superb rebuild brilliantly explained. Keep it coming Roy..
AshimotoK0:
Looking great Roy and fantastic attention to detail and great explanations.
I was told by a Bomber Guru (who owns quite a few and restored and sold even more) that the 4-speed crank bearings were a carry over from the ones used in the Honda racing engines and that the later 5-speed crank bearings were problematic for the K1 and there were quite a few part number changes before the problem was sorted out.
Hope to pop in for a cuppa (or 'brew' as you guys call it ;D ;D) when myself & Cathy are next over your way.
royhall:
--- Quote from: AshimotoK0 on March 09, 2019, 09:42:00 PM ---Looking great Roy and fantastic attention to detail and great explanations.
I was told by a Bomber Guru (who owns quite a few and restored and sold even more) that the 4-speed crank bearings were a carry over from the ones used in the Honda racing engines and that the later 5-speed crank bearings were problematic for the K1 and there were quite a few part number changes before the problem was sorted out.
Hope to pop in for a cuppa (or 'brew' as you guys call it ;D ;D ) when myself & Cathy are next over your way.
--- End quote ---
Your welcome anytime Ash.
royhall:
Now this is the part where I got all excited and forgot to take some pictures so a description will have to do. When I stripped the engine I found a bit of a mess in the cylinder head. It had a total of 12 stripped threads and a stuck exhaust valve that was very stuck. A bit of a dirty gummed up mess all round.
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I considered getting a replacement head but feared that it may be as bad as the one I have. So decision made, I will restore this one. After loads of penetrating oil soak and a good bit of heat the stuck valve gave up and came out. The other three slid out easily. After a total strip and degreasing the head was vapour blasted, it came up really nice.
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Took the head to the local machine shop guy that I use to have the valve guides replaced and the seats re-cut. Whilst it was there he either Helicoiled or fitted brass inserts to the 12 damaged threads. I took a while deciding what to do about the valve guides as there are a number of different items available for this engine. In the end I went to a fair bit of trouble located the correct for the year Bomber items, as you will see later this turned out to be an error.
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One of the guides is radiused up to a sharp edge and this is the correct part for a 1967 Bomber and the one I used, the other has a plain diameter end and this is for the later models.
The guides were fitted and reamed and the seats re-cut. I managed to source 4 new valves that required virtually no lapping in as the re-cut seats were close to perfect. Thats always a relief to me as I find that grinding in job quite boring. I fitted the valves and re-fitted all the torsion bar springs. The first one I found very fiddly to do in such a small space, but after I got it figured out the other three were quite simple. After cleaning and checking the seemingly endless array of cam chain guide wheels I refitted the parts to the head.
Now were at the point where I forgot to take the pictures, sorry.
I fitted the head using a genuine Honda gasket and oil seals, and torqued it down in stages using new nuts and washers. The cam cover studs look to be at an angle, they aren't it's a weird optical illusion in that picture.
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That is one very tall engine. I have a fairly large monitor on my PC and that picture still needs scrolling to see it all.
The problem with the stripped threads arose from the cam covers being held with 8 plain bolts. The constant removal of the cam covers has simply worn out the threads. As some of the other threads are a bit worn plus the problem of Helicoils coming out with the bolts, I decided to come up with a different solution. In the end I obtained some extra long 6mm stainless grub screws which I screwed into the head to check the lengths. The two sides are different lengths due to the fitting of a breather plate on the intake side. After bottoming them out I checked they were all the same lengths then removed the and cut them down one side at a time.
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You will see the finished idea in pictures later on in the build but basically I can hold the stud in place with an allen key whilst I undo a nut with a spanner. That way the thread in the head is not being used and I can easily change a stud if required. This fix will probably upset the purists but it needs to be functional first, then being correct is a second consideration to me. If it's worn out it's worn out, and at least this way I save the engines correct head from the scrap heap.
More soon.
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