1967 CB450K0 Black Bomber Rebuild - By Royhall

[royhall]

Forgot to mention that I checked all the sprocket part numbers and they are all the same from K1 to K7.

[royhall]

Ash. The hub diameter is 1.651" and 1.647" on the worn surface. The bush diameter is around 0.837" although it's hard to measure with a telescopic gauge due to the oil scroll.

[Bryanj]

4 thou is way more than enough to cause the missed starting problem, if you could get some made you could get the grear slightly ground till true and use oversize diameter rollers.

From memory, on 750,  there is only just over a thou in difference between the deep end of the slot and the shallow end of the slot the roller sits in which would suggest anything over a thou wear is too much

[AshimotoK0]

I just measured two that Jason (Woodside) sent me last week to fix a unit for him and they are both on the upper size you gave Roy or more. I really need too take to work to measure though, as my larger micrometer was last calibrated in 2002  ... Interesting that on one of them, you can deffo feel undulation, where the rollers have indented the surface. I will also take the DK sourced one to work to measure and report back.

How about the  outer clutch part Roy ..is that OK? Item 7

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[royhall]

There are indents in the outer but until I assemble it with a good sprocket it's hard to tell. My hub looks very smooth it's just very even wear that you can actually see by eye, defo shot.

[Bryanj]

Way back when i used to have to repair the odd 750 and several 500 twin you could see the gear looked like a threepenny piece(only more facets) whilst new were like a crankpin grind

[AshimotoK0]

Way back when i used to have to repair the odd 750 and several 500 twin you could see the gear looked like a threepenny piece(only more facets) whilst new were like a crankpin grind

Yes you are dead right Bryan.... One of the ones Jason sent me is like that and the one I just got from DK, I just checked and is almost as smooth as a crankpin. My original one is like Roy's ... smooth but obviously worn down BER.

[AshimotoK0]

Here you go Roy the largest diameter one marked with a * is the one that has the Bryan 'three-penny' bit type wear.  You can just about make out the indentations if you look closely at the surface of the hub.

The smallest one is obviously for the early starter clutch.

I will measure the later one from DK tonight for you.


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This is the picture close up of the fooked alternator rotor from my 1967 Bomber. Definitely thin tabs and all the way to the outer edge i.e not stepped in.


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[royhall]

Thanks Ash. So I'm missing between 8 and 13 thou off my hub then, no wonder it doesn't work. Just got to try and find one now. I don't think the K0 rotor thing will ever be proven one way or the other, are you sure the Bomber hasn't been uprated at some point. The two small diameter rotors check out with part numbers etc, I wonder if Honda did a Delta part number at the end of the K0 life and changed it to the larger unit to avoid warranty claims. They have history for that stunt.

[AshimotoK0]

If you want to borrow my complete assembly from DK to suss out what wrong I am prepared to loan you it Roy. Don't really want to unscrew the staked c/sink screws though.
 

[Bryanj]

You would need some old price lists to prove that, if you looked up a price and the part needed other modified bits it used to tell you "Must be used with *******" one of the gears in the 500 is like that where the tooth profile changed

[royhall]

Thanks Ash that's very kind of you. Unfortunately if I can't unstake it I don't think it would help. Last night I found a guy in USA selling the two sprockets and chain for a 72 CL450, he says it's in good nick but he has nothing to measure it with. As it's only £45 including postage and import charges I thought I would risk it. Looks okay in the pictures so here's hoping. Comes early January so I will leave it alone until then. Just hope the outer is okay.

[royhall]

You could probably polish out the three-penny bit marks on the hub, I wouldn't use it like that. Just been reading a post online saying that chatter pushes the metal into tiny peaks that will eventually grab a roller and bend the cap and spring. Once that's happened a roller is held against the revolving hub whilst the engine is running which results in the 10 thou ish wear seen on mine, and also produces a very smooth surface that tricks you into thinking the hubs okay. When I stripped mine originally there were two bent springs and caps so that is probably what happened. He went on to say that ultimately it will grab the hub hard and bend the securing screws and snap off the rotor lugs. I also found slightly bent screws and a very oval dowel hole in the rotor. I think that may be what happened to this sprag clutch as mine fit that scenario perfectly. More ham fisted previous ownership.

[AshimotoK0]

I think I  tracked down that sprocket hub you bought in the States Roy and it looks fairly good from the photo's .....  so fingers crossed.
I agree the PO was  ham fisted but in the case of the starter clutch on the K0 Bomber.... every one of them seems to be fooked unless they have been changed for the later parts or the engine is ultra low miles. You see lovely condition bikes for sale at prices around 7k and it says 'electric starter disconnected' ...we all know what that means.

That theory on the indents sound right...the hub from my bike was very smooth but the wear was horrendous in terms of reduced diameter. I reckon Jason's one with indents had effectivily 'grown' in diameter at the high points created.

As a backup .. Graham Curtis has a scrap sprocket hub of mine and is looking into machining it down and shrinking on a  sleeve and grinding it back to the ideal diameter.

[royhall]

The parts finally arrived from the USA and the sprocket hub measures 1.661" and looks pretty good condition. There's no wear lip on it and slight chatter marks which indicates it's not too worn. So braved the weather yesterday and got it fitted.

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I fitted a new gasket to try to ensure I'm not going in there again. Not sure what it is with these bomber gaskets, I used a different make this time as the NE ones have all been too big. For some reason this one is even bigger but fits well otherwise. I have trimmed the outside down with a scalpel so I suppose it's better too big than too small. I'm wondering if the Bomber casings are slightly smaller than the K1 onwards items. That may account for it, and another thing to watch out for later. As you can see, a slight slip-up has caused a bit of minor damage to the paintwork which will have to be patched up when the weather is warm enough for painting.

Result, the starter now engages really well and spins the engine at a good speed with plugs in. That has been a difficult problem to overcome due to the complete lack of parts available. My plan is to use this bike in the summer so with that in mind I am starting to collect a box of spare parts to keep it on the road. At the top of that list will be replacement starter/alternator parts as they become available.

As my other bikes in the garage have been reluctant to start in this cold weather (although they all did) I think I may postpone trying to start the Bomber for now as I need to warm it up fully to strobe the timing and that would have to be done outside. No thanks, way too frosty for that I think.