1967 CB450K0 Black Bomber Rebuild - By Royhall

[Bryanj]

 Numbers changes dont surprise me , Honda were trying to cure a known problem

[royhall]

I have finally got to the bottom of the K0 numbers for the rotor. Here we go.

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Neither of these parts fit the sprag clutch that I have indicating that at some point in the past it has been upgraded to the later 5 speed parts. So the hunt is now on for a K1 to K4 rotor, not sure about the K2 as the part number is different.

Just to highlight the difficulty and confusion surrounding this part, CMS have this one up for sale that the part number has as late K0, but from the picture clearly isn't (note the part number at the top of the picture).

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[AshimotoK0]

Not quite sure Roy but  that seems incorrect to me

The rotor with the thicker alloy tabs on the outside has the smaller dia. sprocket hub and was for early K0

The rotor with the thinner alloy tabs on the outside has the larger dia  sprocket hub and used n later K0's and the 500T has the same style tabs

I just bought a later one from early 5 speed CB450 from DK  and it has the thin tabs and the larger diameter sprocket hub.

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[royhall]

No I'm sure it's right. Both the K0 rotors take the smaller sprag clutch. The first one has the thin lugs set back from the outside diameter, the second one has thicker lugs right out to the diameter, but they both have the same internal size. I have had both of these items in my hands to measure and they both came with the remnants of the original Honda box with the part number on them. The one you have as later K0 is a K1 item, the one you have as early K0 is the later one. If that makes sense. You see what I mean about confusion.

[AshimotoK0]

Still confused Roy but I think you are correct about that very early one. However, in your photo the later part labelled the -013 part doesn't look like this?

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[royhall]

Pretty sure CMS have it labelled wrongly.

[AshimotoK0]

My main question on all of this is ...will the later 5-speed complete rotor/starter clutch fit a Bomber? ... These are at least available at reasonable cost used, from time to time, (as I just found when I got a really nice one with the chhain and motor sprocket too for £120 from DK). Seems that Honda went though may design changes on the DOHC twin bikes starter system  but the fact that you find the later assemblies in nice condition but every Bomber assembly seems to be, at least, semi-fooked, indicates that if you can fit the later assembly it's the best option in terms of reliability.

According to Nigel Harris (a member here) .... In a post  HondaTwins in 2009, he stated there that he has a K5 system fitted to his Bomber. I will try to contact him via email to confirm.

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[royhall]

To be honest I think any 450 unit will fit but you need to have the whole kit like you got from DK. Trying to replace one part is full of danger. I think even DK have realised that so they now sell them as a complete unit.

[AshimotoK0]

My original 1967 Bomber rotor is at work Roy. But this is a close up of it ... It had thin tabs (look how bad it is though)   

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[royhall]

That looks stepped back from the outer diameter. If so that would be correct. I think they changed it to the thicker lugs to stop them snapping.

[AshimotoK0]

That looks stepped back from the outer diameter. If so that would be correct. I think they changed it to the thicker lugs to stop them snapping.

But all of the later rotors I have seen have thin lugs including the 500T? I have emailed Nigel Harris and Ray Hull to ask if the later parts deffo fit a K0. I thhought i had read somewhere that the really late rotors dont fit ...something to do with the key-way.

 I think I am going to fit an old crank, barrells and pistons and strarter system to some old crankcases and load the other end of the crank up on a test rig at work .. just to check it out and also to test an early K0 used assemby that's from bits that Jason (Woodside) want for his press bike, from the parts he kindly sent to me.

[royhall]

Just had a parcel from CMS with the latest rotor attempt. Will have a go this weekend and report back.

[royhall]

The new parcel from CMS contains an alternator rotor for the K2 that had the odd part number. As everybody in the know was saying that 68-74 were all the same I risked it. The £200 wrong item has gone back to Silvers for a refund so at 75 Euros plus P&P this one is a big saving.

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Don't know why it was priced differently as it turns out to be the same as the K1 to K4 items, some of which are over 700 Euros at CMS. The best part is it fits my starter clutch perfectly and the timing marks are correct. So that's all a bit of a result really.

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Not sure why but the rotor is stamped CP450 instead of CB450, the CP being the police bike version. First thoughts were that the police bike may have a higher output alternator to deal with radios and lights etc but it measures the same and the magnetism (although not scientific) feels the same whilst pulling a piece of mild steel off it.

So happy days, built up the rotor and starter clutch and refitted to the bike. The hope was that now the starter is correctly held on the shaft centre it would engage okay. I couldn't have been more wrong, it was actually worse. The starter would engage for a short time every fourth or fifth try, so that's a fail then. On stripping down again I found the sprocket drum to be worn about 4 thou, would that be enough to stop it working?

Anyway, after a 4 hour internet marathon I have turned up no parts whatsoever either new or old. Other than sit and wait for a possible DK unit, I am now at a loss for what to do. DK told me about a week ago that they didn't have any in stock nor have they got any CB450's in to strip at the moment. Plus there's probably hundreds of other owners worldwide looking for the same parts. I am surprised that nobody has come up with a way of adapting more modern parts to do the job as this problem has been around for a long time.

Any ideas would be most helpful thanks.

[AshimotoK0]

I wonder why that part is dished on the front Roy,compared with all of the other 450/500 rotors I have seen or is it just the illusion on the photo?  Image off CMS is below. I guess it was cheaper because of the surface rust (which is only cosmetic).

The CP Police model has a 360° crank AFAIK.
 
Do you have the figure for the correct diameter of the sprocket part hub that you need?


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[royhall]

No it's definitely not dished Ash just an illusion. I miked all dimensions and it's the same, although miking a strong magnet was interesting. Is the dimension you need on the sprocket the part that engages the rollers, I will measure it this afternoon. It has a step worn into it at the rollers edge so I will measure the diameter there. I'm in old school English money though. Thou's will never be beaten.