Topic: When did airbox change??

[techy5025]

At what point/serial number did the airbox change from the colored
plastic one to the black one?  As a second question... when did the
tach red marker move from 8500 to 8000? A search here did not
yield any answers.

The bike in question is in the 750-1029000 range and I can't decide
if all the parts are correct.

I seem to have lost the url of the website that had a lot of these type
of details....but the experts here always do 

Jim

[Bob Wessner]

I believe the changes you are asking about occurred with the K1, for sure the airbox color. The K1 started with frame numbers 1044XXX, so yours should be pre-K1.

[techy5025]

Thanks Bob,

I think this bike has some new...almost correct parts.  I agree with
you about the airbox...not sure on the tach.  hmmmmm

Maybe I will look at it again.

Jim

[Bob Wessner]

I took another look at some material I have, in Mark Haycock's book it verifies that the tach redline changed from 8,500 rpm to 8,000 rpm with the K1. At the same time, the construction of the instruments themselves changed from acrylic materials to metal cases with actual glass lenses. I have a CB750 (aka K0) that is mostly correct save for the airbox and a K2 tank.

[techy5025]

Bob.

Thanks for the research.

This is the bike in question...

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=4614885232&sspagename=STRK%3AMEWA%3AIT

The tank should have black badge color rather than white...I think it is a K1 tank.  Also it looks like the baffles are missing
from the pipes, wrong airbox.....and didn't all the K0's have a cut (not rolled) front edge to the front fender?

This is a local bike and, even with the faults, looks pretty good.  I haven't been able to coordinate with the seller to
inspect it, but he is a good salesman on the phone. 

Jim

[Bob Wessner]

I couldn't find anything specific about the rolled vs. cut fender. I know it changed from one to the other, but I don't know when (e.g. during the K0 run or between the K0 and K1). I downloaded the pic from the rear and enhanced it a bit. The baffles are there and they appear to be correct. I can say it is in better shape than mine. Do you know what the engine ser# is? Good luck with the bidding.

[techy5025]

Bob,

I don't know what the engine serial number is yet.  Would also like to look at the guages
and a few other high ticket items.    It looks pretty good though.

Thanks for the help.

Jim

[Bob Wessner]

It looks pretty good though.

Jim,

I agree. Let us know how it turns out.

[Bob Wessner]

Jim,

Took another look at the pictures for the auction, the instruments appear correct in terms of their construction.

[techy5025]

Bob,

I agree.  He has no face shots so I can't tell if they are the original plastic lenses
or the K1 glass....could tell by the tach red range.

Also can't tell if it has the short chain guard.  Need a touchy/feely here. 

Jim

[Bob Wessner]

I went through "play detective" on mine as well. I believe the gauges are correct because the lenses appear flush at the edges. I believe the later glass ones had a rim/lip to hold the lenses in place. I don't think it has the short chain guard though. The only shot is through the rear wheel and it looks like the back tip of the gaurd extends out to the rear too far.

[Ted Nomura]

At what point/serial number did the airbox change from the colored
plastic one to the black one?  As a second question... when did the
tach red marker move from 8500 to 8000? A search here did not
yield any answers.

The bike in question is in the 750-1029000 range and I can't decide
if all the parts are correct.

I seem to have lost the url of the website that had a lot of these type
of details....but the experts here always do 

Jim

Your bike is a 1970 CB750 model which should have the original non-ribbed colored airbox.
The true CB750KO serial numbers are: Frame# CB750 1044826-1044947 and Engine # CB750E 1044848-1045145. There were only 121 of them. They had CB750K1 carburators but it's not certain if they carried the original CB750 air boxes. Any CB750s before that number are either 1969 0r 1970 CB750s although American Honda misidentifies them as CB750K0s. Any CB750 after that serial number that starts with "1" is a CB750K1 model.

[techy5025]

Well, the guages were correct...forgot to look at the
chainguard.  The bike is in very good shape.

Unfortunately, I didn't win the auction so booooooooo.

I still want another K0 and there will be others.

Jim

[techy5025]

Well....too bad....got outbid by the Orange County Chopper guy whose starting a museum. Not
quite sure why he wants a diecast...with his money I would think a "sandcast" would be better.

Oh well.

Jim

[dusterdude]

figured he would be dumb enough to pay 5 grand for that bike

[Magpie]

Dumb like fox I think.