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A question i can not answer.

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MrDavo:
My late K1 (engine 111xxxx) has the 18T sprocket, no sign of a chain guard ever having been fitted. I saw one one for the first time on a mate's CB750 diecast engine last week, it looked as if it was made from armour plate.

The engine and frame numbers on that one are 103xxxx, according to John Wyatt's book that makes it a Dutch market bike, assembled after the Uk 101xxxx series and not a (so called) K0, which start at engine 1044848. It has the four separate carb cables.

Trigger:

--- Quote from: MrDavo on December 14, 2016, 03:35:07 PM ---My late K1 (engine 111xxxx) has the 18T sprocket, no sign of a chain guard ever having been fitted. I saw one one for the first time on a mate's CB750 diecast engine last week, it looked as if it was made from armour plate.

The engine and frame numbers on that one are 103xxxx, according to John Wyatt's book that makes it a Dutch market bike, assembled after the Uk 101xxxx series and not a (so called) K0, which start at engine 1044848. It has the four separate carb cables.

--- End quote ---

From Triggers knowledge and experience, 103xxxx is a K0 and I have a shed load in for re builds from the states  ;)   

K2-K6:
Yes there's not much clearance on a chain guide of that type. If there was too much gap it would still allow the chain pins to get onto the top of the sprocket teeth. �
The guide is usually the same thickness as the sprocket, or close to it. It has to fit between the inner chain plates to get it close enough to the sprocket teeth to be effective. If the chain can get up on top of the teeth with chain guide in place, failure will take the chain guide and the cases with it. There's obviously a lot of torque pulling the chain through there as it's got the full inertia of the bike pulling it.

Interestingly, a new chain with the pitch matching the sprocket pitch will never run up outside the sprocket teeth, you have to have the chain with a lengthened pitch to achieve it. So really coping with a worn chain is the purpose as I see it. I guess if they got more favourable geometry by going up a sprocket tooth,  then they could delete one production's item and at the same time reasonably offer a longer mileage cure for chains in service.

MrDavo:

--- Quote from: Trigger on December 14, 2016, 04:15:43 PM ---From Triggers knowledge and experience, 103xxxx is a K0 and I have a shed load in for re builds from the states  ;)

--- End quote ---

My mate only has Wyatt's book to go on, so this will be useful info for him. He got the bike in bits and knows little about it, other than it's not a sandcast, and too low a number to be a K1.

ETA: @ Trigger - We may be talking at cross purposes here Graham - when I say my mates bike is 'not a K0' I mean it was an original CB750. This whole 'K0' thing confuses the hell out of me. My original 1970's parts book has numbers for CB750, K1 and K2, and photos of each. At no time does it mention any model called the K0, and nor does the manual in Ashimoto's drop box. I'm sure I've read there was, as far as Honda were concerned, no such thing, though just to be awkward Wyatt claims it was an interim thing that they made a handful of. I know we all call anything pre K1 a K0, but as I understand it 'Original CB750' would be more accurate.

Trigger:

--- Quote from: MrDavo on December 14, 2016, 05:11:01 PM ---
--- Quote from: Trigger on December 14, 2016, 04:15:43 PM ---From Triggers knowledge and experience, 103xxxx is a K0 and I have a shed load in for re builds from the states  ;)

--- End quote ---

My mate only has Wyatt's book to go on, so this will be useful info for him. He got the bike in bits and knows little about it, other than it's not a sandcast, and too low a number to be a K1.

ETA: @ Trigger - We may be talking at cross purposes here Graham - when I say my mates bike is 'not a K0' I mean it was an original CB750. This whole 'K0' thing confuses the hell out of me. My original 1970's parts book has numbers for CB750, K1 and K2, and photos of each. At no time does it mention any model called the K0, and nor does the manual in Ashimoto's drop box. I'm sure I've read there was, as far as Honda were concerned, no such thing, though just to be awkward Wyatt claims it was an interim thing that they made a handful of. I know we all call anything pre K1 a K0, but as I understand it 'Original CB750' would be more accurate.

--- End quote ---

Yes, you are correct. The whole K0 thing was invented by the yanks, who also have F0 in some bike units.
The 103++++ engines are a little different than the K1 units. I always call the 103++++ a original die cast engine with a rough finish to the casings and the oil jet has the strainer on the back.

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