Topic: Early K0 primary sprockets - which one is it?

[Magpie]

Hi!
I have several primary sprockets unfortunately the K0 motors I have didn't come with sprockets. My parts book says it should be a 16 and the illustration shows a flat sprocket. I have a 17 tooth like that and an 18 tooth with shoulders on it. The 18 tooth will go on the output shaft but the retainer will not go on far enough to go in the groove on the shaft. I've learned the hard way not to force it. The flat 17 tooth will go on but has a bit of sideplay. The other consideration is the early ones had 16 tooth sprockets and many had chains break. I think this smaller sprocket may have helped the chain breakage.
Wii the 17 be ok even if it has a bit of play?
Thanks,
Cliff.

[Johnie]

Cliff...on my KO I went with the 17T with the shoulders. However, when I ordered it from Honda it came without the shoulders. I sent it back and got the 17T from Yamiya with shoulders. Why? Well, my original had the shoulders and the flat one made the chain off center. Hope this helps...

[GammaFlat]

I'm not a K0 expert (I do have some reference hardware, however), but I believe side play is normal on K6 and prior.  The K7 and K8 have a weird shaped washer that holds the sprocket firmly on the shoulder of the output shaft.  The output shaft is definitely different on K7/K8 compared to K6 and prior.  If you need pics, I can dig them up. 

John

[Magpie]

Well to complicate things further I have a 17t with the shoulder on one side. I didn't try it but I think I better. Questions is - does the shoulder go inside or outside? Hopefully there's a mark where the keeper was. All these questions!
Cheers,
Cliff.

[Johnie]

Well to complicate things further I have a 17t with the shoulder on one side. I didn't try it but I think I better. Questions is - does the shoulder go inside or outside? Hopefully there's a mark where the keeper was. All these questions!
Cheers,
Cliff.

Cliff...my OEM came with shoulders on both sides. That brought it to center. But if I were to use yours I would put the shoulder on the inside to center the chain better. Just a side note, don't forget to put some blue Locktite on the 2 small bolts that hold that front sprocket in place.

[754]

Shoulder to inside, I am thinking..
Not having a shoulder wont throw it out of tolerance..IMO..but I have ripped the middle out on a  non shouldered at the drags.. which then welded itself to the shaft..so now I know.. you can re & re in an evening or less than a day..1 run at a track we drove hours to get to, and one start where it broke as I left the light..



Speaking of out of line... I was so pleased to obtain a low miltage 77 wreck 750. I put the nice motor in a 72..

and ran it for a long time...


and then one day while oiling the chain, I noticed..


wear on one side of the sprocket..

and same but opposite side on the other..hmmmmmm


 Thats how I found out, they had a longer shaft...


 My buddy had a nice black F motor, he wanted to run in the future..at first he did not believe the shaft change, so I showed him.. he was so pissed, he odered a brand new early style shaft, split the cases of a very nice F motor and installed it.. probably around 81 or 82.. probably has not yet used the motor..which now wont fit in a stock F..

[kos]

Hi!
I have several primary sprockets unfortunately the K0 motors I have didn't come with sprockets. My parts book says it should be a 16 and the illustration shows a flat sprocket. I have a 17 tooth like that and an 18 tooth with shoulders on it. The 18 tooth will go on the output shaft but the retainer will not go on far enough to go in the groove on the shaft. I've learned the hard way not to force it. The flat 17 tooth will go on but has a bit of sideplay. The other consideration is the early ones had 16 tooth sprockets and many had chains break. I think this smaller sprocket may have helped the chain breakage.
Wii the 17 be ok even if it has a bit of play?
Thanks,
Cliff.

Exactly...one of the primary reasons for chains breaking on the early CB750's was the 16T front sprocket.   If fact they did not eave enough room at the front where the C/S was located. In a real world with room not being a problem. 18-19 would be better with the corresponding larger sprocket on rear wheel to make for correct final drive ratio.

Another reason for chains breaking was that chain technology was not up to the state of the arts... newest  and first Superbike ever massed produced.

I was working in the Honda shop during these times and it was not the bike that most of us mechanics wanted to see come in the door.

[Magpie]

I went out late last night and tried the shoulder on one side sprocket and still not enough room for the keeper so the flat one will have to go on. My parts book says a change to the final drive shaft was made at around 3527, this is engine 260, so it may have a shorter shaft. The play is from the keeper being a bit sloppy in the groove it sits in.
I'll be sure to use the blue Locktite here.
Thanks for all your replies! I love this forum!
Cliff.

[Johnie]

As I recall my new 17T did hit on the inside of the cover. So I just had to grind a little bit out of the tang area that stuck down and it was fine.

[754]

Cliif, your motor probably had a few unique parts.. there was a complete case change around 221 I think, the crank change around 1100 or 1300..alternator bolt size.. lots of changes in the first 3000.

 I spent HOURS poring over my parts book and found that pre 1300 sandcast had around 20 parts or more, that were not on the last sandcast..

 This is very significant, as say for a early CB 500 the 10th bike has the same parts as # 4000.. the same holds true for most bikes. a Z-1 for example, is mostly all the same, throughout the first model year.

 This was simply not true on the sandcasts.  They are not a matter of getting a part that fits, rather it is getting the Correct part that fits.. and a lot of them are not correct. All of which makes a restoration far more difficilt than most Japanese bikes..

[Magpie]

754, I kind of had an idea of that when I was looking at this motor and hesitated at first. But, I didn't want to let it pass by and be upset with myself forever so here I stand............parts book in hand.
Johnie, the 17t doesn't hit the cover so it's ok. Interesting that I have another K0 sprocket cover and with it on, the gear change cover and the sprocket cover don't match where they meet. The sprocket covers edge sits out from the gear change cover. The earlier sprocket cover is much thinner. As 754 says, lots of subtle changes.
Cliff.

[Johnie]

Cliff...just for reference my KO is a 1/70 built with engine #1020821.

[Magpie]

Hey Johnie!
My K0 is a 12/69, frame number 1016113, engine 1016446, and using sandcast 260. This was a very sad K0 when I started although the engine was not seized much to my amazement. Many of the early parts had been removed. I'll clean up the die cast engine as well for shows as a display. Maybe I'll even find a low numbered frame in my travels!
Cheers,
Cliff.

[ekpent]

Cliff you already bought my K0 swingarm when are you going to take the rest of the frame 

[Magpie]

Is it between 1000200 and 1000300? 
Cliff.

[ekpent]

I WISH 

[Terry in Australia]

Shoulder to inside, I am thinking..
Not having a shoulder wont throw it out of tolerance..IMO..but I have ripped the middle out on a  non shouldered at the drags.. which then welded itself to the shaft..so now I know.. you can re & re in an evening or less than a day..1 run at a track we drove hours to get to, and one start where it broke as I left the light..



Speaking of out of line... I was so pleased to obtain a low miltage 77 wreck 750. I put the nice motor in a 72..

and ran it for a long time...


and then one day while oiling the chain, I noticed..


wear on one side of the sprocket..

and same but opposite side on the other..hmmmmmm


 Thats how I found out, they had a longer shaft...


 My buddy had a nice black F motor, he wanted to run in the future..at first he did not believe the shaft change, so I showed him.. he was so pissed, he odered a brand new early style shaft, split the cases of a very nice F motor and installed it.. probably around 81 or 82.. probably has not yet used the motor..which now wont fit in a stock F..

That's interesting Frank, Mick asked me the same question recently and I went out to my garage and compared a K2 shaft to an F2 shaft, and in actual fact, the K2 shaft was slightly longer. Interestingly enough though, the output shaft bearings were in two different locations on the shafts, which might account for the later shaft apparently sticking out further, so I'd be interested to see if an early shaft would work in a later engine? I'll post the pic I sent Mick when I get home tonight that compares the two shafts/bearing positions, etc. Cheers, Terry.

[754]

There are 2 diff bearings up to 76.. not sure if  that means 2 shafts to 76.. if that is true, then he may have used  mid shaft.

[Terry in Australia]

Here you go Frank, the shaft on the left is out of my F2, and the one on the right is from my K2. The gears are a different pitch too, and won't mesh, so their opposite numbers would need to be changed too. Cheers, Terry.

[bryanj]

If you look at where the sprocket would sit on those pictures its nearly the same as the F2 is heald on with a boly and big washer whilst the early ones had the keeper plate and 2 small bolts