Topic: Serial number and drive chain/sprockets

[Jay]

Hi everybody,

I'm very new to this forum and to motorcycles. I'm learning a lot, but now I'm stuck on a couple of issues and I'm hoping somebody here can help me.

I've bought a cb750 K7 a couple of months ago. It was leaking oil and I've replaced the top end gaskets. The problem seems to be fixed, so this issue is over for now (thanks to the very useful posts on this forum).

1)

The bike has the wide K7 fuel tank and the frame serial number is correct for a K7, but I'm wondering about the engine serial number. The engine serial number is CB750E-2541654. Does this mean it is an F1 engine?
This page seems to confirm this: http://www.hondachopper.com/engine/engine_timeline/timeline.html


2)

My second question is about the drive chain and sprockets. When I bought the bike it had a 630 drive chain on it with the standard K7 front sprocket (15 teeth, 10.7 milimeters thick). http://www.jtsprockets.com/catalogue/model/495

I've read on this forum that the front sprocket of a K7 is held on with a washer and a center bolt (instead of a retainer with two bolts like the other models). The K7 parts list confirms this. However, the front sprocket on my K7 was held on with a circlip in the groove of the shaft. I've checked the parts lists of several models and there never is a circlip to hold the sprocket on the shaft. The shaft on my bike does have a hole in the end (I think 8 milimeters wide), but the hole doesn't have a thread to screw a center bolt in.

Parts:
- K7: http://www.cmsnl.com/honda-cb750k7-four-general-export-kph_model14388/partslist/E16.html#results
- K1: http://www.cmsnl.com/honda-cb750k1-four-european-direct-sales_model14361/partslist/E21.html#results

My pictures:
- front sprocket and circlip: https://www.dropbox.com/s/prm4dk8kckq5804/2015-04-30%2021.17.28.jpg?dl=0
- shaft with groove and hole: https://www.dropbox.com/s/uaq4f6azw5r4yaa/2015-04-30%2021.17.54.jpg?dl=0

Do I keep the circlip on? Is this safe?
And why isn't there a thread for the center bolt?
Could I buy a 530 chain and sprocket kit (as for the K1-K6 models) and install it on my engine with the circlip (and no retainer)?

Thanks for your help!

[flybox1]

Welcome to the forum.  What country are you in?
Im unable to view the photos in dropbox.

I would not trust a circlip to hold my front sprocket on.
Ive only seen/used the 8mm bolt, lock washer, retaining washer, (#18, #25 in the CMSNL diag) and adequate red locktite.

[calj737]

He's Belgian, Fly

[flybox1]

He's Belgian, Fly

Are you Carnac the Magnificent reincarnated?   

[Jay]

Belgian indeed 

I've changed the links to the pictures. A circlip doesn't seem very safe to me either, but why isn't there a screw thread?

[Powderman]

Engine number looks like F6 motor. Motor could have a F or an E in the number.

[calj737]

He's Belgian, Fly

Are you CalNac the Magnificent reincarnated?   

FTFY, Fly 

[flybox1]

He's Belgian, Fly

Are you CalNac the Magnificent reincarnated?   

FTFY, Fly 

Haha...my bad. 

[scottly]

That engine is definitely not a K7; the seal on the counter-shaft is flush with the case, while the K7 protrudes outward, and the shaft has no groove. What someone has done is install the K7 630 sprocket on the earlier motor, and secured it with a circlip as it lacked the threaded holes for the early style retainer. The K7 front sprocket and rear sprockets are mounted about 10mm further outboard than earlier models, so an early motor in a K7 frame causes a 10mm misalignment, as is evident from the side wear on your sprocket. You can get either an off-set front sprocket, an off-set rear sprocket, or fit an earlier sprocket carrier onto the K7 rear wheel.

[Jay]

You're right, the rear sprocket doesn't align with the front sprocket. It's clear with the chain guard off and with the front sprocket just passed the groove in the shaft:

https://www.dropbox.com/s/b490ps0rf4y58ir/2015-05-01%2018.04.24.jpg?dl=0

I guess it will be easiest to install a 3/8" off-set (outward) 530 front sprocket with an early style retainer.

Something like this: http://cognitomoto.com/products/17-tooth-3-8-9-5mm-offset-sprocket-for-cb750-cb550-cb500t

I hope I can find one nearby 

Thanks!