Topic: 78 CB 750k chain guard cover plate question

[veritas723]

Hello,   fairly new here. 

recently bought a 1978 honda cb 750 k...  the previous owner mentioned it leaked oil.   chain is coated with oil... so i'm thinking best first place to look is the self oiler on the counter shaft sprocket.  (then maybe the tubes back there that feed the oil tank or atmo tube... really just hoping it's not a crack or hole in the engine case)

The metal chain guard cover plate (was missing one screw... dunno if that's a bad sign)   won't wiggle free of the frame.     

Was attempting to remove the mission guard plate(the plate over the gear shift lever...  but one of those screws was stripped.    my logic was,  without that plate... be easier to free the chain guard plate. 


So...that's my question.   Do i have to remove the mission guard plate (not sure if that's the right word for it... it's what it's called on the parts list) to get the chain guard plate off?   


thanks to anyone who answers... 

[Erny]

Well... To my knowledge '78 750 does not have "self oiler". I have K7 750 and it does not have it. From' 77 Honda introduced O ring chains (630). '78 shall have the same engine and is it almost the same bike as' 77.

But still, if you want to acess sprocket area, yes, you have to remove that bloody plate (called COVER, L. RR. CRANKCASE https://www.partzilla.com/catalog/honda/motorcycle/1977/cb750k-a-750-four-k/starting-motor-crankcase-rear-cover).
It is possible, but might not be easy for the first time, you have to turn twist to get it out. But way back can be even more challenging. I was fighting too. Hope don't need to touch it in near future

[madmtnmotors]

LOL, you guys are going to make me shoot a video of this, aren't you? I, too, struggled with my K8s and F2s front sprocket cover in the beginning. During one of my sprocket changes I worked and worked and worked to remove the front sprocket cover until it finally lifted out without any undue effort. WTF??!!! I had to keep reinserting and removing the front sprocket cover repeatedly (and effortlessly) until I had committed the movement to memory. You do not have to remove the transmission cover, and I never have, other than to replace the transmission cover gasket and/or shift shaft seal. You can also replace the countershaft (output shaft) seal without removing the transmission cover. This question comes up from time to time and I usually have trouble describing the movement in words, at least based on the exasperated replies I receive, but I'll give it another try:

The shape of the rear of this cover, as well as the shape of the frame in this area, make it appear as though the rear of the sprocket cover should swing out to clear the frame first. THIS IS WRONG. Once the two machine screws are removed from the front sprocket cover, the cover then slides straight back towards the rear wheel, following the path of the chain, with the rear of the cover behind the frame tube. Now swing the front of the cover outward while rotating upward at the same time. Do this right and you can remove the front sprocket cover without the cover even touching the engine case or the frame. The first time I did this I failed to commit the process to memory and so much time would pass between removal of this cover that I would forget the next time! Once I focused on the movement and rotation I then kept repeating it so that I would not forget. The first movement of the sprocket cover to the rear, keeping it behind the frame tube, is key. After that, just rotate the front of the cover upwards while rotating the bottom of the cover outwards. It takes me longer to remove the two screws than it does to remove the front sprocket cover. Total process, including screw removal, takes about 30 seconds.

EZPZ 

[rotortiller]

Just play with the chain cover , it will come off. It goes on just as difficult,  it's like a bent wire puzzle once you figure it out. LOL

[754]

 I know of an owner that ground away part of the frame to make it easier..
 And I was like grind the cover, its Easy to replace.
 But good to know there is no need to grind it.
 
In too have probably got it out easy once, and then forgot why.,

[BenelliSEI]

On my K8 (and my buddie’s), the chain cover is impossible to get off, until you figure it out. Then it’s easy. There is no chain Oiler and the sprocket shaft seal may be leaking.

Also check the overflow hose from the oil tank. It’s suppose to connect to a small emissions breather box, but often they are hanging back there. If the previous owner continually over filled the oil tank, it all ends up there. 

[veritas723]

oof. 

first off thanks for the replies.     Appears,like a n00b  have been looking at that parts list for K3,4,5 bikes... which i'm now realizing means it's for older model bikes. 

is there a simple pdf  version of that parts list like there is in the documentation area for the 78/K8 cb 750?    on various parts websites they seem to have the exploded parts diagrams,   but... they chop the part #/spec section off... so you have to look at their info to buy from their site.   Anyone just have this in a straight up pdf?

[Erny]

I'm not aware of such pdf in English. Seen one Japanese but too manz pagodas for me

[the-chauffeur]

Without wanting to sound like a tool, complex machines come with complex diagrams, and since the K bikes went through any number of changes during the 10-ish years when they were made, you probably won't find one simple PDF.  There are any number of parts catalogues available on eBay; whether they're available as PDFs, I don't know, but the originals are about the best you can get.

Failing that, you might want to try looking at the CMSNL website.  Yours can be found with this link taking you directly to their 750 page. Pick yours or the closest to it, and you should see exploded diagrams of all of the bits of your bike.  The nice thing about that site is they have pictures of lots of the parts so you can see what many of them look like in something other than line drawings.

You can also get some very useful information from those lists for things like oil seals and bearings.  They will often (but not always) give oil seals a five or six digit code; that code is the seal dimensions. For example, a seal with the code 26427 translates as follows - 26mm internal diameter (the hole in the middle); 42mm external diameter (the size of the outer edge); 7mm deep.

Since your bike shouldn't have an oiler, it sounds like an oil seal might be your issue . . .

[madmtnmotors]

Okay ladies, hold on to your hats. Here is the 77/78 CB750 F and K front sprocket cover removal video making its worldwide debut:

[Erny]

That's really easy!!
I don't recall how much time I spent to find way how to assembly it back  (after I took it off, what was easy, it stayed dissassembled for few weeks)

MANY THANKS for this video! 

[madmtnmotors]

That's really easy!!
I don't recall how much time I spent to find way how to assembly it back  (after I took it off, what was easy, it stayed dissassembled for few weeks)

MANY THANKS for this video! 

Happy to help. Turns out it was easier to show the process with a video than to continue trying to describe the motion in words.

Piece of cake! 

[spotty]

having now watched the video i can see what i was doing wrong all the time but........

how the hell do you keep it that clean under that cover ? even the sprocket looked brand new

i have been grime shamed

[madmtnmotors]

having now watched the video i can see what i was doing wrong all the time but........

how the hell do you keep it that clean under that cover ? even the sprocket looked brand new

i have been grime shamed

LOL! The sprocket and chain are both new. I am freshening up my first K8 and haven't quite finished reassembly, hence the absence of carbs and airbox. Zero miles so far since the "cleanup".

The removal of the sprocket cover is not intuitive, but once you get the movement/rotation figured out it is pretty straightforward. 

[Erny]

If I see well, you "converted" 630 chain to smaller one, correct?
If so what type and sprockets you used?

I regret that I did not do on my K7... 630 is really heavy and makes also quite some noise

[madmtnmotors]

If I see well, you "converted" 630 chain to smaller one, correct?
If so what type and sprockets you used?

You are correct. The 530 front sprocket for the 79-83 CB650 works perfectly. It has the same "single shoulder' as the K8 630 sprocket:

http://www.jtsprockets.com/catalogue/sprocket/JTF338/

Pretty cheap too:

https://www.amazon.com/gp/product/B000N5MTL0/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

[Erny]

Great!

And rear sprocket? How many chain links?

I think I'll make change next year.

E

[madmtnmotors]

Great!

And rear sprocket? How many chain links?

I think I'll make change next year.

E

Rear sprocket is the same as the early CB750's (69-76) that used the 530 chain. Use the earlier models (69-76) as a guide for tooth count. I'll have to count the chain links after I get home this evening. I'm using 16/52 530 sprockets on the drag bike:

[veritas723]

I really appreciate you taking the time to make that video.      hopefully you'll earn some sweet .0001 cents from youtube from my click

[madmtnmotors]

I really appreciate you taking the time to make that video.      hopefully you'll earn some sweet .0001 cents from youtube from my click

LOL! The greater reward would be if the short video saves hours of frustration. Hopefully you were able to free the sprocket cover as easily as I showed?