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Topics - leadnavel

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CB750 / Problem with initial valve adjustment after rebuild

« on: May 23, 2022, 10:39:48 AM »

I've been rebuilding the Engine on my 750 K7 (77) and i'm trying to set up the valve clearance, this is where i'm having the problem! When I try to set up the valve timing by the book - set the "T" mark for 1.4 with cylinder 1 at TDC and the key groove towards the top - I should be able to (if I'm reading things correctly in the workshop manual with the "O"s and "X"s diagram) set the valve clearances for INLET and EXHAUST on No.1, EXHAUST for No.2 and the INLET for No.3. This is my problem, i'm finding that I cannot set the clearance for cylinders No.2 EXHAUST and No.3 INLET as they are on the cam!

What am I doing or have I done wrong? I hope that someone out there can can advise me on what to do to put it right. I've been searching the forums but i'm either not putting the right search terms in to get a result or it's to simple an error on my part that it's not referenced! Any help that you guys could give would be muchly appreciated.

Also to note that when I rotate the crankshaft 360 to set the remaining valve clearances the same problem occurs. I can set the clearances (INLET & EXHAUST) for Cylinder No.4 but the INLET for No.2 and EXHAUST for No.3 are on cam and cannot be set!

Engine rebuild info...

My bike had previously been running. On strip down I backed off all the adjusters so I didn't have a reference from them as to where the adjusters should be. I bagged and tagged everything. Is it possible that I tagged some rocker arms incorrectly, could I have put them back in the wrong place?

When installing my camshaft/cam sprocket on the top end rebuild I had No.1 and No.4 cylinders to top-dead-centre (TDC) and aligned the "T" mark on the spark advancer also aligning the Timing index line so it was parallel to the top surface of the camshaft holder with the key groove was towards the top, so i'm thinking that I did everything correctly with the camshaft installation.

CB750 / Oil Pump 750K7 - Are the rotors wrong way up/down?

« on: January 18, 2022, 09:24:47 PM »

I have a quandary, do I leave things how they are or do I flip the rotors to the workshop manual orientation?

On stripping down the oil pump on my 750K7 to renew the seal and O-rings I noticed that the rotors have been installed the wrong way up NB: when taking off the end cover of the rotor the ‘punch marks’ are not visible, they are on the underside and facing downwards!

This is where things get a bit more confusing, I was hoping for more clarity when I bought a second oil pump.

The rotor surfaces on my oil pump looked a bit marked/scored so not knowing if this was serious (I have subsequently found out that the light scoring on the my original rotors isn’t terminal so I will use my original pump) I bought a second hand K7 pump, primarily as a replacement and potentially for spares. I have stripped the pump and if a spare is not required will rebuild to sell on. On stripping down this second pump I also found that the rotors have also been installed with the ‘punch marks’ downward!

This is my quandary, on reassembly should I leave things as they are and insert the rotors ‘punch marks’ downwards or flip them and install as per the manual? My workshop manual does mention the the punch marks it says “Install the rotors with the puntch mark facing to the outside”. My Haynes manual does not mention punch marks on rotors at all.

My bike has 36'000 Miles on it and was working fine before strip down, although, FYI, the bike has been off the road since 1985, the engine strip down was started in 2019. I don’t know the history of the replacement pump.

Any advice on this would be welcome.

CB750 / Where are the front brake stop switch cables?

« on: January 24, 2021, 12:18:58 PM »

Can anyone tell me where I can find the cable connections for the stop switch for the front brake? In case other 750 variety's differ my stop switch is attached to three way joint. Is there a spur coming from the main wiring loom or does an extension come from the cluster of cables in the headlamp? Any assistance would be much appreciated.

CB750 / Swinging Arm Bush appears to be a non standard size, why?

« on: October 12, 2020, 05:56:47 PM »

I’m a good way through my 750 K7 rebuild and thought that I would replace the bushes for the swinging arm as the end of one of the existing units are a bit knarled (image attached), here’s the problem, the replacement bushes from CMS (part number:52108-457-300) measure up different from my existing bushes! The inside diameter of the new bushes measure 21.80mm, the inside diameter of the old bushes measure between 21.39-21.40mm. In short the new bushes have a larger inside diameter than the old ones, so it’s defo not a ware issue!

I have questioned the part with CMS and they assure me that the correct part has been sent for the K7. I have also measured my existing Center Collar which measures between 21.34-21.38mm at the bush ends. I’ve had the bike since 1983 with very few modifications to it and she’s been off the road since 1986 (27’000 miles on the clock) so very few parts are worn. Does anyone know what’s going on here? Luckily I haven't taken out the old bushes as I would've been right up dump dyke!

CB750 / Should I reassemble the clutch like this or flip and move the plates?

« on: April 27, 2018, 08:29:05 AM »

Any help you guys can give on this would be much appreciated.

I'm part way through a rebuild of my 78 K7 and am unsure if I should reassemble the clutch plates in the order/orientation that I found them? I've read quite a few posts on here and on the US site regarding the orientation of the plates but haven't found an answer. All the metal plates have a round edge and a flat edge and must all face the same direction but as you can all hopefully see from my image the two steel plates below the double-steel plate (the plates in question sit closest to the engine casing if that helps) are flipped to the opposite 'flat edge' direction! Should I flip them to the norm? I have also read on a post that the double-steel plate can be moved to the top of the stack but I can't find the post that mentions the reason for this.

The engine has been sitting idle for 30+ yrs and time has clouded my memory as to whether I was getting problems with the clutch when it was last on the road.

CB750 / Would you use these piston rings?

« on: February 23, 2018, 11:22:32 AM »

Hi guys your help would be appreciated with this dilemma. I'm continuing with my first 750 K7 engine rebuild, 32 yrs after removing the engine from the frame. The engine has been sitting without oil in it for all this time but I have been sticking some oil into any open engine holes over this period and hand cranking it to keep things moving. I'm in the process of stripping and cleaning the oily rust from the exposed surfaces and am unsure if would be OK to use the old piston rings as they have various markings on them, are these markings/stains normal. Although they look iffy all the rings feel smooth to the touch! What do you guys think?