SOHC.co.uk Forums > CB750
Some Minor Issues to Sort
Martin6:
I did a slightly longer ride today, gaining more confidence! The harsh ride becomes evident above 40mph, in any gear. It smooths out over 65mph.
The K6 has a later design of fork. It takes 155cc to 165cc of oil, about 50cc less than the original forks. It's not immediately obvious in the Honda or Haynes manuals. I guess it is possible previous maintenance might have been to the original fork oil quantity specified. Would too much fork oil give harsh riding symptoms like this?
I re-checked the rear wheel (I recently re-built) and it still seems true and spokes tensioned. Chain seems OK. It spins nicely without any lateral play in the bearings and the rear brake is smooth. So i think the used, replacement hub is fine. The chain is not in the first flush of youth, but doesn't particularly lift off the rear sprocket. Tension is there-abouts. So, in my mind, I've ruled out rear wheel and chain.
I do notice, when I spin the wheel, a ticking sound from the front sprocket area. A quiet rhythmic ticking, like the old Sturmey Archer bicycle gears, when they freewheel. The sprocket is tight, it's not particularly worn and the chain runs smoothly on it. The shaft the front sprocket is on has a small amount of lateral movement, 1-2mm maybe. The ticking is coming from within the engine cover (inside the gearbox?). Is this all normal? If so, I'll concentrate on the front forks.
Thanks, Martin
Oddjob:
Ticking sound then when the wheels spun but the drive cover is off?
I'm a little concerned about the lateral movement on the final driven shaft. In theory there shouldn't be any, the shaft is pressed onto the large sprocket bearing behind the oil seal there, that's normally locked into the crankcase with what's called a setring, this locates in a groove inside the crankcase and so in theory the shaft isn't able to move laterally. Are you pulling the shaft or the sprocket?
The front sprocket can cause some problems if you buy cheap, it's essentially a castellated hole that slides onto the drive shaft, this is then locked in place by a fixing plate, that locates, spins 90 degrees and bolts onto the sprocket. If the sprocket is a cheap make it's been known for the castellations to deform, so that the sprocket moves on the shaft forwards and backwards, better make sprockets use harder metal and they tend not to do this for much much longer, by the time they do the teeth are buggered anyway. Check the fixing plate for wear marks, if that's worn it will allow the sprocket some lateral movement, the sprocket shouldn't be rigid, it has to have a small amount of freeplay to adjust to the drive chain angle as it lashes about but it shouldn't be a great deal. Is the front sprocket maker marked?
Martin6:
You're right. It is the sprocket moving laterally on the shaft. The shaft is solid, no lateral play. The sprocket has no rotating play on the shaft, when attempted by hand. I didn't remove the retainer that's bolted into the sprocket. I couldn't see any manufacturer stampings. Does that all seem right?
Getting quicker at taking the cover off!
Oddjob:
You may not get the movement on the sprocket with the chain still attached, best to check this with it off the sprocket. Also remove the fixing plate and check that and also check the sprocket again then, it's a bind but it's the best way to check for problems. Plus you an spin the drive shaft with the chain off and see if the ticking sound is coming from that, could be the bearing making the sound.
Martin6:
Thanks Oddjob. Makes sense. I've not yet taken it apart. From what I can hear, it could be a bearing noise. I will have a better look tomorrow, I was wary of damaging the locking tabs on the fixing plate.
If it is the bearing, there's a seal behind the sprocket and then the bearing. Is this the "final driven shaft" (fig. 5.18 on pg 70 of the factory manual)? It looks like it would need to have the engine case open to replace that bearing?
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