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?

[Oddjob]

Yeah it's a casing split to replace that one AFAIK, not the expert on the 750 as some members on here, didn't like them back in the day, still don't like them, I avoided working on them whenever possible. Not saying the 750 is a bad bike, far from it but I thought the 500 was a far superior bike and I concentrated on that model in preference.

[Johnny4428]

For what it’s worth definately worth splitting and whilst in there checking everything all cogs, dogs, bearings etc. Also phobia about lateral movement in that fifth gear, which in my case I had to shim to take out about >1.5mm, doesn’t sound a lot but when you’ve only got 3mm of insertion 2/3 into 5 cog it’s too much as I found out to my cost.

[Martin6]

Thanks. I've removed the chain and the front sprocket rotates freelywith no noise. I've removed the sprocket and confirmed there is no lateral movement in the final drive shaft. The shaft looks quite clean and sharp machined castellated edges.

So, I am relieved. I can’t afford a strip down at the moment. I want a season to ride the bike, find any more issues and then, maybe next year is the renovation year, if needed.

A picture of the front sprocket and retaining plate is attached. I will replace these, new chain and tab washer. Rear sprocket looks fine.

On a 1976 made K6, is it a 520 or 530 chain, I think it's a 520? 102 links? Can't find it in the Honda manual.

[Bryanj]

That sprocket is definately worn out, put up a pic of the rear wheel sprocket before you buy any thing as a kit can be cheaper

[McCabe-Thiele (Ted)]

I agree with Bryan that front sprocket shows quite a bit of wear - in my head they become more spikey with mileage. It's a little used technical term I've learnt.

[Martin6]

That sprocket is definately worn out, put up a pic of the rear wheel sprocket before you buy any thing as a kit can be cheaper

Picture attached. Where would you recommend for decent quality chain and sprocket sets?

[Bryanj]

It may be the pic and resolution but the teeth dont look even to me so i would change both, as to where to buy thats a minefieldi prefer not to give advice on because a fantastic chain for a steady rider may snap with somebody else, i would stick to DID or maybe RK.
Visualy looks like 530 to me which is the old British 5/8x3/8 so try measuring between pins and width of roller, i also thought all the 620 front sprockets were held on with a central bolt but its been over 40yrs since i did one so no guarantee.
You could try looking up the parts for your bike at cmsnl it should tell you there.

[Bryanj]

Adition to above i have bought from www.motorcycleproducts.co.uk (incuding the lock plate)


Further to that you need to trawl through all the pages as you will find the same things at different prices on different pages, also do oil and ail filters, plugs,etc

[Martin6]

Thanks Bryan. I called Jason the Chainman. He did my excCommando chain. It is a 530, he got me to measure the old one, to confirm. Now on order.

I'll search online to get the sprockets.

👍

[Bryanj]

You will find them on the site i gave you with several variations of tooth count, and the lockplate if you want it