Topic: K6 gearbox problem

[Geoff Hastings]

Hi guys, I've just rebuilt a totally abused and neglected K6, I've done about 60 gentle miles on it and generally it’s running sweet. The only concern I have is a slight random knock at tick over, the strange thing is that the final drive chain snatches slightly with each knock, almost as if it’s not quite in neutral. The only thing I can think is excess wear in the selector fork allowing the gear dogs to touch although they seemed ok. The knock stops if I lean the bike to the right but returns when I lean it on the side stand.

[scottly]

Another case of deja vu?

http://forums.sohc4.net/index.php?topic=86429.0

[bryanj]

Read my post on transmission circlips

[PeWe]

This can cappen when clips on transmission shafts are mounted wrong, flipped
 AND gear shifting has been performed really hard, maybe bike has fallen to left with gear shifting pedal taking the hit, right?
Clip then off, gear can slide causing really bad things....

[Geoff Hastings]

Hi guys, having read the replies I realise what a common problem this is. So,reluctantly, having only done 60miles since the rebuild I pulled the engine back out and stripped the engine. Before taking the gears out I leant engine over towards the drive side and spun the gears. Sure enough there was slight contact between two gears. The thrust washer is missing between the gear and circlip. I should have gone through the parts list when I first stripped it but didn’t expect there to be missing parts. I’m not surprised though, this engine was the most butchered and bodged I’ve ever worked on. I gave up with the cylinder head when the stripped thread count got past 12, I didn’t have that many heli-coils. Thanks for pointing me in the right direction.

[bryanj]

At least you found it before the rear wheel locked. Terry in Australia was doing about 30 when his rear wheel locked solid!!

[PeWe]

Only 12 stripped threads?
My K6 head have thread inserts in all holes, for valve covers as well as cam holders, threads for studs included. I'm sure many tighten these too much.
Honda spec more than it can hold up with.

My old K1 head might have a few cam holder threads not fixed. The alu is very grainy in that head, probably extra brittle threads.
My restored ported K2 head have all threads done, even old repairs with helicoils where screws were hard to fit and loose old helicoils.

Better to fix 5 threads too many than skip 1 in need.

[Geoff Hastings]

Only 12 stripped threads?
My K6 head have thread inserts in all holes, for valve covers as well as cam holders, threads for studs included. I'm sure many tighten these too much.
Honda spec more than it can hold up with.

My old K1 head might have a few cam holder threads not fixed. The alu is very grainy in that head, probably extra brittle threads.
My restored ported K2 head have all threads done, even old repairs with helicoils where screws were hard to fit and loose old helicoils.

I got a replacement head with only one damaged thread for £60, I don’t normally give in that easily but this whole bike fought me all the way. Cracked cases, smashed piston, totally rusty, cracked rear hub etc etc. It really was on the edge of being scrap.

Better to fix 5 threads too many than skip 1 in need.

[HondaMan]

Only 12 stripped threads?
My K6 head have thread inserts in all holes, for valve covers as well as cam holders, threads for studs included. I'm sure many tighten these too much.
Honda spec more than it can hold up with.

My old K1 head might have a few cam holder threads not fixed. The alu is very grainy in that head, probably extra brittle threads.
My restored ported K2 head have all threads done, even old repairs with helicoils where screws were hard to fit and loose old helicoils.

Better to fix 5 threads too many than skip 1 in need.

One of the 'secrets' to hopping up these engines for more torque/HP came from Russ Collins in the 1970s. He started by Helicoiling every engine bolt and head stud, even the cam bearings' hold-down bolts/studs, to get more "grip" on the cases. Then he used HD bolts everywhere. It works great!

[Geoff Hastings]

Just done about 10 miles after fitting the gearbox thrust washer. I’m pleased to say its cured the random knock, amazing how quick you can pull the bike apart without having to deal with seized or snapped off nuts and bolts. Put the bike on the ramp at 2pm, had the engine out and gearbox stripped by 5pm. Ordered the thrust washer from motorcycle spares in Germany, it was here in 4 days. Only down side has been the powder coated frame got a few extra scratches.

[HondaMan]

Just done about 10 miles after fitting the gearbox thrust washer. I’m pleased to say its cured the random knock, amazing how quick you can pull the bike apart without having to deal with seized or snapped off nuts and bolts. Put the bike on the ramp at 2pm, had the engine out and gearbox stripped by 5pm. Ordered the thrust washer from motorcycle spares in Germany, it was here in 4 days. Only down side has been the powder coated frame got a few extra scratches.

You're encouraging me!
I discovered that the oil pool at the left side of my bike (drooling down the kickstand after a run) was caused by a random rock (or similar item) that got between the countersprocket and the engine last year and tore the lip of the seal on the countershaft. Of all the things to have to remove my engine for... 

[PeWe]

How is the chance for that to happen Mark?
Watch out for meteorites!

I have read about people replacing that seal without open the cases nor pull engine. Just remove sprocket, drill a wooden screw or 2 into it and bend it out.
Press in a new. Maybe something to hammer with and correct diam socket to hammer on. Oil surface first must be a help.