Honda CB 250 RS Clutch issue dragging I think

[CMXCol]

Hi all

I have a problem with the clutch I think it is the clutch
Symptoms are
A gear grind going into 2nd or first from neutral I can 'force it in but I don't want to do that in case it causes damage to gears.
Engine revs markedly drop when clutch is applied.

What I have tried

Changing the springs
Changing the friction plates
Steel clutch plates are flat as an accurate stright edge no warp
Clutch is correctly assembled

I have tried two differnet clutches the original and the replacmenet which was a second hand spare.
Both baskets had some grooving on the basket faces but not too bad so I gently cleaned slight burrs off.

I suppose it is possible both baskets were bad?
Oil is correct 10/40
Oil level is correct.
Clutch is assembled correctly as per Haynes manual.
I have tried adjusting the cable up and down

I am stumped any ideas what else it could be?
Is it possibly a gearbox issue?
Any ideas or if anyone has seen this behaviour before appreciated!
It's a head scratcher indeed?

[McCabe-Thiele (Ted)]

My first thought is are you sure the clutch cable is in good condition & routed correctly?

[CMXCol]

New cable it moves freely so not that but thanks

[Laverda Dave]

Is the clutch operating mechanism correctly assembled in the clutch side cover with the spring the correct way around and not broken?
Have you compared the new cable with the old one to check inner and outer cable lengths are the same and did you have this issue with the old cable fitted?
If you have tried two clutches and the problem is the same I would guess it is something in the gear selector mechanism, pretty easy to check on these.

[McCabe-Thiele (Ted)]

 You have probably tried this but worth mentioning.

Assuming you have a center stand, with the engine at idle or just above, , have you tried engaging first gear, as there is now little  load on the wheel it should not cause any damage. As the rear wheel rotates, put on the rear brake with the clutch lever pulled fully in.

If the engine stalls on braking or the rpm drops significantly this should mean the clutch is not fully disengaging.

[CMXCol]

Laverda Dave and McCabe

I will try both and get back with the results
I am beggining to think it may be a selector issue as I can push the bike in 2nd with the clutch pulled in there is a lttile resistance far more than in neutral but it's not too difficult to push.

[CMXCol]

Update

The selecter drum see attached pic with gear selector cap in neutral position it appears to have a lot of play on it.
Clockwise or anticlockwise about 10 degrees i.e noise it makes a dunk dunk sort of noise, LOL
Clutch test on stand no dragging so it's likely not that.
I think the gear selector forks are either damaged or incorrectly fitted somehow or the drum is worn or possible a shaft bearing or the selector rings on the shaft it takes a bit of effort to get it to change gear fortunately I have some spares for these items and a main shaft in good condition so it's looking like I'll need to split the gearbox and check it out.
A few days work I'll post the results once I have got it split.

[Skoti]

Good luck with the gear selector problem.

I've just had a close look at the photo, if that's silicone sealer visible please don't use it on your Honda engine because it's liable to block the oil feed passages to the camshaft and cause it to seize in the cylinder head, can also choke up the oil pump strainer gauze with predictable results.

Try to clean all traces of the stuff away when you split the engine, reassemble with new gaskets, spotlessly clean and dry gasket joint faces and you'll have a nice safe oil tight engine.



 

   

[CMXCol]

Got the issue definitely gear box there are two problems shown red arrowed see attached image

1.The gear selector fork arrowed is not standard I have one off a spare shaft and that one looks like the one on the left not th eone arrowed the correct one.
2.The split ring is missing off the bearing I had to order one from CMSNL only place I could find one its a common classic honda part the 400/4 uses it as well

When I changed the selector fork and reassembled the gear change is smooth when I turn the drive shaft by hand and the shift selectorr shaft has little play clockwise or anti clockwise.
I also suspect this missing split ring may be affecting the clutch as this shaft has the clutch on it so any axial play even a small bit may have abn effect all that was holding this shaft in place was the clamping force of the two gearbox case halves.
Onc eI get the split ring I will rebuild it it'll take a few days from Holland.

[Laverda Dave]

Whilst the engine is apart I strongly recommend you replace the balance chain because they do stretch and wear. A genuine Honda item is only available from CMSNL @£280+. A much better and stronger alternative is a DID go-kart racing chain available from £15 if you can find one as they are becoming pretty rare these days but try eBay. The chain is a DID 219HTM racing go-kart chain. You will need to shorten it to the correct length and mark the timing marks on it using dabs of white paint. The timing marks are set at O, 18 & 26 links.
If you can't find one contact the chain man, it used to be called Andy the Chain Man but Andy retired and his son runs it now. They always attend the Kempton Park Autojumble (on this weekend)..

[CMXCol]

Update

Yes it was the gearbox clutch works fine now gears change snoothly engine revs stay constant when clutch is pulled in same clutch no modifications to that.
Rode it around the block first ride.
Balance chain was in good condition the bike had only done 14000 when I got it but it a bit rusty and tatty 600 quid so to be expected.
It needed a rebore though as the barrel had rusted a bit I think it had been lying around for a while in a shed.
Now it's just getting the riding position better I think I need to move the rearset footpegs forward a bit will need to make some new plates for mounting them but ally flat bar is reasonably cheap 100mm wide.
Also need to decrease the angle on the clip ons a little so they're a bit straighter but all the engine issues are sorted.
Enclosed picture of the nearly finished project.
Thanks for your help!