Is there much that can be done about this?

[Dr. Quack]

I lost drive today, the front cog has worn the inside of it's guard too.
Cheers.

https://img811.imageshack.us/img811/2166/fbuj.jpg

https://img96.imageshack.us/img96/3972/yzu7.jpg

[P.addy]

Sure there is a simple fix for this.

Weld it?

[mentalboy]

Stick to downhill only.
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Make mine a Corona.

[Teflon-Mike]

That looks... though pictures pretty dire, to be the output shaft & sprocket from a small honda. CG? CG copy? Pit-Bike?

And it LOOKs like there's no sprocket retainer been fitted.

Sprocket slides onto splines of shaft, then a thin plate with similar splines slides on, BUT that plate has the spline teeth out of line to those on the sprocket, to once slid up to the sprocket, to line up the holes in it that screw to the two in the sprocket, you have to line it up in that groove then twist it a little, locking the sprocket from side to side movement when you tighten it up.

If forced off or not fitted by numpty who couldn't twig how it went together... then the sprocket would rock around and be inclined to chew itself up.

Cant tell from pics if the splines on the out-put shaft are still good enough... but of so, cure would be a new sprocket; fitted properly with the retaining plate and screws.

Dave Silvers Spares, sprocket retaining plate AND genuine OE Honda screws, and new approved replacement sprocket, lot ought not cost much more than a pack of fags; and not worth trying to bodge.

If the splines on the out-put shaft are fucked.... then propper fix would suggest a complete engine tear-down to get the old out-put shaft out, and replace it with one with splines.

I would not try and even tack-weld the sprocket to the out-put shaft as a mega-bodge... if your lucky weld might hold it on, and there may be enough splines left to transmit drive... if your unlucky, you'll tak the sprocket on skew so its running like a buckled wheel, and just as likely to snap again... meanwhile heat of welding, likely to melt output shaft seal, and your bike ent gonna hold oil too well.
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[wilz1234]

Having the clip on would have prevented it. Is there still enough of a groove for the clip to go into?

Edit: What he said ^^^^

one of these:
https://i412.photobucket.com/albums/pp202/thebrightstuffdotcom/TAmongoliaSprocketIssue/newRetainer3OnSprocket.jpg
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RS50 - ZXR400 - ZXR 400 - ZX7R - Bandit 600 - NTV 650

[Dr. Quack]

K thanks Teflon, does this look goosed then. (Judging by the above pic)
The teeth look worn to me.
The bikes an XR400

https://img571.imageshack.us/img571/76/3gjh.jpg

[Teflon-Mike]

Here you are of CMSL schematics.

https://images.cmsnl.com/img/partslists/honda-cb125t-germany-full-power-type-transmission_bigma000161e14_95dc.gif
Part 2 is the out-put shaft, which may be different on your bike, this is for CB125T, which uses same sprocket and location arrangement as other small Hondas.
Part 15 is the sprocket
Part 25, the sprocket retaining plate
Part 24, the retaining plate screws.

Dave Silvers list the screws at 55p each, the plate at 95p, and the sprocket at £25.. for the gen Honda one.. but 'pattern' alternative, for £5 exactly...

Err, totals up at, £7.05 plus VAT plus P&P.... My fags are £8.10 a pack... its close enough!
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Teflon-Mike]

[Dr. Quack]

Out put shaft splines are fine apart from the out rim.
So if I buy Part 15, 24 and 25, do you think it's worth risking it without replacing the the output shaft, say with a weld or two?

[mentalboy]

[Teflon-Mike]

[Dr. Quack]

Going to the shop for some nurofen, got head ache.

https://img69.imageshack.us/img69/8315/j45q.jpg
https://img585.imageshack.us/img585/6387/f59l.jpg
https://img545.imageshack.us/img545/3033/ulrt.jpg
https://img843.imageshack.us/img843/6955/4y9s.jpg

[stinkwheel]

You'll probably get away with that.

Looks to be just about enough meat on the end splines to hold a new retaining plate on. The splines themselves look ok in those pictures.

The only way to be absolutely sure would be to try one on it and see if it is going to stay put.

That retaining plate does two things: 1) Stops the sprocket sliding off the end of the shaft. Its ability to do this is currently questionable and 2) Hold the sprocket in position near the end of the output shaft. The splines responsible for doing this part look relatively shipshape.

If it were me (so this is not the be-all and end-all, or even necessarily correct), I'd try fitting a new one and see if it holds up. If it doesn't, first thing I'd do is see if I can fit a circlip round that shaft to the outside of the retaining clip.

Another thing I'd be tempted to try would be drilling a hole across the end of the shaft and fitting a rowl-pin in it to prevent the place coming off.

Getting increasingly ratty, dangerous and irreversible. I have seen someone cut a lovely groove for a circlip in the end of a hardened steel shaft by rotating the shaft in a pillar drill while cutting the groove freehand using a thin cutting disc. I see no reason why that couldn't be done by putting the engine in top gear at idle and going to it with a dremel.

Mates video (his was a cutdown starter motor shaft being modified to take a circlip to stop the bendix being thrown off the end):
https://youtu.be/n8HIxJoIYtk
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Teflon-Mike]

Sprockets knocked about half the splines out-board of the retainer groove off, by looks of that, and all on one side... I DONT think you'd get retainer to hold the sprocket square with that little location.

Hmm... still worried what caused it... but.

Effecting fix for sprocket. Shaft is hardened, thats why spline ends have cracked off, not mangled.

If the shaft was out the engine, and pure unobtainium, building up that lip with weld may salvage it, but probably not worth the while.

Trying to do something on the bike, with a welder, is likely to do more harm than good.

Case hardening... is just that, a surface treatment, hardens the outside 'skin' of the metal, underneath that skin, its usually quite soft.

If it were my bike; after looking for faults that have caused the failure; and eliminated them; If I didn't bite the billet and do full rebuild or engine swap; I MAY be tempted to look at a 'Salvage Scheme' or if you preffer an 'elegant Bodge'.

Looking at that, you have an extraction or centering dimple in the middle of the shaft end. IF you are lucky, the hardening around that wont be too deep, and if you are VERY fucking careful, you might be able to carefully drill into the middle of the end of teh shaft, and tap it out, probably M5 or M6.

Then, grind off the remaining spline ends where the retaining plate groove was, carefully, using plenty of water on teh shaft to stop heat from grinding damaging the out-put seal.

Fit new sprocket to shaft, with retaining plate, and to hold in on, in absence of that groove in the spline ends, pack with washers to the end of the shaft, and then use tapped hole, M5 or M6 screw and a large washer to hold the sprocket on the shaft.

Without bits in mi mits, I dont know if that's all that do-able, or if there might be more elegant bodge still.

BUT still concerned, IF that retaining plate was fitted, why the thing was rocking around on the shaft enough to crack shaft splines off.

Lot of bikes run 'floating' sprockets, that aren't located as positively as the Honda plate and groove arrangement, and what movement there is between the bits dont do that kind of damage; have seen many a small honda without that plate, run for many miles, and the sprocket might have got a bit chewed if the chain was over tightened or neglected, but other-wise be OK, and certainly never seen them shear splines on the shaft... though your XR shaft does look to have much finer splining than usual small honda arrangement.

Bottom line, is its your bike, your call.

I think at this stage, I'd still be looking for causing problem, presuming this a symptom, rather than looking for a fix; quick or otherwise.
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Pete.]

I agree with stinky, you'll probably get away with fitting a brand new sprocket and retainer, with plenty of grease on the splines.

If it doesn't hold, fit the sprocket and retainer back on and then put three blobs of weld on the end of the shaft evenly spaced and on the top of a spline each but DON'T weld the retainer (or the sprocket) to the shaft. The welds will stop the sprocket sliding off but don't go mad, because you'll have to grind them off again to change that sprocket.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Dr. Quack]

K, thanks guys.

[Pete.]

The splines are a bit worn, but plain and simple you lost the circlip, causing the sprocket to run off the end of the shaft and chew up the end spline.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[temeluchus]

on the grease front, a high moly paste is best for fretting wear like that.
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Some shite cruiser. Now with guns and FREEDOM!

[Dr. Quack]

Thanks, decided on trying both circlips and retaining plate for now.
I'll see how the retaining plate is, then try a tight fitting circlip.
looks like anything from 20mm to 22mm across.

[Pete.]

[Dr. Quack]

OK thanks, gunna try the retaining plate first, see how it is.
The I'll get the needle file out.
Saved me loads of times that little needle file.
(Maybe two circlips with a couple of spot wields)

[stinkwheel]

[Dr. Quack]

Yeah, couple of circlips, and two spot wields on the area where the splines have flattened. Cheers !

They're on the way.
https://simplybearings.co.uk/shop/Bearings-External+Circlips/c3_4519/p82838/External+Circlip+20mm+Diameter+Un-Sprung+Dia+18.5mm/product_info.html
https://simplybearings.co.uk/shop/product_info.php?products_id=82840&gclid=CO_-ovTqu7sCFUUOwwodPCYApA

[STONEY!]

Just another possible solution, use a couple of spots of loctite to help hold the sprocket/retainer ring , only thing is you will need a puller to get it off when you need to change it next. Done this on a few bikes with decent success.

[devojunior]

if it was me id get a new steel sprocket set and chain and just weld it on trying to get a good weld without melting that oil seal although it should be fine