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Georgiev

YBR 125 Front sprocket fell off while riding

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Hi All,

This is my first topic in ths forum and I'm starting with a technical problem.

This morning while riding I heard unusual noise and sudden loss of motive power.

Initially I thought the chain has broken, but it wasn't broken. The front sprocket was missing.

Furtunately I was not far from home.

Does anyone know what can cause the front sprocket to fell?

Of course I'm going to put new pair of sprockets and new chain.

I selected a front sprocket with a tooth less (13T).

I expect this to cause a bit more torque trasfered to the rear wheel.

Are there any side effects of replacing 14T sprocket with a 13T ?

I appreciate any suggestions.

regards

Georgi

p.s. I bought the bike without the standard tool kit. What tools does the standard tool kit include? I don't want to place separate topic for this question only.

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changing one tooth down will in crease acceleration but maybe loose a little top speed depending if your bike could reach the red line in top gear before.

the sprocket should have a fail safe on it, most older bikes used to have a large flimsy washer under the nut that you bent up against one of the flats of the nut so it could not undo.

not sure on your bike they may have come up with something more technical now but it looks like it dont work to well. chris

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if i remember rightly on the DT... there was a circlip and a washer holding the sprocket on, failure of this circlip could cause the sprocket to f*ck off on its own.

13T sprocket would give slightly better acceleration at the expense of some top speed

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hi ,iv'e just had a look at your sprocket set up ,it contains a castilated cover that is held down with two bolts.use ,,locktite,,on the threads of the two bolts when you do the job,so that they don't unscrew,,as for tools ,,if you have none,,don't run out and buy from the pound shop,they are cheap for one reason ,cos they are shite,you will end up damaging nuts bolts and your tools ,but more so ,you will end up hurting yourself,,,so only buy quality tools,they wont last a lifetime,cos you'l lose some and lend some,if you can't afford them then borrow them ,dont compromise by buying trash.

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Hi guys,

Thanks for the response.

I found a drawing of sprocket mounting. "Locktite" seems good idea for this tipe of mounting.

About the tools ... I learnde the lesson of good and bad quality tools some years ago while repairing my car.

The question about the tools is what do I need to have with me while riding. For example screwdriver, spaners.

What is usually inside a motorbikes toolkit?

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double ended screwdriver,,sparkplug socket,,,10mm 13mm spanner,,pliers,,clean rag,,adjustable spanner,,,:unsure: all this is usualy pointless as you never seem to have what you need in case of an emergancy,,allan keys,,tyre weld,,oh dont bother,,do as i do and join the breakdown,,let them fuck about at the roadside while you have a smoke,,it's only £40 12mts.

ps i personnely carry double ended screw driver and one pair of pliers,,1 pair of sergical gloves....

Edited by up.yours

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Received the new sprockets and chain today. Hopefully the retainer and bolts will be here soon. Otherwise I'll have to work out some decent temporary sprocket mounting to put the bike back on the road.

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I finaly found some time to share my experience.

I received the retainer and the bolts in 3 days. So far so good... But it appeard that the retainer wasn't exactly what it should be. The bolt holes were 5 mm diameter instead of 6mm (bolts are M6). The other thin I noticed is that internal diameter of the spline is 17mm instead of 16, but it's not too bad.

Anyway, I had to use power drill to fix the bolt holes.

Last week I had the chance to finish the repairs and tested the bike with the 1-tooth-less front sprocket.

It is running definetly better. Now I have significantly improved acceleration on 5-th gear. Now I can reach 60 - 65 mph. I couldn't do that before.

Certainly the top speed has gone down, but I couldn't get to more than 60 mph before anyway.

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