piemuncher Posted July 6, 2010 Share Posted July 6, 2010 Hi all, New to this forum, but have been browsing around anonymously for weeks! Basically I'm an aspiring biker, hopefully getting through my 'big bike' tests in the next few months. Yesterday I went out and bought a little SR 125 'R reg' for £450, it has 20,000 miles on it and drove sweet when I took it out so thought I had a deal! This morning I have pulled out of my drive, full throttled it and the chains just bloody popped off. After taking off the covers to see the front sprocket its obvious the chain had come off there. I've put it all back on but it does seem the chain is very loose at the moment. If the chain comes off, and jumps under hard (as hard as you can get on a 125!?) acceleration does this mean new sprockets and chain are required? Bit annoying, so much for cheap carefree motoring! I've spent years playing with cars so not adverse to a little DIY, but annoying as I want to be out on my new bike!! Pie Link to comment Share on other sites More sharing options...
Paulwhite Posted July 6, 2010 Share Posted July 6, 2010 probs best getting new chain and sprockets as you dont know how long they have been on for plus you can compare the old ones to the new ones to see how worn they are, but is the back wheel all the way to the end of the swingarm? have you tightened up the chain? if you cant tighten the chain any further then you will definatly need a new chain and probably sprockets but hard to tell without taking a look Link to comment Share on other sites More sharing options...
piemuncher Posted July 6, 2010 Author Share Posted July 6, 2010 Sorry mate its difficult to describe it fully! Its got one of those snail type chain tensioners (hope that makes sense!?) and yes its as tight as it'll go! I must admit, the sprockets do look a little worn, and the chain is hanging possibly 2 inches more than it should do i'd think. I've ordered a new chain and sprockets for £35 and the tool (£35!!)... Anyone else ever feel conned with tools? Any tips I should know for changing these items over? As said, I can replace a car engine but bikes are a new entity to me! Thanks Link to comment Share on other sites More sharing options...
DTGordo Posted July 6, 2010 Share Posted July 6, 2010 Hi pie, You can move the rear wheel further back, taking the excessive slack out of the chain which causes it too jump off. That's something that needs regular checking. It can change depending on wether the chain is lubed or dry and the chain will gradually stretch out anyway over its life. I reckon adjusted right it should have about half to one inch of movement if you push it up and down in the middle. If it's too tight you move the wheel forward. Sometimes the chainring might be slightly offset so you should spin it right round to check that it's not too tight or too loose in different spots. To move the wheel, loosen the axle a bit then there should be a mechanism to move it on the left and right side (so it;s even). Either a camber thing or a bolt on either side. It's worth checking regularly as the chain can do a lot of damage if it comes off. That should get you out of trouble. Check the sprockets to see how much the teeth have worn. Once they start to look dodgy and really uneven on the front and back surface (in relation to the bike) you should replace the chain and both sprockets at the same time. Gordo Hi all, New to this forum, but have been browsing around anonymously for weeks! Basically I'm an aspiring biker, hopefully getting through my 'big bike' tests in the next few months. Yesterday I went out and bought a little SR 125 'R reg' for £450, it has 20,000 miles on it and drove sweet when I took it out so thought I had a deal! This morning I have pulled out of my drive, full throttled it and the chains just bloody popped off. After taking off the covers to see the front sprocket its obvious the chain had come off there. I've put it all back on but it does seem the chain is very loose at the moment. If the chain comes off, and jumps under hard (as hard as you can get on a 125!?) acceleration does this mean new sprockets and chain are required? Bit annoying, so much for cheap carefree motoring! I've spent years playing with cars so not adverse to a little DIY, but annoying as I want to be out on my new bike!! Pie Link to comment Share on other sites More sharing options...
piemuncher Posted July 6, 2010 Author Share Posted July 6, 2010 Hi pie, You can move the rear wheel further back, taking the excessive slack out of the chain which causes it too jump off. That's something that needs regular checking. It can change depending on wether the chain is lubed or dry and the chain will gradually stretch out anyway over its life. I reckon adjusted right it should have about half to one inch of movement if you push it up and down in the middle. If it's too tight you move the wheel forward. Sometimes the chainring might be slightly offset so you should spin it right round to check that it's not too tight or too loose in different spots. To move the wheel, loosen the axle a bit then there should be a mechanism to move it on the left and right side (so it;s even). Either a camber thing or a bolt on either side. It's worth checking regularly as the chain can do a lot of damage if it comes off. That should get you out of trouble. Check the sprockets to see how much the teeth have worn. Once they start to look dodgy and really uneven on the front and back surface (in relation to the bike) you should replace the chain and both sprockets at the same time. Gordo Thanks Gordo, apart from the snail type chain tensioner on the SR 125 do you know of it is possible to move the rear wheel back further still? I honestly cant see any way it can unless I'm being stupid? On my old CBR it was just a matter of moving the wheel by turning a screw at the end of the swingarm! The reason I ask is that I should be travelling into London later on today, and the car adds another 2 hours onto the round journey... baaa Pie Link to comment Share on other sites More sharing options...
Speedshop Posted July 6, 2010 Share Posted July 6, 2010 If your chain has come off once thats a big hint you need to change both chain and sprockets. Even if you never adjusted the chain so it became loose it will tend to stay on the sprockets if it is not worn. Its only when the chain and sprockets are very badly worn the chain comes off (generally, there are limits as to how loose you can let a chain get) . Riding a bike round with a worn chain just bloody dangerous and stupid. The chain can snap and come flying off the bike rearwards if not arrested by the chain guard. Or it can become entangled in the wheel, locking it solid causing you to loose control, or possibly it can jam the front sprocket and smash a hole through the engine case. Been there and got the T shirt, I thought I couldn't afford to replace a chain when I was younger - a new engine due to the crank case being smashed beyond use as the chain tore through it was even less affordable. Link to comment Share on other sites More sharing options...
Moderator mervin Posted July 6, 2010 Moderator Share Posted July 6, 2010 If your chain has come off once thats a big hint you need to change both chain and sprockets. Even if you never adjusted the chain so it became loose it will tend to stay on the sprockets if it is not worn. Its only when the chain and sprockets are very badly worn the chain comes off (generally, there are limits as to how loose you can let a chain get) . Riding a bike round with a worn chain just bloody dangerous and stupid. The chain can snap and come flying off the bike rearwards if not arrested by the chain guard. Or it can become entangled in the wheel, locking it solid causing you to loose control, or possibly it can jam the front sprocket and smash a hole through the engine case. Been there and got the T shirt, I thought I couldn't afford to replace a chain when I was younger - a new engine due to the crank case being smashed beyond use as the chain tore through it was even less affordable. i can only say the same as speedshop, been there done that myself luckily i did not have to replace the engine, some araladite and silver paint repaired it as it was only a non stressed cover Link to comment Share on other sites More sharing options...
DTGordo Posted July 6, 2010 Share Posted July 6, 2010 Sorry Pie, I don't know enough about that bike but from what you say: chain too loose, it came off before, can't adjust the wheel any further, don't have the new chain yet, riding through the city and add to that the comments from the others......... Take the car. 2hrs extra sounds like a fair trade. The bike will still be there when you get back. Gordo Thanks Gordo, apart from the snail type chain tensioner on the SR 125 do you know of it is possible to move the rear wheel back further still? I honestly cant see any way it can unless I'm being stupid? On my old CBR it was just a matter of moving the wheel by turning a screw at the end of the swingarm! The reason I ask is that I should be travelling into London later on today, and the car adds another 2 hours onto the round journey... baaa Pie Link to comment Share on other sites More sharing options...
KirriePete Posted July 6, 2010 Share Posted July 6, 2010 Thanks Gordo, apart from the snail type chain tensioner on the SR 125 do you know of it is possible to move the rear wheel back further still? I honestly cant see any way it can unless I'm being stupid? On my old CBR it was just a matter of moving the wheel by turning a screw at the end of the swingarm! The reason I ask is that I should be travelling into London later on today, and the car adds another 2 hours onto the round journey... baaa Pie The screw adjuster on the CBR does the same job as the snail cam on the SR - IMHO the snail cam is a superior method as it's much easier to check alignment (assuming it was put together straight at the factory, that is!). You could always just slacken off the axle and pull the wheel back as far as it will go, regardless of whether the cam is hitting it's little blob, getting the wheel straight could be fun in this case .... As for correct tension - in the bottom run of the chainguard there should be a vertical slot - with the bike on it's wheels and rider seated, the chain should be visible in this slot at about the halfway mark - seemples! Am I reading you correctly in saying that you've bought a chain tool? Shouldn't be necessary for the wee SR as most chains for these are of the split link variety - joining link held in place by a wee spring clip - so no tool required. Having said that, it will come in handy in future as bigger machines need stronger chains of the 'endless' variety so an investment now will pay off later ..... Link to comment Share on other sites More sharing options...
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