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ybr125 trying to get at clutch, really have to disassemble whole bike??


dannyoneill42
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Hi all,

Complete newbie to bikes so apologies in advance for stupidity. Am not new to working on engines, just new to bikes (last thing I did to one of my cars was to build an electric supercharger (literally fabricate the thing from scratch), 30 more HP and mostly at the bottom end; whoo-hoo!).

I have killed some part of my clutch on my little ybr 125, the thing is slipping badly and the biting point has shifted to about 1cm of lever depression. Tried adjusting cable at lever and engine end to no avail, silly thing to try really as unless the cable had magically shrunk that really wasn't going to be the issue! Far more likely was my low-speed maneuvering practice last weekend fried the poor thing, hopefully it is wrecked friction plates rather than somehow ruined springs as I have some new plates soaking in oil right now, but haven't found anywhere with springs in stock south of Watford.

Problem is: getting side of engine off. I have the service manual and it pretty much says that I have to take the entire bike apart to get at the clutch. It would seem that it is definitely right that I need to remove the footrest, but that seems to necessitate removing the break lever and that seems to require removal of the whole exhaust pipe (or muffler as it calls it). Apart from anything else, I'm not entirely convinced that I can do all this a) while it is on the centre stand, and B) without some magical sockets/wrenches that can be located on inaccessible bolts and then turned by thought alone.

Please tell me I am being a prat and massively over complicating this. Perhaps I just need to man-up and go out, buy some stands and take the entire thing apart, but seriously, it cant be this hard! I could have changed the clutch in one of my cars by now! If anyone could give me some hints as to what I really need to remove to get at the clutch and whether it can be done while it is on the centre stand, then I will go out and try some more. Really would be very emasculating to have to take the thing to a garage and admit to failing to just get at the part in question!

Any help greatly appreciated, apologies for maniacal rant above and sorry if there is a guide on this forum somewhere pertinent to my efforts, but 15mins forum searching is all can ever stomach; ignoring irked peeps who know their way around websites and their rebukments about lacking etiquette is always preferable to engaging in psychological battle to the death with poorly written forum search engines ;)

Thanks,

Danny

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  • Moderator

You just need to take the offside crank cover off. Drain the oil first.

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Hey,

Finally got it off. Foot rest finally came off with some spanner jiggery pokery (well, when I say 'off' I managed to rotate is so that it's guard which was preventing it coming off was no longer in the way), and once that was out of the way getting the crank case off was suddenly easy!

Thanks anyway,

D

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Nuts, there was I all smug and thinking it had all gone so well and it would seem that I spoke too soon. Starter motor fires but cant turn engine, just kinda clicks asif immediately getting stuck. Kick starter doesn't look like it's as far in as it used to be, methinks that it's not engaged in the right place. It (the KS) can turn the engine, but obviously don't want to actually start the engine with everything not in the right places!

Was such a ballache to get the foot rest out of the way, have to basically do it all again. Arses. Hopefully when I do get it all apart again its easy to get the kickstarter back in place. And hopefully that's all that is wrong! The starter motor is certainly flush and it doesn't spin away so I think that must be connected mechanically to the engine correctly.

Will report back later just incase my moronic experience is ever useful for anyone else.

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This is not going at all well!! So progress was impeded by well-meaning but exceedingly drunk neighbour who rolled out of taxi and mooched over to give a hand. Great guy, but didn't exactly speed things up! :)

Upsettingly, all is still not well, starter still only manages a dull click and gets no further. Kick-start no longer loose, but not returning to top and I swear its not as far in as it should be, but I might be imagining that. What I did this time was to push the shaft and its gear back into the crank case such that it meshed with the gear above it, then held everything still by holding the clutch, and pulled the spring around the shaft of the KS clock wise and seated it's end a hole clearly set there for that purpose.

But no starting still... Might get some sleep and try again in the morning.

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you need to check that you haven't jammed something. Out with the plug, into gear and slowly push the bike to see if all turns over freely.

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hehe, my madness continues, so starter is now definitely arranged correctly - dratted schematic I was working from did not show the rear gear clip in the correct place, some google-images-ing and I found a photo of it correctly arranged. So thats all fine now.

BUT... it still wont start, the starter motor just clicks and wont turn the engine over. I tried as DirtyDT suggested and tried rolling the bike about to work out if everythign was free and it certainly is: in neutral bike can roll about, in gear with clutch lever in it rolls, with clutch out (engaged) and wih it in gear the bike smoothly pushes the engine round, that distinctive satisfying squishy sensation as the cylinder goes up and down, easier in 5th, harder in 1st, and all sounds smooth, so all as I'd expect, and yet... starter motor cant turn anything.

Have confirmed the starter hasn't blown with any of my messing around - got it out and bolted it back on backwards, ie with its base impotently pointing towards the bike and gear engaged with thin air pointing away from chassis (bolted it on to get an earth you understand), and it spins like a daemon.

What could be jamming I wonder, or could this be some kind of electronic stop, I don' think is is because 1) it certainly sounds mechanical - clanking noise from left side of crank case where it's gear engages, and 2) if I hold the button down (only for about 1s you understand, don't want to fry it) after it clanks to a halt (about 1ms after I depress the starter button) the lights all stay dim until I release the button, so I would think that must mean there is still current being fed to the starter, and hence dropping the voltage available to the rest of the bike.

I suppose I just need to get the right crank case off again and figure out why the starter cant turn everything.

I'm starting to stop enjoying this!! :)

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.............BUT... it still wont start, the starter motor just clicks and wont turn the engine over. I tried as DirtyDT suggested and tried rolling the bike about to work out if everythign was free and it certainly is: in neutral bike can roll about, in gear with clutch lever in it rolls, with clutch out (engaged) and wih it in gear the bike smoothly pushes the engine round, that distinctive satisfying squishy sensation as the cylinder goes up and down, easier in 5th, harder in 1st, and all sounds smooth, so all as I'd expect, and yet... starter motor cant turn anything.

............

If the cyinder is going up and down, that could be part of the problem...perhaps It is colliding with the petrol tank? :eusa_snooty:

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[ Hi there AirHead, am not sure I follow I must be misunderstanding you, the cylinder going up and down is not a problem, thats how the engine works - petrol explodes, pushes cylinder down, crank then pushes it back up again etc... if I were manually able to cause the cylinder to burst through the top of the engine and make it hit the underside of the petrol tank I would be applying to be in The Avengers. The engine turns happily. ]

So I now have both sides of the crank case off. With the kick starter I can turn the engine over (not fire it you understand, just slowly turn everything) and everythign turns as you would imagine.

I have (with both sides still off the crank case) tried slotting the starter motor back in, I can't bolt it in place and try getting it to spin because it can only bolt to the outside of the left crank case. But, slotting it in there does allow me to drive the gear it normally drives by just slowly turning it. It happily turns everything smothly, it's not especialy hard to turn or anything.

Trying to turn it in the other direction does nothing (as I would expect as I presume there is a directional clutch somewhere between the starter motor and the crankshaft.

Why is it then that when I put it all together (by which I mean just putting the crank cases back on) does the starter fail to turn everything. Anyone have any ideas? I have my mod 1 test in a week and really want to get some practice in and working on the bikes on week nights isn't so easy as work is crazy at the moment :(

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so am I reading this right? the starter is fixed to a casing that you remove to get to the clutch etc?

there is a gear on the end of the starter shaft...right?

Fit the casing back with the starter loose in that casing and as you offer the casing up on re-fit just waggle the starter motor so the gear doesnt jam up anywhere, it should all go back without any resistance...then re-tighten the starter

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Sounds like something is pinching when the cases go on. There is a directional starter clutch behind the rotor.

With the kickstart gears and cases off but the starter in and the plug out then the starter should turn the engine. This assumes the push in gear test was successful as it seems in a previous post. If it doesn't then where the starter gear locates will be the part jamming. When you locate the starter can you see which cog it locates onto?

I guess pictures would help and also what you have removed to change the clutch to make sure that all of the cogs have been put back the right way around and are locating properly.

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Hi there DirtyDT, you were basically there. Annoyingly I couldn't do exactly as you suggested because with the cases off it's impossible to actually test the starter - its only bolt locations are on the outside of the crank case, so although I could get the starter in and engaged and turn it by hand I couldn't fire it because it wasn't held by anything, it would have just spun backwards and ripped off the live wire.

But, I could turn it by hand and everything worked. Following some advise from other forums I, working on the assumption that the starter's clutch was messing up, I tapped it with a spanner whilst turning it back and forth (with the starter motor in it's limbo-situe). Then put the cases back on and hey presto, all was well, starter spun the engine and it fired happy as ever.

Oh and my new clutch plates and all the various alignments seem to have been good - it works nicely. Well I've only tested it on the stand so far - I want to run a few litres of oil through her to make sure all the crap I probably introduced with the 37 case removals!

Thanks guys.

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Glad you got it sorted.

The way to instal the starter without the case on is to run a couple of nuts up the starter bolts and use them to space the distance.

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Glad you got it sorted.

The way to instal the starter without the case on is to run a couple of nuts up the starter bolts and use them to space the distance.

Thanks for you help! Just an fyi, and not at all snubbing your attempt at helping, but actually the starter doesn't bolt into the some of the bolt holes which hold the rest of the case on, they actually have two dedicated tapped holes of their own which are on the case, so once its removed the only choice would be (as you say, spacers, then...) two of the proximal case bolt holes, but these are far too far away sadly. Would have posted pics, but there only seems to be an option to link to pics already on the net somewhere, not to actually upload them, but am probably missing somethign - brain a bit fried after efforts with the bike!

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Thanks for you help! Just an fyi, and not at all snubbing your attempt at helping, but actually the starter doesn't bolt into the some of the bolt holes which hold the rest of the case on, they actually have two dedicated tapped holes of their own which are on the case.............

Understood. That makes it difficult then!

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