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Oil drain plug on SR125 is on left side of crankcase, it has a rubber o ring which (IMO) doesn't need replacing, rather than the traditional copper crush washer. Bike on side stand will drain better than on main stand. Get a haynes - (a little) money well spent, and doesn't mention replacement of that o ring at oil change. These bikes are relatively simple, but having the manual is a help, esp when it comes to finding the cause of some strange fault. The SR has to be totally upright before oil level in the sight glass can be read - luckily, its not a heavy bike!

+1 for what others have said - watch out for spring loaded fork top bolts. I support the bike on the main stand with a bit of 2x4" up to just underneath the headstock. Take the top cowling off - its a pita, but gives you the access you'll need, esp if bearings are suspect (order new well nuts from wemoto if necessary....) remove front brake caliper (and service it while you're in there - it will probably need it), then the wheel etc. Check head bearings while you have the front off the ground. Loosen the top yoke allen bolts before attempting fork top removal. For dismantling the forks and getting the seals out, you'll need to take out the damper rod bolt at the bottom of the fork leg. The internals of the fork will turn, making this awkward. An air impact wrench will probably do it, but if you can contrive to get a 14mm nut on the end of a rod, it will hold the damper rod inside the fork so you can turn the damper rod bolt to undo it. I ground 14mm hex on the end of an old honda VFR400 rear axle - works a treat. Then you use the fork like a slide hammer to get the seals out. A piece of plastic drain pipe of the right size makes a good seal drift for putting the seals back in. You may have to replace the seal circlips too - they rot when water gets past the dust seal. Silicon grease is your friend on these to make them last. Fork bushings will probably be fine. Check for pitting - autosol it off before pushing new seals down over it. Reinstall forks before trying to get top bolts back into them - socket, extension bar and ratchet, full body weight and try not to cross thread them - one person to turn the ratchet, the other provides weight against the springs works well. 10W fork oil should be fine. When you're done, you will have good forks, serviced front brake, and be practised at top cowl removal... HTH, Nigel

Had this happen on my diversion - Haynes manual suggested some measurements, which would have led to suspicion falling on the flasher relay. turned out to be a bad connection in the loom, closer to the switch gear. But, its probably your earth..

Moving with almost glacial speed (and having torn down the diversion for an engine out ground up rebuild/paint, fettle etc - MoT'd yesterday ) on the SR125, we could not get it started at all - low compression, so despite spark, fuel, air etc, I have torn it down again. Seat off, tank off, carb off, exhaust off, cracked the bolts and head/barrel off (o karp - must run to xj600 MoT.....10min late ). Anyhoo, some measurements this evening were illuminating, to say the least: 0.5 over piston is actually 57.2mm (one might expect up to 57.455mm). Supplied piston is thus more akin to a 0.25mm oversize. Barrel is 57.4mm at the top, 57.46 at bottom (!!) Top Ring end gap is more or less 0.01", rising to ~0.015" top to bottom of barrel. 2nd Ring end gap is more or less 0.0145-0.016" top to bottom - a bit too big, limit is up to 0.013", as for top ring. Suggests rings are correct for the piston, were it in a bore that wasn't 57.4mm. Not a bit wonder there was no bliddy compression!!!! I did wonder at how easily the piston&rings pushed into the bore! A 57.355mm diameter piston would be the thing now, if it can be got. i.e. piston/bore clearance of 0.045mm. On the upside, the xj600 looks great.

ok, a bit of a bump up for this thread as I delurk once again. Just finished rebuilding the sr125 engine (I'm a master procrastinator, and the garage is unheated...), everything timed and turning over nicely, new gaskets all round, a 0.5 piston and matching rings, valves set, fully charged battery, 2pints of oil in, clean spark plug (which produces sparks!) and new fuel. The bu66er won't start! Leak down test on lapped valves was ok - nothing coming through within a few hours. Cold, I'm getting ~90-100psi from the cylinder; would expect more when hot (its currently more than I was getting warm, pre rebuild! (75ish psi), if I could get it going. Got compression, fuel, air, spark.... Any thoughts? Last time the engine ran was over a year ago, burning dang near as much oil as petrol. There are no obvious leaks that I can see or hear, starter spins fine, carb is clean... I'm outta ideas, at least until the starter motor cools down again so I can have another go

...rumbled! Tight git has sorted out out said paste and a lapping stick this evening. The autosol didn't make any difference, so the proper kit is in order...just waiting on the postman now.

ok, a certain shop "at the end of the world" came up trumps. Turns out the inlet and exhaust valve stem oil seals are the same size... Valves out, a LOT of carbon on the exhaust, some in the inlet, the seats look like a polish would be in order, but would I be better lapping them in a little until there is an unbroken grind line on both the valve and the seat? If so, could I use autosol, or must it be proper grinding paste - I'm really only talking about tidying up the mirror finish on valves/seats - they are relatively shiny, but with some dulling here and there. Cheers, Nigel

Y'know, that's a damn good idea!!! An so bleeding obvious, with the sister in Preston an' all.... I'll try fowlers tomorrow for the seals as well - as I recall, they don't stick the arm in.

Further inspection reveals that ring end gap increases as the ring is pushed down the barrel. So its, er, barrel shaped... However, an oversize+0.5mm piston kit inc. rings, plus free rebore to that piston, sourced for £35. Sorted. Now I need both inlet and exhaust valve stem oil seals from somewhere that won't charge £6.99 for delivery to N. Ireland, or insist upon selling me 10 off each and then gouging for offshore postage on top of that!! I mean, they are a quid each, £1.50 max! "Full gasket sets" don't have these, it seems... Any tips for getting the cam follower shafts out? Cheers, Nigel

My sr125 had become very hard to start, was oiling the plug, bogging on max throttle and blowing a lot of blue smoke - a compression test showed 75psi (!!) warm, rising to 115 with a squirt of oil in the cylinder. So the rings are suspect. Stripped it down, and made some measurements... Bore: 57.02mm top and bottom, all directions.Fair enough, std is 57.00-57.10. Piston: 56.48 at the top, 56.88 at the bottom. Std is 56.945 - -oops! it gets better.... rings: end gap, top ring >0.5mm. Std is 0.15-0.35; 2nd ring 0.45mm, std is 0.15-0.35mm. Totally phooked, it would seem. Piston bore clearance is a thumbnail, greater than the acceptable 0.065mm. The bore has a series of vertical scores in it, which match wear points on the rings. These scores are ~2mm wide, spaced evenly (~7mm) all the way around the bore, and are **just** detectable with a fingernail. My question is, should I rebore to say, 0.25mm oversize, and install a piston/rings to suit, or simply take the view that the original piston is worn out, the bore is fine, and replace piston/rings with the standard size, no rebore? Happy to hear recommendations for either option; given the bike cost me £150 with 40k of the current 42k on it, its not been expensive so far, although a rebore will probably be as much again as a piston kit (~£30) and new gaskets (£30) put together, assuming I can find a place that will bore/hone AND supply a suitable piston locally (N. ireland). Cheers, Nigel

Clutch release bearing. Goto yamaha diversion club boards and have a poke around - its a common problem, and easily fixed for less than £20. Get the bearings from simply bearings, plus two 1mm washers, and a gasket from wemoto. You can do the job with the bike on the side stand, so no need to drop the oil. There is also a rattle that all diversions make : that's fixable too, although not necessary. See the boards. "internal drive chain tensioner" my ar5e! All the best, Nigel

Mine's busted. A cack handed removal broke the swithc body in two, and lost the internalpin/bar/plunger thingy Anyone know 1. what the internals of the switch look like (I am lattempting a rebuild, but gluing the plastic may not hold) 2. What the OEM part no is? (and HOW MUCH!!!?) 3. Will any other model switch fit? Cheers, Nigel

Steel allen headed bolt into alloy. You get galvanic (?) corrosion, and they stick like crazy - you WILL ruin the bolt head. I generally take a hex bit, put it in the bolt head, and hit it a couple of times with a big hammer. This cracks the corrosion that will be preventing the bolt from turning. Bolt then comes out easily, I have found. HTH, Nigel

Ummm.... nice tidy job! Let us know if it continues to do the job.

A lumpy idle could be the carbs need (re)balanced - also, check pilot screws all at same setting - usually 1.5 turns out from lightly seated. Sounds like things are a bit rich - is the air filter clean? Could be worn jets, but if these are new a while ago, probably not... Struggle below 4k - same thing when its nicely warmed up? As for lack of go above 60mph....I don't know, however, "engine break in" sounds like mechanic's double speak - removing the cams, replacing a bunch of shims (and in an ideal world, re measuring once the new shims are in) and putting it back together again correctly should not require any subsequent "break in". It sounds more like the cam timing has been inadvertently moved, hence the loss of top end. ver' importn't on a SR125, more so on a YZF. One tooth off is enough to bu66er the power, but not wreck the engine. On an SR125, you can get away with 7degrees off...