Carlos B

My 1989 SR125 has that bolt upside down too. 10mm head. Often thought it was daft, but the bike's had various other things changed before I got it so it might be off something else, or the lever broke off in the past and was welded back onto the spline end the wrong way round! Loctite anyone?

Hi, posting this reply in 2016 as this post still comes up when you Google 'how to check oil window on SR125' and I thought my recent experience with my 1989 bike might help someone looking now. OK, my oil window was dark and useless at any angle and with or without oil in the bike. Eventually took the side cover off (note: don't need to drain oil first, footpeg needs to come off, 10 cover screws not all the same length, if stuck you can get small moles sideways on them *very carefully* to start them off, if the cover sticks on there's a small leverage point bottom left, look out for two tubular spacers, one on each side, don't lose them into the gearbox as the cover comes off.) Turned out the oil window has a little metal 'cage' on the inside with a shiny silvery disc facing the window. This gives a bright contrast against the oil when you look in, except this one was brown and dark with oil deposits so it didn't work! Cleaned it with kitchen roll and WD40 on a piece of wire. You will need a new gasket before you start! Of course the old paper gasket tore as the cover came off, and being off grid had to cut a new one from gasket paper. Silicone gasket seal probably won't work as the gasket partially covers certain voids and shapes inside the clutch area, with specific cutouts in it for oil movement. Remember to tighten the new gasket down slowly and carefully, going from one screw to the one opposite on the cover, criss crossing and gradually tightening evenly. Oil will gradually seep into the gasket as you ride and swell it up and make a better seal. Check screw tightness again after riding for a bit. Last thing, I'd put 1litre of oil in when I previously changed it, as per spec and the capacity stamped onto the casing; with the newly clean oil window and the bike LEVEL I could see it was over-filled. Drained out the oil and put in 600ml fresh and it came to just under the max line on the window. Ran the engine, turned it off and waited for the oil to drain back down, came to halfway. Topped up a little and I check it cold before I ride out. Hope this helps anyone like me finding this post years after the original question.

Hi all, middle aged English guy here. I keep an old SR125 in Cyprus for cheap sunny winter holidays and it's great for exploring on and off road. The trails here are fantastic and when I've gained some more experience I'll probably get a small Yamaha dirt bike, but for now the SR is so much fun! Typical Cyprus mods include holes drilled in back end of exhaust for heroic sounds and a 16 tooth front sprocket for a bit more top speed. Just changed chain and sprockets back to original spec to get lower 1st gear for steep gravelly hills. And I filled the exhaust holes because I was shaking the plaster off old houses as I rode past! Carlos