paulhanle Posted August 20, 2017 Share Posted August 20, 2017 Almost definitely due to carb diaphragm split, I serviced my latest purchase , bought a new inlet manifold as bike was running too weak ( no mixture adjusting screw on mikuni carb ) scratched my head a little , bike was flat out at 55 mph , fresh plug new oil and air/fuel filter no change , stripped carb , found replacement diaphragm for £10 instant power increase to 70 mph on the flat Quote Link to comment Share on other sites More sharing options...
paulhanle Posted August 20, 2017 Share Posted August 20, 2017 Next step now it's up and running correctly is to fit a 115 main jet , ditch the standard air filter for k&n type that's about all you can do to these 125 single 4 strokes , I once did this to a cg 125 made it much more rideable with more get up and go off the mark , Quote Link to comment Share on other sites More sharing options...
fastbob Posted August 21, 2017 Share Posted August 21, 2017 Happy days! Good to hear about a positive outcome for once. Quote Link to comment Share on other sites More sharing options...
tomh65 Posted January 8, 2018 Author Share Posted January 8, 2018 Thanks Paulhanle. After so many weeks of poor performance, I took out the carb and replaced it with a new one. Sure enough, the diaphragm was perforated. It had about 12 holes in it. Now it runs like a 250. I can get up hills in 5th gear - no problem. There was one tiny problem though - the fuel pipe into the carb had rotted. I left the bike in the garage overnight, only to find that it leaked all over the floor. Over 2 gallons of petrol wasted!! I should have replaced the pipe at the same time, but we live and learn... Quote Link to comment Share on other sites More sharing options...
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