plank Posted June 25, 2015 Share Posted June 25, 2015 (edited) Hi Guys, I bought my SR a few weeks ago, and the poor thing had not been very well taken care of. Gave it a service - new oil, air filter, spark plug, brakes, sprockets, chain. Didn't touch the valve adjustment, and it is a bit noisy on the top end, so I need to get to that. Recently it has developed a bit of a dead patch between 1/4 throttle and 1/2 throttle, which led me to pulling the carb and cleaning everything out. I didn't pull any of the jets, just blew through them all with carb cleaner, and wiped everything down well. The throttle valve has some indentation where it rests against the idle adjuster, which I dressed slightly, but there's still a divet there, albeit without raised edges. I checked the haynes manual for the pilot screw adjustment, went to reset it, and found that it required several turns in to close it up, then opened it back out 1.5 turns. Set the idle adjust screw all the way in, fired up the bike, then backed it out until it sounded right (sadly I'm doing this on my driveway and not in my workshop). At this point, giving it throttle would result in a very odd rev pattern - Idle - give a twist of throttle - high revs for 5 or so seconds then slowly returning to idle, rather than a rapid return as I was used to before. Backing off the idle adjust any further made the bike sound like it was choking a bit. Adjusted the pilot screw out a further half turn, and now the throttle became more responsive - idle - twist of throttle - revs - returns immediately. It seems to be running hot though. Pulled the carb again, checked everything carefully for stickiness - the throttle valve moves okay in the tube, but looking from the side it seems that the needle pulls to one side when throttle is applied. Apart from that I couldn't really see any other issues, and the float seems to be set correctly. Put it all back together, went out for a ride - still has the dead patch at 1/4 throttle, and now the idle rpm is too high. Adjusted that back down when I got home and it seemed ok. Got up this morning to go to work, wouldn't start without the choke (before I messed with it, it would fire right up without any choke being needed, and the choke application would just worsen the starting), manually held the choke out as the little spring clip that holds the button out was broken. Needed a bit of throttle too, but eventually it warmed up enough that I could let the choke out. It sat there idling at probably 600rpm, and sounding like a bag of crap with a misfire every few seconds - this is with the same settings I had had the previous night with ok to possibly a bit high idle rpm. Left it warming up while I got ready for 5 minutes, came outside, twisted the throttle and it dogged heavily. Twisted more slowly and it caught back up and revs increased then settled into a smoother and faster idle. Left it another 2 minutes, came out, engaged a gear, turned the throttle and it died. Restarting was an absolute pain in the ass, required some throttle and then adjustment of the idle screw to get it idling again. Set off for work, and half way through the commute it was idling at ~2000rpm, to the point that I was riding the brakes while filtering to stop it from accelerating in 2nd gear. Adjusted the idle screw back a bit along the way, and eventually got it into a drivable state. I'm really not sure what to replace, the ancient art of carb tuning is not something I ever learnt - give me a laptop and EFI and I can throw a decent tune at something that will run good numbers on a dyno, but this feels like voodoo (combined with the fact that this is my first ever bike), and I'm really not sure what to do. Does anyone have any suggestions, beyond my idea of "screw it... let me just buy one of everything", which has so far come up to £200 in my shopping basket? I was thinking maybe replace the needle, but then I got reading about CDI issues, and various other things, and now I feel seriously frustrated as the bike was running alright bar the stumble and gap in power at the settings it had before, and I've made it much much worse now. Thanks in advance! Amy Edited June 25, 2015 by plank Link to comment Share on other sites More sharing options...
plank Posted June 25, 2015 Author Share Posted June 25, 2015 I figure if a picture is worth a thousand words, a video is probably worth a bunch more. Picture of the needle - I cleaned it up real well but that made no difference really. Long video is before I dialled it in to the point that it was running ok albeit with a light misfire. Short video is the misfire Link to comment Share on other sites More sharing options...
AndrewElvisFan Posted June 28, 2015 Share Posted June 28, 2015 (edited) Hi and welcome!No expert here, but....Similar symptoms as mine had not so long ago. If the the carb is 100% clean and put back exactly right and set back to standard then that suggests something else is not quite right. My exhaust was the main culprit recently but even after changing the exhaust I still had issues. You mention new air filter etc but no new battery? It wasn't until I fitted one that mine started running sweet. Is your camchain tightened correctly - could just be the audio on the vid but sounds like something is a little loose or your exhaust isn't quite right.Have you checked the spark plug for colour after running the engine? Edited June 28, 2015 by AndrewElvisFan Link to comment Share on other sites More sharing options...
AndrewElvisFan Posted June 28, 2015 Share Posted June 28, 2015 Oh and just one another thing, as the site seems to be running properly now, if you go over to the New Members section and do a little intro you'll get a lot more help There is a whole load of experience on here and all are very happy to help if you say hi! Link to comment Share on other sites More sharing options...
Moderator Cynic Posted June 28, 2015 Moderator Share Posted June 28, 2015 Idle circuit issues or an air leak, unless the valves are buggered, but them SR's take some killing so air leak/ idle circuit is what I would be looking at. 1 Link to comment Share on other sites More sharing options...
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