skikman Posted July 12, 2012 Posted July 12, 2012 hi all.the last few times i went out for a run on my yamaha sr250 it cut out after 15-20 miles.it was like i had flicked the kill switch.it starts up again ok but keeps doing it now and again.today though it started up again but after a big backfire.where do you think i should start looking? Quote
pointblank0 Posted July 14, 2012 Posted July 14, 2012 I think maybe start looking at the plug and plug cap. Can't remember but is it a single or a twin? Quote
skikman Posted July 15, 2012 Author Posted July 15, 2012 I think maybe start looking at the plug and plug cap. Can't remember but is it a single or a twin?its a single and a new plug set to spec.right.carb taken off and cleaned.no sign of water.new plug,not new but filter cleaned with filter cleaner,oiled and put back on,battery charged and ht lead sprayed.took it for a run and only got about 1/2 a mile when it cut out.started straight up again first push of the button.so took it home again.starting to think its electrical because of the backfire last time.could it be it stopped sparking,fuel still going into cylinder,resparks,to much fuel,bang heance backfire right Question .anyway took off headlight,tank,seat and side panels.started bike and looked at all wires and connections.could'nt see anything wrong.shook and played around with wires but nothing happened.so maybe not electrical.what next???? Quote
Tango Posted July 15, 2012 Posted July 15, 2012 Backfire possibly due to unburned fuel in the exhaust......so it could be to do with the spark. Maybe a problem with the CDI module? Another thought is are your valve clearances OK? May be worth a check to see.... Quote
skikman Posted July 15, 2012 Author Posted July 15, 2012 Backfire possibly due to unburned fuel in the exhaust......so it could be to do with the spark. Maybe a problem with the CDI module? Another thought is are your valve clearances OK? May be worth a check to see.... i reset the valve clearance.they wer'nt that much out.tell me anything but the cdi thoese are expensive Quote
eastanglianbiker Posted July 15, 2012 Posted July 15, 2012 is it points ign or electronic,if its points it cold be the condensor packing up or the points need replacing Quote
skikman Posted July 16, 2012 Author Posted July 16, 2012 is it points ign or electronic,if its points it cold be the condensor packing up or the points need replacingits electronic.been using the bike last few days and it has only stoped once and that was after 60 mile,it started up straight away and no backfire.it only backfired the once.been thinking maybe there's a bit of crap in the tank stopping fuel getting through as it can go for 60 mile one time and 1/2 next.i'll flush out tank and see what happens Quote
Dazzled Posted July 16, 2012 Posted July 16, 2012 Sounds like a problem I had with one of my XJ550s years ago. In that case the fuse holder had corroded through and was intermitently losing contact (it was used hard in all weathers). I fixed it by making a new fuse holder out of brass sheet. If you have a fuse box on the bike maybe you could check that. It certainly sounds electrical to me.Another idea would be to use a multimeter to check the ignition wiring through the kill switch and ignition switch. Quote
skikman Posted July 25, 2012 Author Posted July 25, 2012 Sounds like a problem I had with one of my XJ550s years ago. In that case the fuse holder had corroded through and was intermitently losing contact (it was used hard in all weathers). I fixed it by making a new fuse holder out of brass sheet. If you have a fuse box on the bike maybe you could check that. It certainly sounds electrical to me.Another idea would be to use a multimeter to check the ignition wiring through the kill switch and ignition switch.fuse holder looks fine also the wires and connections from the kill switch look fine.not sure how to check them with multimeter but the bike only cuts out for a split second so would be hard to dected.i have since flushed out tank and cleaned petcock filter,went round all connections with wd40.the one to the cdi seemed a bit loose so was hoping that was it.was away for a week.came back yesterday.took bike out today and done 40ish miles and engine cut out.brought it to a stop and tried starting it again.BANG.big backfire.tried again and it started no prob and has run well the rest of the day.this is doing my head in.any more ideas?????? Quote
eastanglianbiker Posted July 26, 2012 Posted July 26, 2012 might be worth checking that the breather in the fuel cap isnt blocked next time it cuts out on you open the fuel cap see if you get a hiss of air enter the tank ,if the breather is blocked it creates a vaccum within the tank stopping the fuel flow to the carb and once you stop for a second it is at times long enough for it to recover on its own Quote
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