Tango Posted August 30, 2012 Posted August 30, 2012 BonneiBird's Bonneville developed a misfire when we went away at the weekend......which seemed to disappear when the bike got warm and after a short distance of running. Anyway, we had a look the other day and the misfire seemed to be on the lefthand cylinder.......so BonnieBird got some new plugs (they were only changed around March anyway)....and as I was at a loose end today I swapped them. I also checked the HT leads were plugged into the coil OK and the plug caps were tight. When I started the bike (with the seat off) I heard a small electrical type of pop when I hit the starter. So I investigated and found the -ve battery terminal was slightly loose....tightened it up and fired the bike up......no sign of any misfire now.... So.......Loose battery terminal?....but the starter span OK....and why would it only affect the lefthand cylinder?.......plugs?.....they were only replaced a couple of months back and have only covered a couple of thousand miles tops.HT Leads?......but they all look clean (no corrosion) and were fully seated in the coils.Hmmmm......don't you just hate it when you can't put your finger on the actual cause.... Haven't really run the bike yet....but the misfire when it was cold looks like it's now sorted.... Quote
davefly76 Posted August 30, 2012 Posted August 30, 2012 Might be the HT lead breaking up inside..? Quote
Bonniebird Posted August 31, 2012 Posted August 31, 2012 Took the Bonnie out for a longish run today and it still has some problems.Started up fine from cold and first 20 odd miles up to Webbs at reasonable speed also fine but, when slowed down through sub-30mph village at Eye it was missing and generally pretty 'lumpy'. Fine again once moving but had a few intermittent problems when revs dropped e.g. roundabouts - not every time though. Sorted itself out for a while and then problems again later on in traffic. Run back from Webbs and then slow through Huntingdon, fine again.V.frustratingThinking maybe air filter????Have ordered one on fleabay Quote
Stu Posted August 31, 2012 Posted August 31, 2012 Might need the carbs/throttle bodies balancing Quote
Bonniebird Posted August 31, 2012 Posted August 31, 2012 Gonna be due a major service soon - valve clearances, carb balancing etc.. ie. probably not a DIY job but £450 from Triumph. Eeek Webbs reckon I'll get a discount if I do it some time over the winter so I'll try a few cheap options first Quote
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