Hi Can any of you good people help? My brothers 2006 20k miles Bonneville has developed an idle problem. It goes like this.... Bike starts up fine from cold and runs good. 'Choke' off and it will idle OK around 1000 rpm, throttle response good, seems to be no problems. After about 10 minutes idling, the revs gradually start to fall over a period of about 5 mins. Revs get down to about 500 rpm then stalls. Temperature related? Bike will start up fine then just will not idle, just keeps stalling. The bike is completely stock apart from ignition module replacement a few years ago, but I don't think it's an ignition problem. He has owned it about 6 years and in that time the carbs have not been touched. I have suggested a carb clean and set up. It looks to me like a problem with the pilot/idle system. Thanks Paul
There is a very outside chance you have an air leak in an inlet boot. The normal thing is for an air leak to create a high idle, not a low one. However, if that has been adjusted out on the knurled knob then a thorough warm up will expand the metal inlet manifold into the rubber boot, seal the leak and the revs will drop. Counter intuitive but might explain why it takes a little while to present as a problem. Spraying WD40 or soapy water round the boots and vacuum caps will rule reveal any air getting sucked in.
Just as a matter of interest, why is he letting the bike idle for 10 mins ? It's an air/oil cooled bike so letting it idle for so long won't do it any favours. I would say it's likely to be heat-related so something electrical.
Thanks. Yeah, I get that about long idle periods. It's not a regular thing, he was showing me the symptoms. I was a bit concerned as well. But it does it whilst out riding. Stopping for junctions etc. it keeps wanting to stall.
Could be a breather in the fuel cap blockage or a coil is on the way out ? Coil gets weaker spark as it gets too hot, the weak spark causes poor running and stalling even at speed ! I rebuilt my motor with higher compression pistons, the coils couldn't produce a big/strong enough spark it produced symptoms similar to yours ! As coil was breaking down with heat, had to cool right down to run properly again.
Update on this... Some of this has gone through the carbs and there is some improvement. We went out for a decent ride the other day and it is definitely better, though still not quite right. Any length of time stuck at lights and the idle speed starts slowly falling away. I am fairly sure it's not electrical, when it's revved it is fine and there is no lack of power when opened up. Paul
I've just found this little filter, not a mention of it in the Haynes manual. where the fuel pipe goes between the carbs it is inside the fuel pipe where it joins the "T" piece. I will remove it, and fit new fuel pipe and external type filter from local car shop.
I’ve never had a problem with “old” petrol, I’ve often left fuel in my bikes over winter while they have been off road and they’ve always started and run fine when the time comes to get them out again.
This wasn't my post Joe But perhaps I should have finished this thread off... The bike continued to improve after using the stuff suggested by Dozer's Dad. Must have been jets gummed up after being stood idle for a long time. Paul
