Why.

Hi.
I've not been able to take the bike out for a few weeks but I have started her up and had her ticking over every day for a few minutes just to turn the juice around. Once warmed up and with the choke of she sounds pretty good and ticks over nicely.

Yesterday I had some time and went for a ride but found that once actually running there was a problem. Without giving the throttle any more she would suddenly take off and if I shut the throttle down she still carried on roaring.

I stripped down and cleaned the carbs some time ago and have a new throttle cable (well lubed) have checked the choke linkage and that seems ok. I've also had the boots off (hate that job)and checked that the slides come crashing down

It's bloody dangerous anyone have any ideas as to what may be the cause?

Faighaigh.

 

Hard to say, but most of the threads I've read dealing with a racing idle problem trace it back to a vacuum leak of some sort, usually around the boots between the carbs and the cylinder head.

Another possibility is that there is a vacuum leak, not in the carb boots -- but in the petcock. Example: I had a racing idle problem of my own a few months back. Long story short, I ended up putting a stronger spring on the vacuum diaphragm side of the petcock. Problem solved. (It didn't fix the dribbling fuel problem I put it on there to solve... but that's another post.)

I'd also check to see if the bit on the carbs that the cable hooks into isn't binding somewhere. Also doublecheck the cable routing; I misrouted my clutch and choke cables some time ago, which had the unintended side effect of causing my engine to rev higher when I cranked the handlebars over to the left.

Anybody else care to chime in?

 

Agreed.

Re-check everything from the start, hopefully it is a simple fix

 

Thanks fella's.
The cable is routed as per the manual but I'll check for vac leaks. This fault does'nt seem to be regular just occurs now and then which is one of the big worries, really would'nt fancy sudden and unexpected acceleration just as I'm cranking her down round a nasty bend with a 400 foot vertical drop to my right.

Mick Faighaigh.

 

Could also be a rich mixture via one or more carbs have a leaking float valve.