I have a standard 3en2. Standard exhaust/fuelling/airbox.

Basically the bike seems to have a surging fast idle, idle adjustment in any form does very little however the surging idle will stop if the engines revved hard, the engine will then slow and stop. (This is all stationary)

I have checked over airbox, carbs and fuel, all seems OK. Started playing around with the exup cable and valve and decided to disconect the servo cables as a test. I opened the valve and jammed it fully open. PRESTO consistent idling and no cutting out. However now the bike idles too high and is on the very lowest adjustment both idle adjust and the throttle adjuster!

At idle the servo or cables (im guessing) arent correctly set up. Any advice, ideas or ways to do away with the ruddy exup and getting an acceptable idle?

Cheers All

James

You say the cables are set up right ...
are the cables frayed at the exup end where they come out of the sheath ?
Are they slack when they're on the valve - you can adjust them at the servo end. They're only supposed to be finger tight.
A high idle can be fuel starvation check the fuel filter's clean or preferably new andcheck the filter on top of the fuel tap.
Have a look at the air box and see if it's seated properly - if the rubbers have gone hard get some new ones from Fowlers in Bristol (you have to quote your frame number).

Now for the complicated bit.
The 400 engine revs high and this causes the valves to stretch until the tollerance between the cam and followers is reduced to zero. It's only my theory atm but if it close to this the compression drops as the valves don't seat properly. Give it a compression test to to get an idea.