Hi all,

After a fair lay up I got my bike prepped for its MOT, but found mice had nested in the airbox and eaten my foam filter! Luckily the wire mesh seemed to prevent any it of dropping into the carbs. I carefully vacuumed and cleaned around the mouths/slides and I think it looked pretty clean, I got hold of another piece of foam (slightly thinner) and put this in its place.

Anyway, it starts on choke and sits at about 3k rpm, but as I ease off the choke, it slowly dies on tickover. Off choke and out on the road, it seems to rev out with good pick up until about 8k then feels restricted and lumpy. I whipped the tank off again and checked the filter and housing - all looks ok. I drained the tank, checked the tap filters and put in fresh fuel. Same again. Any ideas? Is this replacement foam possibly the problem (perhaps I could try it without it?) or do I need to (gulp) strip the carbs?

Cheers all

I would get a new filter first, these bikes are very fikle when it comes to carb setup. Go back to standard and see what happens. the foam you have used may be way too free flowing.
Did you drain the carbs before the lay up? or did you run it regularly?

Cheers Skinnydog, it had a 'tuned' performance foam filter a few years back and was running great. I may give the tuner a call and see if he has the same material still, kick my self for not keeping a remnant of it. If I try it without the filter (just the mesh in the airbox) and it runs well would that suggest the foam is restricting flow? or would you expect the opposite i.e. it would run even worse?

Capitano wrote:Cheers Skinnydog, it had a 'tuned' performance foam filter a few years back and was running great. I may give the tuner a call and see if he has the same material still, kick my self for not keeping a remnant of it. If I try it without the filter (just the mesh in the airbox) and it runs well would that suggest the foam is restricting flow? or would you expect the opposite i.e. it would run even worse?

itll likely run like a bag of spanners with no filter but you can try it

proably filter isnt filtering enough..

The wrong or no filter may kill the 8k plus rev range but not the tick over.
It will run weak without filter but should tick over, not just die, but pick up will be poor.

Mouse piss is corrosive, a friends V4 needed a new front head and injector bodies when they nested in his air box, but not sure for how long as the bike was not being used.

Strip and clean the carbs, sounds like pilot jets/airways are blocked if it runs on choke [bypasses pilot circuit]

So I went back to it, and realized I'd missed out the sub-filter from the box (the little one at the front). This has made an improvement, so I think the root is the new filter. I'm going to swap it out for something else, maybe a paper element and see if that helps. it ticks over now when warm but only if the idling speed is set 2k+, below this is falters then stops.

Capitano wrote:So I went back to it, and realized I'd missed out the sub-filter from the box (the little one at the front). This has made an improvement, so I think the root is the new filter. I'm going to swap it out for something else, maybe a paper element and see if that helps. it ticks over now when warm but only if the idling speed is set 2k+, below this is falters then stops.

having re-read it do as arsey30 has said and clean the carbs out / check the jets / tubes and float heights and youll have a good solid base to tune from.

sub air filter shouldnt ake a difference to running as it only cleans air going to the carb slides..