Where should this pipe go to?

17th September 2016, 20:11

I've blanked this pipe off when I took the original airbox off, is that right?

It's still hunting on tickover but new ICV fitted & it's the same

17th September 2016, 20:21

Got a feeling that one needs a mini breather filter fitted to it.

17th September 2016, 20:25

Might try pulling the bolt out as a first stop then to see if it cures the issue, then get a filter if it does.

17th September 2016, 21:25

It's a breather pipe that connects to the crankcase,don't block it off

17th September 2016, 21:50

It's the vacuum part of what is called the 'Positive Crankcase Ventilation System' and it does pass a small amount of air that will help supply adequate air quantity to maintain the correct idle speed.
The JP4 crankcase doesn't breathe in quite the same way as the J4 and doesn't have that pipe so it would be better to introduce a small amount of air via the pipe that you have to get a stable idle. However, leaving it completely open is probably going to be too much air, so make a bush to fit inside it. Make the bush out of brass or Ally so it's easy to drill. Start with a centre hole about 1.5mm diameter and increase it in 0.5mm steps until it idles properly.