Ahh...There's the air leak!

[Nelly]

I knew I was having issues with the bike running lean last year, so I knocked up a homebrew leak down set up using some plumbing fittings and boiler parts mated to a bike inner tube valve. Sealed the exhaust port with a 40mm waste pipe stop end and pumped it up. Liberally sprayed gas leak detector around the top end............... spot the leak!
It's a poor seal between the Atomic mini reed valve and the body. It's not actually leaking from the rubber.

[Digger]

[coaster]

I'm intrigued about the way you sealed the exhaust, any more details?

Colin

[Nelly]

I'm intrigued about the way you sealed the exhaust, any more details?

Colin

I used a McAlpine 40mm Multifit waste pipe stop end. http://www.screwfix.com/p/mcalpine-t23u ... 40mm/96079
It blew off like a cannon at first but I then utilised the springs from the BGM Clubman exhaust to pull it down onto the stub. May not be a completely perfect seal but it allowed me to get enough pressure built up to find the air leaks.

[coaster]

I'm intrigued about the way you sealed the exhaust, any more details?

Colin

I used a McAlpine 40mm Multifit waste pipe stop end. http://www.screwfix.com/p/mcalpine-t23u ... 40mm/96079
It blew off like a cannon at first but I then utilised the springs from the BGM Clubman exhaust to pull it down onto the stub. May not be a completely perfect seal but it allowed me to get enough pressure built up to find the air leaks.

Thanks, I used the dead simple method of using a short section out of a bicycle inner tube complete with valve and attaching one end to the inlet and the other to the exhaust stub. However, even when I'd corrected the leak on the exhaust flange, the inner tube just inflated and I couldn't see any meaningful pressure on the gauge. It still revealed a significant leak on the flange though.

[Nelly]

I tried that method first, hence where the valve stem came from, but it wasn't really working too well for me. As you say, the inner tube inflates and becomes a bit of a nuisance.
The contraption came about from scraping through my "bitsa" box I carry on the van. (bitsa this, bitsa that) just bits left over from replacing boiler parts.
The bottom part that fits perfectly into the carb rubber is the base of an auto air vent from an Ideal Isar combi boiler. Any heating engineer will tell you these are the combi's from hell, but this part sort of redeems itself, I couldn't believe what a perfect fit it is, even the groove lines up perfect! Just unscrew from the brass upper body and remove the o ring from the groove.

[Nelly]

Here's a pic of the modified leak tester which now includes a 1 Bar/15 psi scale pressure gauge. It can be pumped up and the pump removed, so it can be ensured the leaks are not coming from the pump apparatus.
Note also that the waste pipe stop end, which was sealing the exhaust stub, has been replaced by a rubber bung from King Scientific, bung no 37, which can be found here
http://www.kingscientific.co.uk/lab-equ ... -number-37
They do quite a range of different size bungs, with and without holes.
The leak detector spray is from screwfix and is a product I use a lot to test for leaks on gas systems and compressed air systems.

[coaster]

Thanks for the update Nelly

[Dimitrios_231]

Very useful info,thanks for sharing

[Nelly]

No Problem.
This set up works a treat. I pumped it up to around 7.5 psi and left it whilst I got on with the wiring for the SIP speedo etc.
The engine is now back in the bike, it's been a productive evening.

[rossclark]

Does the 'h' shaped bit of piping come with the gauge?

[Nelly]

Does the 'h' shaped bit of piping come with the gauge?

The h shape is a 1/4" BSP Tee and elbow screwed together.
All the fittings and gauge came from a hydraulics/pneumatics supplier, Linden Hose in Newton Aycliffe, except the brass fitting which is a 10mm compression plumbing connector and the part described above off the auto air vent. The valve stem was cut from a bike inner tube and fitted in the 10mm fitting perfectly but it was trial and error with a few knackered inner tubes from a bike shop.