Do you own a GB400/500?

**JeremyW** · 7th April 2008, 13:05

I have a carb off a GB400 which I am using on a SRX400 project. Just there are some holes in the carb which I am not sure about as in the pics below.

Could anyone please look on their bikes and let me know what they are attached to or where they go? Will be much appreciated.

**Henk** · 9th April 2008, 04:29

This is a guess as I don't have one of these bikes so don't have one to look at but have been fiddling with bikes for years.
Have a look down the What and airbleed holes, I think you will probably see a little brass ball driven in there. If thats the case they are blanked of holes that are used to make channels in the carb during manufacture. I have no idea what the second pic shows, it looks a bit like a the pump on a pumper carb from the outside but they usualy get their fuel internaly if I recall correctly.

**F5 Dave** · 9th April 2008, 17:24

A pump on a pumper carb usually looks like a plunger, that looks like a diaphragm which is usually used to stop gas when the engine isn't running, but on the tank, see if you can blow through the fuel inlet or if this needs suction to open. The brass tube at the very front on the top would be what I would expect to connect to the tank petcock. Perhaps there wasn't room in the GB design, need to look at a tank.

The simple tubes look like gas overflows. take carb float off & blow down them with some tube & should correspond to drillings or brass vent tubes.

that inlet manifold looks a bit like some keewhee injun-eewity from a cut off cortina manifold

.

**JeremyW** · 9th April 2008, 18:32

Haha yea the manifold is a little rough. It does fit perfectly which is good, its from a yfm660 grizzly.

Thanks for the ideas guys, I will take her apart and try what you mentioned. The diaphragm does confuse me. The original SRX carbs had a similar diaphragm but that was between the two carbs whereas the GB is a single carb setup.

**Bonez** · 9th April 2008, 19:10

The under the cover is an air shut off valve, it just has a hose connected to the brass vacuum tube on the front of the carb. USA model 500s have a t-peice which goes to the secondary air supply system. I'll have a gander at my gb400s carb tomorrow in daylight and post some pics if it.

The big tube on the same side as the fuel inlet(as correctly labeled) is the air vent and normally has a tube connected and routed over to the other side/rear of the carb though a tab connected to the of the air shut off valve mounting screw. This tab looks pushed down in your pic.This tube is then routed down behind and below the rear of the engine/frame.

**JeremyW** · 9th April 2008, 19:48

Originally Posted by Bonez

The under the cover is an air shut off valve, it just has a tube with a t-piece on it connected to the vacuum tube on the front of the carb. I'll have a gander at my gb400s carb tomorrow in daylight and post some pics if it.

Wicked. Thanks

**Bonez** · 10th April 2008, 15:46

The pics didn't come out that well Jeremy. Carbs tucked well up in the frame. Connect hoses as I mentioned in the previous post and post them in this thread and I'll tell you whether it's correct or not. The smaller front lower cast tube, the one you have noted as air bleed, has nothing attached to it.