Petrol tap issues, and the fix.

[Chancho196]

Hey folks, I know the usual consensus on here is to just buy a new one, but I like to fix everything I possibly can so here's the ins and outs of the humble petrol tap on my GS550E.

It's the one with the brass screw for priming, instead of the three-position lever. I'll keep you posted on its performance.

http://biketech7.blogspot.com.au/2016/07/suzuki-gs550-petrol-tap-overhaul.html

[Johnny]

Where did you get those O-rings? Do you know the part numbers for these? I think I have that same Wemoto kit laying somewhere, and this doesn't include the O-rings, right? I ordered the kit, 'cause I thought that the tap was leaking, but didn't try to install it, 'cause realized that it was just my new fuel line leaking which I had not clamped on properly. Now been thinking about installing this kit just in case, just 'cause I have it, but your detailed overview of the process doesn't make me any braver about fiddling with that tap... :/ At least I learned now about the PRI function, which I have believed for three years to be non-existent on my bike.

[Gorminrider]

So, the wemoto replacement is not a match for the OEM (the plunger being too short). That's interesting. Can you share the part number of the diaphragm? I have a petcock like that and have found it difficult to match the correct size from the descriptions other vendors provide...


I might be wrong but in your web link, with the new diaphragm installed, I get the impression that your float needle on that overflowed carb is also at fault ...because even if the vacuum tap is not sealing, your carb should not overflow- not via the vacuum line anyways-given the new diaphragm is installed correctly.

Also yes, the fibre gasket is indeed important. If it is on the wrong side of the diaphragm, I've seen instances where its thickness alone might not allow the plunger to seal properly. When I read your page, I wondered first if this was the cause....but if it's the plunger, it might explain why rebuilding these has such a high fail rate. I wish you had taken a picture to compare the two!

[Chancho196]

I should've measured the plungers, I'd guess at being 2mm maximum between the two, and yes I know one, or more, of the carbs is flooding and will sort that out soon. Took it out last night and it's going really well (very surprised how quick it is actually for a heavy 550). Pulled the hose off the tap and no dribbles, so that seems to be cured.

There was a tiny amount of petrol coming out of the airbox drain so I ran it for a while without the tap connected to drop the fuel level and today no smell of petrol in the garage. I need to take the carbs off to fit the original choke lever system anyway so all is good.
I've thrown the box away for the diaphragm so can't give you the actual part number, suffice to say it's the kit to repair the 44300-49172. It only includes the O-rings for the lever and the top of the petrol tap.

I bought the O-rings for the Prime screw from Lancashire Seals in the UK (on eBay). I measured the grooves in the screw as 3.28mm and 2.24mm, and ordered the following sizes in Viton material: 3mm x 1mm, 2.5mm x 1mm and 2mm x 1mm. A dab of vaseline helped them go in smoothly and so far, so good.

Johnny, if your tap is working properly I'd leave it. No point in attempting this repair unless the tap is knackered. I had no option at this stage and enjoy the challenge.

[Johnny]

I bought the O-rings for the Prime screw from Lancashire Seals in the UK (on eBay). I measured the grooves in the screw as 3.28mm and 2.24mm, and ordered the following sizes in Viton material: 3mm x 1mm, 2.5mm x 1mm and 2mm x 1mm. A dab of vaseline helped them go in smoothly and so far, so good.

Johnny, if your tap is working properly I'd leave it. No point in attempting this repair unless the tap is knackered. I had no option at this stage and enjoy the challenge.

Yeah, I'll leave that tap be for now, but thank you for these O-ring sizes, may come handy in the future. The original parts catalogue for my bike doesn't even list these O-rings, nor the diaphragm.