[GK76A] Sticky(tricky?) vacuum chamber in fuel tap

Forum rules
Please can you post items for sale or wanted in the correct For Sale section. Items / bikes for sale here will be removed without warning. Reasons for this are in the FAQ. Thanks
Post Reply
vinibali
Settled in member
Reactions:
Posts: 6
Joined: Tue May 29, 2018 3:19 pm
[GK76A] Sticky(tricky?) vacuum chamber in fuel tap

Post by vinibali » Sat Apr 27, 2019 7:58 am

Hello there,

does anybody have some idea what can I do? I had so much problem with the fuel cock in the past months.
I checked and cleaned everything, but later ended up to buy the Tourmax FCK-24 kit.
After I exchanged all the parts from the kit, I started to play with it (making vacuum with my mouth) and realized that doesn't seem to work so well.
I know how should it work and the fundamentals of the tap. So the auto fuel cock function is not working at all, even I try to jogging the tap. The only way of course if I open the screws on the chamber and the vacuum goes away. So this might be a silly question:
May I do so much pressure which couldn't handle by the small spring?
What could be the rough amount vacuum which can I measure in the 4th cylinder when the engine is running?

Image

Thank you

moforockband
Familiar Member
Reactions:
Posts: 340
Joined: Wed Jun 03, 2015 9:41 am
Bike owned: GK73a SP CRM250 mk3
Re: [GK76A] Sticky(tricky?) vacuum chamber in fuel tap

Post by moforockband » Mon Apr 29, 2019 11:07 am

That kit isn't for the 400. I'd buy a 2nd hand 400 unit, or a short manual RH 8mm tap with 35mm spacing, which work better than the auto units. Just remember to shut it off every time if you get one.

vinibali
Settled in member
Reactions:
Posts: 6
Joined: Tue May 29, 2018 3:19 pm
Re: [GK76A] Sticky(tricky?) vacuum chamber in fuel tap

Post by vinibali » Tue Apr 30, 2019 8:34 pm

hmmm seems like it is, look at the URL below:
https://hu.fowlersparts.co.uk/parts/596 ... /fuel-cock

at least mine was equipped with this one.

moforockband
Familiar Member
Reactions:
Posts: 340
Joined: Wed Jun 03, 2015 9:41 am
Bike owned: GK73a SP CRM250 mk3
Re: [GK76A] Sticky(tricky?) vacuum chamber in fuel tap

Post by moforockband » Tue Apr 30, 2019 9:04 pm

The only listing for that tourmax kit is for the 1100. If it all fits well it should work. Check that the valve is free to move in the tap body. You could polish the bore with metal polish to try and make it easier to open.

Hubbskiboy
Settled in member
Reactions:
Posts: 77
Joined: Tue Feb 02, 2016 8:57 pm
Bike owned: GK76A 1994 and 1990
Location: Stourbridge, West Midlands
Re: [GK76A] Sticky(tricky?) vacuum chamber in fuel tap

Post by Hubbskiboy » Fri May 10, 2019 3:15 pm

Best way to clean these fuel taps is to completely strip them, which includes removing the press fit collared washer.
I didn't do this before because I was afraid of damaging the washer and the seal, but it's the only way to properly clean the internals.
I also had both fuel taps vapour blasted which caused a large amount of the glass grit to get stuck inside.
Used a blind bearing puller and some heat to get it out, no problems.
Much smoother turning now!

Image Image Image Image

vinibali
Settled in member
Reactions:
Posts: 6
Joined: Tue May 29, 2018 3:19 pm
Re: [GK76A] Sticky(tricky?) vacuum chamber in fuel tap

Post by vinibali » Sat Jun 08, 2019 11:14 am

I think I'll have another try without touch the tap again and hopefully it won't leak anymore.
The bore and the plastic plug don't look so bad, and I already changed the outer seal on the tap.

Thank you guys, I'll make a feedback soon


Post Reply