Fueling issue

[Walters]

Hi Guy

Took the 1982 1100 Katana out for its 1st ride, it stared & ran perfectly ( in Prime position ) until I turned the fuel tap back to the On position. I've checked the vacuum pipe for connection issues or kinks but all seems good.
As it runs perfectly in prime position does this point to fuel tap vacuum problem or should I start looking elsewhere?

Any advice will be greatly appreciated.

Many thanks

[fossie]

It does sound like the tap diaphram is stuck or holed .
Have you checked the actual suck of the diaphram from the engine to end of pipe it may have an unnoticible crack or hole in it.

[Walters]

Many thanks

I’ll work back from the fuel tap & see how it goes - I should have mentioned that the fuel tap is very stiff & a pliers is needed to turn it from on to reserve & back - have a strip down & see what’s happening, I may be back for advice later

[Uncle Bob]

If you are taking it apart get a new fuel tap diaphragm kit from NRP and fit it. Only £18
https://nrp-carbs.co.uk/shop/index.php? ... ct_id=3288

[Kryten]

If you are taking it apart get a new fuel tap diaphragm kit from NRP and fit it. Only £18
https://nrp-carbs.co.uk/shop/index.php? ... ct_id=3288

Wot 'Ee Sed!

[Walters]

Cheers Guys - ordered

[Walters]

Hi Guys, - I,ve replaced the diaphragm kit as advised but still having trouble with the feeling, having replaced all the parts now there’s no fuel passing in the prime position but creating a vacuum astarte the flow, this is the same for the on position but I believe that’s correct, any ideas where I’m going wrong, I’ve tried refining the old diaphragm but this now gives the same problem ?

I’d be grateful for any input

Cheers

[fossie]

The fuel should flow in the prime position which is obviously pointing back towards the seat.
In ON position shouldn't flow until the vacuum is operated via the induction of the running engine.

Now the prime is actually operated by a bent bit of metal which pushes the diaphram open . It is very possible that the metal piece that looks like a spacer/washer is not bent correctly now.

[Uncle Bob]

Now the prime actually operated by a bent bit of metal which pushes the diaphram open . It is very possible that the metal piece that looks like a spacer/washer is not bent correctly now.

I have had this issue in one of my taps before. Bit crude how the prime works like that, but it does work as long as that metal prong is there to push the diaphragm back.
You can test all that with the tap off the bike. Get the prime working first and then take it from there.

[Walters]

Cheers for the info, does anyone know where I can find an exploded drawing of the assembly online, the one i’ve found in the service manual doesn’t show a vacuum operated petcock / just the standard on/ off / reserve version.

Thanks in anticipation