GPZ900R Vacuum Fuel Tap...............Questions.

2 things come to mind Pete.
First, are you using vacuum line for the vacuum hose from the intake manifold to the fuel valve? If your using fuel line, the wall thickness may not be substantial enough to handle the vacuum. The hose may collapse and cause an issue. also, do you have a good fit to both the vacuum nipple on the intake manifold and a good fit on the fuel valve? A minor leak in the vacuum hose just may be enough to cause a low vacuum in that hose such that the spring in the fuel valve diaphragm can overcome the vacuum and close the valve.
Second, you've elected to go with a GPZ900 vacuum operated valve and just maybe the spring in that diaphragm is stiffer than what would have been in the original KZ1300 fuel valve. Just throwing it out there for thought.

Hi Pete,

For info. I installed one of these and I’ve had no issues.

eBay No 372813185987

Kawboy,
Thanks for your reply.

The original KZ1300 Petrol Tap does not have a Vacuum Inlet, its just a gravity fed tap, its only the GPZ900R tap that has a vacuum inlet / diaphram. Thats the whole point of fitting it, to prevent it leaking past and flooding the carbs and airbox when the bike is not running.

I have fitted 2 or 3 of these taps in the past to previous 1300's and not had any problems, which is why I cannot work out why I am having the issues with this one.
I always use a thick walled pipe for all fuel and vacuum taps as I have done with this one and keep the vacuum pipe as short as possible and its always been 100% ok in the past
I did fit a new diaphram kit to the tap before fitting onto the tank just to be sure it was ok and this had a new spring included.
As you say, I think the only thing that can be restrcting it now is the spring itself, as when its in the PRI position (bypassing the vacuum spring entrance) its perfectly ok.

Needs further investigation.

Pete F
UK

Mizz,
Thank you for your reply.

Looking at the tap you have fitted as seen on Ebay, the petrol pipe nozzle is in the wrong direction to the original tap (as seen in the Ebay photo below).
The original tap has the nozzle facing BACKWARDS (as seen in my earlier photos) towards the middle of the carbs and your tap has it facing the the RIGHT.........towards the rear of the bike. ??

Can you please take a photo of your tap as fitted to your bike........I would like to see how it looks and works and how you route your petrol pipe to this tap. ???

Thanks again.

Pete F
UK

Hi Pete,

I put a in-line filter on as an added precaution. If you omitted the filter there would probably be enough room to route the fuel pipe in front of the down tube instead of behind the tube like I have.

I don't know if you've looked at your previous posts on this subject, Pete, but a few years ago it seems you had a similar problem -

www.kz1300.com/index.php/forum/carburato...tap-problems?start=0

It would be interesting to connect the vacuum side of the tap to your Mityvac vacuum pump ( or similar ) and check the flow of fuel into a container when you apply a vacuum, and compare the flow with the tap in "Prime " position. Also, it would reveal a possible vacuum leak at the tap / diaphragm.