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TOPIC: ZG1300 running much to lean

ZG1300 running much to lean 2 weeks 12 hours ago #24604

  • Kawboy
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Phil wrote: Hi Gavin, I fitted an adjustable fuel pressure regulator to my ZG some years ago, but there's a guy on the European Z1300 Facebook page that's fitted a Herko PR4055 fuel pressure regulator that's pre-set to 45 psi & he says it works fine, I've set my adjustable regulator to about the same pressure & it runs better. Can be found on Ebay & is pretty reasonable at about 15 quid. As far as fuel pumps go I fitted a Pierburg automotive fuel injection pump some time ago too, wasn't cheap, but there is a cheaper alternative, search for "Holden Commodore VL Main EFI External Fuel Pump RB20E RB30ET 070" on Ebay, that will do the same job.

I'm a little concerned with the Holden pump. It's rated to feed a 5.0 L V8 engine which is almost 2-1/2 times more fuel than the ZG would need.
I found a fuel pump on EBay for Kawasaki Vulcan 1500 that I think would be more in line with the fuel needs of the ZG. See
EBAY inline fuel pump

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Last edit: by Kawboy.

ZG1300 running much to lean 2 weeks 55 minutes ago #24606

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Well I went to the bike this morning and the fuel pump that didn’t work yesterday now does( we don’t know how long this pump has been dry as it came in a box of spares) , anyway I have done more pressure test with exactly the same results as with the original
Ignition on pump priming = 33psi
Tick over = 30 psi
4500rpm 28psi

There doesn’t appear to be any leakage apart from what normally occurs when switched off as after several minutes the pressure has only dropped 5psi.
I have been thinking on what gives the required pressure other than the pump and regulator or leaks , could a weak tank return valve cause the drop as it is only a few psi, I know a blocked one causes over fuelling so in theory a weak one or not being able to fully close would cause an opposite effect

Cheers Gavin

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Last edit: by Gavin.

ZG1300 running much to lean 1 week 6 days ago #24610

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Kawboy wrote:

Phil wrote: Hi Gavin, I fitted an adjustable fuel pressure regulator to my ZG some years ago, but there's a guy on the European Z1300 Facebook page that's fitted a Herko PR4055 fuel pressure regulator that's pre-set to 45 psi & he says it works fine, I've set my adjustable regulator to about the same pressure & it runs better. Can be found on Ebay & is pretty reasonable at about 15 quid. As far as fuel pumps go I fitted a Pierburg automotive fuel injection pump some time ago too, wasn't cheap, but there is a cheaper alternative, search for "Holden Commodore VL Main EFI External Fuel Pump RB20E RB30ET 070" on Ebay, that will do the same job.

I'm a little concerned with the Holden pump. It's rated to feed a 5.0 L V8 engine which is almost 2-1/2 times more fuel than the ZG would need.
I found a fuel pump on EBay for Kawasaki Vulcan 1500 that I think would be more in line with the fuel needs of the ZG. See
EBAY inline fuel pump

The fuel pressure regulator maintains rail pressure regardless of what is supplied form the pump, excess is put back into the fuel tank via the fuel return line. The Pierburg pump I fitted to my ZG was originally intended for a Volvo 3.0 V6 & has been fine. Looking at that VN1500 pump you'd have to do a bit of extra plumbing to make it work as both pipe connection stubs are on the same side.
Only dead fish go with the flow

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ZG1300 running much to lean 1 week 6 days ago #24611

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Gavin wrote: Well I went to the bike this morning and the fuel pump that didn’t work yesterday now does( we don’t know how long this pump has been dry as it came in a box of spares) , anyway I have done more pressure test with exactly the same results as with the original
Ignition on pump priming = 33psi
Tick over = 30 psi
4500rpm 28psi

There doesn’t appear to be any leakage apart from what normally occurs when switched off as after several minutes the pressure has only dropped 5psi.
I have been thinking on what gives the required pressure other than the pump and regulator or leaks , could a weak tank return valve cause the drop as it is only a few psi, I know a blocked one causes over fuelling so in theory a weak one or not being able to fully close would cause an opposite effect

Cheers Gavin

Not really, that valve serves only to stop fuel leaking out when the tank is removed.
Only dead fish go with the flow

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