Anyone use a fuel pump on their scoot?

I _FINALLY_ took a little time out from homework to get my scooter back on the road. I just got her going and filled the tank a few weekends ago. Tonight, I filled the tank again. It runs pretty good; scratch that, it runs like a scalded ape, but it "runs out of fuel" early.
By that I mean it runs better, _MUCH_ better when I have a full fuel tank than when I have only a gallon and a half left. I have broken the seal on the fuel cap, driving down the road while low on fuel and it makes no difference in engine performance. I have taken the vacuum petcock apart and 'rebuilt' it, making sure the ports, screen and tank are all clear of obstructions of any type. I checked vacuum to the petcock. Not only am I assured that I have plenty of vacuum, meaning no vacuum leaks, but I can actually feel the petcock 'hammering' as the vacuum switches on and off. Check for yourself and see. I'll bet you can feel yours 'clicking' as well if it is working properly. The only non-stock item, so far as I can recall is two additional, new, tiny inline filters between tank and carb inputs.
Have any of youse guys ever used this delphi.com/shared/pdf/ppd/pwrtrn/gas_t11.pdf
I am interested in a full time micro pump, primarily to lend a little assist when fuel level drops.

JimatMilkyWay wrote:

...runs better, _MUCH_ better when I have a full fuel tank than when I have only a gallon and a half left. I have broken the seal on the fuel cap, driving down the road while low on fuel and it makes no difference in engine performance. I have taken the vacuum petcock apart and 'rebuilt' it, making sure the ports, screen and tank are all clear of obstructions of any type. I checked vacuum to the petcock. Not only am I assured that I have plenty of vacuum, meaning no vacuum leaks, but I can actually feel the petcock 'hammering' as the vacuum switches on and off...am interested in a full time micro pump, primarily to lend a little assist when fuel level drops.

If not already done, could try running with petcock in PRI position to determine whether that makes any difference.

Am thinking a fuel pump would over-power the designed float interaction with needles and seats, and disallow control of fuel level in bowls (among other bad things too horrible to mention near bedtime ).

Good Luck!

Patton wrote:

If not already done, could try running with petcock in PRI position to determine whether that makes any difference.

Am thinking a fuel pump would over-power the designed float interaction with needles and seats, and disallow control of fuel level in bowls (among other bad things too horrible to mention near bedtime ).

Good Luck!

Thanks for the rapid reply Patton. With your number of posts I think you must know your stuff pretty well.
The switch from "ON" to "PRI" position on the petcock has little-to-no effect. What does cause immediate, measurable response is to pull the choke full-on for a split second then back off, further confirming fuel starvation? Yes? No?
You may be right on the pressure increase at carb intake causing a rise in the fuelbowl service level. I have not tried to do so, but I suppose one could take the known component lengths and calculate torques produced by the float on the fuel shut-off needle. This might tell you if enough pressure is produced to essentially halt fuel flow when the bowls are full, even with the pump running.

...can actually feel the petcock 'hammering' as the vacuum switches on and off...bet you can feel yours 'clicking'

Could be wrong, but am thinking the hammering and clicking seem suspicious.

The tube from the carb supplies vacuum pulses to the petcock. A check-valve in the diaphragm cover is supposed to convert the pulses into a constant (non-pulsing) negative pressure in the diaphragm vacuum chamber.

Could be misinterpreting the quoted information, but am thinking the hammering and clicking should not be present while running. My understanding is the constant negative pressure should keep the diaphragm held open against the spring tension keeping the o-ring pulled out of its seat thereby allowing fuel to flow between the o-ring and its seat. And that the diaphragm should not be continuously hammering and clicking -- opening and closing -- while the engine is running.

Is it possible the o-ring may be damaged, or the check-valve clogged or damaged?

Btw, I don't know squat about fuel pumps .

time for a pingle petcock or two!

My dad installed one on his '80 Kz1300. I also bought him a Pingle petcock to go with it. I can't remember the exact model it came off but I know it was a Yamaha.
If you get one, try to make sure that its off a carburated bike. That'll insure that it doesn't make enough pressure to overwhelm the needle and seat. It also makes starting it easier.

Later, Doug

With the 10,000+ KZ's here at KZR I don't believe anybody has used a pump? The gravity system is so simple it's perfect. As far as a full tank vs low tank and runability.... that one has me a little baffled. The pulses you feel are just how it feels running vacuum off one cyl as opposed to multi cyl. Giving it choke and running better is a BIG clue!, but nothing else makes sense. Gotta think about this one... :dry:

For reference

Eliminate the fuel filters temporarily.

This has been a problem recently. I've had small paper fuel filters inline for years and years. In the last couple years something in the filters have changed or maybe the gas has changed, but now the filters stop flowing after a while. It's been happening to almost everyone I know running inline paper filters. Usually replacing the filter will cure it for awhile. But after a few weeks or months you can disconnect the output from the filter, put it on prime, and not a drop comes out. The problem occurs most often on hot days after the bike's been sitting for several days. If you can get it flowing again, it will usually work fine for a while. I think something in the filter, like glue, gets dissolved in the gas and when it sits, the glue settles on the paper, sealing it. If you can break the seal, the glue once again dissolves and the gas starts flowing again (albeit slower).

Post edited by: loudhvx, at: 2007/11/29 15:18

Patton wrote:

...can actually feel the petcock 'hammering' as the vacuum switches on and off...bet you can feel yours 'clicking'

Could be wrong, but am thinking the hammering and clicking seem suspicious.

The tube from the carb supplies vacuum pulses to the petcock. A check-valve in the diaphragm cover is supposed to convert the pulses into a constant (non-pulsing) negative pressure in the diaphragm vacuum chamber.

Could be misinterpreting the quoted information, but am thinking the hammering and clicking should not be present while running. My understanding is the constant negative pressure should keep the diaphragm held open against the spring tension keeping the o-ring pulled out of its seat thereby allowing fuel to flow between the o-ring and its seat. And that the diaphragm should not be continuously hammering and clicking -- opening and closing -- while the engine is running.

Is it possible the o-ring may be damaged, or the check-valve clogged or damaged?

Btw, I don't know squat about fuel pumps .

Thanks Patton
I was not sure my symptom/description made sense, but your reply seems to reflect otherwise. I shall investigate further to see if the check valve operation seems normal. Will also see if I really am "feeling" what seems like petcocking clicking. Hope I get time to work on it a little this weekend.
Jim@MilkyWay

themachine wrote:

time for a pingle petcock or two!

What would you know! You must be a total, out of control, super scary wild-man yourself, judging from your cats expression, which obviously lives in constant, mortal fear of it's very life, at all times.:laugh: :laugh: :laugh:

StreetfighterKz wrote:

My dad installed one on his '80 Kz1300....

Later, Doug

Are you saying that he installed a fuel pump?