Anyone use a fuel pump on their scoot?

Bluemeanie wrote:

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:

A little more info concerning the performance difference between full vs low tank level.
I am not talking about cruising down the road thinking to myself...'hhummm, did I notice a little skip back down the road, there?'
I am talking,,"_OH CRAP, I'm _NOT_ going to make it home at this rate".
I am certain of one thing; As Blue pointed out, if I needed a fuel pump, then someone else would have needed one long before I came along. I have not even synced the carbs yet, so I have a little more experimentation to do.
Dahlonega is in the north GA. mountains if anyone has a little insight into a great mechanic for these old scooters.
Speaking of which, youse guys haven't seen it yet, so I intend to hook up with one of my girlfriends at university this weekend or next week and take a few pics. I can then post one as my new avitar. My cats are all way too calm looking to be fun, except for Lapis, that is.

Thanks for the exploded view Patton. Is the check valve in the center of the diaphragm or does it vent out the back side, center of the diaphragm cover? Further, how do I check this particular check valve for proper functionation.

There's a simple test you can do.

Let's say worst case scenario your bike gets 20 miles per gallon. At 100 miles per hour, you would need 5 gallons per hour. That is 1 gallon in 12 minutes. Fill the tank and put it on prime. See if you can fill a one-gallon container in less than 12 minutes (through the fuel filters).

Post edited by: loudhvx, at: 2007/11/29 21:01

loudhvx wrote:

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).<br><br>Post edited by: loudhvx, at: 2007/11/29 15:18

Thanks Loud
You must have STP or something, because I never actually stated I was using paper filters.
I do, however suspect when my tank level is low, that you are dead-on in your prediction; that of no continuous fuel flow, and I mean not even a drip, even though the filters are "brand new".
The thing pulls like a total bitch when it gets a good supply of petrol. This leads me to believe that I don't have a very big issue.

Yeah I haven't really figured out a good solution yet. The paper definitely filters better than the scintered brass filters I've tried. So far, the last couple years, I've just been throwing new filters on every couple months... I used to go years before changing a filter with no problems and the carbs stayed very clean.

BTW, my first symptoms show up when the tank is low. It acts like I ran out of gas, but going to reserve doesn't help. When I go to fill the tank it only takes about a gallon of gas to fill up. Then it runs fine. That's when I know it's time for a new filter. I try to keep the tank full until I can slap in a new filter.

loudhvx wrote:

There's a simple test you can do.

Let's say worst case scenario your bike gets 20 miles per gallon. At 100 miles per hour, you would need 5 gallons per hour. That is 1 gallon in 12 minutes. Fill the tank and put it on prime. See if you can fill a one-gallon container in less than 12 minutes (through the fuel filters).<br><br>Post edited by: loudhvx, at: 2007/11/29 21:01

_WOW LOUD_
You need a job? I could benefit from having you and your kind of logic around here for a while.
Everyone is making some really good suggestions as far I am concerned. It is however, a little too late to get started tonight plus it is about 45°F and my garage is not heated. I have to work the planet and observatory tomorrow after work, so I won't get a chance to check anything till the weekend. Stay tuned for chapter two.
Also over the weekend, I will probably try out my homemade manometer unless someone in the area has a four tube one for sale, cheap. No joke. I would like to do it right, and I read that the single tube is too 'fiddly'.

JimatMilkyWay wrote:

StreetfighterKz wrote:

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

Later, Doug

Are you saying that he installed a fuel pump?

Yeah, he installed a fuel pump, from a Yamaha, on his 1300. He mounted it to an aluminum plate that's hidden by the lower fairing.

I can take a pic if you want.

Later, Doug

Could the problem be low float levels?

FloridaBiker wrote:

Could the problem be low float levels?

Nope. But a good question FloridaBiker. I set them myself and service level is not a difficult concept to understand. I didn't need to bend the tangs on any one float more than a fraction of a mm. Further, if I had known about WG's coil repower mod at the time, I would have started with that and would not have even checked float/service levels. It is possible that I just assumed, without adequate detective work that black as pitch plugsX4 meant fuel issues, not ignition & compression issues. I did the repower mod first, with success apparent only by the fact that my coil voltages were then 11Vdc+ instead of 9Vdc-, but no improvement in performance. Then I went out and bought myself a ('another', actually) compression gauge and found out the biggest problem was most likely valve gap related. She hummms like a mother---*§&#911;&#1174;&#1498;&#1569;* now!

JimatMilkyWay, I have never had a fuel filter on my bike. I've looked at the strainer in the tank and it appears to be fine enough to filter anything out. I've run bike for 27 years and over 51,000 mi with no carb problems at all. This is just my opinion...

This is just a theory here, and I'm basing it on something I encountered just the other day with a gas-operated paint sprayer that I repaired...

The paint sprayers engine ran great with a full tank of fuel, but anything below half a tank (either at idle or under load) and it would sputter/backfire, then eventually die. It wouldn't restart until the tank was full again.
I pulled the fuel tank and drained it, then generously sprayed carb cleaner into it while tilting it sideways - I noticed a powder like sediment (it was paint) swishing around in there.
Apparently the painters weren't careful when refilling the tank. :whistle:
After thoroughly flushing the tank/fuel hose and cleaning the carb, the problem was gone.

Now here's the theory part.

If there is a similar type of sediment (fine rust particles, etc.) in your bikes tank, with it full the sediment would be diluted enough (plus the pressure of the fuel due to it's weight) for enough fuel to make it through the petcock filter in the tank and keep your bike running.
At a lower fuel level the sediment would be less diluted, and there will be less pressure to "force" the fuel through the petcock filter in the tank since the overall weight of the fuel is less = fuel starvation.

My suggestion would be to pull the tank and drain it into a clean, open bucket/clear container so that you can check for debris/sediment. Then remove the petcock and thoroughly check the filter (and both the "ON" and "RES" tubes in it) for any signs of clogs.
Then use something that's clear (acetone, etc) to flush the tank and check for any sediment.
Once that's done, then try running the petcock w/o the in-tank filter on it, which should eliminate any issues relating to it causing the problem.

If this doesn't remedy the problem, you'll at least know that your fuel tank and petcock are clean as a whistle and not suspect.

I had the same thought process but did not know how to explain it. Good job Chris..