Any 550's out there running with no fuel pump?

[MikeScoot]

Hi Rohan,
I appreciate your well intentioned suggestions and comments, and also those of others.
There are, as you correctly state, many factors which can affect starting and running of an XZ engine or any other engine.
I have no reason to firmly believe that the fuel pump is causing me trouble - but nor do I have any reason to rule it out as a potential cause of trouble. But I am happy to have revisited the subject as doing so has revealed more good information.
Cheers,
Mike

[Ken Williams]

Rikugun, since your 3 Visions all filled their carbs with the petcock on prime, it seems safe to assume that behavior is normal.  Finding a Vision will not fill on prime is apparently an indication the pump diaphragms are stretched, as mine were. 

I also have the factory USA RK manual.  In the RK section, step 3 removes the 6 screws that hold the pump together.  Step 4 removes 3 additional screws to remove the regulator cover etc.  This step was incorrectly copied from the RJ section of the manual.  There are a total of 6 screws on the RK pump.  The RK pump contains diaphragms and check valves, no regulator.  The portion of the RJ pump casting that contains the regulator is not present on the RK.  Also, note there is no discussion of inspecting or installing RK regulator parts or the regulator cover.  After rebuilding my fuel pump, I discarded the unneeded parts from the RJ/RK rebuild kit. 

The pump return connects to the extra fitting on the petcock.  Inside the tank, that line extends upward roughly 8 inches. 

[Walt_M.]

I did not mention that I have an '82 tank and fuel tap on my '83 so I didn't have to deal with the return line when I installed the electric pump.

[Rikugun]

Ken, thanks for the clarification. I threw that caveat in about the manual possibly being in error for the very reasons you listed. Seemed odd to not even show a picture of those components. I tried an online parts diagram but it showed '82 carbs and petcock for the '83 model. Not much help there.

Rikugun, since your 3 Visions all filled their carbs with the petcock on prime, it seems safe to assume that behavior is normal.  Finding a Vision will not fill on prime is apparently an indication the pump diaphragms are stretched, as mine were.

I could only go so far to say the '82's likely all functioned like mine. EDIT: I read back through the thread a bit and had missed where kevin g indicated his RK did work as the RJ's. Thanks for the additional info Kevin.

I did not mention that I have an '82 tank and fuel tap on my '83 so I didn't have to deal with the return line when I installed the electric pump.

Sounds like a much easier install that way Walt.

[injuhneer]

I am late to this party so forgive me if I missed something. I am going to step back a bit. The simple comments here are just for clarity.

A few terms:
Vacuum Fuel Pump - Pump diaphragm operated by vacuum pulsations (stock)
Mechanical Fuel Pump - Pump diaphragm operated connected reciprocating element (cam, lever, etc)
Electric Fuel Pump(s) -
- Diaphram type: electro-mechanical movement of the diaphragm
- Positive displacement (gear, rotor): motor rotates displacement assembly

Now...

Stuff to consider in the quest for delivery:
Head - Amount of standing pressure due to gravity (matters on inlet and if pump against gravity)
Lift - The amount of liquid a pump can lift (suction) in a given system

There are other variables like the fluid itself, the diameter of supply and return (if any), volume per unit time, etc.

In the case of these bikes the vacuum pump only operates with, well, vacuum pulses. This being the reason one side of the diaphragm is connected to one cylinder. The intake pulsations move the diaphragm that in turn moves fuel. The check valves control the inlet and outlet to keep the fuel moving. The small amount of head is needed because the vacuum operated pumps don't pump air effectively if at all. This means that if the engine isn't cranking/running or if you have intake vacuum problems the pump isn't operating. With vacuum pulse present and a pump in good nick it will move fluid.

In the case of the XZ the fuel petcock is also connected to vacuum for similar purposes. Vacuum opens the valve when greater than the spring pressure allowing fuel to flow. PRI bypasses that function allowing fuel to flow by gravity.

I won't go down the mechanical pump road (think old cam/lever automotive fuel pumps) because I don't think anyone is running one of those although a very effective pump could be driven from many points on the engine.

The electric diaphragm pumps are self-regulating by virtue of the pressure relay inside the pump. Residual pressure holds the contacts open. When pressure drops the solenoid cycles and pressure is generated. Most of these require some head to operate. The usually don't have much lift (suction). My personal choice for a pump of this type of implementation is the automatic pump from a Honda CN250 Helix. There is a Virago pump that is nearly identical to the Honda pump. These pumps are durable and will prime and run with just a little inlet pressure (head). Also self regulating and dead reliable. Return line is optional but maybe desirable to circulate fuel.

Electric positive displacement pumps usually have high lift values. These are common on vehicles these days. Many varieties and all with good lift, pressure and output. Probably complete overkill for the bike. No regulation (external regulator needed). Also need a return. They heat the fuel if not allowed to circulate. Also generate enough pressure to overwhelm the float valve in the carb.

That is my little info-mercial.

Go forth and multi-pump!

[MikeScoot]

Thanks for the excellent summary, Mike.

[pinholenz]

In my opinion the biggest advantage of not having a fuel pump is that there is one less vacuum tube to leak. Switch activated electric pump makes sense. Presumably the vacuum activated fuel stop diaphragm on the fuel tank tap is also removed. Yet another source of vacuum leakage.

In the last couple of weeks I have been helping mates with flooded engines. They had full tanks and the entire contents of their tanks have ended up inside the engine and the sump. One on a Honda VTX1300  the other on a Yamaha 250 single. The Honda had a vacuum activated fuel stop at the tap, the Yammie was a straight forward fuel valve that had failed. A sticky float valve probably allowed the carbs to flood into the engine in both cases. Very messy, but I haven't heard of the same problem with an XZ.

An ignition activated electric pump that also acted as a fuel stop valve makes a lot of sense. Just carry around a length of pipe to bypass the electric pump if it fails

[The Prophet of Doom]

An ignition activated electric pump that also acted as a fuel stop valve makes a lot of sense. Just carry around a length of pipe to bypass the electric pump if it fails

When I bought my first XZ, everyone told me it was daft to not have a kickstarter, and I'd get stuck somewhere.
Sometimes you just have to trust the engineering - fuel pumps are pretty reliable.

[injuhneer]

I have an opportunity to a little work on my XZ fuel system.

The 40 year old fuel pump seems to have failed. Maybe diaphragms in the vacuum pump have failed?

Disassembly shows that the main diaphragms are OK. The problem is in the check valve membranes, good old-fashioned wear. The two stage check valves are a thin membrane made of the same material as the diaphragms. The contact surface in the pump has worn these valve membranes. Also of note is that the sealing faces/seats for these check valves appears to have worn also. The the two problems combined result in a failure to seal with each pump cycle.

I will find some suitable replacement material and probably dress/polish the sealing face.

 In the meantime I have a Virago fuel pump available. I may just lash this up to see where it can be installed, etc.

[The Prophet of Doom]

Is it electric or vacuum?  I think you can find Virago models with either.  I've got two electric pumps - both specify that they need to be placed below the float bowls so that  might be something to consider.


Alternatively you can get a diaphragm kit from Keyster for $30 or so on ebay.  Experimentation is always more fun though than just replacing failed parts.

[fret not]

Electric fuel pumps are available in various pressure ratings.  The one I got is for 2psi - 5psi.  More pressure is not needed or probably wanted.  I figured that as long as the pump makes slightly more than gravity pressure it should be fine because some Visions work well enough with just gravity feed until the tank is nearly empty.  More pressure brings more possible issues like leaks,  and forcing fuel past the float valve.

[injuhneer]

Alternatively you can get a diaphragm kit from Keyster for $30 or so on ebay.  Experimentation is always more fun though than just replacing failed parts.

No argument there. :-)

[injuhneer]

Is it electric or vacuum?  I think you can find Virago models with either.  I've got two electric pumps - both specify that they need to be placed below the float bowls so that  might be something to consider.

Electric. It will fit nicely in the V of the engine.

[fret not]

"it will fit nicely in the V" IF you don't have carburetors.  I have been poking about fitting carbs into that "V of the engine" and I find there is significantly less room for ANYTHING between the cylinders and heads.  Try to remember that parts sometimes need to be removed or adjusted, so access is rather important.  The fewer obstacles you set for yourself the easier Life will be.

[injuhneer]

"it will fit nicely in the V" IF you don't have carburetors.  I have been poking about fitting carbs into that "V of the engine" and I find there is significantly less room for ANYTHING between the cylinders and heads.  Try to remember that parts sometimes need to be removed or adjusted, so access is rather important.  The fewer obstacles you set for yourself the easier Life will be.

Noted and thanks. With no YICs box in place there is plenty of space. I promise I'll post photos.

I would have mounted it today but instead spent the day making a custom chain tensioner for my son's kart.

[Walt_M.]

I put mine on the left frame rail and used the FZ fuel filter that came with the pump. In the event of a pump failure, mine doesn't pass fuel if the pump isn't running , I can easily bypass the pump. If there's enough fuel, I can disconnect the pump inlet hose and connect to the filter inlet and go on my way.

[injuhneer]

Yep, it has been a year. Since I started on the XZ we had a wedding! All of the activity and associated COVID complications consumed my time for many months.

Here is my test rig. This is a Virago pump installed on temporary mounting (right in the V). It works nicely. Click-click-click and the carbs are filled. It did expose a problem. The rear carb float is set a tiny amount too high. Where the factory pump did not deliver enough volume to expose this with the engine running the electric pump did. Now I need to remove the carbs and check/reset the float level(s).