well I tried to search the forum for this topic and have found nothing. So does anybody know what type of fuel filter to use w/o the fuel pump? Iv read several places that the gravity feed works fine so I ran a direct line to the carb and it ran fine at all speeds. When I put the stock filter or another(5gph) in the line the carb gets starved for fuel at speed. Any suggestions.. besides putting the pump back in.?

You might be able to get this to work Pancho, but I couldn't. Some folks have reported that they were able to make it work.

The source of the problem is the fuel inlet in our carbs rather than the filter. We have needle valves in our float bowls that have a 2mm orifice in them for the fuel to pass through. That is the size inlet that is typical for this size carb when it is designed to be used with a fuel pump.

The HSR42 Mikuni carb is a real popular replacement for bikes in the engine size range that ours are, so let me use it as an example here.

On the HSR42, you can obtain replacement fuel inlet valves that are specific to your usage (its an aftermarket carb that is real popular for a lot of bikes, so has a lot of options available). You can get a 2.0mm inlet valve for use with a fuel pump, or (if I remember thse sizes correctly, its been a while) a 3.8 to 4.2mm fuel inlet for use with gravity feed.

I have searched the ends of the earth looking for a replacement inlet valve for our stock 40mm carbs, and just can't find one. It is just unique enough (in spite of being manufactured by Mikuni) that there are no interchangeable parts available for any other carbs that will suffice.

The tip of the needle has a rubber tip that is just over 2mm that seals the hole when the valve closes. Unfortunately, this prevents us from widening the hole since anything wider than that will not seal when the valve closes.

I am not sure what to recommend, as I could never make it work without having fuel starvation events. I suspect that your jetting and driving are just within what this 2.0mm valve can supply fuel for with your normal driving. Might want to test it on a large high speed uphill grade.

IF you find a fuel filter that seems to work, please let us know and keep us updated on how its is going. There are a ton of folks out there that would like to loose their fuel pumps.

GRAM

I was going to eliminate the fuel pump on the 40mm stock carb but changed my mind. I did save a couple posts from the R* forum on this topic and post them for piece of mind. I don't remember who posted them. Just remember what Gram posted above. Enjoy.

EDIT NOTE:

Draco has consented to having certain information in his post removed that could have been deemed as Copyrighted material which belonged to Delphi Forums. The information was however excellent for this topic. We are sorry to have to remove it, but must respect Delphi's wishes in regard to information they claim Copyright to.

We will see if we can duplicate it with original posts here.

Huge thanks to Draco, both for prividing the content to begin with, and for his cooperation in this sensitive matter.

-GRAM
Ride to Satisfaction





http://www.jpcycles.com/productgroup.aspx?GID=1081ED94-70EC-456E-AE38-D96762A160F2<br><br>Post edited by: GRAM, at: 2005/02/20 13:50

Excellent post Draco!

GRAM

Gram please delete my post above if its not the right thing to do without permission from the writers.

Since these posts were original posts from Delphi, it would probably be best to do so Draco. No foul, your intents were very good in trying to help Pancho with his project. I would suggest using our internal messaging component to send these subjects directly to him.

Its great information. In fact, if you can send me the names (or forum names) of the original posters, I will contact them and ask them to duplicate their posts here on the clinic.

Thanks Draco,

GRAM

Folks have tried to use the stock carb without a pump before, but I do not know of anyone that had any luck without starving the carb in higher rpm.

For a good fuel filter, use a Pingel fuel filter. I use it along with a Pingel petcock.

http://www.pingelonline.com/fuel_valves.htm<br><br>Post edited by: USAFRETIRED, at: 2005/02/21 01:14

I bought my 99 running great without the fuelpump. I havnt noticed any fuel feed problems at any speed. The engine looks better without it.

I am running the Mikuni HSR 42mm flatslide carb which reqiures removal of stock fuel pump.

I had read of problems with fuel starvation with the above set-up under certain circumstances.

I ended up using a Pingel high flow petcock and Pingel high flow fuel filter.

In addition I used a fuel bowl spacer to allow more reserve in the fuel bowl.

I have over 2000 miles since this modification and have never been starved for fuel at various elevations and under various conditions from long distance interstate cruising to city stop and go to an ocassional friendly rivalry with a Harley.

Good luck and ride safe

&quot;In addition I used a fuel bowl spacer to allow more reserve in the fuel bowl.&quot;

Elaborate!

I run a vacuum fuel pump so I'm not about to change but this infor may be useful for others.

Thanks

Doc