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Weber carb Fuel Pump Question on 906

Posted: Fri Aug 25, 2017 11:52 pm
by englishstiv
Hi folks I know it's quiet around here what with summer and holidays all around us, but I have a question regarding a 906 I am tinkering with.

It has a weber carb as originally fitted and when I attach the live feed onto the battery the fuel pump starts cranking over. No ignition switch is live and the kill switch can be in the off or on position and it just keeps cranking over.
I have followed the wires etc but cannot seem to fathom out why it keeps cranking over.

There is no fuel in the system as of yet as I don't want to throw it around the engine etc.

The only alteration to the electrics that I have done is remove the clock from the speedo nacelle

Any ideas any one.

Also can the pump be removed and the fuel allowed to flow with gravity on a weber?

many thanks

Re: Weber carb Fuel Pump Question on 906

Posted: Sat Aug 26, 2017 3:01 am
by Mc tool
Its fed from the switched green/black wire that feeds just about everything else , so I can only think that someone has "modified" it or there is a short somewhere . Id start at the fuse box as that's where the unswitched and switched wires are physically close . Aparently Paso will run on gravity feed for about the top 1/3 of the tank and then fuel level drops so low fuel is reluctant to flow at all let alone fast enough for a hungry Paso.

Re: Weber carb Fuel Pump Question on 906

Posted: Sat Aug 26, 2017 10:07 am
by englishstiv
Cheers Hamish I have identified the electrical feed leads but not being familiar with the 906 set up was reluctant to start pulling apart. The loom wiring has been altered but it was doing this when I first attached the battery. I have since returned the offending wires to their rightful place and nothing else appears altered as per the manual etc. But the pump is still chugging away happily :banghead:

So next question assuming pump has a fault as fuse box is okay what is the best replacement?

Re: Weber carb Fuel Pump Question on 906

Posted: Sun Aug 27, 2017 1:24 am
by nickta
Lo Stiv.

If the pump is cranking all the time, a replacement wouldn't make much difference. The pump must be getting 12 volts from somewhere? If the wiring has been changed at some point, then the fuel pump 12 volts may have been connected direct to the battery to try and take load away from the kill switch.

Anyway, tucked away in Lane's story on his 906 is a bit about the fuel pump. I think he may have even put in a vacuum pump but went back to the electric as it didn't work out.

Have you put in the relay mod yet? It made the world of difference to the 907 when I did it, so it couldn't hurt.

Cheers.

Nick.

Re: Weber carb Fuel Pump Question on 906

Posted: Tue Aug 29, 2017 10:23 pm
by englishstiv
Hi Nick

I am still trying to suss the permanent power supply on the loom, I think I'll stick with whats on as it is obviously working :beer: There has been some tampering with the loom as I can see a small cut in the permanent live feed to the key. Looking at the suggestions thus far and various searches I am going to first strip the pump down as best possible just in case it is stuck from standing idle for so long, you never know :thumbup:

As for the relay mod well my 907 managed to dead short on the Alternator yesterday after a lovely days ride about 25 miles away from home. so having replaced the Starter solenoid, the rectifier, the plugs, the coils and re wiring the fuse box after finding some over cooked and welded leads I now have to strip out the Alternator and see what is occurring here before I even think of the mod to the starter..... it will get done though. :cool:

Re: Weber carb Fuel Pump Question on 906

Posted: Wed Aug 30, 2017 3:59 am
by nickta
Lo Stiv.

Sounds like a standard ride on a 907! The relay mod works on the 907. I bought Lane's 906 back when it was for sale, and he had done the mod on that too, and it works a treat. Its living in another state at the moment (don't ask), so can't even go out and check things from afar for you.

Hope you didn't have to push the 907 home after the alternator short? Did you replace the rectifier before or after the short?

Cheers.

Nick.

Re: Weber carb Fuel Pump Question on 906

Posted: Wed Aug 30, 2017 10:00 pm
by englishstiv
The 907 battery very kindly allowed me to turn the ignition on fill the carbs with fuel and ride for about a mile or less until all the fuel and fumes had been exhausted. I then let the battery rest and continued this procedure for about 15 miles until it became too dark to risk it. An hour later my contacted rescue services arrived and I strapped a car battery to the bike and finished the journey home with full lights on. The bike wasn't overly happy with this procedure but it got me home and I think all the bump starts may have created a few issues. As well as totally wrecking my already knackered knee cap.

All the replacement parts were fitted before this last episode so it's back to square one, I most likely will do a rewire.

My time now will be spent getting the 906 running and then deciding what action to take thereafter.

As for the 907 I must just swap the whole engine with a spare I have tucked in the corner of the garage just to get some riding time with whats left of the English Summer.

Re: Weber carb Fuel Pump Question on 906

Posted: Thu Aug 31, 2017 12:01 am
by Mc tool
Push starting a Paso by yourself is a real mission :x Do check the start relay plug ( just right there under the seat ) before you discover the shape of the seat makes it all but impossible to leap aboard and hoik 2nd gear before you loose enough speed and just stall, and wind up sprawling on ones knees with a Paso 1/2 on top ( as the crowd gathers........ a most unhelpful pack of bastards they were too, although they did seem to have a eager sense of humor ).......yeah , check that plug :)