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Facet Pump Spring Change


cb750

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The cars fitted with a brand new red top competition pump so I don't want to get rid of it. Bit suspicious of the regulator that's currently fitted, I seem to be getting misfiring due to fuel starvation at continuous 2000 revs and above. The engine will go to the redline in a short burst but accelerating steadily produces the misfire. The spring is cheaper than replacing the regulator!

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That red top is rated to deliver 40 gallons per hour. Bike carbs have float chambers? I think you may have problems with suck not blow with surge a likely culprit. Brim the tank and take another drive will eliminate surge from the equation. Where in the tank does it draw from? Hopefully not from the base of the front wall.

 

Nigel

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Thanks for the input Nigel, I had brimmed the tank and it still did it. Take off is 10-12mm off the bottom of the tank and points to near midway along the tanks length ( I made the pick up). As an improvement to stop tank surges I am looking at filling the tank with the foam blocks that are available. It won't affect the sender as it's an Isspro cylindrical type. Need to pluck up courage for that though as I hate putting anything other than fuel in a tank, I had enough problems on a motorcycle tank with so-called fuel proof sealant which dissolved and blocked the carbs up!

 

Glencoe Ltd are the ones that suggested fitting the lower rated spring so I am ringing them today for the part and instructions plus a replacement diaphragm spring for the Filterking as I found that was faulty late last night, it's bent and measures too short against specification. The plan now is to sort the regulator and reset it. If the problem still exists then I will fit the pump spring and bypass the regulator and see what happens.

 

What's annoying is all parts including the ignition system are new.

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Agreed then. If it still does it with the tank full it's not surge allowing the pump to suck air. With carbs that have a float chamber you should not need a baffled tank for the road. So the problem should be elsewhere. New inline filters would rule out blockages in them. A fuel pressure gauge (cheap type from ebay) may also help in diagnosis between rich stumble and lean missfire. Good hunting.

 

Nigel

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Just out of interest, if you are using Champion plugs, try changing them for NGK.

I have had two faulty brand new champions in my Pinto days.

Similar symptoms too.

 

Check your plugs immediately after the misfire to determine if too weak ro too rich.

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Hi

 

I'm running a facet pump with bike carbs too, no modifications, but i do have a filter king set at just under 3 psi.

 

All runs just fine, whenever i did have issues with misfire etc, it has always been ignition rather than fuel.

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Bob, I always run ngk plugs after I had similar problems with champion plugs years ago. Will have to do a plug test when I can get out again (that's if this rain ever clears).

 

Fossett, I will set the regulator to 3psi when I get my replacement diaphragm spring and see what happens. It's been suggested by a garage that I use that it could be the new ignition coil pack playing up as they are known for breaking down especially when hot so I may have to look at that as a possibility.

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