Carb Problem

[baycrazy]

Hi There I'm new to this forum but was hoping someone might be able to help, I have a 71 Westy with a 1600 twin port, runs ok a little hesitent when back on throttle from off throttle/changing gear etc. But worse is every now and then when the engine is hot it will go from idling fine to spluttery and stall, the carb at this stage has fuel coming out, it hisses and spits and will only start after removing the air filter and allowing the fuel to evaporate. Its a new 34pct and fuel pump(dead embarrassing when it happens) any suggestions would be much appreciated. Really don't want my bus to catch fire!!

Great forum by the way been meaning to join for some time, will get some pics together and post at some point!

Cheers Paul

 

[Joval]

I'd check the float and valve to make sure it's sealing properly.

 

[noddy]

Sounds like it could be flooding when you let off the throtal.

This could be cause by a couple of things.

1. Tick over mixture is rest way too rich, small mixture screw should be backed out from home by about 2.5 to 2.75 turns, use large air screw to reset tick over to 800 to 900 rpm.

Secondly you say you have fitted a new fuel pump.

2. The push rod on the fuel pump should be 13mm above the plastic stand when at max height, if the pump push rod is longer than this the pump pressure will be enough to force the needle valve open in the top of the float bowl. This will cause the carb to fill with too much fuel which will over flow into the manifold, and flood the engine.
The solution is to put extra gaskets under the pump till you get the correct measurement.( just a thought did you get the correct fuel pump for your year and engine).

I would start by taking the pump off and check the length of the push rod at max stroke, then the carb if pump checks out.

One last thing it could also be that the needle valve as Joval said, in the top of the carb float bowl is sticking open this will have the same affect as the pump delivering too higher fuel pressure.

Let me know how you get on.

Ian

 

[baycrazy]

Thanks Guys. I haven't had chance to get out there yet but everything your saying makes sense, i wasn't aware that it was so critical, i will get out there and check the measurements etc and let you know how it all goes.

Cheers Paul

 

[matt-me]

If you had an old style fuel pump and changed for a new style, did you change the rod? From memory the new rod is 104mm the old 108mm, or was it the other way round? Ties in with what Noddy says if you didn't buy a new rod..

 

[baycrazy]

Yeah should have mentioned i did fit a new style fuel pump (the lent over one to clear the alternater i fitted at the same time) and i did replace the rod, but i didn't measure and adjust the height of the pedastal to achieve 13mm lift( wasn't aware of this).But obviously with what its doing thats the first thing i'm gunna check and if by chance that is already spot on 13mm then i'll move up to the Carb and needle valve assembly. Really want to get out there and make some adjustments but the weather has been terrible and i have no light in my garage(the bus isn't completely water tight yet coming from such dry climates.) Will keep you all updated!

Cheers Paul

 

[baycrazy]

well i managed to get out and work on the camper, because its got the late type pump fitted with the short rod i had to come back in and look up what the setting for the short rod was supposed to pretude(4-5mm) on measuring mine it was on 6mm so have re gasketed it to approx 4.25mm. readjusted the timing and carb and now purring like a kitten, and hasn't flooded so hopefully its all good now. many thanks for the advice, will try and post some pics of my bus soon!

cheers Paul

 

[noddy]

Good news, just need a road test now