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Ok guys I am looking for some input. I am working on a UD18 power unit. When I bought this I was told it ran good on gas but the pump had two seized elements. (Bosch pump). SO I have changed the pump and have been trying to get this going. 

I am have MAJOR problems on the gas side running VERY rich. So I did change the needle and seat. But that is not it. Tried it again today but it is still rich. Is it possible that the fuel jet in the carb is too big? I don't have anything to swap it with but I may measure it then drill it out and tap it so I can make a jet and screw it in. Whatya think?

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No it doesn't run ok. The spark plugs that where in it where really old. But they where clean. So it couldn't have be running like it is. You can tell when you find a problem part by the bolts. As in something has been apart alot. The screw head on the carb are VERY worn. Tells me it has been apart toooo many times. Waterloo

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  • 3 weeks later...

Maybe no one is interested but this is what I done to my Fuel system. So problem is when running on gas mixture is very rich. Carb has a fixed main jet. Removed the jet and drilled out the orfice and tapped to 8-32. Check the hole size before drilling was about .072. Made a jig to drill out a brass screw which I cut down to the right length and drilled it to .060. WHAT a difference it made. Now I can try to get the diesel side working. Governor not working in american bosch pump.

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On 5/19/2020 at 7:30 PM, waterloo said:

Maybe no one is interested but this is what I done to my Fuel system. So problem is when running on gas mixture is very rich. Carb has a fixed main jet. Removed the jet and drilled out the orfice and tapped to 8-32. Check the hole size before drilling was about .072. Made a jig to drill out a brass screw which I cut down to the right length and drilled it to .060. WHAT a difference it made. Now I can try to get the diesel side working. Governor not working in american bosch pump.

Good luck on the pump, and good job on the jet screw. That must have taken some time and thinking to figure that one out. I have a pump if you end up needing parts for yours.

Ross

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On 5/19/2020 at 7:30 PM, waterloo said:

Maybe no one is interested but this is what I done to my Fuel system. So problem is when running on gas mixture is very rich. Carb has a fixed main jet. Removed the jet and drilled out the orfice and tapped to 8-32. Check the hole size before drilling was about .072. Made a jig to drill out a brass screw which I cut down to the right length and drilled it to .060. WHAT a difference it made. Now I can try to get the diesel side working. Governor not working in american bosch pump.

good work around

others have done similar mods to regular carbs to slow the flow

as todays %^&^&&) gas is uniform , flows like water ,while all the removed "bad" stuff made power on less which took the larger orifice

also why many other idle speeds are high now...sm, 656, holley on trucks /main screw can near be full in and still run high idle but give no load power.

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