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75 Datsun 620 carb issues


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Hey guys my 75 620 L20 was running just fine then it started dying. It idles fine and revs up but the min you put it in drive it dies. I replaced the fuel pump and it took off like it was fixed but then I couldn't even get it home. I look in the carb and it seems only one side is getting gas. I'm lost not sure what to do.

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I hope you kept the fuel pump as original parts are best. Keep as a spare as obviously it wasn't the problem. Simply looking at the sight glass on the front of the carburetor would tell you if there is gas in it or the pump has failed. Got gas???

 

 

 

 Your description is a bit contradictory. If it idles fine and revs up in neutral, it should idle fine in gear. So.... does it idle in gear?

 

When you say it quits when you put it in gear do you mean it quits when you try to drive it above idle?

 

 

The reason I ask is to find out if this is an idle circuit problem or is it related to the primary circuit. If it will idle in gear warmed up then not the idle circuit. If it's not drive-able above idle then probably the primary jet is plugged and no gas is getting in.

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Well I can rev it up but as soon as I let off the clutch it dies. So I guess your right it won't run above idle. When I look down in the carb I'm only seeing fuel on one side. Not sure if it suppose to be that way. I did put some cleaner in the fuel tank which has caused me to go through about 3 fuel filters. How do I clean out main jet?

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If it's the Hitachi carb the secondary is closed normally unless out on the highway and floored. It runs on the primary only. Well this is good to know.

 

I never use any type of fuel system cleaner for the very reason that it's best not to disturb things and just let the filter catch everything. Filters should be replaced every two years or less as needed.

 

 

You will probably find it easier to clean it with the carburetor removed from the intake. The primary and secondary jets are on the front of the carb below the front cover of the float chamber. The float chamber may have a glass front or a small circular window to show the fuel level. If dirt was loosened and is in one jet it may be in the other as well and there may be more in the float chamber so probably best to take the front cover off and clean it out as well. Have a care as there are some really small parts that will fall out when the cover is off. The rubber seal or gasket can be cleaned and re-used. Flush out the float chamber with carb spray.

 

This is the only picture I have that shows the jets. You don't need to take the carburetor this far apart, and it's upside down. The float chamber is to the bottom.

 

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The two 12mm cover plugs hide the jets that are up inside. Buy a spray can of carb cleaner with a plastic straw. Spray from the float chamber side then from this side to flush them out. If you remove the jets take care that you put them back in the correct place as they will interchange. To remove them you need a good size screwdriver with the sides ground down that will fit up into the holes yet fit the jets snugly. The brass jets are very soft. 

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