Your typical "New user with carb questions" thread

[1001001SOS]

Hello, glad to be here! My name is Jay, long time lurker and Nissan hobbyist getting back into older cars. Appreciate the great forum yall have here!

 

I picked up a real bucket of a 720 recently for a pretty good deal, mainly because it reminded me of my first car back in high school. Could I have found a nicer one with fewer issues? Yeah, but the nostalgia factor is so real with this one.

 

 

The guy I bought it from drove it for a while, had some carb issue of some type, and then parked it for about a year. He then tried to get it running to sell it and didn't have much luck.

 

Here was the state of it after I got it home, and again after the initial cleaning and throwing on things from the obligatory box-o-parts he included to see what I had to work with:

 

 

 

As you can probably see, it has a fake Weber of some kind on it, I believe it is a 38D clone? I bought this truck to learn more about carbs and things so I am no expert by any means. Only other non-EFI vehicle I owned was my old 720 in high school and it ran like a song.

With the truck exactly as you see above, it will try to start and idle but is dumping waaaaay too much fuel (best guess). If I pedal it a bit I can get it to catch, and then it revs up super high as it hits the other jets. I have the mixture screws like not even 1/4 turn out and the idle screw a smidge over 0.

 

Now, obviously this carb is trash and can't be trusted. But, I also got a second carb in the deal, a brand new knockoff OEM unit:

 

 

So, that's where I am at. Main question would be, what to do? Continue with trash carb 1 or try out trash carb 2? Just wondering if it is even worth going down either road, or should I just bite the bullet and get something else. Not opposed to spending some money, like I said this is just a project of love.

[datzenmike]

First, there will be an adapter between carburetor and intake manifold. They are know for cracking and causing a vacuum leak making starting and tuning impossible. This is caused by the bolts loosening and owners over tingeing them so remove and make sure there are good gaskets and the adapter in not cracked.

 

Check that there are no vacuum leaks such as hoses off that connect to the intake manifold. Good idle vacuum is important for good idle. All air must go through the carburetor.

 

 

 

Lets ID the Weber first. Does it have these two 'gears' for opening the secondary. It's at the back near the throttle cable. If yes this IS a 38/38 and it's really for a V6 small V8. It will work.... but it's just too big. A smaller 32/36 would be more driveable.  

 

If instead it's a 32/36 then go through the following Weber idle mixture set ups...

 

http://redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm

 

 

And a You Tube just to see things....

 

If it IS a 38/38 I would immediately go and fit the stock replacement carburetor.

[1001001SOS]

Appreciate the info, yes it has the gear drive on the back:

 

 

Bonus 1mm+ gap between the mounting plates on the engine side. Fun!

 

Thanks again for the help, I have an FSM on the way from eBay now and will throw on the other one this weekend to see what happens.

[DwayneOxford]

Got one of the China clones so I could stay with factory breather. Had to do considerable tweaking to make choke and fast idle work right but it does. Accel. pump check ball was too small. 1st it got off to the side. Put it back, later it went down below seat. Put .030 or so bigger one in, so far, so good.

Edited September 26, 2023 by DwayneOxford