This is my first post here. I bought a '68 520 with a J13 about a month ago. It ran really great, and I have been spending my time getting it to stop, and plugging leaks and all that maintenance the PO didn't do. Anyway, I was driving it Sunday and about a mile and a half from my house it started bogging down and wouldn't go. Idled fine, but if I put any gas to it it just died. Started up and idled, but had to push it off the road. Found that there was fuel coming out the inlet fitting. Turned out that whole fitting hand come loose a bit. So I tightened it up and now it runs better, but under load it still sputters and kind of jerks. My guess is that something got in the jet. Any other likely possibilities? How do I clean the jet out? Do I need a rebuild kit? Can I clean the jet with the carb on the truck? I really don't want to do a total rebuild. It was running so great before.

Any advice or help appreciated.

a rebuild would be your best bet... but that fitting you found is probably still the issue... make sure you put it back in completely properly before doing anything else and see if that fixes it... start small so you don't waste your money on bigger things

I have played with the fitting a bit, took it entirely apart and all. It is the banjo bolt where the gas enters the float bowl. The bowl stays full, and doesn't seem to fluctuate much. I took the screen out and cleaned it a bit and reassembled trying different positions etc, but nothing seemed to remedy the problem. I am wondering if the old fuel line flaked a bit when the fitting came loose and moved. Anyway, I am pretty confident it is no longer the issue. I also know that the fuel pump is working because of all the gas that spewed out when I loosened the hose clamp! I do see some tiny particles now in the float bowl. I don't want to have to rebuild if it was running well before. I just want to get the jet flushed out if I can, so I am going to start there with the carb on. If that fails and the carb comes off I can try removing the jet. If that fails, rebuild time I guess. Not excited about that since I can only find one place with an available kit and it is $60. If I was sure the $60 would solve my problems that would be okay, but I am not exactly confident in my rebuilding skills.

My plan is to remove the jet plug from below the bowl and the jet itself and let the fuel flush out. Then, if I don't see and obstructions, run a nylon guitar string, or some mono filament fishing line through the jet, reassemble and see where I stand. If it is driveable then, I could do a SeaFoam treatment that I have been told works wonders for motorcycle fuel systems. Never tried it though.

I pulled the jet plugs, flushed the fuel out, ran some 10# test fishing line through both the primary and secondary jets, blew in some carb cleaner and then some compressed air, and vualah! She's running like a champ again. Started over with a new filter, and all new fuel lines. Next step is SeaFoam in the fuel tank and we'll see if we can a few more miles out of this 42 year old truck!

Rebuild it, that's the best option man.