70 c20 fuel stumbling issues

[ak808]

So my C20 has been driving great, many tanks of fuel through it... it started stumbling when I was taking off from a light last weekend. Would stay running, but only low rpm. Limped to the side of the road... scratched my head, tried it again, same thing.

I ended up switching to one of the saddle tanks, it ran great. Drove it home and figured it must be either the filter sock on the fuel sender or crud in the main tank.

I take the seat out to get at the sender. It doesnt appear in bad shape. Inside the tank looks pretty darn clean. I blew out the lines to the three way valve. The inline filter did have some crud in it, but it is inline after the valve meaning if it was the culprit it should be stumbling no matter the tank I am pulling fuel off of.

So, new inline filter, blown out fuel lines, it seems to run ok and rev up fine in the garage. Before I put the seat back in, is there anything else I should check?

It has stumbled before in the past, but only when I was really getting after it leaving a light. I always assumed it was the carb not quite tuned just right... never put much thought into it past that.

Thanks

[tdangle]

Since it's a 70, I believe you must use a vented gas cap. Wonder if you have a non-vented gas cap and that is the problem.