Thanks for all the help. A bit more please? '57 Lark carb kit.

Sorry about all of the questions, but it seems like every time I get one system working, I find another that needs help. Now that I have new ignition components, compression release valves that seal and all the other newly fixed things I've been helped with, I'm getting a cut-out at WOT. I'm assuming that this is either a sinking carb float or some other similar problem, so I figure it's time to rebuild. However, I can't find the kit. The number on my carb is 3040*1 (can't make out the fifth number) and it's the model with both high and low speed needle valves. I've found the packings for the needles and the float, but I'm looking for a complete kit that will replace all the gaskets, the float, the packings and the float valve. Does anyone know the part number for this?<br /><br />Thanks again!!<br /><br />Steve

Re: Thanks for all the help. A bit more please? '57 Lark carb kit.

You have to go to the dealer for the kit with the new, fuel tolerant float. P/N 439074 for the whole kit (needle & seat, gaskets, packing, welsh plug, float, etc).<br /><br />But I'm a little suspicious this isn't your problem. can you describe the cut-out at WOT? Is it sudden and temporary? Does it only happen right at WOT?<br /><br />If the float sinks, then you run rich and the carb floods fuel everywhere. If it just sunk a bit, you should be able to compensate with your mixture controls.

Re: Thanks for all the help. A bit more please? '57 Lark carb kit.

Thanks for responding, Paul. I'm assuming this is a fuel starvation issue--maybe not a sinking float but something else in the carb. I can cruise at WOT for fifteen seconds or so, then the engine stalls and cuts back to idle. On a couple of occasions it has completely died. If I let it sit, or if I choke it or pump the fuel bulb, it will get right back up to speed. Oh, and it has a later model fuel pump on it, not the pressure system. I'm thinking a rebuild of the fuel pump and carb wouldn't be a bad idea, and it isn't acting like a problem with the pressure switch. What else might cause a problem like this one?

Re: Thanks for all the help. A bit more please? '57 Lark carb kit.

The fuel pump is a likely suspect. Do you have the period rebuildable fuel pump with the sight-glass? If so, it's well worth rebuilding if only to make sure you've got the large plunger fix in there (comes with the factory kit). A quick test is to remove the line that runs over to the bypass cover, pump the primer bulb up hard and see if you see any fuel run out of that port.<br /><br />It could conceivably be a leak in the fuel line/connector as well (ie, sucking in air), but I think the pump is more likely.<br /><br />EDIT: Old style fuel pump rebuild kit is 379777.

Re: Thanks for all the help. A bit more please? '57 Lark carb kit.

Yep, I have the old style fuel pump, and it's never been rebuilt. I'll be ordering that right away. <br /><br />Thanks.

Re: Thanks for all the help. A bit more please? '57 Lark carb kit.

Forgive my ignorance, but what's the "large plunger fix"? I purchased the Sierra kit and wasn't impressed. Twelve bucks seems like a lot of money for an o-ring, a rubber figure eight, a badminton birdie and sheet of thin rubber. Nothing in there related to a plunger.<br /><br />I believe I figured out my problem though. All the setting of the mixture needles disturbed the packing, resulting in little balls of whatever the original packing was made out of lodging in the main jet and elsewhere in the carb. <br /><br />I have a carb kit on order. Is the original float just straight cork, or does it have a coating on it? The float in my carb has a reddish varnish on it that may be old gas, or may show that it's an aftermarket float. <br /><br />Two more weeks of boating weather--two more days until my parts arrive.

Re: Thanks for all the help. A bit more please? '57 Lark carb kit.

Badminton birdie! Yeah, you don't get much with the aftermarket (Sierra) kit. You know the little protectors that go over the springs? Well on the original pumps the protector for the large spring (works from the inside) was just as small as the protector for the small spring. It can sometimes work its way off and then the spring will punch a hole in the diaphram.<br /><br />The bits of packing are often a problem. The worst place they get is to the base of the low speed mix valve, which is why removing the welsh plug overhead is so important on a carb rebuild.<br /><br />The cork floats were used up until modern times when they switched to plastic ones. Cork by itself will eventually take on fuel and sink, so they're coated with shellac. Unfortunately, the shellac will dissolve in alcohol bearing fuels like we get today. People who have to reuse their cork floats will need to recoat them with model airplane dope or (what I use) plumbing PVC cement.<br /><br />The factory fuel pump kit comes with new check valves and the pluger/spring, and runs only a couple bucks more than the Sierra kit (depending on where you get it, SRP is about $18.) Still, it's better than the post-'63 pumps that (theoretically) have to be replaced in their entirety for ~$50.

Re: Thanks for all the help. A bit more please? '57 Lark carb kit.

Just quick observation. is it possible you have a vent problem?? Or could you have crap in the bottom o the tank that get sucked up and chokes the motor only to fall off once the suction is gone??<br /><br />I had this probelm once and found a whole pile of crap floating aoround the bottom of the tank..

Re: Thanks for all the help. A bit more please? '57 Lark carb kit.

I guess that's possible, especially since the old fuel filter had split at the seam. The tank looked clean, but you never know who's living in the fuel lines. Now that I've put on the Mark IV fuel pump, I have an extra glass-bowl-type filter that was stock with the pressure tank, and the extra filter sock that came with the carb kit. I might just put that in as an inline, just in case. Gas can never be too clean.