Bubbles, Tiny Bubbles

[LaqueRatt]

Am I running champagne? Where are all these bubbles in the fuel line from the pump to the carb coming from? Motor is a 65 Fastwin 18. Been having fits with this thing. I knew it had problems, but it seems like nothing works right on it. Was losing spark on one cylinder when engine warmed up. Replaced points, condensers, and coils. Nice hot spark now. Today when testing in the barrel started seeing a few bubbles after 10 mins of mostly idling. Got worse and worse until I had more air than fuel and it quit. Previously I fixed the elbow leak on the fuel tank and replaced one leaking quick connect. Now I see no gas leaking out, so does that mean no air is getting in?

Why would it only do this when it gets hot? Never have liked the looks of the fuel pump. Has this big oversized gasket that looks like asbestos or something and the whole top is just hanging. Not attached to anything. Should I make a new one out of normal gasket material? Also it seems I have one fouled plug. Why one only? What am I missing?

One last question could this have anything to do with running it too long at too low of an idle?

 

[kbait]

I bet you have a pin hole in pump diaphragm, and the fouled plug is the same cylinder that the pump gets it’s pulse from. Fuel is leaking into cylinder crankcase behind pump - flooding that cylinder, and air is getting through pump to carb, all through that pinhole.
You can replace that pump with a newer square one, but beware of cheap-o aftermarket pumps. Good luck!

 

[racerone]

That floppy loose material is not a gasket.----It is a heat shield.

 

[LaqueRatt]

OK, that makes a lot of sense. Guess I need to pull the pump off. What's the smartest thing to do though? Rebuild what I got or just roll the dice on a cheap-o and hope I get a good one? I'm really not wanting to pour a whole lot more money into this thing, but it's not going to do me a bit of good if I can't get it reliable. Should I just seek out an OEM replacement? Seems to me I've seen them for like a hundred bucks or something. That's a whole lot of cash for something so simple. Does anybody make a quality aftermarket part?

Heat shield comment makes sense too, but I'm surprised it needs one. Don't think there's one on my 9.9 'rude.

 

[racerone]

Most of these in the 1960's used the heat shield----A new diaphragm is all that this pump would need at less than $10 for a quality fix.-----These 22 cube motors ( 1958 to 1976 ) are some of the best , most reliable , easiest to maintain motors.-----Parts are cheap and plentiful if you know where to look.

 

[LaqueRatt]

Thanks R1, I'll see if can dig one up. If anybody knows a good cheap source I'd appreciate a link.

 

[LaqueRatt]

Well what do you know. It wasn't the pump after all. Swapped out the fuel line going into it and no more bubbles. 20 mins in the barrel without a hiccup!