I have read people do sand the bore to loosen it up on a carb forum this was mentioned. I think there is too much surface area holding the rubber to the zinc housing. Sanding like putting in fine scratches does lessen the surface area of the metal held tight against the rubber apron of the pump. It may seem counter intuitive. I did try polishing the bore with stove top cleaner, but it was no help.
The bore is very smooth and shiny, I think of it maybe like a suction cup against a shiny smooth surface, it grabs tightly.
I do not really know what else to try. You have to exert a significant force using pliers to pull up the plunger rod. The spring feels very normal tension to me.
Other thing might be remove the circular spring behind the rubber apron. So less force pushing the rubber against the bore. I have rebuilt many quads and this is the first one with weird problems.
Its original problem was massive flooding of the engine. When I took off the air horn, the needle valve was laying in the float chamber.
I dont even know how that can happen! It worked fine before. How can a needle valve escape the bronze seat and float arm. Everything looked as it should.
I adjusted the U hinge clip to make certain it can not lift up and perhaps allow the needle to come out.
I rebuilt with a new float, tried it again and massive flooding like I had done nothing.
So I removed airhorn and physically held the float hinge pin down while cranking the engine. The flooding was still happening, and I thought maybe float arms too close to the center tower, bent them outward so less likely to scrape the tower and hang up the float, and the flooding finally stopped.
He had cranked the engine so much, he burned out the starter and crankcase was way overfilled as tons of gas had washed by the rings.
So oil was replaced. Then the thing was back firing out the top of the carb, as in leaping flames about a foot high.
I pulled the plugs and they were all wet with loads of gas and very black, fouled, and the shells were loaded with rust. So we did this Sunday and later this week will put in new plugs and try it again.
Those plugs looked decades old. Several of them I was barely able to remove from the head, at least none broke off in the head. That is a worry with old rusty plugs not taken out in decades. Alsways use some marine grease on plug threads, or antiseize.
