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Keihin FCR Question Concerning AP Circuit

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I have a 99 WR400 with the first series FCR carb. My AP does not work. In trying to find out why I found that the metal push rod that pushed on the AP diaphram was moving freely along with the diaphram looking like it was OK with no obvious tears. In tracing the fuel flow to the AP diaphram and body I see that it receives fuel by way of a passage from the bottom of the float bowl. I tried to scuirt carb cleaner threw this passage hole and could barely get a drizzle at first but after letting the bottom float bowl soak with carb cleaner I was able to now get a decent squirt threw this passage if I sprayed the carb cleaner directly into the orifice with the small spray tube pushed tightly against the orifice opening.

I then filled the bottom of the float bowl full with fuel so that it would cover over this orifice opening but no fuel would flow threw into the AP body as I had the diaphram off so I could look directly on the AP side of this passage. I believe the passage has a check valve in it so that the fuel does not flow backwords when the diaphram is pushed.

I also put the float bowl back on the carb and connected a small gas filled bottle to the gas line but still left the AP body open to see if gas would come out of the orifice but it didn't. I verified that the float bowl was full of gas by measuring the fuel when I emptied it.

Does anyone have any experience with this problem that can help me figure out how to get a AP induced squirt into my carb. Sorry if I was a little wordy but I am trying to explain all that I have done so far so that you may give advice based on everything I have done so far. Please help.

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I have let carb cleaner and Laquer Thinner soak in the bottom of the float bowl for a night and neither one did much. Any suggestion as to what to use to clear out the gunk?

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I don't think you have a problem? Any diaphram pump (including your heart) has a check valve each side of the diaphram. Although it takes little to open that check valve the pressure from the weight of gas stacked a 1/2 inch high will not open it. I think it is waiting for or relys upon the vacuum of the pumps stroke.

There is another check up stream between the diaphram and the spray nozzel that I have never seen but I had one of those gummed up once, that was a diognostic nightmare! That bike (new but had be on the showrom floor nearly two years) ran ugly, after hours of tinkering we tried another carb and it came to life. Carb body upside down and lacquer thinner squirted up the passage with a syringe is the answer.

If the bottom of the float bowl is not green with varnish your only problem is being overly anal (which I respect)

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You have done all that the cleaner can do. Now you need the force of compressed air. If you do not have a compressor, use a bottle of the computer "air in a can" stuff. It comes with the same nozzle tip that the carb cleaner comes with. Blast the gunk out. I had the same issue but it was on the discharge check of the diaphragm.

ps - keep the carb cleaner away from the diaghragm. It will eat it up quickly.

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