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sledhead999

AP Pump Leak 07WR450

9 posts in this topic

OK, so I pulled my carb apart to jet for elevation(4500+). I opened the AP cover thinking that the leak jet was in there, forgot it was on the other side. I put it all back together, now it leaks fuel between the cover and housing. Thinking maybe I dinged one of the flat surfaces, I filed it flat. That didnt fix it. So I threw on my stock YFZ AP cover, still leaks. I thought maybe the small o-ring might be flat, replaced it, still leaks. I noticed that it will hold fuel just fine till I cycle the AP rod, then it leaks.

Do you think it could be the AP diaphram? It doesnt look to have any tears, but I'm running out of options. It doesnt seem like these seal all that well.

Ideas?

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Well, you confirmed the cover is flat, the small oring is good, all that is left is the diaphragm (assuming it is not in upside down.)

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Its almost gotta be the diaphram. I actually tried it both ways, leaks about the same both ways. Is there a sealing surface or groove I've overlooked by chance?

In the microfiche it looks like the "cup" part faces up, not down covering the spring. Is this correct?

FCR_Carb.jpg

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The long 'end' of the rivet faces down, into the AP cover, away from the carb .

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Check out this manual. It's written by a guy who I think was at Factory Pro for a while. It's oriented more towards a streetbike with a rack of carbs but other than that the info still applies.

http://www.scribd.com/doc/13354160/Keihin-FCR-Tuning-Manual

Good luck!

trailhead

Excellent link! The writter states the realities of jetting well.

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If I recall correctly, there should be two O-rings under the AP cover - one bigger than the other. Are both present?

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If I recall correctly, there should be two O-rings under the AP cover - one bigger than the other. Are both present?

Good call. I went home last night to look. The smaller flat o-ring sits in the cavity in the cover(leak jet). The bigger round o-ring sits in a cavity in the float bowl. The small one had fallen out and I didn't realize it, I thought the cavity in the cover mated to the larger one.

Thanks!

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Good call. I went home last night to look. The smaller flat o-ring sits in the cavity in the cover(leak jet). The bigger round o-ring sits in a cavity in the float bowl. The small one had fallen out and I didn't realize it, I thought the cavity in the cover mated to the larger one.

Thanks!

No worries:thumbsup:

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