Jump to content

Need FCR 39 Carb Help Please

Recommended Posts

Hi all, I have a problem with my 2001 DR Z400 (Kick). I had a terrible bog on my DR Z, so I tore down the carb and found my Accel Pump Nossle was plugged. I got that cleaned out, reassembled the carb, and still had no squirt out of the Accel Pump Nossle. When I opened up the accel pump chamber, I found it was bone dry. I blew carb cleaner thru the accel pump fill port from inside the float bowl, and the fluid squirts out the other side with good force. However, if I fill the float bowl with gasoline, it will not run out the other side to fill the accel pump chamber. Here are 2 pics of what I am talking about. I am correct. aren't I , that gasoline should flow thru this port to fill the accel pump chamber? Thanks for any help you can give on this!

Accel Pump Inside.jpg

Accel Pump Port.jpg

Share this post


Link to post
Share on other sites

The AP has a inlet port and an exit port.  The fill port is float chamber to the AP. The exit is the AP to the discharge nozzle.  Each has a check valve forward biased. So gas can flow from the float chamber to the AP then from the AP to the nozzle but not in reverse.  I do not have a carb in front of me to identify which port is which but I'm sure you have derermied that. Your carb spray cleaner will unseat the check ball when spraying from the float chamber and should close the check (prevent flow) when spraying from the AP.  I suspect you need the AP up stroke to draw the fuel forward to unseat the check ball.

Share this post


Link to post
Share on other sites

Thanks for your help, Noble! I did not know there was check valves in there, but that does make sense. And yes I did think that maybe the AP diaphragm up-stroke would be needed to suck the fuel thru that orifice to fill the AP chamber. However, I filled the float bowl (off the carb) with fuel and used an Allen wrench to pump the diaphragm, but still no fuel would come out of the port that goes to the AP nozzle. This is really frustrating, as I can't figure out what else to do.

Share this post


Link to post
Share on other sites

Now I would suspect the check valve between the AP and the discharge nozzle is not seating- so no negative pressure to draw fuel from the bowl on the upstroke. You get reverse flow on the discharge side.

Share this post


Link to post
Share on other sites

Hmm, I think I understand what you are saying. I didn't think about the discharge side not seating. I will check that in the morning. Thanks Noble!

Share this post


Link to post
Share on other sites

Well, I put the carb back together, and the AP is working now. While I had the float bowl off the carb, I pumped the AP with a finger tip over the AP discharge port. If I kept my finger tight on that port during the up-stroke of the AP, the AP chamber would not fill with gasoline, but if I let air pass slightly past my finger tip over that port, the AP chamber would fill. So, I think the small whole in the actual AP nozzle gives the AP chamber fill port enough negative pressure to open it's check valve and fill the AP chamber. However, I noticed my AP spray duration is only about 3/4 of a second. It is a fairly good stream, but I don't know if that is enough. I did notice the hole in the plastic AP arm is elongated from years of use. The timing still seems right, but not sure if that wear makes the duration of the squirt shorter? I do know about the Eddy mod, just not sure I want to do that without having a spare AP diaphragm in case the mod does not turn out well for me. Any thoughts?   

Share this post


Link to post
Share on other sites

The elongated hole is original.  The short duration could be several things.  My guess is the AP is only partially filling.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×