Fcr 39

My buddy pick up a 2000 xr4 Al Baker edition. From what I understand it's a beefed up xr4 with a fcr39 carb on it. We cleaned it up got it running and starting good when warm runs like a champ. But man it's a bitch to start cold and we can't figure it out. I'm thinking jetting because he bought it at sea level and we are at 4600ft. What would be the correct jetting for this altitude. I think these are 440 bore with big gun exhaust and unit filter. Any help would be appreciated thx.

If it was jetted and tuned right for sea level, it should be plenty rich enough for starting at the higher elevation, maybe too rich. Are you starting it with or without choke? If with choke, try starting it cold without choke. Leave the throttle alone, don't twist it. Its a pumper carb and every time you twist the throttle you shoot raw fuel into the carb and you can flood it, make it too rich for starting. If it starts cold better without choke, you know the pilot circuit is too rich.

 

If you haven't readjusted the fuel screw since moving to the higher elevation, leaning it out would probably help. Get the bike started and warmed and retune the fuel screw for best/highest idle and response off idle.

 

You didn't say what jetting it currently has, but I normally go 1 size smaller on jets for every 3k I go up in elevation.

 

Did you ever start it or hear it run when it was at the lower elevation?

 

Out of spec valve clearances, too tight, can cause difficult starting when cold.

Yeah I've been twisting the throttle probably flooded it I'll try with no throttle. Don't see a choke on it though and I forgot the dang jetting should have wrote it down. The valves are my next stop if this doesn't work I know I should done those already I'm a idiot.

I was wondering about the choke. Never used one but read that a FCR for the XR400 was offered for a while but had no choke. I'm not really sure if it's a pumper or not either. Might be just a old FCR flat slide. Heard they worked well either way but the no choke made starting a bitch.

Well tried with no throttle prime it and kicked it. Started second kick thx TR42 for the help really appreciate it.

I was wondering about the choke. Never used one but read that a FCR for the XR400 was offered for a while but had no choke. I'm not really sure if it's a pumper or not either. Might be just a old FCR flat slide. Heard they worked well either way but the no choke made starting a bitch.

yeah I don't know if it's a pumper or not I thought I read in another post that's what's on these Al Baker Edition's. It just says Keihin fcr on it all other writing is to degraded to make out. Edited by dlock5

Just pulled up a pic of the pumper it looks the same .

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