Author Topic: FL400R Jetting  (Read 1483 times)


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FL400R Jetting
« on: March 26, 2007, 07:07:46 PM »
I am a little stumped. I've been running pretty fat. So, I just changed the reeds to boyseen. I used the stock cage and bolted them on. The stock reeds did have a gap between the seat and the reed. Still fat. I dropped the pilot jet from 52 to 50 to 48 and the main from a 140 to a 138. I even moved the needle from the #2 groove to the #1 groove. Making all these changes I can get the snap into the throttle. No problem.

My problem is I can't get the idle to move no matter what jetting I have tried so far. It will barely idle at 700 rpm and won't go up or down when I turn the idle screw. I can screw it all the way in or almost all the way out and no difference. The same with the air screw. No change. I was getting ready to go to the 145 on the pilot screw tonight to see if that would help any but lost the clip on the needle. Have to wait till I get another now.

I thought maybe the float had a hole in it and was sinking. No fluid inside it. I don't have a float guage but I tried using a 6in machinist rule and when it touches the seat it looks to be spot on 16mm.

Any ideas?

Also, my son dropped the needle clip in the gravel and it can't be found. Can I just use a c-clip from a automotive store or do I need to spring for the $18 needle set?



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FL400R Jetting
« Reply #1 on: April 01, 2007, 07:59:15 AM »
Sounds like you have a grip on what's going on.  Good!!!

Just to cover the bases, these are general:

Main jet - from about 2/3rds throttle up
Needle - about 1/3 to 2/3rds
pilot - down low.

If you can't control the idle, then the pilot jet's too large.  Seems like most run closer to a 36 or 38, from what I recall.

The air screw should make the engine start to rev up if you turn it out and blubber when you turn it in.  If you can't get any reaction that points to the pilot jet.  Your description says it's fat.

Once you get the bottom end controlled, start messing with the top end.  Work from rich to the correct jetting.  Two bangers don't like being lean at all.  

Do the good ol' plug chop and work to a pancake brown on the electrode.  You want to start out with a fresh plug.  If you're really rich at first and end up with a sooty plug, put in a new plug with the next jetting change.

Once you find the correct jetting, stick the sooty plug back in and run it - that will get rid of the black stuff and you'll have a spare plug to carry around with you, "just in case".

The little c-clip - just a regular piece.  Just make sure it fits well and doesn't flop around.  It's a metric piece more than likely, but I'll bet you can find a replacement at the local hardware store or auto parts place.

For some more info, give this a read:
Moskito - Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming \'WOW-What a Ride!\'