Needle shim modification

Road_Clam · 02-13-2012, 12:14 PM

Too funny I just read this tip, and one of my first mods to any bike that has a slight lean stumble off idle and into the mid range is to shim the needle. Modern bikes come so EPA lean with respect to low speed jetting they run like absolute garbage in cooler temps (like we have up here in New England). I drove our new GZ for about 1/2 hr in colder temps and knew right away my carb need some richening. I have a bunch of 3mm X .020" washers I got from Radio Shack, and they work perfect for shimming needles. I also pulled the "epa" plug for the air fuel screw, and added 1/2 turn CCW for some much needed cold starting ease. Now even if it's 40F, our GZ fires right up on 1/2 choke as soon as I hear elevated clean rpm's I shut the choke off and the engine purrs perfect. No mid range stumble either. I've shimmed needles and many times also have to bump the pilot jet(s) one size richer too, but so far doesn't seem like the GZ will need a richer pilot jet. Great tech thread !

02-13-2012, 12:14 PM	#38
Road_Clam Senior Member Join Date: Feb 2012 Location: sounthern NH Posts: 146	Re: Needle shim modification Too funny I just read this tip, and one of my first mods to any bike that has a slight lean stumble off idle and into the mid range is to shim the needle. Modern bikes come so EPA lean with respect to low speed jetting they run like absolute garbage in cooler temps (like we have up here in New England). I drove our new GZ for about 1/2 hr in colder temps and knew right away my carb need some richening. I have a bunch of 3mm X .020" washers I got from Radio Shack, and they work perfect for shimming needles. I also pulled the "epa" plug for the air fuel screw, and added 1/2 turn CCW for some much needed cold starting ease. Now even if it's 40F, our GZ fires right up on 1/2 choke as soon as I hear elevated clean rpm's I shut the choke off and the engine purrs perfect. No mid range stumble either. I've shimmed needles and many times also have to bump the pilot jet(s) one size richer too, but so far doesn't seem like the GZ will need a richer pilot jet. Great tech thread ! __________________ 1984 GPz1100 1987 GSX-R 750 2006 HD Fatboy 2001 KX500 2007 YZ450F 2001 GZ250 (Wife's !)
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