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Old 09-02-2018, 05:48 PM
AZRickD AZRickD is offline
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Join Date: Feb 2007
Posts: 1,839
Default Stock Jetting in 2018 XC300

I'm going through my new-to-me Demo 2018 XC300 (with EC pipe). Carb was said to have stock-ish jetting.

It's about 100F to 110F right now (37.8C to 43.3C) here in Phoenix with the riding elevation about 2000 to 3000 feet (1000m). But most prefer to head up to the mountains from 5000' to 7000+ feet and the temps dropping to 85F (or 70F after a rain).

So, essentially, in the past (pre-Lectron) I have had my winter jeting (central Arizona foothills at 3000 feet and about 40-60F), and my summer jetting (Prescott and Flagstaff at 7000 and about 80F). In my 2011 EC250 (with head mod), that would be 172/42 in the winter (maybe a little fatter), and 162/38 for Flagstaff summers.

I had been riding the new-to-me 2018 EC300 around, taking it easy, as my shoulder heals. I found the bike to run very clean. Starts right up. Idles nicely. No smoke after warm up. No spooge (zero spooge, not even a dusting).

The plug has many hours on it and is black and dry. It is jetted almost the way I would want it: Soft. It's probably a little too soft right now. I'd jet it leaner. When I swapped the FMF Power Core for a Turbine Core, the top-end got a little burbly.

So today I started digging into the bike to decide if I wanted to go to the bother of measuring the squish for modding and/or get a Lectron or just do the jetting dance.

I rotated the carb around to verify the jetting. N1EF needle with clip in the 2nd position from top. Whenever I see the clip moved to drop the needle, I wonder what profile is being compensated for. Main Jet is a 175. Pilot Jet is 40. Air screw 1.5 turns out. The N1EF needle has a pronounced taper that would be useful for our very long, deep sand washes to keep things cool. Other than that, I'm looking for another needle.

Jakobi and other have mentioned using other needels such as the NEDW needle. Any particular advice for my situation?

Since I have been using a Lectron for the last few years, I have given away most of my brass, so I need to buy some. Any advice for that?

[Edit] The results of the squish band measurement are in. 1.78mm with carboned up piston. 1.85mm with carbon scritched away with a razor blade.

Attached Images
File Type: jpg 2018GGEC300NeedlePlub.jpg (112.5 KB, 16 views)
File Type: jpg 2018GGEC300HeadPiston.jpg (116.6 KB, 18 views)

Last edited by AZRickD; 09-02-2018 at 07:19 PM.
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