Here's the specs I ran on my 98 380MXC. 50 pilot, 1.5 out on the airscrew, the stock slide, a 170 main, and an R1467N needle (most critical part) in the middle position. It's a Honda needle. The Keihin part number for this needle is DGH.
Seems odd to move up the pilot to a 50 but trust me, it works. This was at about 1000', stock exhaust, 40:1 Y2R with 92 pump premium. I went to a 175 main when I put an FMF pipe and TCII silencer on. I'm not sure what the elevation will do to the jetting but I'd still think this would be a good spec to start with, at least.
Setting the bike to barely idle helps get rid of the spooge, too. I had ZERO spooge with this setup on both exhaust systems.
This setting has been used and approved by several other 98/99/00 380 owners.
Strick, your setup sounds pretty rich. I realize that tempetures play a huge role in jetting. The temps up here range from 40 - 85 in the summer during our rides. Don't these bikes come stock with a 175 main? The slide #7, I assume you mean a 7 degree cut? Is this leaner or richer than my stock 6?
What temps are you running at. Right now I have a 160 main, 45 pilot with stock needle and stock slide, needle is NOZG??
Single taper needles in conjunction with the #7 slide, mandate the use of richer main jets. #6 vs #7 is in reference to the cutaway portion the #7 has 1mm more cut out of the cutaway portion of the slide. This yields a leaner condition.
Strick '99 KTM 300mxc, AMA & BRC member
Boy what a variation in jetting. I've spent alot of time jetting my Y2K 380 EXC for 500-1000 feet altitude along the Colorado River with high temperatures. My plug is perfectly tan colored, and I run a #7 slide, 180-182 main, 40 pilot, and a CEK (1369N) needle. When I try and run a smaller main my bike doesn't rev out. My responce off the bottom is awsome as is the entire range with this setup.
Had a '98 380. Now have a 2000 380. Dropped float level a tad on both, as carbs angle down and engines tend to run a little rich. The 2000's and later come with a jetting guide. It has worked perfect for me and two other A riders on our 300's and 380's. We run 40:1 with premium fuel - 92 octane. One of our three bikes has 3200 miles on it with one piston. We don't foul plugs....
Get with a buddy to get the chart or I'll email you one....