I have a 97 scrambler 400. When getting on it, about 3/4 throttle, it bogs down. It is a 38mm Mikuni TMX carb. Mods include Aaen topend pipe and clutch kit. My plug looks a little black. I am running a 260 main jet. It had a 280 jet and kept fouling plugs it why I went to the 260. But it never had a bog down with the 280. What now?

 

I have a 95 xplorer 400 with a 38mm TMX Flatside carb with an AAEN mid/low range pipe and silencer, UNI air filter(stock air box without snorkel), .040" over Wiseco,.010" off the head, heelclicker clutch. Currently I am using a 390 main and 35 pilot with 1.25 turns on the air screw. The plug has a good rust color, bike doen't bog down any and i have not had any problems with fouling the plug. i run 50:1 Klotz oil with premium gas - this coming weekend i have an indoor flat track race and will be running race fuel - this should give me a good ideal how this set up will work because i will be checking the plug after each heat( i'm in western KY). The has only been on for a week but i love the extra boost.
Hope this helps some.
hunt

 

A 390? dON'T YOU MEAN A 290?

 

No, it's a 390 main jet from Carb Part Warehouse... on my stock 34mm i used a 230 main.
hunt

 

Hey I am new here, but just thought I would tell you my set-up. I had a 38 carb, Aaen topend pipe and clutch kit also with the exception of a UNI filter. My jetting was 290 Main, 30 primary, needle clip in middle groove, and air screw at 1.5 turns out. I am at about 1800 ft. above sea level, and this was a summertime jetting. Maybe this will help.