Do Boyesen two stage reeds in a 2.9 require leaner jetting? I was running 36/118 with the needle next to the richest position. Recently, the bike has started fouling plugs occasionally and the plug is always black. It is now 35/118 with the needle in the leanest position and is still kind of black/ brown. The only change I can think of is the reeds. I tried a 114 main but it knocked (pinked) like crazy.

Recently installed the Boyesens and have had no problem but I did lean out the Fuel Screw a bit for the warmer weather now.

Currently at 35/122, needle in 3rd slot(next to rich)and about 2 1/4 turns out on the screw, 80:1 mix full synthetic and a blend of premium 93 pump gas and 100 octane avgas to bump it a bit. Plug gapped at .020

The VX plug that the Dabster speaks of may have better anti-fouling properties but I cannot recall the exact number.

Mine seems slightly "blubbery" off idle at about 1/8 throttle but not bad.

I have considered playing with the needle or the low jet more but have not had time.

I consider the Dellorto to be a fair 15 dollar carb so I don't complain much. I have a Kiehin which is a better carb and may just install it instead as it seems to be a better mixing device at low revs.

You still need to rev the crap out of it on occasion just to keep it clean!

MC

At low revs a plug will always turn black and it is the low temperature that is to blame, not yr mixture. So go back to yr best mixture setting and occasionally heat the motor by doing some full throttle runs.

When the fan is on, it doesn't mean that yr motor is overheating only that yr temp-switch is working