When to rejet?

[Bartolucci]

Snowed a little yesterday, but was 50 and sunny today which afforded an opportunity to put some miles on the bike. Two mods I made concern fuel mixture: change to the airbox and removal of a baffle from ea exhaust (this is an xs400 twin). After a 20 + mi ride i pulled the plugs for a look-see. Both were clean but whitish. This leads me to believe I'm running a bit lean. Question is, does this demand that I rejet? Would it be permissible to keep it as is? The bike runs great (and the plugs show no damage), but I don't want to do any harm.

TAB

[cywelchjr]

Snowed a little yesterday, but was 50 and sunny today which afforded an opportunity to put some miles on the bike. Two mods I made concern fuel mixture: change to the airbox and removal of a baffle from ea exhaust (this is an xs400 twin). After a 20 + mi ride i pulled the plugs for a look-see. Both were clean but whitish. This leads me to believe I'm running a bit lean. Question is, does this demand that I rejet? Would it be permissible to keep it as is? The bike runs great (and the plugs show no damage), but I don't want to do any harm.

TAB

It will run hotter with the lean condition, which on the newer models is normal anyways, but if it's not really white (still some gray to it) I would likely leave it alone, I run mine on the lean side above idle, but I'm still disappointed in the gas mileage (back when I got it I used to get around 52 to 56 MPG, now I'm doing good to get mid 40's. Of course, I wish my 11 got that, but then I also wish my 400 had the grunt and go of the 11, so I guess it just works out that way.

[boediddly]

your plugs should be a light tan color. Running lean will lower your fuel economy , also your cylinders wont be getting the amount of lubrication and cooling they need. heres what i would do id go to your local bike shop and ask a technician if they have any half step washers from dyno jet kits (ive found that usually changes in exhaust have to be met with raising the jet needle)offer the technician ten or twenty bucks believe me he doesnt make what you think he would. install these under the circlip on the needle jets to raise the needle one half step raising this allows the fuel to enter sooner. then ride it and check your plugs-black or dark brown take out the washers and go up a few jet sizes. light tan leave it alone-white-go up a few main jet sizes . man it takes a lot of patience a lot of carb removal(usually) and plan to spend some money on jets. but if you get your bike tuned in right youll be glad you did and you might pick up a few horses on the way---P.S. im a seasoned bike technician and it still takes me a long time.but once in a great while i get it right quickly good luck.