Carbs help really need

[ktc333]

I got a nice running bike from a friend a year or so ago but it was it not running right at mid and low RPM, seamed to be rich and plugs were a little dark. It has a pipe 4-1, brand unknown, stock air box. I decide to work on the carbs and to make it easy I took off the stock air box and put on 4 K&N's. and wow the low and mid got worse and the new plugs were all black carbon. It seemed to want to clear up at the higher RPM's. I have not pulled the carbs yet and do not know what is inside. I really need some guidance as to where to start with main jet etc. I am at 4000'. Any help will be appreciated as I love this bike

[dragxs11]

People have said that when they put cone filters on. You'd think your mixture would lean out. But when you pull the carbs off, look to see if they have been apart before(rounded screw slots, marks,etc.) The carb rebuild kits don't always contain the right size jets, so if someone has been in there before, they may have unknowingly put oversize jets in. Your mains should be 110's or 115's. The pilot jets which control mixture at idle and partially low and mid range might also be wrong. I found out the hard way that even though the numbers may be the same, the actual size may be different(kits vs. OEM). Also, your float needles and seats may not be sealing causing your bowls to overfill while running.

[TopCatGr58]

Hey there KTC333,

First off, please EDIT your profile, put in at least what year/model your XS11 is, the carbs are different between 78-79 and 80-81 series, and the main jets are way different in size requirement for each. The early models take stock 137's, the later take 110/120's so you can see, the more info you provide, the better "OUR" advice can be!

Secondly, aside from the mains not being true to size stamped on them for aftermarket brands, the PILOT JETS, which feed the idle circuit and contribute heavily to the low/mid range have been known to be bad from after market sources ie. K&L kits, so if the P.O. did them, this could also be a contributor.

The float height can also cause a very rich condition!
Your K&N filters, were they truly brand name, or generics? Did you soak/spray them with the oil and then remove the excess before mounting them? A recent Xsive had this problem and was chocking his engine due to too much oil in filters!!

If your bike is 78-79, are the vent tubes coming off the carbs, just above the bowls well vented, vs. plugged, this can also cause this problem!

As "Johnny V" said......."Input, we need more Input!"
PS, there is great tech tip on carbs also, please read it!