110cc Carb & Jet Specs Rattler - Confirm pls?

[genuinedraft8]

Hey guys. Just looking for a quick confirmation on specs of the main jets on the stock carb.

Carb = Keihin "PB"
Main jets = 99101-116

Look about right to you?

What's the size of the air inlet on the carb? What size would be the right Unifilter inner dia?

Thanks in advance.

Blake

[Keys]

I couldn't tell you what the part number is of the stock main jet, but it is an "85". I just replaced mine with an "88" and removed the foam "pre-filter" from the airbox and got an immediate increase in mid and high rpm power. No more top speed, but it holds speed better and pulls hills better.

--Keys

[nissanman]

I'm running a 100 main and still think it can handle more gas

[genuinedraft8]

I went with the 110 main, with a unifilter pod. That was too rich. Ran fine for a couple of months and soot started building up on the plug, causing bogs and eventually died on me (fouled the plug), had to replace the spark.

I'm ordering the 95, 100, and 105 and will do some tests to find the optimum. Will update in a few weeks.

Question: is there a better way to tell if I'm running lean or rich, other than checking the spark plug after moderate to extensive test riding?

Blake

[nissanman]

Weld on a bung to the exhaust and install a wide-band O2 sensor... or keep checking your plugs

[dynarex]

Question: is there a better way to tell if I'm running lean or rich, other than checking the spark plug after moderate to extensive test riding?

ck piston wash
run 1 step colder plug
start with low speed
then test the midrange then test top end
use new plugs for each test and set it up with what you think is on the rich side to start with-plugs are cheaper than pistons

[B02S4]

An A/F meter with a heated wideband O2 sensor would be best. I have one on my motorcycle, but not on the Rat. I'm not so sure how well an o2 sensor would last on a 2T motor, though.

Most serious performance tuners that I know start with the mains first, then the needles, then the pilot jets & screws, just the opposite of your tuning progression. FWIW.

Question: is there a better way to tell if I'm running lean or rich, other than checking the spark plug after moderate to extensive test riding?

ck piston wash
run 1 step colder plug
start with low speed
then test the midrange then test top end
use new plugs for each test and set it up with what you think is on the rich side to start with-plugs are cheaper than pistons

[dynarex]

i was taught that if you start with mains first and the mid and idle is too lean-it could cause you to seize on decel or part throttle decel
unless you def know the mid and idle is on the rich side

there ar also several egt sensors out there that will work and are designed for 2 strokes
o2 sensors n/g

[B02S4]

i was taught that if you start with mains first and the mid and idle is too lean-it could cause you to seize on decel or part throttle decel
unless you def know the mid and idle is on the rich side ...

It is important to start rich & work down. The most efficient way is to start with rich mains & downjet from there. There is much more tail-chasing starting bottom from top.

I personally don't worry about lean conditions on decel, because that's what happens to motors (4T & 2T) regardless on decel with closed throttle.

As a general rule, ovely lean-jetted 2T motors don't want to rev; overly rich jetted 2T motors won't rev.

[dynarex]

good point
so i jetted my scoot today after installing the ncy manifold reeds and 26mm kehein carb
why did i have to lean out the mains compared to the stock carb mains
i went from 112 in the stock carb-and running a 104 in this one with no air box!
gotta be the prima pipe huh?