Mikuni tinkering
 

I't thinking about changing the low speed jet in the Mikuni on the EVO.
It seems to be too lean on cold days. Coughs, spits, and sputters when cold.
It is a little lean in the summer but warms up pretty quickly.
When the weather is below 55, the leaness is more noticeable.
When riding to work, it just starts to come around when I arrive as I have
a ride of less than 7 miles.

I guess I'll open it up and see what size jet is there as I have forgotten.
(and some doof forgot to write the jet sizes in the manual during assembly)
I think I could just change back next spring after the weather warms up.

Comments?

When I tuned the Mik on my Wide Glide, I called Mikuni USA and talked to a tech. He was very helpful. You can also download the manual from their website.

I had luck running a 22.5 low and a 160 MJ on my Mik 42.... but I bet it's different for each setup.
What do your plugs look like?

Have you tried the air screw?
That, and the accellerator pump were all that needed attention on my Mik 42 on my TC...

Follow the manual, set the Idle air screw and if it is not within the correct number of turns, change the jet per the manual.
If you are only riding that thing 7 miles at a pop, change your oil twice as often.

Plugs are quite clean.
Idle air is set.
It was 58 this am, so it started and ran without much fuss. Just a couple of coughs.
When the temps fall into the 40's, she is quite tempermental.
However, she is fine once she warms up.
Almost 70 here today at lunch, ran just fine. :woohoo:

I have a copy of the manual.
Since there is no choke butterfly to close when she is cold, I'm thinking
the choice is to richen her up to the next jet. If I start to soot the plugs,
I'll change her back.

(wonder is heavier oil on the air filter would make a difference?)

:nothing1:

I'm glad I have EFI...

















and a laptop...
















and a Daytona TwinScan II/WEGO...
















:blink:

:Poke:

I'll keep the carb....

Most carbs have to be re jetted in winter. Careful, I had to LEAN mine in cold weather. Colder air = more air molecules=more gas carried into the cylinder.

Good point.
The obsolete evo runs fine after it warms up in cold weather.
It is just the first 5 minutes or so. I get all kinds of coughs and spitbacks
like it is very lean.
I pulled my plugs last night and looked at them. Clean.

I've decided that I will pull the carb and clean it out. Might have some
trash in the low speed jet. I will check to see if any of my extra jets
are one up from the one I have. I think it will be worth a try to go
up one size. I'll just have to watch the plugs to see if it is too rich after
it warms up.

I never knew that ......

I lived about 120 north of New York City for 17 years. I rode a Kowalski when I lived up there ...... I NEVER touched the carbs on that bike, winter or summer. Never noticed that it ran any different in the winter than it did in the summer. I rode year round, when road conditions permitted. Temp was never a consideration for not taking the bike, everyone thought I was a nut, when in fact I've always just been a doof ..........

Just remember that "carburetor" is a French word meaning "leave it alone"

Always a good point.
I will check. (although it runs fine after it warms up)

rode Saturday to a poker run. Was the only bike to show so they called it
on account of rain.

Rode Sunday, temp was about 58. It ran fine. Still a little fussy when first
started but not so bad as on cold mornings.

You sure have that right!!!!!