Airhead Mikuni Owners - Sticky Proposal

[Uncle Pollo]

Since I am installing mikunis on my r80 (why god why? :p ), I believe it would be useful to the poor souls out there to have an idea what type of jetting are we running on our machines.

I was thinking on a format like my signature, so the next poor bastard that tries to figure out his carburetors will have a baseline in which where to start.

Altitude matters ... so if you may ... show off your carb type and jetting!

We could compile them here on the first post for reference ...

[hardwaregrrl]

Hey, I've got TM32's on my R80. Still working on jetting. I am running a 155 main right now (might be a touch lean), pilot is a 20 but I've got to work on the pilot circuit as she is cold natured. needle jet is a series 389 Q-2, and jet needle is an FP17, air jet is a 2.5. needle is at the leanest positon. Bike runs well, still is a hard start, air screw is 1 1/2 turns.

[Uncle Pollo]

Cmon .... if you google mikuni airhead this is the second hit!

[ontic]

I've got vm34's on their way to me now, jetted to some specs that were provided to me for my particular engine set-up. I won't bother trying to publicly provide any specs until I can actually test them, they might run like dogs!

[hardwaregrrl]

Well, currently I have 165 mains, 25 pilot air screw 2 turns out, needle jet is P2, and 5FP17 jet needle. Bike still is cold natured at cold starts, but runs like a top.

[Kai Ju]

For this to be useful, posters need to add Model/Year/level of modifications such as exhaust and intake/airbox. Cylinder head work, cam, compression etc.

So here goes:

1977 R100/7 with stock replica mufflers ( EMGO), '79 starter cover with the cast aluminum intake opening, stock clamshell airbox with stock paper filter and the stock elbows going into the bellmouth of the carbs and sealed. Stock engine with 42,000 miles and 150 lbs compression.

VM38

Main Jet 210
Pilot Jet 30
Airscrew 1 2/3 turns from seated
Needle Jet 166 P-8
Jet Needle 6DH3
Slide Cut Away 2
Main Air Jet 0.5
Needle Valve Ass'y 3.3

I started with a 200 Main Jet but power would increase when I backed the throttle off some. May go to 220 to see what happens.
Pilot jet was a 17.5 which was recommended by a friend of a friend. Totally inadequate, engine wouldn't run/idle unless the airscrew was seated all the way. Worked my way up to 25s and was pretty happy except slow to warm up. Went to 30s a couple of days ago. No change in warm up but off idle transition at speed,i.e accelerating from steady state throttle, feels better.
In mixed riding I used to get 35 mpg with the Bings, now I get right at 40 mpg. The engine pulls really clean through the rev range and, if I use common sense, giving it a handful results in clean acceleration. No hole to climb out of, just acceleration.

[DeutschMark]

I'll play. Engine is a follows in my 89 R100RS:

9.4:1, 44mm intake valves, dual-plugged heads, Scheffer asymmetrical camshaft, timing at 28 degrees BTDC at max advance, two large snorkels on the airbox, baffle in the mufflers punched out (for a slightly better sound more than anything else).

Mikuni VM34 carburetors
6DH4 Needle
2.5 Slide
195 Mains
PO (159) Needle Jet
35 Pilot Jet

I edited this to reflect the change to 195 mains from 170's. I picked up 4 mph on the top end.

[Beater]

I have VM32's on the Dobber (a '85 R100 G/Sified). I will post what works for it ... but as of right now, the carbs are WAY out. They came off a '76 R75.

This thread can be a great 'tuning' thread ... or at least some great places to 'start'.

[Uncle Pollo]

Post the settings anyhow. It may one day help someone

[oldroadie]

1972 R75/5, stock air box, K&N filter, two into one exhaust with SuperTrapp end cap:
Mikuni VM32, 200 main, 30 pilot, 6DH3 needle clip in middle, P-0 needle jet, 1 1/2 turns out
1000 ft above sea level.
Still too fat but very smooth. More jets coming right up....

Update: Exhaust changed to baffled pipe, Supertrapp is shelved for now. Mains 190, pilot 30; both feel too rich and the plugs are dark chocolate brown. 180s and 170s along with 25 pilots on order. I'm guessing 25 pilots and 170 mains is going to be the order of the day.

[Uncle Pollo]

Update: ran fine 2 up to sandia mountain. 10000 feet. Id pulls well over 5k rpms after 9k feet altitude. Idle was a little low at 10.5 k feet altitude but it made it!

That is my butt dyno.

[dvblue_2000]

I made the Mikuni conversion on an R60/7. I got the kit from Rocky Point and they were jetted way too rich for 5300 feet. I eventually put in the leaner jets provided and lowered my slide needle a couple notches and now it runs great, but I remember getting better gas mileage than 37-40 mpg on the R60/6 I used to have. The plugs look pretty good, and I'm not going to monkey with it anymore. One thing that gave me fits is that the choke plungers weren't going all the way back down when I lifted the choke levers so it would run real rich, wouldn't idle, and dribble gas out the carbs (so I fiddled with the floats). Once I figured this out it tuned up nicely. Every time i lift the choke levers I also push the plungers down with my finger. I also gave them a little shot of WD40.

[Uncle Pollo]

Originally Posted by dvblue_2000

I made the Mikuni conversion on an R60/7. I got the kit from Rocky Point and they were jetted way too rich for 5300 feet. I eventually put in the leaner jets provided and lowered my slide needle a couple notches and now it runs great, but I remember getting better gas mileage than 37-40 mpg on the R60/6 I used to have. The plugs look pretty good, and I'm not going to monkey with it anymore. One thing that gave me fits is that the choke plungers weren't going all the way back down when I lifted the choke levers so it would run real rich, wouldn't idle, and dribble gas out the carbs (so I fiddled with the floats). Once I figured this out it tuned up nicely. Every time i lift the choke levers I also push the plungers down with my finger. I also gave them a little shot of WD40.

You here too?

[Uncle Pollo]

Originally Posted by oldroadie

1972 R75/5, stock air box, K&N filter, two into one exhaust with SuperTrapp end cap:
Mikuni VM32, 200 main, 30 pilot, 6DH3 needle clip in middle, P-0 needle jet, 1 1/2 turns out
1000 ft above sea level.
Still too fat but very smooth. More jets coming right up....

Update: Exhaust changed to baffled pipe, Supertrapp is shelved for now. Mains 190, pilot 30; both feel too rich and the plugs are dark chocolate brown. 180s and 170s along with 25 pilots on order. I'm guessing 25 pilots and 170 mains is going to be the order of the day.

I am going to swap my main from 140 to 135 and see.

[dvblue_2000]

Originally Posted by Uncle Pollo

You here too?

Rio Rancho