Anyone using a Mikuni VM16 ?

Ratchetbirds · Sep 6, 2011

Okay, I did a few more miles yesterday and pulled my plug. A real light grey. Put the e-ring on my needle back to the center position and rode her to work today. Much better. A big warm-up makes a big difference. Just pulled my plug from my 6 miles of riding today. Still grey but slightly deeper in color. Better top end at WOT today also. Next step will be to move the e-clip down one more notch to richen it all up. Doing that tonight so I can do another test in the morning.....did a short test drive just to make sure it would run in the morning. Did I mention that I hate the Chinagirl chain drive system? It always comes off, at the least opportune time. It did. I pedaled home, but the engine runs well enough for my morning commute.

motorhead419 · Sep 11, 2011

Ratchetbirds said:
Hello and asking if anyone has experimented installing the Mikuni VM16 on a chinese 66cc bike? I've been searching here all day off and on and haven't found too much posted. Hoping to not re-invent the wheel so to speak, but can do it myself if needed. Any info would be appreciated.

I use the VM 18mm...Runs perfect and highly tunable. You must make an intake spacer as the carb will be too big for the intake mount...While you're at it get a Jim's straight intake manifold and port out the hole for the bigger carb.. .shft.

Ratchetbirds · Sep 27, 2011

Thank you for the input Motorhead. I need to apologize to everyone for being gone so long, had a wierd infection and just got out of the hospital after 2 1/2 weeks there. Much better now. Will be able to ride in about a week or so and will be able to add more info on dialing in my VM16. Infection was in the right leg, so I can't ride til the last of the swelling goes down. Really hate not being able to ride for so long. I built this, my first MB, over 4th of July weekend this year. Now that I have finally found out how much I love riding my MB it is funny that for so long I never knew what I was missing, until I wasn't able to ride it. I am already figuring out how I will ride it throughout the entire winter. Mainly as work transportation, of course....grin. That will be another post I will start as we get closer to snow. Once again I thank everyone for their patience on my posts in this thread.

Ratchetbirds · Oct 8, 2011

Okay,

Finally got to spend some time on my bike today and was able to start it and do some test stand runs. Can't ride just yet, but hopefully next weekend. I was able to run tests for needle clip adjustment and completed 3 test runs with cooldown time and plug inspection. I did the three middle grooves and am still running rich. I will try the leanest needle setting tomorrow. Here are pics as of today of the Mikuni install. Engine was actually running while I shot these. This might not be the best data on any adjustments yet, being run without a load and all.

MotorBicycleRacing · Oct 8, 2011

I can't believe that you are still using the standard exhaust
with that Mikuni carb and manic mechanic gen II billet head.

You are strangling that motor.
Are you going to put an expansion chamber on?

Ratchetbirds · Oct 9, 2011

Yes I have a SBP x-chamber. I will be buying an SBP shift kit soon as well. Since the motor mounting changes when installing the shift kit I decided to wait and install the pipe once, not twice. I have made wayyyy too many changes to be fiddling with more all at once. All the mods you see, and don't see, have been installed all at the same time. The wiser choice is to do one mod at a time IMHO. This thing has monster power compared to the old head. Very hard to start on the test stand. I am also running a brand new hand built ignition. As was said on "Kung Fu"..."Patience, Grasshopper". I am in the process of rewinding a magneto for more ignition power and no white wire at all. All this while trying to dial in my sweet new carb

dmb · Oct 19, 2011

changing the clips will only help 1/4 to 3/4 throttle. wot is the main jet and idle is the pilot and air adj. fine tune with the slide and needle taper. yes your right one mod at a time. i like you cant stop tinkering and cruzin around town but snow? thats hardcore!

Ratchetbirds · Oct 19, 2011

Still can't ride just yet, maybe this weekend but still thinking and working on winding my magnito (hopefully tomorrow), Smoothing out my Suzuki JR 50 fuel tank I just bought, as well as working on the third wheel frame for snow riding. Oh yeah and building yet another simple CDI from Rohmell's post. I only drive 3 miles one way and most is dirt back roads. The only hard part is staying warm enough. It only takes me 7 minutes in good weather. I just love the gas money it saves me with 6 miles a day, and now in winter there will be no gas guzzler warm-up period to pay for.

Ratchetbirds · Oct 23, 2011

dmb said:
changing the clips will only help 1/4 to 3/4 throttle. wot is the main jet and idle is the pilot and air adj. fine tune with the slide and needle taper. yes your right one mod at a time. i like you cant stop tinkering and cruzin around town but snow? thats hardcore!

I forgot to explain that there are 5 adjustments on this Mikuni, not just 3. Starting from the fully closed throttle going up towards WOT they are: 1) Pilot air screw & jet: 2) Throttle valve: 3) Jet needle: 4) Needle jet: 5) Main jet & Air jet. Also there are 5 grooves on the needle instead of 3. I need to see what jet sizes I have and purchase some smaller stuff. I am running rich. I also changed the old mixed gas I had (2 months old), with a different oil and things are working much better today. Almost no smoke.

Ratchetbirds · Oct 30, 2011

asdfhgdf !!!

The 2 largest motorcycle shops in town and they don't carry smaller Mikuni jets. Even the used bike shop didn't have them. I was able to get a smaller pilot jet from one place but it was 2 sizes smaller than what I have. Went ahead and ordered jets online. Just more waiting, grrrrr.

rustycase · Oct 30, 2011

Hey Rbirds, glad to see you're still having fun with mabs!

Is there some reason why you haven't yet bought a few little number drill bits, and soldered your main jet to drill it to the size you wish?

Here in my 2 horse town there is a discount tool store, and the tiny little numbered bits cost from a buck and a half to 2 dollars each.

Any kind of propane torch and a bit of solder will be more than sufficient to solder a main jet.

Best
rc

Ratchetbirds · Nov 20, 2011

Heya RC, Yeah I could drill but I wanted a few bits of brass to play with. Anyway, winter is here at my home and I have shelved the Mikuni until spring since I have no shop to work in and I can't have gas fumes in my home. I put a cheap factory carb on and am riding instantly again, just slower. I have all the clothing needed to survive the cold, so riding to work in the morning<G>. Forecast for this week is rain and snow.

ivan H · Jan 12, 2012

Hey RB, hows it going. Have u made any progress with the 16mm VM Mikuni carb. I have 66cc that at the moment is pretty stock other than home made cdi along the jaguar modified kdx circuit theme, some port matching & a 10x14x15 small end bearing. The cdi smooth it out thru entire rev range & allows much higher rpm. I have 4 new quality bearings to install, (crank & clutch shafts) & have ordered sbp shift kit & expansion chamber. While its apart I intend balancing the crank to 57 percent recipricating weight. I am considering the 16mm vm mikuni over the 16mm PHGB Delorto & it would be handy to know what jets etc to use to get me in the ballpark. Thanks mate, regards

Ratchetbirds · Jan 13, 2012

Heya Ivan, would love to give you info but winter just started 3 weeks ago and there is much more left. Running a 1st series carb for the winter and it is working, kinda. Just a flat lil carb, performance wise. 18 degrees last 2 days for ride to work, chilly but tolerable. Bike is slightly cold blooded but not too bad. Almost hit a pedestrian yesterday morning in the early morning dark. He was dressed totally in black and walking against traffic in the very wide paved shoulder. I was riding in the car lane within 1 foot of the shoulder. Didn't see him till he was beside me, less than 18 inches away. I was going about 25. Scared me bad. Him, too. He had a flashlight this morning. I have a 3 LED head light that is very bright but has a very narrow beam. Back to the Mikuni. I have purchased many jets and need a prolonged period of nicer weather to test and set it all up correctly. I am not super experienced in 2 stroke and have learned more about them through this forum than from anywhere else. It may take me a bit to start getting the hang of the carb next spring.

ivan H · Jan 15, 2012

Hi RB, u obviously enjoy riding,, that is commitment, & man thats cold. We're about a month into summer here & in S E Queensland here in oz that means temps of 37 or 38 celcius, or around 100 F & getting hotter, & usually around 80% humidity, although its raining 2day, so no ride. I'm currently waiting on couple of orders from sbp, (they are such helpful guys, I'm computer illiterate so without their help ordering would be impossible), but the next planned item is the mikuni. With a bit of luck I may get to share learned knowledge with u. Regards, Ivan

ivan H · Feb 5, 2012

G'day R/birds, how going. Well, got the bike back together, replaced crank/counter bearings with quality items, new crank seals, rings & jug, fitted SBP xpansion chamber & shift kit. Runs a bit richer with the x chamber. Ordered VM16-516U Mikuni Friday just past, arrived today (monday). Quality. Now just gotta order a billet manifold from piston bikes. I'll let you know how I go tuning it when I do. Cheers mate

Ratchetbirds · Feb 6, 2012

Heya Ivan,
Since it was too cold for my ignition there for awhile, I decided to order my SBP shift kit. I will be tearing down the bike for paint as well as the install of shifting and my SBP x-chamber. I cleared out a small space in my second bedroom <storage area> where I can do the teardown. I bought the HD shift kit because I increased my compression. Hopfully winter is nearing it's end here and I can work outside easier. I look forward to hearing your progress....and lets see some pics, too <G>.

ivan H · Feb 6, 2012

Hi R/birds, how goin. Man, thays cold when ur cdi wont fire. Try changing the scr to an industrial grade, much greater thermal tolerance. The SBP shifter & x chamber are quality items & a straightforward install. I'd love to give u some pics, but I have to work out how to post them. I'm posting from a nokia phone & posting on this forum & struggling to order from SBP is the total of my computer/internet experience.. Can u tell me, what is the cooling ability of the manic mechanix head. I am not so much looking for high compression as cooling fin area, & a better chamber design with a squish band although a mild increase would be nice. Also, on page 4 of this thread motorhead 419 mentions a"Jims intake manifold". Does anyone have any info on this.. I'll see about getting some pics posted. I could msm them to u. Cheers mate

Ratchetbirds · Feb 6, 2012

Hi Ivan,

I don't have a temp gauge but from all indicators this head runs nice and cool. This has been the largest increase in power I have added yet and I assume it will be the only item that has that much bang for the buck. I even decked the cyl .062" and got a very nice compression increase. About 9.5:1 now instead of 6.7:1. I have about 50 miles on it now and will never take it off. Cooling is not an issue.

The Jim's intake is something I have never heard of, ask Motorhead about it.

ivan H · Feb 14, 2012

Hi R/birds, hows it going. I intend ordering a manifold from pistonbikes in a day or 2 so thats ok. Where is the manic mechanic head available from & at what cost. Pistonbikes site lists the billet intakes but not the head. I emailed them a couple of days ago but as yet havent heard back. I can get one locally from rocksolid engines, $95 + freight which wouldnt be much & it appears to be a quality item,,, I'm just weghing up the options. Cheers mate

Ratchetbirds · Feb 14, 2012

Heya Ivan,

Going okay. All stripped down now and working on taking all the paint off my frame. Converting this old Huffy from caliper brakes to V-brakes. Have to weld on posts for the brakes, front and rear. Decided to paint the engine black and leave the Manic head in white aluminum. Also making and welding on a mount for my Suzuki gas tank. Once all that work is done then I can install my SBP shift kit. Nice looking kit. High quality stuff.

The head I got from piston bikes but it is not on their site. Bikeberry lists it for $69.99 US. Manic had a tree fall last October and took out a power line, in turn taking out the control on their CNC machining center. They are back up and running again now as their website explains. Cheers buddy.

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Anyone using a Mikuni VM16 ?

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