mikuni carbs, suppliers

Ok, let me ask this question,(I do appreciate the feedback) If stock jetting won't work, where should I start?

I have other project bikes going right now so i'm keeping an eye on the cash flow.
Building a second 83 IT250 for my son to race.

Stock jetting is
430 main
Q8 Needle
2.0 slide
6DH3 Needle jet

My current race bikes.
83 IT250 is my favorite.

To fine tune it we can play with a richer or leaner needle. If it's on the last clip and still not right. We still can turn the pilot screw last. I like the pilot screw at one turn so we have room to go either way. It depends on how fine you want to tune it.

try it that way but you will likely find the bottom end and mid rich..a 2.5 slide (is leaner), leaner needle jet, and leaner pilot will be needed. that was my experience along with several other 430 users. some have had to richen the main.

the 6dh3 is your needle..dont forget about your pilot, too, as i see you do not have it listed.
you will need to swap jets and run it to get it tuned. another reason doug and i made the recommendation we did. it can take time, and time is money sometimes.
the bike can be made to run excellent with the mikuni. took me awhile to get the 87 430 jetted but i ended up with
35 pilot
q6 needle jet
6dh2 needle (stock)
2.5 slide
410 main
dynoport pipe and stock silencer w/ spark arrestor.

i guess what im saying is you may be buying some jets. nature of the beast. do some searches on "430 jetting"..yours is air cooled so some other threads may be a little more helpful.

sharp yamahammers!

Great thread, I am just about to order up parts for my 38 mikuni. Justintendo what is the elevation were you live?

I do know a little about jetting but really don't really tune bikes to the optimum. Most often I start with factory jetting and work my way from there. My criteria, It Starts, Idles, doesn't blubber I'm good.
Having said that, I'm going to learn a little from you guys and again I appreciate the information. Mike

The cleanliness of your shop amazes/embarrasses me. Nice bikes!

nothing wrong with that i guess, unless something is lean and it seizes or doesnt live as long as it should, or doesnt get the mileage it should, etc etc,.....leaves a lot on the table. sometimes you dont know what you are missing. the 430 will four stroke (blubber) a bit with stock jetting. i havent experienced it with mine much but some say the 430 is too lean on top as well. ironically my 88 250 runs its best very close to stock spec jetting.

1100 ft average..im also running a 50/50 91 puregas/110 vp mix, which makes things a bit rich. if i were just running regular fuel i would likely be a size richer on everything.

A couple more photos. finished this MX250 Rustolium Racer, It's going to get a flogging in the NETRA series. Anyway something to look at. By no means is this a showpiece but it's more fun to ride than I originally though.
Kind of feels like you are that kid growing up that had the really cool dirt bike. I took it to a club event and had more attention than the new KTM's.

With our old bikes I get older riders who either had one and raced it or lost racing against them. Older riders heck most are younger than me. Nice looking yamme. I did meet one older fellow who raced a Penton to this day he hated Husqvarnas. This tells me that in there hay day Husqvarna must of been a force to reckon with.

bike looks good! having the mechanics and function is the priority. it probably is pretty fun to flog around. the old bikes have a sound thats all their own.

Fact, For anyone restoring a bike don't forget to adjust the brakes before you ride it. I was so excited to get my very first 83/250wr husky running and test ride it I forgot to adjust the rear brake. I wicked it in first gear and she stood up. I had no rear brake to get the front wheel back down. I just rode it out. She had more power that my 72 Suzuki ts185. Twenty five years ago the huskys weren't cool like they are now. Here's come the milkman.

Nice 250! What NETRA events are you gonna ride that in? I wouldn't want to hare scramble it.

YUP NETRA hare scrambles.. Truthfully I'm going to pick a few that are not rock infested. NETRA has several that are vintage friendly events. Hoosick Falls NY is hilly but no real rocks to speak of.
I have a skid plate for it but it's steel and weighs as much as a front bumper on a 1978 Ford F150.
We have 12 events, I rode 6 last season in EVO Drum Brake class. I want to mix it up a bit.
If this 430 is ready to ride, I may take that to NY instead of the IT. Who knows, I usually ride whatever is ready and closest to the door.
I'd like to ride Vintage class 100%. (1977 or earlier)

They do a netra vintage/post vintage ride at thomaston dam in thomaston,ct.

The only thing is the dead start left kicker? (Husky) unless you practice standing on a box with your right leg and kick with your left leg? Practice, practice your dead starts.

I wish we had the vintage, style motocross.

We tried to get one going up at Winchester but not many showed. It was a blast. Winchester is a perfect vintage track.

Heres the way i jetted the keihin, started with pilot jet lean 35 (same sizing as mikuni) warmed it up did some high speed runs noticed surging at idle screwed air screw all way in surging stops so went up to a 38 with air screw at 1 turn out.main jet started rich at 180 did some plug chops went to 170 ended up at 165 main (keihin sizing is orifice od 165=1.65mm mikuni is flow rate but willbe a crossover somewhere on the net) my slide is 6 cut which is leaner than a 4 think the number relates to how many mm higher the cut section is above normal, needle position and size/shape can be altered for best transition.one thing to take into accout is if your doingalot of high speed low rpm road sections is you will need to richen up the circuit or risk cold seize.

Yes I like the 110 vp also, Ill have to play around with a few jets and needles.