Air jet info needed

[Don O]

Is the size of the air jet critical? I don't find the recommended size for a 440 or 340 but find the chart showing size relating to rich or lean and it confuses me, (doesn't take much anymore), the smaller numbers are lean and higher are rich. My 440 cyclone has the smallest # 0.5. I would like to get more air as it seeems to run rich. The air adjust screw doesn't seem to do much, about 1 1/2 turns out now.
I have cleaned this carb so much it is shiny inside and out!
It is suggested to increase the cutout size on the throttle valve, now a 3.0 What are your thoughts?
Changed pilot jet to 17.5, moved clip to top or # 1 slot. High speed run leaves the plugs a good color.
It is a lot better than a couple weeks ago when getting all the help.

Don O

[harleysportster]

The oem air jet for the '76 340/440 is AM66499 which is the 0.5 jet. The Service Manual or the Fine Tune does not mention anything about changing the air jet size. What is your elevation. The tuning is based around that.

[400brian]

I don't think you'll notice any difference if you took it out.

[Don O]

O K , Thanks for that part.
Should I try a 3.5 throttle valve?
What are the symtoms of leaking inside seals

Don O

[JDT]

Don they tend to deflate your wallet.

Seriuosly, hard starting, poor idle, slugish performance, running hot, burned plugs.

[Don O]

Thanks Todd,
I knew about the deflated wallet part.
I don't think seals are the problem, starts one pull,no choke, idles good, sluggish at low speed but top end goes great, plug color looks good. Howard rode it Sunday and we checked plugs after a run across the lake and they were just right.
It sounds like the gas should be turned down.
Took the fuel pump apart today to be sure, it is good.
Down sized the pilot jet to a 17.5, moved jet needle clip to the top.
Would like to try a 3.5 throttle valve.

Don

[lwb140]

you said the air screw doesnt seem to do much , it should make large changes in the way it runs my expereinces are when you screw it all the way in the sled dies screwing it out the same effect if no change occures while adjusting it id say you still may have some goo in the mikuni somewhere . ive had more fits this year with gommy carbs than ... well i dont know when wade

[400brian]

you said the air screw doesnt seem to do much , it should make large changes in the way it runs my expereinces are when you screw it all the way in the sled dies screwing it out the same effect if no change occures while adjusting it id say you still may have some goo in the mikuni somewhere . ive had more fits this year with gommy carbs than ... well i dont know when wade

No Wade, Air jet. A very small brass orifice screwed into the air horn. It seems that many Mikunis used on Deeres didn't even have one installed.