Mikuni on an R80 help

Discussion in 'Airheads' started by hardwaregrrl, Sep 6, 2012.

  1. hardwaregrrl

    hardwaregrrl ignore list

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    thanks for your help:thumb
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  2. supershaft

    supershaft because I can

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    I wil try to help. All carbs jet the same. The difference carb to carb is how much and where the jets overlap.

    I haven't read all the posts but it sounded like you found too lean on the mains. Just richer than too lean is perfect on the mains. Don't go back too rich. A bigger needle jet (richer) mainly effects just off idle to quarter throttle. A different base diameter jet needle does the same thing. The other biggie is the slide angle and they effect about the same range. BIG mileage changers since you are in these jets during a lot of cruise. Slides are expensive but you can make them leaner with a file. The tricky part is matching them on multi-cylinder bikes.

    Idle jets do not turn off out of their effective range. Too rich an idle jet WILL effect mileage.

    Part of the trick jetting just off idle is that different combo's of slide angle/needle jets/jet needles/idle jets do different things. To really find out what works best, you have to try a lot of different combo's. It's a lot of time and a lot of jets (times two!).

    Like I always advise about Bings, it says right in the Sudco manual somewhere that needle jets are crucial. It really is true with Dell's too. That and the slide angle makes all the difference in the world. Good luck and I hope I am not poking the bear! :D
    #42
  3. hardwaregrrl

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    Thanks Billy! I struck out at Barber as no one had a Mikuni tune up box....weird....lots of Amal stuff though.

    I'm planning on mimicking the VM32 needle jet and jet needle. I think P4 or P2 will do it...and not sure which jet needle yet. I'm going to keep the mains around 160/165, don't want to change too much at once. I won't touch the slide, that scares me and I think none other are avaliable for the TM series, again not sure. I may just shelve them and buy another spliter and just swap the Mikunis on before race day. But that developes another problem, throttling out of turns will be a learning process while racing.:huh That might be a stoopid idear!
    #43
  4. Uncle Pollo

    Uncle Pollo Long timer

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    ihave the one on my signature that its a hair too rich. the next leaner one is in the mail. i am certain that it would work if the air density was higher here. try that one. i am getting the two next richer pilot jetts too ... reading sparkplugs is easy . chocolate color is what you want. my mainn is dialed in as far i can tell. top rmp top gear full open = chocolate. running around town is darker and getting 45 mpg. but i am riding like an asshole too.
    #44
  5. RecycledRS

    RecycledRS Along for the ride

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    Chocolate brown is too rich IMO.
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  6. Uncle Pollo

    Uncle Pollo Long timer

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    milk chocolate with peanut butter
    #46
  7. RecycledRS

    RecycledRS Along for the ride

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    Oh, OK. It'll be alright with peanut butter!:D
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  8. Uncle Pollo

    Uncle Pollo Long timer

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    my 32s run better than my bings. waiting for the fatter needle and see.
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  9. hardwaregrrl

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    Why am I in the pantry with jif and a banana?
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  10. Uncle Pollo

    Uncle Pollo Long timer

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    i have that effect on women.

    "pheh .... rather be eating"
    #50
  11. supershaft

    supershaft because I can

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    IMO reading plugs is too hard for most. Most everybody jets way too rich based on plug reading. I have had people look at my plugs and say my engine is going to melt. It never did. It sniffed on the dyno right around perfect too after I went back down to the mains that I thought were running best but wanted to be safe. My plugs run mostly white on pump gas. They run pure white on race gas. On race gas you are not even in the ball park until your pipes start running white. Then I lean it from there until it doesn't run right and richen it back up a bit. The same thing holds true through the rev range if you keep in mind that from idle up to the mains a little too rich for steady revs usually gets you reved up quicker. In other words. They often run best just a RCH rich except for up on the mains. A RCH rich on the mains will cost you at least a pony or two. It can be running and sounding real good and still be quite a bit more than a RCH too rich on the mains. It costs you quite a few ponies that are otherwise free for the taking. Better mileage, more power, cleaner engine. Win/win IF you don't melt your engine!
    #51
  12. RecycledRS

    RecycledRS Along for the ride

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    Agreed that most run too rich and plugs are hard to read. After tuning for many years I have found that using an air/fuel gauge to be the only certain way to be sure the jetting is right. Not saying more talented folks can't do it by reading plugs but with all the additives in the fuel today I find it a "guesstimate" at best.

    Of course a dyno run to two would also help.
    #52
  13. Sniper X

    Sniper X De Oppresso Liber

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    Ok itis a little hard reading all the posts so please outline exactly what is going on starting with idle, off idle, transition to needles and on the mains. What happens when you (try to) ride normally like you did with the stock Bings?
    #53
  14. hardwaregrrl

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    Bike runs fine....better. But it's eating gas. Plugs are slightly carbon fouled.
    #54
  15. Uncle Pollo

    Uncle Pollo Long timer

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    http://www.amckayltd.com/VM34-36.pdf

    Simply the best tuning guide from the xs650 forums.

    The pollobusa is finally tuned.

    ...for now.

    I will try a bigger main and see.

    42 miles per gallon riding around town like an idiot.
    #55
  16. mark1305

    mark1305 Old Enough To Know Better

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    You ever work as a surveyor? :lol3 That takes me back to when I pulled chain and gave shots over turn points the old fashioned way before infrared gadgets took over the measuring. Yeah, I'm getting that old...:cry
    #56
  17. Stagehand

    Stagehand Imperfectionist

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    Read the whole thing.

    ANybody know anything about hte flatslides with rollers as opposed to those with out?
    #57
  18. Kai Ju

    Kai Ju Long timer

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    The rollers are there to negate the friction created when the throttle is being closed and the slide is sucked against the body. It also allows the use of softer throttle return springs, just for that reason.
    #58
  19. hardwaregrrl

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    Wow! Great tuning manual! Thanks for that!!! Hoping to have my new needle jets tomorrow.
    #59
  20. Stagehand

    Stagehand Imperfectionist

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    ok, I get it... I have heard the roller units were more expensive than the non's.. I also havent heard how to tell them apart, or which model numbers differentiated them. Any help there?
    #60