ummm, 80' SG carbs

[apg0106]

Hello again long my lost/didnt know about/glad i found ya, favorite family members! k, so, i've posted a ton of crap about this bike i've been fiddling with, and well, its come A LONG ways. runs, moves under its own power, it even stops now! so, someone, PO decided to make this thing go FAST apparently by just throwing in some 130# mains...thats it...hmmmm. well, when i first got the bike, i went to a local motorcycle parts shop, and got the 4 new rebuild kits. great, right? well, i never looked at the manual until recently, and i found a few problems.
- manual says 110's on 1 and 4, and 120's on 2 and 3. okay, no big deal. well, before reading, i did up the carbs, put 125# all the way across with 42.5 pilots, the kit came with 120's and 125's and 42.5 pilots with a Y80 jet needle? anyways, i didnt know any better. well i got the bike sync'd and running, just had a stumble to about 1/4 throttle, which is why i started reading, and reading, and researching on this site(thanks). figured, need bigger pilots. now i've opened a brand new, my very own, CAN OF CRAP! so now im back to square one, kinda. hope your still reading this.
- stock the carbs have 110's and 120's, with my pods and open pipe, with the math equals 4 jet sizes, so i'd upgrade to 120's and 130's, awsome, i've got both, ordered new 45 pilots due to the more than 3 jet sizes. PROBLEM- the needles that were already there, for the magic go fast kit the guy did, protrude about 1/16 through the main, the new needles that came with the obviously wrong mikuni kit dont go into the jet at all, sits in the bottom of the bowl of the main, and doesn't go into the passageway at all, how is the needle supposed to seat? I apologize for the long post, but, i haven't found my difinitive answer in the search engine here. Thank you for all your patience!

[TopCatGr58]

Hey there APG,

Looks like you might just had not done enough reading, but it can be tough when you search for carbs and find hundreds of threads!

First, from where did you get the carb kits....GeorgeFix on ebay, or carbkitcapital.com in canada??

Secondly, the 80 carbs have been reported to sometimes have a bastardized setup of jets, because this was during the transition from the 78-79 series to the 80-81 series, and Yamaha was using up their old stock before fulling converting to the newer stuff.

SO...the older carbs had a small tunnel between the main jet and pilot jet towers....that fed the pilot jets thru this tunnel and the main jet, and so they used much larger mains...ie. 135, and the PILOT JET TOWER was capped/plugged.

Later, they ran out of those carb bodies, and so no more tunnels, and so the mains went to 110-120 and the pilot tower was uncapped so it could feed directly from the bowl. Using the mixed richer jets in the inner 2 cylinders was tried early, but found not really necessary, and so running same size across all four is fine. Some of the early carbs also used different Main Jet NOZZLES/emulsion tubes with different # of holes, more in outer and less in inner...again in attempt to richen up center for better cooling.

With running a STRAIGHT EXHAUST PIPE...especially if it's short, will cause you a fair amount of tuning problems....little to no backpressure, tough for the low rpm range tuning.

Sounds like you need to put in the old OEM slide needles, can't say much about the Y80 needles?

T.C.

[apg0106]

so i've got some good o'le bastard carbs...sweet! lol, i bought the kit from local parts shop, everybody i called around here had the same thing. i'll have to do some reading, i bought the bike without the exhaust and pods already on. i do have a set of 07' harley nightster mufflers from my buddies bike that he didnt want, dont know how that would turn out, but they were free. well, into the books i go again! thanks again for the reply! should the needle go into the mains at all, or seat to the bottom?