Is My Carb Too Big?

Does your Spree/Elite already run great, and you're trying to make it quicker/faster? Need a monster motor swap? Discuss your ideas here.

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Polarisxlt96
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Is My Carb Too Big?

Post by Polarisxlt96 »

setup is a 2001 Elite 50 with a polini corsa 72, piarel exhaust,zx trans, stage 6 intake, yellow contra spring, polini variator, 5 gram weights, kind of having issues getting this thing tuned properly have a weird midrange problem at light throttle cruising at about 35-40 and maintaining speed starts to make a weird noise kind of like its running lean but the plug reads good and cylinder head temp isnt hot. im currently running a polini 28mm with a 116 main, 45 pilot and needle one clip lean the throttle response isnt the greatest thinking that maybe i should be looking into a smaller carb?
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Meatball
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Re: Is My Carb Too Big?

Post by Meatball »

28mm is too big for 72cc.....Ive seen people use 19mm, 21mm and 24mm with their Corsa all with great success....Ive also seen somebody run a 19mm Mikuni on his 90cc ATV and it ran like a dream. I suggest getting a smaller carb in the 21mm area, give or take. Some sites suggest using AT LEAST a 17.5mm carb with the Corsa but I wouldnt go that small, especially with your other mods.
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eclark5483
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Re: Is My Carb Too Big?

Post by eclark5483 »

When it comes to carbs, bigger is not always better, you lose vacuum the larger you go, you'll want to find a sweet spot for your specific engine. I'd go with a 19 or maybe a 21mm for a 72cc setup. But no bigger then that. Not sure, but guessing for what you have, a 19mm would probably serve due diligence.
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Rip_City_Spree
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Re: Is My Carb Too Big?

Post by Rip_City_Spree »

I am currently running a 26 on my corsa set up and I think its to big. I have run a 24 on mine with great success and will be going back to that set up very soon. even with a great port job from oneman I know guys that are only running 26 on theirs. I am struggling with jetting mine currently running a 118 mj with a 38 pilot clip all the way down. if I go any leaner it runs like crap and currently am running as rich as I can as I can find any bigger mjs that arent in the 130s. I have literally tried every combo and cant find the a happy medium. with a 24 I can have it dialed in no time. its funny how differently the exact setup with a different carb can act so drastically different. its very strange because my temps are super low like in running rich but if I go any leaner it runs like crap. tried new plugs and every jet combo I can think of to no avail. so solution is going back to a 24. I think personally the 24 is perfect for the unported corsa. I have had my bike 72mph @10k rpms with a 24mm.
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Hppowdercoatings
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Re: Is My Carb Too Big?

Post by Hppowdercoatings »

24mm...
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Gearhart
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Re: Is My Carb Too Big?

Post by Gearhart »

24mm runs great on that setup. The 21 & 23mm polini cp's are also great carbs for a 72
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Wheelman-111
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Re: Is My Carb Too Big?

Post by Wheelman-111 »

Greetings:

Ten years or more ago, our Hawai'ian brothers did a lot of the pioneer work tuning these things. There began the affection for the affordable OKO clone of the Keihin PWK 28mm prototype carb. Other sizes, as I recall, were hard to obtain, but vendors quickly caught on to that fact and filled the need.

I too ran a Corsa 24mm carb with primitive tuning "skills" and never broke 70MPH. (Flash 3.1) Possibly it was a coincidence with better transmission tuning, but I finally went over 71MPH shortly after installing a 26mm OKO. I do recall it was rougher in the low-end and midrange, but there's no denying it went a bit better on top. Whether or not the bigger carb was the reason is in question.
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Re: Is My Carb Too Big?

Post by burnt_toast »

I'd have to agree. Running 28 OKO is oldschool. was all the rage back then, but its def overkill nowadays.
I'm guilty of a Corsa/28OKO/PG Long setup myself, and thoroughly loved and enjoyed it but it was PITA to dial in. But it could be done.

My best with the 28 OKO:
Pilot = 55
Main = 142
Needle = 1clip rich from middle
A/F = ~1.5turns out

Polini's are more fuel efficient from what I hear, so prob won't help you much. Unless there's an OKO to Polini converstion table somewhere.. :lol:
Was getting like 30mpg with that setup :surprise: terrible.. loll

In closing, later went to a 24mm OKO then a a 21mm OKO and enjoyed that one the best. Next build, will be trying a Polini CP23
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