What is the difference between all of these carbs?

[johnny248]

I was browsing along at scooter parts. This is what I do now on my off time since I am all of the sudden obsessed with Dio scooters. All I do is think about what I'm doing/going to do to my Elite that I am building lol and will football news being super slow now, this is all I look at hahah

Anyway, what is the difference between all of these different carbs? People say the OKO's are junk. Ok? Pwk looks like the same thing to me, but these are good? Then I see Dellorto around. Was just on the Stage6 site and they have S6 R/t, Dellorto, PWM, and TM24 types. BTW the black S6 carbs look bad *. The Naruku carbs SL look pretty good. I bought this Polini 24mm by recommendation.

But all of these carbs "look" very similar. What makes one different than the others? And what is good or bad about all of these different guys?

Also, what is the deal with a "flat side" carb, and what makes them special? These Naraku Flat Side v2 carbs say something about a power jet for extra power! That always sounds like a good thing

[Wheelman-111]

Greetings:

Carbs use air velocity generated by the action of the piston to suck gasoline into the stream and funnel it into the engine. I've always had fair luck with the OKO carbs I've bought, but would agree that they're not the most precisely-made mixers out there. Round-slide, Flat-slide are different flavors of throttle shape, and of course everyone who sells one will claim theirs is the best. The PowerJet in theory lets the engine run with leaner jetting, then opens up a third channel for fuel only at WOT. Works great in Theory, not so much in practice, because when you close reduce the throttle that hot engine spinning down suddenly has less cooling vapor and spikes a sudden temperature. You end up jetting richer to compensate, only to find that now you're way TOO rich at WOT.

Keihin PWK was the prototype for OKO, and for the Polini version I now own. The quality of the metal and the fit of the various parts seems better, and Signori Polini has apparently furthered the "science" because they seem to run smaller jets than a comparable OKO. I'm not as sure as some people how much better it is, but I'm satisfied despite paying about twice as much as an OKO can fetch.

Just be careful about getting a bigger carb than your engine really needs. The gains on top are little or nothing, but it's a whole lot harder to tune the idle and low-end.

[johnny248]

Wow, thanks for all the info. While reading about Malossi, it says they started off tuning Dell'orto carbs and have long had a relationship with them. Also, according to the Polini site, their carbs are designed and built in Italy by Bergamo.

I have their 24mm carb to go with the Corsa kit. I have a couple of jet kits on the way. What would help is if I could get a base idea of where to start with it to get it running. Can you recommend what size main and slow jet to start with (again, I know it will have to be tuned, but I'm just looking for a starting point) and also where to start the needle height. It looks like it came from the factory with the needle clip in the middle, and I'd have to look to see what jets were installed.

[johnny248]

OK cool. I'll start there. Should I change the needle clip position?

[DirtyE]

Ive yet to use my polini carb, but I always bought dellorto black 21mm phbg carbs before. Its a truly great carb. Ive used them on all sorts of setups.
if ur using a ct manifold, dont go bigger than 26. Its kinda pointless with the inner diameter of the manifold at 26mm. For that reason I chose the 26mm polini. A 21mm dellorto black wouldve been fine though, but its fitment is smaller.