Is my carb too small?

[korayyzb]

Hi I have bws 100 fitted with 55mm big bore cylinder(113cc & 1.5mm rised bore) and tecnigas rs2 pipe. Engine runs with stock carb(same as project 90 stock carb). Thr carb jetted to 97. 5 main. 1/4 and 1/2 throtle is Fine but more is same feeling (feels likr not any more power) as 1/2 and wot is tiny ritch. What causes this symptoms? Does my carb is too small for this setup?

Thanks for advices!
(and sorry for my bad english)

['O'Verse]

90cc and up I'd go with a 21mm. Yes you could run a bigger carb but I wouldn't run anything smaller than a 19mm. Bigger cylinder, pipe, intake, needs to breathe. At 21mm your right at your limit on fuel consumption. If your gonna get a carb. Make sure its name brand. Dellorto, Polini, etc. 90cc-100cc+ Air cooled are torquey engines. I haven't really had one that showed much of an improvement power wise over 3/4 throttle. Just streamlining and the belt slowly climbing up the variator. 

[repherence2]

If it is rich at 1/2 to full throttle, as you say you think it is, then it's a matter of going down on the main jet size...that is if it is actually rich.

Does it bog or does it sputter from 1/2
to full throttle?

My 90cc block came with a "stock" rubberized forward facing intake manifold. Looks like it was intended for a stock/small carb. I never did use that manifold. I tried my "stock" aluminum rear facing manifold along with a Polini CP 24 carb with Uni pod filter. I don't recall the main jet size that was installed. The 24 ran pretty decent.

To experiment, I installed a CT intake manifold along with an OKO clone 26mm with power jet. Took a while for me to understand how to tune a carb with a power jet, but I did get it tuned. My last carb was a 28mm OKO with a 125 jet (oil injected no premix). The engine has the 41mm stroke crank and I'm running a 54mm bore, I think that puts me in the 94cc realm. I have come to like the performance of the 28 OKO. It guzzles fuel, the low end is not as good as the Polini CP 24, but I like the top end of the 28mm carb. I noticed more power at full throttle with the big OKO as opposed to the Polini CP. I like to go ripping at wide open throttle a lot, so the big OKO suits my needs. It cad dump more than enough fuel to keep the cylinder cool during long full throttle runs. The low end on the OKO was shitty until I installed a venturi diffuser on the carb. You can check out "Rich's Taylor's Porting" to read about the venturi diffuser. I made and installed it myself.

I really boils down to your riding style and how you want the engine to perform. I would highly suggest you get a Cylinder Head Temp gage for carb tuning. Once you get a CHT, stay below 350°F.

[korayyzb]

Thanks for the replys. Deffently I m gonna try 28mm Keihin PWK + venturi diffuser setup