any reason why my intake manifold is tapered from large to small hole?

[wolframazer]

so I bought this carburetor for my ybr 125 and the carburetor is pz27 so it means it is a 27mm, and the manifold I already bought is for ybr euro i ii so it was really made for my bike, https://imgur.com/2G8zi0B and this is the manifold I bought https://www.aliexpress.com/item/3301...27a64c4dT1ur0a tapered from 27mm to 22.5mm so it means the carburetor I bought is the correct size for this manifold and for my engine?

[franque]

My guess (if you're saying that the manifold internally tapers down) would be that it is either intended to be restrictive, or perhaps to increase port velocity/turbulence/swirl so that the engine has more torque down low. I'd buy another one, bore it out, and see if it runs better/worse.

Also the PZ carbs run smaller than indicated size, for example the PZ30 is effectively a 26mm carb due to the shape/effective size of the venturi. I would imagine the PZ27, being smaller than the PZ30, probably has an effective area of around 22-24mm, so it might not be as radical of a step as you think. As long as the transitions are smooth, between the carb to manifold, and manifold to head, I would keep it as is.

[wolframazer]

so it means that pz26 and pz27 has a very slightly difference? I look at my engine fuel inlet port and it's the same size to my manifold 22.5mm, I already tried riding my motorcycle, the low end is a little bit weak compared to my previous carburetor teikei mv28, I was thinking of trying a 2 types of carburetors, the pz26 and the pz22 I don't know if I can mount the pz22 because it's shorter than pz26 and pz27 and I really don't know if pz22 will work out because I heard that it is designed for gy6 engine or horizontal engines, I want to achieve a very efficient setup for my motorcycle sir

[humanbeing]

That Jianshe thingy is a solution for the PZ27(6) possible to work w/ the stock YBR (VM22) config...
Japanese https://blog.goo.ne.jp/lightning-ybr...02d1aa0dab0f23 had some tips already...

[wolframazer]

thank you that was a very good information, I think the only thing I can do is to sell this pz27 and replace it with vm22 and pz26

[franque]

Why not get another Teikei?

[wolframazer]

so expensive, I can buy a 4 sheng wey carburetors for that price in my local skygo lifan stores

[wolframazer]

Originally Posted by franque

Why not get another Teikei?

anyway I think I am happy with my carburetor for now, I fix the vacuum leak with using a ball bearing and a fuel hose, I hope it doesn't melt tnx sir for a helping me out