Sf polini cp21 question
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05 Px150, 74 primavera 125, Honda super cub
Joined: 08 Nov 2017
Posts: 138
Location: Ma
Thu Feb 18, 2021 1:53 pm quote
Considering getting a polini cp21 clamp on carb for stock 74 primavera 125 smallframe hopefully eliminating air leaks once and for all.
Does the cp21 clamp right on stock manifold?
What jetting should I use for a stock bike? I have no idea about polini carbs. Any help would be appreciated.
63 GL, 76 Super (x 2), 74 Primavera (x 2), 06 Fly 150
Joined: 26 Sep 2013
Posts: 5653
Location: So Cal
Thu Feb 18, 2021 3:46 pm quote
CPís are terrific carbs - small, lightweight, really nicely made. I have a CP24 on my smallie. I recommend em.

sdjohn has a clamp on CP21 and likes it a lot. Iím sure heíll be around shortly to tell you about it.

I have an extra CP21 if youíre interested. Itís not clamp on, but you can get the clamp separately.

They arenít hard to jet. Polini uses their own idle jets and PWK mains. If you do some googling you can find a chart published by Polini with suggested jetting for some common set ups.
2015 GTS300, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 4589
Location: San Diego, CA
Fri Feb 19, 2021 8:32 am quote
They are good carbs, I like them.

was 130 DR loss of power - now CP21 jetting

There is my topic on how I jetted in my DR130. Jack helped out, per usual.

Jetting - main jets not too far from stock if you don't use the air brake thing. If you do, the main jet will end up quite a bit larger than otherwise. I would not worry about getting the alternate slides or needle, use what comes in there. I'd get a box of main jets that runs from like 75-100 if you are stock, you should be fine with that. For pilot jets they are Polini CP specific, and I think it's 30's to 40ish, can't remember and I think that's probably enough info to find it.

I get all my carb parts for it (floats and anything like slides, etc) from Treatland.tv. They are a moped shop in san fran. The jet kits - I think I got them from SIP (at least the pilot one). The mains are common to any PWK, so go find them wherever you like, you will be fine.
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