Ask The Editors: PZ27 Carb Tuning
A tale of many PZs.
Based on the photo you provided, this doesn’t appear to be the stock carburetor that came on your Honda TRX (that would have been a Keihin OEM Part Number 16100-HB3-771). It gets difficult to be sure as the OEM Keihin is also designated a PZ27. Chinese companies began to issue PZ27s that do use Keihin spec but are much simpler/ contain fewer external adjustments. Telling them apart is usually a matter of the serial number stamped into the plate below the “P27” on the actual Keihins. We will provide you with a tuning guide below in the event that we’re wrong about this being a Chinese replica carb.
The aftermarket PZ27 is a pretty simple unit and shouldn’t be too difficult to get back into spec. However, if your machine is indeed running rich (from the sound of it), there is no mixture regulation screw to mess with here. The only screw you will find on an aftermarket PZ27 is the idle adjustment. The actual fuel mixture is being regulated by the slide and main jet (located within the float bowl).
You can lean out the mixture a bit by lowering the needle valve and seeing if that improves the situation.
Most often the trouble with Chinese carburetors is that the main jet and air jet are much smaller than the OEM spec for machines like yours. What this means is fine tuning your air/fuel mixture is going to be a matter of experimentation with these jets until you land on the right combination. If you happen to have access to the stock carburetor still, we have seen jetting transplants work okay with Chinese carbs (that is remove the correct jets from the Keihin and insert them into the Chinese PZ27).
A simpler method would be to simply buy a jet kit like this 40 piece off eBay for $16.20 and jet the machine up or down until you land on the configuration that gets you running smooth.
Here is a guide to fine tuning the actual Keihin PZ series carburetor that you may find useful regardless of whether yours is OEM or aftermarket.
