Is the stock carb choke supposed to have 2 levels? I always use mine all the way out until warmed up, but there seems to be a mid-way out point on the choke that makes faster idle. Also, lately the choke has been popping in by itself when riding, is this just normal wear? (Caused bike to stall today at a stoplight). Once warmed up she runs fine without choke, but I am usually too impatient to fully warm up before riding.

Also, I got a Sportster muffler which I haven't installed yet. (won ebay bid for $5!)- Rather than mess with the stock carb and jets, I was thinking of getting a pwk38, and keeping the stock carb and muffler in case i want to go back without messing with anything. Anyone tried a Nibbi PWK38? This is the one I am looking at: https://www.amazon.com/Carburetor-350cc-450cc-Motorcycle-KAWASAKI-SUZUKIApoll...
Think this carb will work?

Dave wrote on 06/26/25 at 03:53:39:


Thanks Dave.
What is the purpose of the 2 choke levels? Either one seems to work for starting the bike. Am I supposed to be using one or the other, or switching between at some point? Also I forgot to mention, the previous owner apparently rebuilt the stock carb, and all the external screw heads look pretty boogered up - hence another reason I was looking at that carb.

The advantage of the CV carb is the ability for the carb to keep the engine vacuum stable.  If(when) you crack open the throttle too quickly and the vacuum begins to drop - the vacuum operated slide keeps that in check and opens as the vacuum builds.  The CV carb is likely the best choice for the motorcycle masses of all skill levels.

Carbs that have the slide operated by a cable can react a little bit faster - but they also have the potential to fall on their face if you open the throttle too quickly (the vacuum can drop below what is required to pull the fuel out of the float bowl and into the jets and/or carb throat).  I am sure some of you are familiar with the 'cough" that can happen when the vacuum drops too low while you crack the throttle open from low rpm.  In minor cases it is just a bit of a lag in acceleration as the vacuum drops and the mixture goes lean....then the engine begins to pull strongly again as the vacuum recovers.  The engine is always happiest if you roll the throttle on - rather than just crack it open instantly.

The 2 choke levels are likely far more useful for folks who live and ride in very cold weather (as is the compression release to help get the engine spinning in freezing weather).  Once the bike is started it may be necessary to ride with the choke pulled half way out to get a decent idle until the engine gets fully warmed up.....in really cold weather the engine may never get warm enough to ride with the choke fully off.  We had one forum member who lived in the Pacific Northwest and rode is motorcycle all year long - the ferry he had to ride on to get to work allowed instant access to motorcycles....while the cars often had long a long wait time (his ride was often in the single digit temperatures!).

The stock carb when properly cleaned and jetted runs very well on a stock engine.  There are not any massive power or mpg improvements to be had from switching to an aftermarket carb.

uranusklingon wrote on Today at 14:20:54:


Nope.  The only thing that vacuum line did was tell the vacuum operated petcock that it is OK to flow fuel to the carb.

In the 70's I had a 2 stroke Suzuki TM125 motocross bike - my friends had Honda SL100's.  When we traded bikes I was not used to riding a 4 stroke, and the Honda's did not have CV carbs.  If I opened the throttle quickly like I did on my Suzuki - the Honda's would "cough" and instantly stop accelerating.....the guys who owned them did not have this problem as they had learned to roll the throttle on and allow the engine to build revs as they opened the throttle.  Honda started using CV carbs to resolve that issue.