Since I am stuck with the PZ30 Pumper carb a bit longer as I try to find an intake that will work, I figured I would correct and tweak the setup/tune on it and try to get it to behave just a bit better.
First thing I wanted to correct was the pumper jet nozzle orientation. In this picture the blue line represents what the jet spray angle was like out of the box. It functioned well enough as it was and didn't cause any running issues, but it bothered me. I now have it spraying in what is represented by the green line. Aimed right at the center of the carb exit, just next to the needle.
The nozzle itself is a press fit with a knurled end that simply fits into the hole. Using a bit of wood dowel I tapped it out. On the end of the nozzle is a notch that shows the direction of the nozzle. Using line of sight I tried to orient it the best I could with the center of the rear of the carb and then pressed it back in using a small bit of rod. It's a fiddley process to get it aimed and seated without the darn thing turning though.
The other thing I really wanted to correct was the throttle cam for the pumper plunger. I was having an issue with it binding and causing the throttle to have stiff points, the cam binding up against the flange and side of the carb due to slop, and getting stuck because the stop would end up past the protrusion on the carb body.
My solution was a simple one, a thrust washer between the bracket for the throttle cable and the cam itself. It turns nice and free now and functions just like it should.
Last but not least I decided to play around with my jetting. Since OneLeggedRider drilled his pilot jet and had nothing but good things to say about it, I decided to give it a try with the other stock K40A jet I had laying around from my first Hawk. One thing that makes it a lot easier to do without breaking bits is having a "Drill press" stand for my rotary tool. I managed to drill it without breaking a single bit. I also used a .4mm bit to line the rotary tool and jet in the clamp before stepping up to the .45 bit. That made sure everything was centered and lined up ahead of time, and then I just drilled very very slowly lol.
With my now 45 pilot jet in hand I installed it and played with the idle mixture, ending up at 1 7/8 turns out with the best idle. After going for a test ride my Main jet was just a TINY bit rich (small surge on roll off) so I stepped down to a 120 main from a 125. Needle is also now up to the third notch from the 4th to try and lean out the middle throttle range. This works much better with the larger pilot and properly aimed pumper nozzle, and should help a bit with fuel economy as well.
Air temp at the time of this setup was 60 degrees and about 50% humidity.
Synopsis. Much stronger off idle throttle response. While the 40 pilot was working just fine, it must have been having just the slightest of lean spots on throttle roll on. When cranking the throttle open from a stop or low speed she just leaps forward and picks the front end up pretty hard. Mid throttle roll on is perfect, and wide open is clean, but now a teeny tiny bit lean. I am waiting for a 122.5 jet in the mail, but I have a feeling the 120 main will be the right size once it gets hot here.
One thing I can tell though, now that the motor is broken in. The carb is definitely a restriction on the top end. She will wind out to 8000 in a hurry, but you can just tell it is being held back a bit. I can't wait to hopefully get the PWK30 installed so I can really compare the two.
As a side note, I am also considering stepping down to a 33 tooth rear sprocket. With the way the power is delivered now (immense low end and mid range torque) I think it could benefit from having a bit more gear under her for street duty. I already have a 12 tooth front on stand by. I am also doing so because the 4.6x18 Shinko 700 is smaller in diameter than the stock 110/100-18, so I am geared a lot more like a stock bike with a 17/47 setup.
My last little update for the day was installing a chain tensioner to the swing arm. With the rear shock having the back end so extended I am running about 2 inches of free play in the chain. This definitely helps take the lash out of the system. I am curious to see how long the roller lasts because it's not the greatest design and build quality. A loose bearing and a cotter pin. I may work on making something else to take its place since the roller is just mounted to a straight rod.
