The team started thinking about a new carburetor for the HAWK last year when the PZ30B was operated at altitude and demonstrated some richness in the tune. No doubt the PZ30B is a great carburetor but has some disadvantages. The backroad performance goals on this team do not include top speed or acceleration. The goals are overall performance on the road, adjustability, consistency, and reliability. Traits that make up a good back road carburetor for the team while considering altitude a factor follow:
1) Performance on the backroad
2) Ease of adjustment with engine running (maintaining performance)
3) Ease of removal for jet changes (maintaining performance)
4) Simplicity
5) Quality of parts (read more expensive)
6) Fitment with existing air filtration
The logical choice is the PE28 and the team prefers the OKO PE28 (genuine Taiwanese manufacture). Whether this carburetor can be consistent and reliable on the backroad for this team remains to be proved.
Tuning story:
The PE 28 was put on last October but another bike project and the weather has hampered getting the tune on. I mean there was barely a few hours of riding window each month to test since October.
The PE28 came with a 38 pilot and 115 main. Upon disassembly the surprise…….installed was a non-adjustable Jet Needle stamped with J6ZG. Research indicates the NIBBI PE 30 and now the PE 28FL come with a Jet needle designated J6ZG. Interesting, considering one is made in Taiwan and the other I believe in China. Whether the needles are actually the same size and taper is not known. I have worked on a smaller genuine OKO PE carburetor that has an adjustable needle and I know the OKO PWK 30 has an adjustable needle. Why would OKO use a nonadjustable jet needle? Not because of cost because the OKO PE28 goes for $80 to $90 same as a NIBBI. They must think it works well in this application, but given the issues I have seen tuning the PE style it does unsettle the nerve.
The team is working toward standardizing jets based on one manufacture so better comparisons can be made between carburetors. We have purchased many jet kits from amazon, ebay, aliexpress, jets that have a number on them but do they really compare to each other? We started purchasing Jets R US OEM Keihin style jets instead of genuine Keihin jets because they are a little cheaper to use for tuning standardization.
This bike is stock except for CAT removal. A 128 main jet was installed, richer than what we believed this bike would eventually use. The 38 pilot was adjusted for best idle at 1 turn out. The 128 had a sharp miss at 3/4 throttle. We assumed it was rich and put in a 125 with the same result, and then a 122, and a 120, and finally a 115, all with the same miss. Ever have a carburetor do what you did not expect? Naaaaaah!! We put in a 130 and the miss was a little better and power better. A 132 got a little better but that was the biggest jet we had on hand. The 135 main arrived last week and in short order we had full pulls in five gears no miss. The carb idles excellent, no hesitations now, and makes good power on top once we got a chance to see it. Ironically, the main jet at 135 is the same size albeit generic jet we installed in the PE30 we tuned. It needs some further testing to confirm but I think we just might be able to get over missing the PZ30B!
