Wide-band Lambda AFR reverse SuperTrapp tuning and FAQ confirmation

[kz550]

This one, the one I just put a Supertrapp aluminum racing series 2" ID x 13" L x 4" OD on.



Had quite the weekend with this bike's carburetors in below freezing outdoor temperatures in a garage with doors cracked to allow ventilation for gasoline fumes. This bike came to me as a third owner bike that looked wonderful on the outside but was basically a butchered mess on the inside. I doubt the second owner did any of that, he didn't seem like the mechanical DIY type. The original owner had dumped some money into it, from obvious inspection, that the bike was a trackbike with lights. One of the major issues I'd been having with it was the carburetors or perhaps exhaust flow. With all of those component settings and options exhausted, the last ditch item must have been the old exhaust muffler. Thus the Supertrapp, which I thought would be my last possible option in restoring the bike's power from idle to about 3/4 throttle. When that didn't do the trick, I knew it had to be an issue with how the carburetors were modified and I was right, finally!

Fortunately for me I had a spare set of decade old unused carburetors that fit my bike. I had purchased a rebuild kit from Parts Unlimited that was an OEM match, so I simply needed to drop in the stock parts from the modified carbs that were on the bike and use those settings as a starting point. In the process I finally saw what had been done to the working set that came with the bike. They'd been modified with a race kit from Factory Pro for the 49-state version of my bike, not my version, which is made for California. The CRB-K88-1.7-RK, 'race kit' wasn't a fit for the bike, even though there's a case study by a shop in Oregon on FP's Web site of doing exactly this modification to exactly this bike model using the 49-state race kit.

They start by saying Peak HP was 131.6 on the dynojet dynomometer and end up saying YEEE HAAA! What do you know.... 144.7 HP! 13.1 HP gained on top and significant gains throughout the RPM range above 5K RPM. I think this was what the original owner tried to emulate. He modified the carburetors exactly as that shop did, less the pilot jet increase. He replaced the stock exhaust with a full Muzzy exhaust, pulled out the main air jet and put in the RK air jet from FP, all basically the same as the shop did, but wow, did it fall short of expectations!!! The bike falls on its face off the line, like I said all the way up until about 3/4 throttle and 7,500 RPMs, when it finally comes alive. I bagged that set of carbs and returned them to the settings I found them at. I'd experimented with all of the possible combinations of components and while I'd see some hope in making one area better, another would go to crap. ENOUGH! As a race set of carburetors, they'd probably be okay. But I don't ride track, so it is of little use to me.

The other tidbits I'll add about the Factory Pro case study was that their 2000 ZX-9R was shop tuned in Hillsboro, OR, which has a base elevation of basically sea-level, 194' AMSL. The motorcycle's owner, Jim Gilbert of Ashland, Oregon, lived at a base elevation of 2,000' AMSL. It's a carbureted bike! You don't jet a carbureted bike rich for sea-level and send the owner up into the mountains with it! JHC! You have to detune it approximately one step for every 2,000' in elevation. Kawasaki recommends a reduction of 4% for 2,000' AMSL and 8% for 4,000.'

The shop tuner noted “customer complained about terrible "lean surge" at cruising and low speeds when he brought it in.” Which, as any ZX-9R owner who knows anything about their bike or has asked other owners online about it will tell you, is a simple combination $1.00 fix with a throttle body synchronization and pilot fuel screw reset. You add a 0.5 mm shim (washer) under the stock jet needle to effectively raise it, synchronized the carburetor throttle bodies, and set all of the pilot air screws to OEM turns out. PROBLEM SOLVED!

The stock settings on a 2000 ZX-9R are: Pilot Fuel Screw 1 5/8 turns out, #38 x 4 pilot jet, 4 mm +/- 2 mm float heights, N9BB jet needles on a standard 0.6 mm OEM wear washer, and a #160 out/#165 inside - Keihin main round jet stagger. The owner had already modified the main jet stagger however prior to dropping it off at the shop, putting in #165 out/#170 inside, an increase of 3% equally on all jet sizes.

The shop apparently missed that fact, one of many. They bumped his #165/#170 main stagger, calling it “stock,” with Factory Pro reverse staggered #178/#175 mains, a bump in fuel delivery of 8% on the outside cylinders and 3% on the inside over the previous jetting and 11% on the outside and 6% on the inside, over stock. They don't explain why they did it this way, but may have concluded incorrectly that Jim's ZX-9R was a 2002, which does use reverse stagger main jets, with staggered jet needles, as well. Factory Pro doesn’t mention reversing the stagger either as the way to install their RK race kit. But they didn’t point out the oddity either on their Web site. On top of all the other richer settings, the shop also bumped Jim's ZX-9R pilot jets 5% richer, from #38 to #40. Lastly, they installed an Akrapovic full exhaust system.

Neither the shop nor Factory Pro caught any of the problematic tuning errors: not the glaring elevation error, raising fuel delivery on a bike whose base elevation is 2,000' above where it is being tuned nor the compounding of larger than stock main jets nor the reverse stagger errors. But that's all beside the point. The shop showed a 10% gain in HP from their near sea-level elevation dyno. Which is either a false flubbing of some corrected dyno result numbers or a brilliant discovery. Jim was sent home with his tuned-for-sea-level carburetted sportbike with the oddest jetting configuration I've ever heard of, outside of some DIY horror stories. http://www.factorypro.com/prod_pages/prodk88.html

I would love to speak to Jim Gilbert to see if he loved the bike and still owns it. However, there is no record or follow-up to the story that I can find. Which is kind of odd in this day of Internet and social media chit-chat. Yeah the shop work was from 2000, but this is the pinnacle case study used as the benchmark of all benchmarks! Other than a final dyno run, we have nothing further to confirm the veracity of this monster tune that somehow turned compounded errors into massive results.

Moving back to my project though. I installed the used spare set with the same best-of settings as were on the FP set of carbs and the results were immediate. Better throttle response and power. Easier to get the bike off the line. Not perfect obviously. And this is where the UEGO comes into play again. There's no guesswork in what needs improving. I cannot diffuser my way out of this with my Supertrapp alone. The UEGO showed me where my initial jetting is deficient, so I know what I need to try next. I might even need to adjust in or out some of the Supertrapp diffusers too.

[kz550]

Super satisfied at the moment. Started the day with some blockage in the spare set of once dirty carburetors I recently installed. One or two of the pilot circuits, maybe all of them, according to the UEGO, were clogged. Was getting 17s at idle this morning and the bike not running too well under 2K RPM.

After taking the bike out to visit with friends, I brought her back home for a cleaning of the pilot circuit. Ran the bike to almost a stall pulling into the garage. Wanted to drain the fuel out of the float bowls, since the carbs were coming off. 1-3 bowls were empty. #4 had fuel. Bingo! Could have been dirt in the pilot air jet at the mouth. Took several shots of carb cleaner before it was blasting out the pilot jet cavity like the others.

Slapped everything back together for a synchronization and idle speed test to verify the cleaning worked. The throttle bodies were enough of a mess that synchronizing them cured the rest of the idle weirdness. Overall jetting still is not perfect, but this isn't even the same bike anymore, way way way better and that slappy Muzzy exhaust note is GONE! My Supertrapp is just roaring! Sounds wonderful! A lot more power throughout. Easier to ride, absolutely no hint of stalling. Decent mid-range and this bike's got some grunt up top too, like I've never seen from it. She's pulling the front wheel off the ground by 8K RPM. And I can see by the UEGO she's not right yet while doing so, low 11s on the gauge, about 1.0 - 1.5 AFR too rich on the main jets.

There's lots of room for improvement, so... it was a good day! Not like before though with the Factory Pro jetting and Muzzy muffler, where the bike felt like it was a lost cause. Now I'm trying to determine if the improvements that remain might be restricted by the Muzzy 4-1 headers or if I perhaps mistook the cams for being stock when I looked last. But who cares, right? I'm just beside myself. Today felt like a giant leap forward. Kind of reminded me of some of the early days with my other Supertrapp ZX-9R, when I was questioning how long I'd keep it, because I didn't think I had the skills to make the bike better. Then after keeping at it, she just snapped out of it and became a dream to ride.

So it goes to show. Don't doubt the unknown. Keep driving forward. I was second guessing myself as I was digging into the bike today, due to all of the failed effort put in when it had the previous set of modified Factory Pro carburetors. This was the shot in my arm of confidence I needed. So telling myself to be thorough and accept putting in additional effort today when I could see the carburetors weren't right; like #4 paid off. 1 - 3 got a cleaning too, because I was already invested with the carbs off the bike anyway. Couldn't hurt to put in the extra 15 minutes to do all four, instead of the one that absolutely needed it.

Flying high tonight!

[kz550]

The primary goal has always been to get this bike to perform and secondarily make it more civilized than it is at the moment. I can report that I'm getting closer to one of the two goals, which means the second won't be far behind.

Right now, I have about 16 diffusers stacked on a 2" ID aluminum racing series. Unfortunately, Supertrapp doesn't mention this, but the small inlet series mufflers are also shorter than the bigger ones. At least, that's the way it is between the 2" and my other 2.5" ID mufflers. So, being that the muffler is smaller and has less internal volume, it's also significantly louder. But I accept that for the performance and observance of motorists on the road that I'm getting in return.

After the last major leap forward with the spare set of carburetors I owned, I adjusted once more to settings only slightly leaner. And with the help from my wide-band UEGO, I was shocked to see how sensitive the bike was. I was not prepared for what I was seeing. The bike was showing undesirable AFRs and letting me know that the main jets were still too big. So, I quickly returned back home and split the difference of the two changes I'd made, putting the washer shims back in under the jet needles, but leaving the pilot fuel screws at 1 3/8 turns. In this setup there is a lean flat spot around 2.5K RPMs and at WOT the mixtures are probably 4% too rich, but power and performance are closing in on my preferences.

At the moment, the bike feels like a 700 below 5 - 6K RPM. Not bad, but not like my other two Supertrapp ZX-9R Ninjas. Above 6K, the bike goes a little mental and feels more like a 900 or 925cc Ninja 9R. I rode it several times this weekend in a mix of street and highway conditions and I can definitely live with these settings. The bike is a little loud still, but when I have more time, I can address the main jet richness issue and revive shifting fuel around to the other carburetor circuits to really dial her in.

What confounds me though is how many people are so convinced that jet kits are better than just rejetting using factory replacement jet sizes. And in the case of the original owner and the case study of a Factory Pro "race kit," touting monstrous power gains throughout the RPM range, I am at a loss for what got lost in translation. I wasn't there to see how this bikes' projects were undertaken, obviously, but what a freaking disaster and waste of money and effort. There's really only a few possibilities to consider.

1) the bike may also have aftermarket cams? That could be true. But the cams appear to be stock, even though the engine does feel peaky.
2) whomever performed the race kit installation drilled or modified the original 50-state California EVAP carburetors incorrectly?
3) neither 1 or 2, the Factory Pro Race Kit, which is designed for the 49-state ZX-9R, does not work right with the 50-state model carburetors, as claimed in the case study?
4) none of the above, the race kit doesn't live up to its claims, which seems impossible given the number of people who have claimed otherwise.

I sure would have loved to take ownership of this bike where it did have monstrous power due to the race kit, just so I could have experienced what others are so brand loyal about with aftermarket jet kits. But on the flip side, any one of us could be deceitful or unable to recognize improvements from a step backwards. When you have a UEGO there is no compelling reason to do so, simply because whatever goal you're after, it'll guide you to it. You won't have to lie nor settle.

When it's time again, the next step will be to lower then main jet one or two steps, bump the JN into the 0.8 - 1.0 mm range and take off four to six Supertrapp diffusers.