[Cycle]

When I got the bike new, it had the OEM NGK DPR6EA-9 spark plug. By 797.4 miles, the bike had developed a rough idle... it originally happened only when cold, but eventually would "hiccup" at idle even when at operating temperature.

So, I bought an NGK DPR7Eix-9 Iridium to try out... it didn't help the lumpy idle at all, the fuel efficiency actually went down, and the bike didn't have the grunt like it usually had. Apparently single-iridium plugs don't work well with waste-spark ignition systems, for some reason. I've read something about it on the web, but can't recall the details, has something to do with the polarity of the spark.

I tried a platinum core plug... no joy. I tried a copper core plug... no joy. I tore the bike apart trying to figure out what was causing it... the ignition coil checked good, the spark plug wire checked good. Valve lash was spot-on. Compression was higher than usual, but the top of the piston was pristine, so it wasn't due to carbon buildup. Spark plug gap was set right. The plug showed no indications of rich or lean air:fuel mixture. So, I resigned myself to the fact that the idle sounded like it had radical cams in it.

It got really bad at 8512.5 miles, so I tore the bike down... come to find out, Costco had given me a bad batch of gas, it had tiny particles in it, smaller than the 12 micron fuel filter, which had partially plugged my fuel injector. I cleaned the tank, put new fuel line, a new fuel filter and a new injector (I disassembled and cleaned the old one and stored it as a backup). While I was at it, I had a suspicion that the lumpy idle was caused by a lazy O2 sensor, so I replaced that, as well.

The idle returned to its usual lumpy state, that is to say, it was no longer as bad as it'd been due to the Costco gas, but it wasn't smooth. The old O2 sensor checked out fine, so I cleaned and stored it. I'm still searching for a 5 micron fuel filter that can fit this scooter and withstand the fuel pressure. I don't want to use a plastic-body filter. The one I'm using now is a Wix 33031 / Napa 3031 filter, metal canister body and paper filter, rated to 60 psi and 12 micron.

On 31 Jan 2015 (at 9407.3 miles), the bike was taken out of service for several changes:

1) dremel-tooled the clutch to make the clutch arms fully retract

2) 1000 RPM clutch springs

3) removed ~0.5 mm off the clutch and variator inner faces to get a slightly wider gear ratio.

4) clutch got a hybrid ceramic bearing and a needle bearing that fits an Aprilia motorcycle... the old needle bearing was rated to 11,000 RPM, but the clutch can go to 13,000 RPM... so it's little wonder that needle bearing was torn up. The new needle bearing is rated to 20,000 RPM with a much higher load capacity.

5) balanced the variator and clutch to within 1/10th of a gram.

6) new Gates Boost+ kevlar belt

7) 20 gram Dr. Pulley sliders... the 16.5 gram OEM rollers and 18 gram sliders I'd used previously proved to be too light. Even these 20 gram sliders are a touch too light. When they wear out, I'll go to 21 grams. This engine's got more grunt than usual because I did a hard break-in of it (changing the oil frequently as it broke in), and used LiquiMoly Ceratec for 1800 miles (3 oil changes) after the engine was broken-in (at ~1000 miles into the Ceratec treatment, I noticed the engine would hit the rev limiter far too easily, which is why I geared up). It's got phenomenal ring seal and thus great compression.

8) micro-polished and tungsten disulfide (WS2) coated hybrid ceramic bearings in the wheels and rear gears

9) new rear gears (spur gears, 15% taller than OEM), micro-polished and WS2 coated

10) new tires (Avon Viper Stryke).

It took much longer than anticipated, because I had to wait for the Aprilia needle bearing to be delivered all the way from Italy. I couldn't find any US sellers. Odd that no one seems to want to sell higher-quality needle bearings in such a common size... the old OEM one (a cheapie Chinese off-brand) had a plastic needle cage. That's what got chewed up.

On 25 May 2015, I put the Pulstar plug in. Results as described above.

On 01 Jun 2015, I changed the engine oil and included 8.5 grams of 0.6 micron tungsten disulfide in the Royal Purple 10W-40 Synthetic with Synerlec. The engine is quieter now, and I just hit my all-time highest MPG on 13 Jun 2015, although I don't attribute this to any one thing... it's a combination of taller rear gears, lower-friction bearings, better combustion due to the Pulstar plug, and friction reduction in the engine.

I'm waiting for the new rear gears to be fully worn-in before I add tungsten disulfide to the gear oil.