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That's the thing, I don't have enough info to "have my mind set". I know the gears will wear in, eventually, and there's not a lot of metal to remove to get there (if there were, I'd not have been able to turn the gears from the clutch end by hand... the only reason the wheel axle side locked up is because it's geared up and took more effort to turn than my hand could provide). Now I can turn the wheel axle side by hand, but I still feel the "cogging".

As an aside, with the OEM bearings and gears, the wheel axle was really hard to turn (due to the gearing, combined with bearing drag and the OEM gears not being micropolished and tungsten sulfide coated). You had to death-grip it and crank hard. Whereas with the hybrid ceramic bearings and new gears, it's pretty easy, except for those three teeth. I'll be putting WS2 in the gear oil to ensure everything's coated with the stuff... it's got a really low coefficient of friction.

But should I just take the gears out and shave them myself or have a metalworking shop do it? If I do so, how much is enough, and how much is too much? I'm apprehensive that I'll have too much metal taken off, and it'll mess it up even more.

Hi, all.

Ok, so I had Jan Vos fabricate new rear gears for me a while back, and I finally got some free time to install them, along with hybrid ceramic bearings.

After I got all the new bearings in, I put in the new rear gears and hand-turned the wheel axle without the gear cover in place, just to be sure everything worked the way it should. It did. Those micro-polished and tungsten-sulfide coated hybrid ceramic bearings are slick.

But, when I put the cover on and tried to hand-turn the rear gears from the wheel axle, they'd turn a bit, and lock up! Thinking I'd messed something up, I pulled the cover, checked the diagram in the service manual, made sure the bearings weren't seizing up, and checked the runout on the gear shafts. It was all good.

So, I tried again... and the same thing happened. Going around to the left-hand side of the bike, I slowly turned the Gear #1 shaft (the shaft that the clutch mounts on)... I could distinctly hear and feel three teeth on the input gear shaft (Gear #1) lightly scraping against the gear teeth on Gear #2.

Confused, I tried again. I pulled the gear cover off, and turned the wheel's axle and the input shaft. All was smooth, turned very easily. Put the cover back on... three gear teeth scraping.

The cover off again, I turned the wheel axle as I squeezed Gear #1 and Gear #2 together with my fingers... ah, that was the problem... three teeth on Gear #1 had been ground just a tiny, tiny bit thicker at their bases than the rest of the teeth when the gear was fabricated. With conventional bearings, you'd likely not even notice since the bearing play would allow the Gear #1 and Gear #2 shafts to move a tiny bit. But the hybrid ceramic bearings don't have much play at all.

So, I buttoned up the rear gears, filled it with 200 ml of Royal Purple 70W-140 Synthetic Gear Oil with SynSlide, and spent the next 8 hours using a ratchet wrench and an electric impact driver, spinning the rear gears in both directions from the input shaft and the wheel axle in an attempt to wear-in those three teeth.

By the end of the 8 hours, I could turn the wheel axle by hand and it wouldn't lock up anymore, but I could still feel a slight "cogging" as those three teeth in Gear #1 engaged with Gear #2. The gear oil had a lot of "glitter" in it when I drained it.

I opened the gear cover again, and I could clearly see the three offending teeth... all the other teeth had minor polishing on the outer ~70% of the teeth face, but those three were polished all the way into the crevice between the teeth. The three teeth sit next to each other, so Jan Vos may have made a mistake when he began cutting the gear, or when he was finishing.

So... should I just ride it and let the teeth wear in? Will it damage the gears to do so? I plan on riding gently until this "cogging" is completely gone.

I think I'll call it the Kymcati FrankenYager. LOL

It's a Honda GY6 derivative, a Kymco SJ40, apparently. It's factory-overbored to 62 mm, with the usual 57.8mm stroke (174.5cc). Fuel injected, liquid cooled. Rev limiter is 9200 RPM, I'll be extending that to 11,000 RPM after I get an offset conrod made, and the rotating assembly professionally balanced. The piston will be WPC treated over its entire surface (to toughen it and reduce stress risers), then ceramic coated on the crown, and WS2 coated on the skirt. The increased piston weight due to the ceramic will be partly offset with a titanium wrist pin (also WPC and WS2 treated).

The main purpose of the build is to get frictional losses as low as possible, and to get mechanical efficiency as high as possible. So an offset connecting rod will help increase mechanical efficiency during the power stroke, the Desmo valve actuation will get rid of having to compress those valve springs, hybrid ceramic MicroBlue bearings will reduce friction, WPC treatment and WS2 coating of rings and cylinder will reduce friction while increasing ring seal, gapless Total Seal top ring will reduce blowby, electrical system mods to reduce electrical waste (ground shunt voltage regulator, chiefly), etc., etc.

I'm even going so far as to put mag-drive electric coolant pumps on it. The microcontroller will vary coolant temperature based upon engine load... hotter at light load for more efficient operation, cooler at heavy load to prevent heat problems. The pumps have the ability to circulate all the coolant in the system every 2 seconds at full speed with both pumps on, so it'll be able to tightly regulate temperature. It'll monitor head, exhaust and coolant temperature and kick on both pumps and the cooling fan in event of an overheat on any of those, so the engine's protected from melting down. The microcontroller and pumps will take ~22 watts with both pumps at full tilt (the engine is tiny, so the pumps are tiny), which replaces the OEM pump which can take upwards of 1/4 HP at WOT.

Combine that with micro-polished and WS2 treated rear gears (7.15:1 to replace the OEM 8.408:1 gears), hybrid ceramic bearings in the wheels and rear gears, and a sprag clutch in the rear rim, and this bike should be able to get up to speed and coast for quite a while.

After the bike's as mechanically efficient as I can make it, I'll design an aerodynamic body for it along the lines of the Akira bike, but more fully enclosed.

At 11,000 RPM with the new rear gears and aerodynamic body, the bike should be able to reach 112 MPH. It'll rarely see that speed, most likely just once for testing (that's insanely fast for a scooter)... the point of the bike is to try to reach 150 MPG at highway speeds.

Eventually, if I can find a toroidal IVT (infinitely variable transmission) transmission, I'll swap that in to replace the CVT. That'll allow me to get up to speed, and keep the engine in its most efficient RPM range for high-fuel-efficiency cruising. The IVT will be controlled via a twist-grip on the left handlebar. A side benefit is that since the IVT has "geared neutral", when the bike is stopped and the engine is running, the bike can't roll backwards when stopped on a hill, even with no brakes applied. Due to the sprag clutch, it'll be able to roll forward, though, but that's not so much a problem as rolling backwards. My legs can hold the bike from rolling forward, whereas my feet just drag if it rolls backward. So that little annoyance will be eliminated. I hate sitting at long lights on steep uphills, having to keep the brake on the whole time. I like to be able to take my hands off the handlebars and relax a bit. Another side benefit of the IVT is that I can tailor the performance on-the-fly... if I want to get the engine screaming and take off fast, I can. If I want to keep the engine in its most efficient RPM range and take off slowly, I can. All with just a twist of the wrist.

I was imagining if it glitched while you were leaned over in a turn, and it attempted to *keep* you leaned over... imagine having to ride home heeled over at a 45 degree angle. You'd definitely get people staring. Especially at the stop lights. LOL

I'm posting this with permission of the owner of MicroBlue Bearings. I'm not affiliated in any way with MicroBlue except as a customer.

Since I've ordered new hybrid ceramic bearings for my bike and gotten the rear gears micro-polished and tungsten sulfide coated by MicroBlue, I got a special offer from them for 10% off my next purchase and free shipping. Since I don't have anything to buy from them right now, I asked the owner if it'd be alright to post the offer here, and he agreed.

So, quoting from the email offer:
======================
From 4/6/15 through 4/13/15 go to www.MicroBlueBearings.com and enter the promo code "Faster" in the Coupon Code box, on the store checkout page, and receive a 10% DISCOUNT on your order, as well as FREE SHIPPING in the United States.
======================

Hope this helps anyone on the fence about ordering hybrid ceramic bearings. They last longer, run cooler and help your vehicle to get more of the engine power to the ground where it can do some good, rather than being eaten up in friction.

Ok, so I did a bit of research.

Come to find out Balance Masters puts their mercury in neoprene tubing. I intend to use metal tubing for mine.

It appears that the best readily available common metal to hold mercury is AM350 stainless. It's pretty close on the galvanic scale, so there won't be any galvanic interaction between the two metals, and mercury doesn't interact with AM350 like it does with some other metals (which dissolve in mercury).

AM350 consists of the following:
Carbon: 0.09%
Manganese: 0.80%
Silicon: 0.30%
Chromium: 16.5%
Nickel: 4.3%
Molybdenum 2.75%
Nitrogen: 0.10%
Iron: 75.16%

According to the Hand Book of Chemistry by Leopold Gmelin and the paper titled 'Mechanism And Kinetics Of Corrosion Of Selected Iron And Cobalt Alloys In Refluxing Mercury' by NASA:
Mercury won't interact with carbon unless there is potash present.
Mercury won't interact with manganese unless there is chloride present.
Mercury won't interact with silicon unless there are nitrates or fluorine present.
Mercury won't interact with chromium unless there is nitric acid present.
Mercury won't interact with nickel unless there is chloride present.
Mercury won't interact with molybdenum unless there is potash and nitric acid present.
Mercury won't interact with nitrogen unless there is hydrofluoric acid and water present.
Mercury doesn't seem to interact with iron at all.

NASA tested AM350 in boiling mercury for as long as 5000 hours at 1300 degrees F, and found only a moderate surface etching and uniform wall recession with only slight surface roughening and grain transformation, with no marked changes in the corrosion zone over time or temperature... so AM350 should stand up pretty easily to mercury that isn't boiling at 1300 degrees F.

AM350 is sold in a variety of tubing sizes, is ductible enough to form it into a loop, and is readily brazed or welded to close the loop.

If I can't find any commercially available active balancers, I plan on buying some mercury and AM350, getting the AM350 cryo-treated (which increases its resistance to corrosion), forming it into a loop and welding it shut, drilling a hole in the inner part of the ring, using a syringe to put the mercury in, then brazing the hole shut.

Then I'll dip the whole thing in liquid neoprene a few times to get a thick coat. It'll slip inside the flywheel, held in place by the force fit between the rubber coating and the inner surface of the flywheel. Since it'll expand a little when it heats up (which I'm assuming it'll do with liquid metal whirring around in it at several thousand RPM, with nowhere for the heat to go since it's insulated by rubber), it'll lock itself in even tighter as it warms up.

I plan on replacing the OEM generator stator with a flywheel that has magnets embedded in it. That second flywheel will fit in the space where the OEM stator sat, and will be connected to the shaft of a proper brushless waterproof alternator, with a proper voltage regulator to replace the OEM ground-shunt regulator. That will increase the electrical generation capabilities of the bike, and save that power that would have otherwise been shunted to ground. So with the new alternator-side flywheel, there'll be room for the balancer inside the engine-side flywheel without interfering with the alternator-side flywheel.

We could use the same method used to balance the Mini Cooper engines... a steel ring inside a thick silicone gel. But that'd increase the overall dimensions due to packaging considerations. There's no danger from mercury if it doesn't leak out. The problem with tiny ball bearings is that they eventually wear, so you get a lot of metal "dust" rather than bearings, which clumps up, prevents the bearings from moving freely, and throws off the balance.

{EDIT}
Another idea... rather than just one ring, have a flat container with thick silicone gel in it, with several differently sized rings. Thus, the different harmonic frequencies of the various rings means the active balancer can absorb a wide range of frequencies of vibration. It'd be shallow, just wider than the rings themselves... but figuring out how and where to mount it would be a pain. Perhaps it could be machined as part of the variator engine-side sheave.

I'll have to get a clear container, some silicone gel, several different ring sizes, and an electric motor and speed controller, and do some experimentation. That could be a pretty effective means of damping vibrations, and a new product category... vibration damping variators.