Aprilia Mille Fuel Leak and Honda VTX1800F Crankshaft

Answers

By Tim Carrithers, Photography by Aprilia

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Italian Incontinence
Q From the first time I rode an Aprilia V-twin I was in love, so I purchased a 2000 RSV Mille with a 2-year warranty and 96 miles on the odometer from a local dealer. The RSV has had a faulty starter relay and a leaking gas tank since '05. The relay was replaced under warranty, but the gas tank is another story.

My apartment manager called to tell me my bike was leaking fuel. Upon further investigation, the plastic tank had warped around the fuel-pump mount and wasn't holding fuel. After pulling the fuel pump off, I discovered the mounting surface had arched so its rubber gasket could not make good contact. A quick call to the local Aprilia dealer revealed this as a known issue. They said it was due to U.S. fuel containing ethanol, and suggested shaving off enough material to make the surface flat again, though that could only be done once. After that, I would need to get a new tank.

I left a number of messages and e-mails with Aprilia USA. They requested the VIN number and said someone would get back to me in the near future. I also filed a case with the NHTSA since I consider a fuel leak a safety problem. It also looks like Aprilia USA isn't doing a whole lot to come up with a fix. For most of these cases the warranty is out, but should a gas tank fail this way after 5 years of normal use?
Oleg Glubochansky
Seattle, WA

A High concentrations of ethanol can attack some plastic fuel tanks, but after talking to our most trusted Aprilia specialists, it sounds like this is a relatively isolated case. Ed Cook at AF1 Racing in New Braunfels, Texas, told us their service department has only seen a couple in more than 9 years of working on these bikes. "The first Aprilia plastic tank was the 2000 Mille R," he says. "Only the R-model got a plastic tank back then. Careless mechanics and owners can also cause tank damage by not routing the vent lines or EVAP-can lines properly. Pressure can build and expand the tank to the point of permanent damage. The fuel-pump plate mounting bolts need to be checked for length as well. If they're too long, they can bottom out and not seal the pump plate to the tank." Cook says there are repair options, such as fuel-proof anaerobic sealers and tank-repair specialists, as well as having the fuel-pump mounting area machined flat again, as you mentioned. Barring that, a suitable used tank from a bike that's been parted out could save time and money over buying a new one. Contact AF1 directly at 830.626.3966 and they'll help you sort things out.

Smooth Move
Q I just retired my '95 Harley-Davidson Fat Boy in favor of a clean '05 Honda VTX1800F. I expected the extra power-Honda's twin is something like 30 cubic inches bigger than my old Evo Big Twin. The shocker was how much smoother the Honda is-it's almost creepy. The VTX's pistons are supposed to be 4 inches across; seems like there should be a lot more shaking going on with so much metal flying around. One of my riding buddies says it's all about the crankshaft. How does that work?
Jordan Schaefer
Indianapolis, IN

A Rubber engine mounts filter out some of the VTX's vibes. Otherwise, your buddy is right: It's all about a king-sized version of the dual-pin crankshaft that debuted in Honda's first proper V-twin cruiser, the '83 Shadow 750. The VTX's rods connect to the crank via a pair of staggered crankpins, as opposed to sharing a common pin as in Harley-Davidson's classic knife-and-fork setup.

Doubling your 52-degree V-angle and adding Honda's crafty 76-degree crankpin offset equals 180 degrees. Voila: Classic lines and the same perfect primary balance as a 90-degree V-twin. The downside is extra width, some lateral rocking-couple vibration and an exhaust note that's somewhat less evocative than that produced by Milwaukee's hallowed arrangement.

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