Todd's ETV 1000 Caponord Page

Mad Props to Ken's Falco Page!

Having a low-RPM stumble?
Vacuum in the gas tank? Whoosh when you open the gas cap? Stumbling even after the EFI map update?


First and foremost, make sure your ECU is up to date. An update for the EFI mappings has been released, and your dealer can either install it themselves, or ship your ECU to Aprilia. They'll do their magic, and overnight it back to you. According to Cory in Customer Service at Aprilia USA, it may be as simple as adjusting the off-idle trim, and forcing the ECU to re-learn where the off position is for the throttle. Any dealer with the Axone tool can also do this for you. Coincidentally, TuneBoy can do both of those things as well.


If that doesn't help, here's what another Capo rider said:

I replaced the check valve at the base of the tank with a straight thru vacuum connector. The kind used for auto vacuum fittings. Bought a pack of four in the autoparts store for $2.00.

Here's why: When I removed the original valve it did appear "stuck" in the closed position, but every time I re-installed it and did a little test by running the engine, it created the persistant vacuum again. And it would not get unstuck.

The carbon canister sucks vapors from the top of the tank (the fumes actually wind their way thru the small passages in gas cap), down thru the one-way valve and into the canister. With the engine running a vacuum is created down by the canister and that is what "opens" the one-way valve. When the engine is stopped the valve is sucked shut, preventing any outside air from going back into the gas tank. Hence the negative pressure in the tank.

To me it appears that the Capo is getting its gas vapors purged, but the tank is really not venting properly. I believe much of the stumbling behavior is due to the fuel pump working harder to overcome the negative pressure in the tank.

Anyway, after cleaning the one-way valve, disassembling the gas cap to ensure it was flowing properly, and staring at the carbon canister diagram included in our manual for about an hour, I decided that the valve was the problem. I replaced it with the straight connector which allows vapors to be pulled from the tank when the engine is running, but also allows the tank to equalize with outside pressure.

It seems to work, and the mechanic at Aprilia essentially said "Yep, that's what I did" when I asked him how he fixed two other Capos that came in similiar complaints.

So that's what I did! I just bought a 1/4" to 1/4" right-angle vacuum fitting, and swapped it in.


Hey, remember, we're all buddies, right? I'm telling you what I did to my bike, you're telling me what you did to yours. If you mess up yourself or your bike, well, I'm sorry, but I wasn't twisting your arm. Of course, Aprilia has trademarked their name and logo, and they don't know me from Adam.

Feel free to contact me: todd at caporider dot com You can always go home again