Aprilia RS660 Tech Discussion

Without a drain or vent it won't function all that well...

 

I raced my Kawasaki 650 for years with no overflow vent though. It seemed to do okay. I never had it boil over but I definitely had fluid go from the radiator into the reservoir a few times when the bike was running hot. But Hong at HSBK did vent my RS660 when he built it so that’s how I run it. I think I’d rather overflow go into the belly pan than n my leg if the overflow flows over.

 

Thanks guys, I will run the vent down to the belly pan.

 

Going to try running without a thermostat.

BUT how do you guys remove it with the seal being part of it. I tried but get a leak.

I was thinking about removing the thermostat part and just keeping the metal ring to hold the rubber seal.

BUT if I do that I can't put it back in if I want to run it. And they are not cheap. Surprised someone doesn't a part without the thermostat to hold the seal

 

@regularguy told me but I sort of forgot and need to do the same. I thought maybe using some side cuts and just cutting the core out of the thermostat and reinstalling the body and seal. Mike?

 

Yeah I just don't want to ruin an expensive thermostat lol

I am going to see if I can find someone to make a seal holder out of aluminum. Basically just a circle with a hole in it.

 

What is diameter? If same use cheap one from other bikes.

 

Now that's a good idea! It's 47.8 mm

Just went to Napa to see if they could match it, but they couldn't find anything.

Not sure how I would find out the diameters of other bikes thermostats though. Might have to bite the bullet and use the aprilia one.

 

Cut the center out of the thermostat and run a 2 bar radiator cap. We ran stock radiators in 2021 and I can tell you the water temp was routinely around 104C on track (pulled from our AIM data) on a not so warm day. Also, after a certain temp (which I don't know off hand) the ECU will pull out timing as a safety measure. Because of this, we left our fans installed in case we had extended periods of idling on the grid waiting for everyone to grid up after the warm up lap. To help with the heat, the Trofeo Cup bikes in CIV use heavy oil weights and a tiny accessory H2O radiator, which is insanely expensive. In 2022 we began running a supplemental radiator and we dropped 20C running around 85C on track.

FYI, the stock thermostat is 44 bucks...

 

Thanks, great info Mike! I will just buy a spare thermostat. I think I am just stuck in the past, last time I bought a thermostat was probably 25 years ago, so a $10 thermostat is still in my head. lol

 

With a little modification and different hose routing, we fitted an RSV4 radiator and lost about the same 20C with a 2 bar cap.

 

That would be a cool setup to see.

 

If you remove the EVAP crap, and run a vented race cap, can you loop these vents to each other with a hose? Instead of draining into the belly pan.

 

So I have been having a issue with the alarm service and alarm atc disabled along with no speedometer.
I tried a new rear speed sensor and unplugging the imu doesn't change anything but wiggling the connection made the alarm go off for a few seconds.
Bad IMU probably?

 

^Do you know anyone with an rs660 that you can maybe borrow their IMU and see if that fixes the problem?

Also what RCS brake master do you guys recommend. The 17 or 19?

RS660 has a 32mm caliper piston
RCS 17 is for a 30mm
RCS 19 is for a 34mm

 

Personally, I'd probably go with an RCS 17, cause I like more lever travel.

I will have an extra IMU with me at Road ATL this weekend.

 

Since this is my first go with a bike that has modern electronics, please help me out. What is the IMU? I’m wondering because I have just spent one weekend at the track with the bike and started getting a service alert then flashes to ATC disabled. I’ve been reading some say this may be IMU related. Performance was not affected when the alert came on.

 

If you get the "Alarm ATC disabled" error, then the most likely cause seems to be vibrations that cause the "inertial management unit" (which measures your orientation in space) to flake out. I switched to a different IMU and mounted it with just zipties, and I haven't gotten the error since. The IMU is a little 1.5" box that is mounted under seat, in front of the battery, and right underneath the rear of the tank.

 

Also check the wheel speed sensor(s) gap and the runout on the tone rings. A bent tone ring or damaged sensor is another common root cause it would seem.

 

Thanks for the responses. A little more information. The previous owner removed the Aprilia race ECU and put the stock one back in upon delivery to me. I did not want to track the bike with the stock ECU as I was concerned about lean fuel mixture with full exhaust. At the track I installed, rather hurriedly, a Rapid Bike piggyback and that is when the error code showed. Every thing is so tightly packed in these bikes that I may have disturbed the IMU and not known. Is it supposed to be oriented a certain way?