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11 Posts
Discussion Starter #1
Last week my SXV550 developed a major oil leak. Oil was leaking from the engine, going into the bashplate and then through to the back tyre.

Initially I thought that maybe I had overfilled the oil tank, but it turned out to be a faulty oil pressure switch. I did an oil change to ensure that there was the correct amount of oil but the leak was still there.

I managed to get another Aprilia pressure switch from someone with a spare SXV engine, but the Aprilia ones are known for failing regularly. The solution is to get one from another brand.

Inside the pressure switch is a diaphragm. This easily wears out and breaks in the Aprilia switch, resulting in oil flowing out of the top of it. As mentioned, this oil will make its way to the back tyre via the bashplate.

The oil pressure switch is item 18 in this parts diagram:

The Aprilia part number is AP9150414 and is currently showing on AF1 with a price of $US23.68.


I went to a car parts shop today and ended up buying two different brand pressure switches - Tridon TPS020 and Champion CPS20. I paid $A6.50 each for them.

Fuelmiser also sell this with a part number of CPS20.

Thread: M10 x 1.0
Contacts: Normally Closed
Opens: At 30Kpa (ie 0.3 Bar)

These alternatives are cheap enough to justify having one as a spare at home. Considering the consequences of having oil on the back tyre, it?s worth replacing the Aprilia one with an alternative as preventative maintenance.

What to look for:
M10 x 1.0 thread
30Kpa or 0.2 Bar
Suitable connection at the top


The oil pressure is easy enough to find - it?s on the right side of the bike, just above where the oil filter goes.

When the switch fails, oil flows out of the top of it and into the bashplate area. Mine was so stuffed that it was leaking this much 200 metres after being cleaned.

Oil will eventually make its way to the back tyre.

The Aprilia version requires a 21mm spanner to remove it. I don?t have a spanner that size, so used a pair of multi-grip pliers.

A photo of the two pressure switches that I bought. The Aprilia one is on the right.

The Aprilia one requires a 21mm spanner, but the other two use a 24mm spanner. The Tridon one has the connection off-centre - the connecting cable has a rubber cap that needs to slide down over the top of the switch, so this might be a problem. However, the Tridon switch also has some thread sealant on the threads.

When I fitted a replacement Aprilia switch to my bike on Sunday I still had the problem of oil on the tyre, and not knowing if or how far the oil had penetrated into the rubber. I put the bike up on a stand, got an electric sander out and rubbed the tyre back. I ran the engine in first gear to keep the wheel rotating and ran the sander side to side over the tyre. This only took a couple of minutes and I then couldn?t feel any difference between the previously oiled sides and the centre of the tyre.


11 Posts
Discussion Starter #2
Part 2

Tonight I fitted the Tridon TPS020 to one of my SXVs and took a few more photos.

As mentioned before, the oil pressure switch is hidden behind the radiator hose. And possibly the exhaust header pipe, depending on which exhaust you have on your SXV. This bike has the standard exhaust, but my other SXV has a Silmoto exhaust which also blocks access to the oil pressure switch.

This bike has the standard Aprilia switch that I fitted on Sunday. Tonight I?m going to fit the Tridon TPS020 that I bought yesterday. I wanted easy access, so chose to remove the radiator hose from the water pump cover. This also showed that there was a small piece missing from the the water pump cover tubing. I?ll probably replace the water pump cover in the near future.

Once I had access, the oil pressure switch was very easy to remove.

There?s also a washer - part number 9150472.

I had trouble getting the Tridon thread to catch, so found it was easier to slide the washer up the thread first.

The Tridon switch in place. Notice how long the connector at the top is.

There?s a rubber cap on the connecting cable that can be slid upward.

The Aprilia connection only slides about half way down the Tridon connector, but this isn?t a problem.

Using some pliers, I slid the rubber cap back down over the top of the pressure switch.

Done. Replacement Tridon pressure switch fitted.

Then it was time to top up the coolant. I removed the radiator shroud to make it easier to poor coolant in.

Finished. The desire to start the bike and get some revenge on the neighbour?s four screaming kids at 1:30am was tempting, but the desire to not piss off the rest of the neighbourhood won out. I?ll start the bike and let it idle for a while during daylight hours.

You can also see how oil that leaks into the bashplate will make its way backward and on to the back tyre.

I?ll be selling this bike later this year and keeping my other SXV550. I think that the Champion CPS20 is the better choice of switch, so I?ll be putting that on the SXV that I?m keeping.

11 Posts
Discussion Starter #4
Great write up Phildo! Very detail oriented. Do you still have your SXV?
Sold that one years ago and replaced it with a near-new one with a whole lot of bling. The replacement had 17 hours on it when I got it. The previous owner kept throwing money at it but hardly ever rode it.

Then it was stolen last year in a house burglary - that bike matters to me so it was stored inside the house, with a lock on the front disc.

It turned up a few months later. Various plastics are missing and the wiring harness has been messed with, but all the main (ie valuable) stuff was still there.

The ironic part was that one of the reasons that it was stored in the house was that I'd cooked the starter motor months earlier, and my attempt at adapting a Yamaha WRF one didn't work out too well. I had bought a new starter motor but hadn't gotten around to fitting it yet.

That bit of laziness and procrastination saved the bike - because it couldn't be started it couldn't be ridden.

All I've got to do is replace the missing plastics and a few other parts, sort out the wiring harness and it will be as it was before the theft. No engine damage, etc.

I'll be keeping this SXV forever. Aside from better locks (ie the Xena alarm lock was broken off easily) it will be getting a GPS tracker soon. In the future I'll be putting GPS trackers on every vehicle that I own.


5 Posts
Nice looking bike! Especially those wheels, what year is that? I noticed you said you bought a new one. Do you live in the UK? I'm not sure when they stopped selling them here in the states but they're hard to find. I found one of the famous 07 models in California that I'm thinking about buying. Supposedly the engine has been rebuilt by an Aprilia expert so hopefully I can get a lot of miles out of it.
Glad to hear you got your bike back, I would do the same as you and park that thing in my house if I had room. :)

11 Posts
Discussion Starter #6
I'm in Perth, Western Australia.

The SXV is a 2008, which the previous owner bought new for track days, but his nearest track was 400km so it was rarely used (hence the 17 hours on it when I bought it in 2013).

When I got the bike I put street stuff back on it (ie lights, switches, headlight, etc) for road use, as well as the later model decals.

In early 2017 I cooked the starter motor when I ran out of petrol in a place where I shouldn't have been, and used the starter motor to get the bike up a staircase. I tried transferring the cheaper internals of a Yamaha WR450F starter motor over to the Aprilia starter casing but it didn't work for very long.

I didn't have the money at the time to buy another starter motor so the bike got put in a spare room of the house and a Xena alarm disc lock fitted, which turned out to be absolutely useless.

At the moment the bike is kept elsewhere. I actually ordered a bunch of parts from AF1 racing last night, so in the next couple of months I'll get it running and on the road again (ie it's just about summer here in Australia).

But, it will always have at least one GPS tracker before it goes anywhere again.
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