Late 90s RS125

[CaptainSlow]

Looking for a winter project and as I came to bikes in my middle age I know nothing about 2 stroke 125s. One is advertised locally that could be an easy project. Is it possible to increase the power on these? Also, do you have to premix the oil in the fuel or do they have a separate tank?

Stupid question alert: Do they also have engine oil or do they just use the oil in the fuel

[Whatsmyname]

Honda or Aprilia?

[CaptainSlow]

Sorry, Aprilia.

[AdamIndy]

I assume it’s an aprilia so they do have a separate oil tank for the 2 stroke oil though they have a habit of getting gummed up, not supplying any/enough oil to the fuel and seizure happens. Most that I’ve known with them just premix to save that happening. Not practicle I grant you.

They do have “engine oil” but it’s more for the gearbox than the actual engine itself.

Iirc there is a resistor that can be drilled out in the cdi unit which unleashes some power add that to an arrow exhaust and it makes for a great fun little screamer. I have seen 120mph on the speedo of one, no doubt very optimistic but anything around/over a ton on a road going 125 is fairly impressive to me!

The power valve(yes an ACTUAL power valve) can get caked in carbon and stick resulting in a loss of power. Easily sorted but something to look out for.

Always, ALWAYS use good 2 stroke oil, not the st you can buy for a fiver at the petrol station. We always used to run silkolene low ash 2t race oil, never had issues with the power valve gunking up using that either.

I’m by no means an expert on them but me and my friends used to thrash the living st out of them back in the day. Looked after they’re great things, buy a dog though and even for a little bike can be a money pit.

[podman]

Theres a few RS/RG /Mito 125 projects ongoing at the 2 stroke forum at the mo...would perhaps you worth joining, you may even find one to buy...

http://2strokeforum.com/

[chunder27]

The Aprilia 125 was never popular in the UK, always more expensive to race and run than the Honda Rs or later the TZ125 Yamaha.

Was a damn quick bike, but all Aprilia race bikes were very tricky to set up the carb and jetting for.

[patchb]

chunder27 said:

The Aprilia 125 was never popular in the UK, always more expensive to race and run than the Honda Rs or later the TZ125 Yamaha.

Was a damn quick bike, but all Aprilia race bikes were very tricky to set up the carb and jetting for.

Yeah he’s on about the RS125 road bike which I’d say was pretty damn popular over here...

[chunder27]

Ah i see, when people say RS125 to me I just think Honda racebike

Dont know much about Priller road bikes, other than most would have been ragged to within an inch

[Don Roque]

My mate had one years ago. He had it de-restricted and rode it on L-plates. Long since sold off and probably trashed now. He bought it new as a grey import, it was an 'Extrema' model that was never officially sold here.

[Whatsmyname]

You need to find out what motor is in the bike, it will either be a Rotax 122 or 123, the earlier 122 engine in the Extrema with the 30mm carb was around 33+bhp but required a lot of maintenance, the 123 is around 29-31bhp and is the more reliable machine. Still the extrema was the one, iirc it may have been banned in the UK because of power output.

[NITO]

I had an Extrema, it was awesome. It blew its piston at about 10k kms. Fitted a Malossi 175 and it absolutely flew for about 2k kms before eating another piston. The chassis is amazing and performance too on nsl single carriageway type roads. Pistons really need to be considered consumables. Mine topped out at 130mph on the clocks. Even accounting for speedo error, they were stupidly quick.

I don’t know how kind time has been to them or what parts availability is like now. I nearly bought a very low miler earlier in the year, I wish I had!

[patchb]

Whatsmyname said:

You need to find out what motor is in the bike, it will either be a Rotax 122 or 123, the earlier 122 engine in the Extrema with the 30mm carb was around 33+bhp but required a lot of maintenance, the 123 is around 29-31bhp and is the more reliable machine. Still the extrema was the one, iirc it may have been banned in the UK because of power output.

From memory the later engine was the 122 and earlier 123.

Mine had a 37mm Dell’orto, power valve, cdi mod and a gianelli expansion chamber, it felt like a rocket at 17, saw over 110 on the clocks so was probably touching 100

[chippy348]

Very good bike, proper 125 2t race rep

This is the place for parts and engine work > http://www.pjme.co.uk/acatalog/Aprilia_RS1252.html
Get it brought and enjoy it

[supercommuter]

Whatsmyname said:

You need to find out what motor is in the bike, it will either be a Rotax 122 or 123, the earlier 122 engine in the Extrema with the 30mm carb was around 33+bhp but required a lot of maintenance, the 123 is around 29-31bhp and is the more reliable machine. Still the extrema was the one, iirc it may have been banned in the UK because of power output.

Emphasis on the maintenance.

[boxedin]

I had a late 1990s Aprilia RS125 Extrema, from Bracken [1] off the Old Kent Road and stuck 10000 miles on it. It was another L plated unrestricted version, though I did pass a couple of months after owning it.

It drank oil like water ( motul's 2 stroke ), was always warmed up properly so never missed a beat, never had a problem.

I even came across it some 15 years later parked up in Wapping so it was still doing ok.

Excellent bike, enjoyed the heck out of it. Still miss it.

[1] great place, great guys.