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View Full Version : Looking for some information on putting a rs 125 front end on to my rs 50



shanejc321
05-07-2014, 06:25 PM
Alright. I'm looking into putting an rs 125 front end onto my rs 50, like forks and brakes. As far as I'm aware I will need to get the forks, yokes, brake and brake parts like disc etc. will I need to change the front wheel, Or does the rs 125 disc fit onto the rs 50 wheel? It's a 2003 model. Also what would I need to do to put a rs 125 engine into it?

RS_Patrick
05-07-2014, 09:13 PM
I wouldnt fit a 125 engine in there, especaily not if your in the UK... and a RS125 engine has the sprocket on the other side, so you would need to convert the rearfork also, or find a engine with the sprocket on the left hand side.
Installing one would require making your own engine cradle.


RS50 2003 fork is fine, could just stiffen it up a little by adding a bushing ontop iof the springs,or buying stiffer springs and maybe installing a second shock absorber (theres only 1 functional shock absorber in one of the legs)

Difrent (thicker) fork oil by it self helps a lot.

Probably modded like that it would make the RS50 fork a better fork than the stock RS125 fork.



If you do want to fit a RS125 front fork you need the whole front end with the wheel and everything (including brake pump etc. etc.)

The main shaft is longer on the 125 fork so you probably need to cut more threading on there and cut it to the right length, or fit some sort of spacer.


p.s. the RS125 headlight fits straight in, does a better job than the RS50 headlight unit.

mattology
05-08-2014, 07:06 AM
Shane, I looked into it and decided against it. the forks are larger, yes, and the triple tree and assembly will go on with just a spacer. it's not so bad. however, the front wheel has to be from the rs125 also, and then it is almost the same size as the rear wheel and looks kind of weird.

I have the AF1 front end kit with thicker oil, stiffer spring, and adjustable preload shims. I also am using two fork tubes that have damping seals in them so both damping rods function properly.

In the near future I will be installing Race Tech cartridge emulators in them as well, as they will in fact fit! At that point, they will be much better than RS125 forks.

shanejc321
05-08-2014, 05:07 PM
It's not that, they look a lot better than the rs 50 forks, more beefy etc.. It's only for a year so not sure if I'm definitely going to do it but was looking into it. Is a rs 125 frame the same as a rs 50 one, if so could I not take the cradle off of it? Would a 125swingarm fit straight onto the rs50 if I was to do the conversion?

Zav
05-08-2014, 05:44 PM
It's not that, they look a lot better than the rs 50 forks, more beefy etc.. It's only for a year so not sure if I'm definitely going to do it but was looking into it. Is a rs 125 frame the same as a rs 50 one, if so could I not take the cradle off of it? Would a 125swingarm fit straight onto the rs50 if I was to do the conversion?

It can be done and has been done one guy in neather lands fitted rs125 engine swing arm wheels and forks into his 50 but even e said was way too much you can just buy a tuned rs125 for how much he spent and a guy on here did it but Coast him a lot less as he raced rs125s

and no the frames are totally different

the new shape rs50 and derbi gpr 125 have same frame and you can swap cradles and engines but that doesn't matter as you have a 2003

If only keeping it for a year don't bother no point

shanejc321
05-08-2014, 06:44 PM
Aw right nah I won't bother with that then. Do you know of any? Twin exhausts for an rs 50? There's a new set on eBay. Endy cans the make is, do you know whether it's a good make cause I've never heard of it and can't get an arrow one in twinners

Zav
05-08-2014, 07:01 PM
Aw right nah I won't bother with that then. Do you know of any? Twin exhausts for an rs 50? There's a new set on eBay. Endy cans the make is, do you know whether it's a good make cause I've never heard of it and can't get an arrow one in twinners

I have a twin endy very loud with pod filter but doesn't really do much performance it's more of a mid range pipe most on here hate them tho as you will find out if they comment but I like the sound and how they ride just hate the look as it looks tacky

mattology
05-08-2014, 08:24 PM
I swapped my RS50 with a CR125R motor. I actually have two of them now.

it was a fair bit of work but at the same time now that I have figured out exactly how to do it, it's quite easy. '

but the only '125' that will likely bolt in to the rs50's frame would be the new rs4 125 motor, if you take the complete cradle and everything out of it, including the swingarm. and all that for a four stroke? nah.

RS_Patrick
05-09-2014, 03:36 AM
Aw right nah I won't bother with that then. Do you know of any? Twin exhausts for an rs 50? There's a new set on eBay. Endy cans the make is, do you know whether it's a good make cause I've never heard of it and can't get an arrow one in twinners


Twin endies are just for looks, performance is really poor, and after a while one of the ends gets blocked with exhaust gunk.


RS50 frame is a difrent from from the RS125 frame, so you have to make your own cradle for it.

But like i said if the cops catch you in the UK your screwed, or worse, if you get into an accident, even if its not your fault at all, your helt responcible and your Insurance wont pay anything.


If you want more performance out of it just fit performance parts to the engine, 21mm carb (keep the stock airbox) and a good axhaust, but i sugest you first learn how to handle the bike as is with just a fast exhaust on there, and than upgrade from there.

Zav
05-09-2014, 04:12 AM
But like i said if the cops catch you in the UK your screwed, or worse, if you get into an accident, even if its not your fault at all, your helt responcible and your Insurance wont pay anything.

Im guessing you've never been the uk Patrick there's more 50cc peds with 172 and 183 and 210 motors shoved into them then there is aprilias. There is 4 Zips at my college and 2 of them have a 125 runner engine with a 172 in it and the third has a 210 4t runner engine and they fly and make so much noise I wouldn't be surprised if they pulled over most days.

It's a common thing in England now that's why it's becoming more common on 50cc forums to be asked if you can fit a 125 in a 50 frame

shanejc321
05-09-2014, 05:53 AM
my bike is tuned a bit like. its got a 90cc bore kit, 21mm carb, lightened crank as well as being geared up. im looking into an exhaust, I know arrow ones have a good performance but I ike the twins. Im off to get a derestricted cdi, clutch upgrade with stiffer springs, reeds aswell as an exhaust. really keen for the fork upgrade also..

RS_Patrick
05-09-2014, 08:25 AM
Im guessing you've never been the uk Patrick there's more 50cc peds with 172 and 183 and 210 motors shoved into them then there is aprilias. There is 4 Zips at my college and 2 of them have a 125 runner engine with a 172 in it and the third has a 210 4t runner engine and they fly and make so much noise I wouldn't be surprised if they pulled over most days.

It's a common thing in England now that's why it's becoming more common on 50cc forums to be asked if you can fit a 125 in a 50 frame

Its a fellony Zav, you get something like a 750 gpb fine if they catch you or worse, if you get into an acident even if its not your fault at all, your the one that gets the blame because your bike never should have been on the road in the firstplace, so than you have to pay all the damadges and expensise caused your self as your Insurance company wont pay anything.

Shame the uk motorcycle cop doesnt get on here anymore, he would have told you the same thing.



@Shanejc321: a 50mm bore is 76cc on these bikes, and thats the biggest bore you can fit, to get more CC out of it you would have to install a long stroke kit.
Dont know what cilinderkit you got, but for 70cc something like a Yasuni R3 exhaust would be great.

The Arrow and Gianelli pipes are not really suited for 70cc anymore as for some reason they fitted way to thin tailpipes on them.


Really nice setup for your bike would be:
TopPerformances Pink 75cc kit (by far the fastest cast iron kit)
Doppler ER1 race crank (reinforced with thicker shaft, so you also need 2 6204 C3 bearings)
21mm Carburator
Yasuni R3 exhaust
Malossi clutch springs
Malossi reeds set (3 pairs, 0.30mm, 0.35mm, and 0.40mm)
TopPerformances Yellow CDI unit, or the Red CDI module with seperate coil.

twinturba
05-09-2014, 11:38 PM
The 125 front end is a sweet upgrade on the rs50, just need to shorten the yoke

http://3.bp.blogspot.com/-pJ5uF_N7RJo/UttFmtnjvwI/AAAAAAAADS8/4m7d9PzqNqI/s1600/photo-712775.JPG

apriliamandan
05-10-2014, 10:24 AM
God that looks sweet TwinTurba! How much heavier is the front end though?

shanejc321
05-10-2014, 02:13 PM
I bought the bore kit off eBay. It says 90cc on there anyways and it's from Poland! Ah well I had an arrow exhaust on my derbi and everything else was standard and it would do like 73mph with a really good acceleration for a 50 would of gave my rs a run for it's money.

apriliamandan
05-10-2014, 03:08 PM
I bought the bore kit off eBay. It says 90cc on there anyways and it's from Poland! Ah well I had an arrow exhaust on my derbi and everything else was standard and it would do like 73mph with a really good acceleration for a 50 would of gave my rs a run for it's money.

73mph down a cliff or huge tail wind maybe! Those 90 Poland kits are 76cc with poor port layout, they don't perform any better than a stock cylinder. Best off with a branded kit, Airsal, top performance, Polini or even a Stickyparts.

RS_Patrick
05-11-2014, 12:09 PM
http://www.ebay.com/itm/Cylindre-kit-Minarelli-AM6-Tuning-90-cc-APRILIA-RS-EXTREMA-50-1995-1998-/150948030161?pt=FR_JG_Moto_Pi%C3%A8ces&hash=item23253426d1

Not this piece of scrap metal i hope?
49mm is only 73.5cc btw, not 90cc.

The heads and barrels on those are know to crack, only good as scrap metal or as paper weight :p:

Fake TopPerformances Pink kits...

MrGouldy to you
12-10-2014, 03:55 PM
if its of any use to anyone in the next few days my frame should be here and i will be using my rs 125 front end to go on my 200o rs 50 frame so will do some pictures and write up's , as has been said though i can jsutifly mine as im going to be running a tzrr engine in mine so more power and weight straight away