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View Full Version : fitting a 250 engine into a rs 125



dannymcclean
04-17-2009, 07:20 AM
hey there, does any know if its possible to fit an aprilia rs 250 engine into an aprilia rs 125? Thinking about doing this as a project. can anybody give me abit of info please? thanks

coffee
04-17-2009, 07:26 AM
Danny,
I think a lot have attempted it but not many if any have completed it. Use the search function and google to find threads etc. Has issues like chain on other side so swing arm needs mods or swapped out with other, plus other things.

kanerdog1x1
04-17-2009, 10:47 AM
its not an easy fit. chain is on the wrong side for a start. you need to look for a rotax 249cc engine, thats a better bet for a conversion. ;)

dan kerson
04-17-2009, 03:46 PM
Ricky Corey, AMA guy put an rm 250 motor in an rs 50 chasis and finished third in an AFM race.
I have the costom swing arm from that and the front forks that fit honda rs 125 wheels with the rear shock from an r6. It worked great for his set up.

FUERA.....1
04-17-2009, 06:51 PM
its not an easy fit. chain is on the wrong side for a start. you need to look for a rotax 249cc engine, thats a better bet for a conversion. ;)

Rotax 257 engine, im pretty sure is the one that is more likely to fit in

jokerio
04-17-2009, 08:29 PM
Ricky Corey, AMA guy put an rm 250 motor in an rs 50 chasis and finished third in an AFM race.
I have the costom swing arm from that and the front forks that fit honda rs 125 wheels with the rear shock from an r6. It worked great for his set up. What class did he race in ?
F2, 250 Superbike, F4...?

Gman2005
04-18-2009, 06:17 AM
it would be easier though using the 257 engine. Someone of tjtuning has started the conversion but stopped due to being skint lol

dannymcclean
04-19-2009, 04:38 PM
is the rotex engine a kart engine? is it two stroke? is it a big job getting it fitted? cheers

Gman2005
04-19-2009, 04:43 PM
custom montings, the frame needs a little work to it. I'll try and find the thread. Its ether on the old RS125 forum or on the new Tjtuning forum.

kanerdog1x1
04-19-2009, 05:09 PM
the rotax engine was originally designed as an enduro/mx engine, as the rs 125 engine was. it was(is still) fitted to lots of european manufacturers bikes, gasgas beta alfer etc. the modern ktm engines are loosly based on the design aswell.

dan kerson
04-21-2009, 12:55 PM
What class did he race in ?
F2, 250 Superbike, F4...?

Fll and then F4 I think.

dannymcclean
06-05-2009, 05:15 AM
is the rotax engine a 2 stroke? were would i find one of these? if i was to fit a rs 250 engine into it, would it fit if i changed the swingarm?

decipher28
06-05-2009, 08:48 AM
i think you need to read this thread if you haven't already done so

http://www.apriliaforum.com/forums/showthread.php?t=99264

ROSSRS
06-06-2009, 03:36 PM
I put a 257 in mine on thursday. You should be able to find non powervalved kart versions of the motor in us kart forums fairly easily. It only requires minor modifications - shorter spark plug to clear the tank, front engine mount holes need re-positioning, spacers for swingarm, a small nibble filing off the bottom left frame spar to clear the water pump housing, new lengths of water hosing, longer throttle cable, lose the oil tank. block off the crank case diaphram pump (kart use)

Syd Tuplin
01-12-2013, 10:54 AM
hi i have an rx 125 and i was wondering whether i would be able to put it all in a rx 50 frame im looking at a rx 50 rolling chassis everything but engine :)? plz help

Syd Tuplin
01-12-2013, 10:55 AM
................. :)