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View Full Version : STARTED THE RS 50 to 125 PROJECT TODAY!!! BUT WHAT 125 ENGINE SHALL I USE???



moto2014
02-02-2014, 12:07 PM
Hi all,

Started the project today so far ive removed the rs 50 engine with carb, all the wiring, oil tank, airbox, exhaust etc ect (all for sale btw)
and got the frame cleaned up and ready for my new 125 engine.......STILL NOT DECIDED WHAT TO GO FOR ANY IDEAS??

Zav
02-02-2014, 12:15 PM
What you wanting 4 stroke or 2 stroke
2 stroke options are
rg125
rg125 fun
tzr125
dt125
gpr125 (is a dt125)
any motocross engine

4stroke
cg125
cb125
cbr125
ybr125
sr125 (Yamaha)
and so on

moto2014
02-02-2014, 12:25 PM
sound zav....

err yea i no what out the but i have a budget of around 250-300 i wouldnt mind a stroker but they seem to cost a bit more than the 4 strokes

moto2014
02-02-2014, 12:26 PM
no whats out there but...thats ment to say

moto2014
02-02-2014, 12:42 PM
i wouldnt mind a cbr sr or ybr either but its a case of shall i go water cooled 4 stroke i.e cbr 125 or air cooled ie. the ybr or sr.... i would if money wasnt a isue go for a full power 125 2t or kmx 200

Zav
02-02-2014, 12:47 PM
sound zav....

err yea i no what out the but i have a budget of around 250-300 i wouldnt mind a stroker but they seem to cost a bit more than the 4 strokes

You will have no chance finding what you need and fitting for 500 never mind 300

its not worth it mate just tune your engine I can make a am6 engine last as long as Stock but preform like a Suzuki rg125 gamma (ace bikes top out at 95mph stock when tuned like my tack day one can do 119mph)

for 300 you could have this setup
airsal m reaching 77cc kit
doppler endurance crank and sky bearings
21mm carb and manifold
keep exhaust you got
fit 15/45 gearing
this setup tops out at 85mph +/- 10mph mattering on weight of rider and lasts a good 15k miles of hard thrashing if take steady will last about 20k with a rings and piston change will last about 30k miles

I have a similar setup on a mate tzr except he has the airsal 77 sport and high comp head and 32mm carb (he keeps changing as he's trying to get the best mpg to power) he's had this setup for a year done 1 ring change and 18k miles his tops out at 90mph 2 up

moto2014
02-02-2014, 12:53 PM
nooo way you can buy a cbr 125 engine with around 6k on it from ebay for 250.....i can get full loom from a place i know for around 50 inc cdi reg rec and all the other components

moto2014
02-02-2014, 12:54 PM
or buy a bike thats been crash damaged and take its loom and lump

Zav
02-02-2014, 01:38 PM
Buy a full bike then buy a full car or cg or rg take engine, exhaust, carb or throttle body, loom and sell the rest then you save money

eg buy a full rg125 game for 500 take engine loom exhaust carb out sell rest for in parts for 600

Spudgun60
02-02-2014, 02:12 PM
I've only ever seen one RS50 that was fitted with a 125cc engine. Even then, it was an abandoned project on Ebay. As for an engine that's within your price range. I've have seen one that turns up on Ebay a lot. However, you're not going to like it. Somebody has bought a job lot of Minsk 2-stroke engines and is flogging them off (I said you wouldn't like it).

Personally, I wouldn't bother. Even if you did manage to do the conversion, it would be impossible to sell.

moto2014
02-02-2014, 03:05 PM
thats the plan zav.......... i will finish this project i have had a cg125 in the same frame before so it can be done and isnt alot of work. I wont be selling the bike after its done THE REASON FOR DOING THIS IS PURELY FOR PLEASURE AND TO HAVE A "ONE OF A KIND BIKE" I HAVE NO INTENTION OF MAKING MONEY OF MY PROJECT

mattology
02-02-2014, 04:26 PM
I've only ever seen one RS50 that was fitted with a 125cc engine. Even then, it was an abandoned project on Ebay. As for an engine that's within your price range. I've have seen one that turns up on Ebay a lot. However, you're not going to like it. Somebody has bought a job lot of Minsk 2-stroke engines and is flogging them off (I said you wouldn't like it).

Personally, I wouldn't bother. Even if you did manage to do the conversion, it would be impossible to sell.


Mine runs perfectly, and I routinely have people begging me to sell it to them... I think you just have to do it right proper and then people will want it. I've never even put it for sale

Spudgun60
02-02-2014, 04:41 PM
I don't know what the rules are in America (I suspect the Laws and culture are different), but over here in the UK, things are different. Anything that appears to be 'bodged' (IE: Abnormal conversions) are avoided or kept at 'arms length' by buyers. Considering that that a standard RS50 is on Moped paperwork, putting a 125cc engine in the frame requires a motorcycle reclassification (A pain in the ass at the best of times). Putting in a 70cc BBK tends to go 'under the radar', but a long as the original bottom end is retained, nobody asks any questions. I still say that putting in a 125cc engine in an RS50 frame over here in the UK (Just to make things clear) is foolish.

Zav
02-02-2014, 04:58 PM
I don't know what the rules are in America (I suspect the Laws and culture are different), but over here in the UK, things are different. Anything that appears to be 'bodged' (IE: Abnormal conversions) are avoided or kept at 'arms length' by buyers. Considering that that a standard RS50 is on Moped paperwork, putting a 125cc engine in the frame requires a motorcycle reclassification (A pain in the ass at the best of times). Putting in a 70cc BBK tends to go 'under the radar', but a long as the original bottom end is retained, nobody asks any questions. I still say that putting in a 125cc engine in an RS50 frame over here in the UK (Just to make things clear) is foolish.

The best and easyest conversion is
derbi GPRS 50 /aprilai my06 to 125 you just buy new cradle rear wheel swing arm engine exhaust cdi carb and done

moto2014
02-03-2014, 06:23 AM
Mine runs perfectly, and I routinely have people begging me to sell it to them... I think you just have to do it right proper and then people will want it. I've never even put it for sale hi..... so u have a rs 50 with a 125 engine? what engine?

apriliamandan
02-06-2014, 03:29 PM
hi..... so u have a rs 50 with a 125 engine? what engine?

Honda CR125 motorcross engine.

mattology
02-08-2014, 06:18 PM
Yup, with a karting cylinder, Honda RS125 exhaust, karting reeds, 38mm power jet carb, billet cylinder head, etc ;)

MrGouldy to you
01-04-2015, 07:14 PM
getton boys loving some of the reply here , im now int he process of fitting a kmx engine into my chassis dumped the dtr motor its gay and under powered compared to the kmx , lots more stuff planned ,

Matt any chance of some pics mate ?

mattology
01-05-2015, 01:45 AM
Look in my thread.

pipdavidson
03-29-2015, 02:30 PM
any links to suppliers ? also after a good exhaust any recommendations

pipdavidson
03-29-2015, 02:32 PM
for 300 you could have this setup
airsal m reaching 77cc kit
doppler endurance crank and sky bearings
21mm carb and manifold
keep exhaust you got
fit 15/45 gearing


any links to suppliers , after a good exhaust any recommendations ? thanks

Zav
03-29-2015, 03:23 PM
Vsmotoparts
Scootfast
Racing planet

RS_Patrick
03-29-2015, 08:09 PM
any links to suppliers ? also after a good exhaust any recommendations

www.easyparts.nl

Exhaust depents on what kit your fitting... if you fit a low powerband pipe on a high powerband kit or the other way around that wont do you much good...