installing 52 tooth sx sprocket on rt125

SM, SX, RT, FunX, and models re-branded as ATK in U.S.

Moderators: DAVID THOMPSON, phlat65

installing 52 tooth sx sprocket on rt125

Postby DAVID THOMPSON » Sun Dec 28, 2003 12:14 pm

Installing 52 tooth SX sprocket on RT125

hello

you can install a 52 tooth SX sprocket on a rt125 in place of its
49 tooth
you must cut the center out of the old 49 tooth sprocket
just above the mounting holes so it can be used as a spacer
it will cut very easy with a hacksaw then have a machine
shop trim the edges so its round on a lathe with a three jaw chuck
this spacer is used to get the offset so the front and rear sprockets
line up as the SX sprocket has no offset but has the same bolt pattern
longer bolts will be required
also it is required so the original snap ring will work to hold the whole
unit together

this will make the bike perform better at speeds up to about 70mph
and give you better pulling power on hills at 55 and 60
it steals some top end but this bike is only 300 LB and much too
light to be going over 65mph any way
:D
IF YOU ARE A ALL THUMBS PERSON GET PROFESSIONAL HELP DONT SCREW SOME THING UP
AR Dave RT125 in WV USA plus 95 Saxon Tour (rotax motor)

update this mod does cut top speed a bunch
the rev limiter cut out at 10500 rpm = 70 mph
wide open so 65 mph is about top speed
but it does ok for me as 99 % of my roads are 55 mph or less
and boy does it pull hills good now
july24 04
after a few months use it also gets less gas miles i get 62 65 mpg
stock i was 72 74 mpg most of the time
but i can put up with that for the better hill climbing
EDIT ON GAS may 22 2014
most of the run problem here in the usa is from the ethanol
in the fuel ..i changed to mower gas 90 octane and no ethanol and
it starts and runs better...ethanol in the fuel is a BIG joke

A NOTE FOR 125SM OWNERS
above may apply if you have alloy wheels
if you have spoke wheels then it may be direct bolt up
as the alloy wheel has an offset sprocket that will not fit an SX
(march2007)
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DAVID THOMPSON
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Re: installing 52 tooth sx sprocket on rt125

Postby DAVID THOMPSON » Thu May 22, 2014 11:13 am

BUMP
just wonder if anyone has tried this and how it worked for them
worked great for ME
Dave

low spot near river level here is 500 feet ASL to about 2000FT ASL
the local joke here is its up hill to where you're going any time you go..
unless you're dreaming
dave
Dave 2002 MZ RT125 +1995 Saxon Tour (rotax500cc)
1997 MZ Skorpion Traveller added 6/13/09
Located in WV USA
"I like the road less traveled if it's PAVED!"
E mail wd8cyv at yahoo dot com
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DAVID THOMPSON
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Posts: 4497
Joined: Sun Nov 23, 2003 11:01 am
Location: Parkersburg, West Virginia USA .questions answered MZ 95 up, BMW 1953 to 1979 and ham radio WD8CYV

Re: installing 52 tooth sx sprocket on rt125

Postby ralf » Fri Oct 07, 2016 1:58 pm

Would it be easier to use a 15 tooth front sprocket with a standard 49 tooth rear? I see they (15 toot front sprockets) are available on ebay. It would allow use of the original chain length and the ratio is almost exactly the same as using a 52 tooth rear with a 16 tooth front. Also I note the dished rear sprocket used on RT's with alloy wheels is pretty difficult to find. Lots of suppliers are offering flat sprockets when dished are needed. ?????
ralf
 
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Joined: Tue Jun 02, 2015 12:32 pm

Re: installing 52 tooth sx sprocket on rt125

Postby DAVID THOMPSON » Fri Oct 07, 2016 5:02 pm

read the how to again
and i am not a fan of smaller front sprockets
and due to supply problems the dished 49 tooth rear is already hard to find
Dave

the adapter i made can also be used to fit stock 49 tooth flat sprockets on the rt wheel
MZ parts are hard to find in the usa where i am
Dave 2002 MZ RT125 +1995 Saxon Tour (rotax500cc)
1997 MZ Skorpion Traveller added 6/13/09
Located in WV USA
"I like the road less traveled if it's PAVED!"
E mail wd8cyv at yahoo dot com
User avatar
DAVID THOMPSON
Moderator
 
Posts: 4497
Joined: Sun Nov 23, 2003 11:01 am
Location: Parkersburg, West Virginia USA .questions answered MZ 95 up, BMW 1953 to 1979 and ham radio WD8CYV


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