SM 125----

[Ezzelino!!]

Hey,I own an SM 125. I`m new here so pls excuse me if I repeat some questions,

SO these are some of my probs. 1) I want to decrease my sprocket size, where can I buy one? aftermarket ? internet ?
2) I`ve decided to buy a smaller carb, how it will effect the motorcyle, anu suggestions where to buy one ?
3) my front tyre is damaged, what tyres can I buy(better than these and mayble slightly more wide) ?
4) What handgaurds fit well with the SM, I like those narrow acersbis
5) any more upgrades I can do(mechanical) ?


Thanks

[DAVID THOMPSON]

please update you profile with area where you live city and country
so we can make our answers better fit your needs
i did this answer for the usa
1 I want to decrease my sprocket size, where can I buy one? aftermarket ? internet ?
see link below for a bunch of 125 info
http://www.mzriders.com/viewtopic.php?t=804
my rt runs very nice with stock front and 52 rear top speed is 69mph wfo
but it sure climbs hills nice :)better to do on rear as smaller fronts wear faster
front is oem only as far as i can tell check www.bikeworx.com
they deal mz parts and may help with sprockets the 52 is from a sx
and i think is a direct bolt up if you have a spoke wheel

chainwheel sprocket chain
1A UPDATE this company lists esjot sprockets they have a listing
for the mz 125 bikes both front and rear
http://www.thorusa.com/esjot.htm
http://www.esjot.com
for the pdf catalog
these sprockets fit some yamaha bikes but not any sold in the usa
so there is no yamaha part number that works in the usa front or
rear check if these guys can order for you
ar dave 04/08/06 dont you just love bastard parts i spent 5 days trying to find sprockets for the 125's as aftermarket parts


2) I`ve decided to buy a smaller carb, how it will effect the motorcyle, anu suggestions where to buy one ?
A it will not improve anything and is a waste of money

3 my front tyre is damaged, what tyres can I buy(better than these and mayble slightly more wide) ?
A=wider is not better if yours is an SM see a local shop that can order
kenda k671
front = 110/70-17 54h p#k67103 rear 130/70-17 62/h p#k67121
from parts unlimited
if yours has spoke wheels you need tubes never use an old tube except as a trip spair
part

4) What handgaurds fit well with the SM, I like those narrow acersbis
a=just have to go to a dirt bike shop and see what fits

5) any more upgrades I can do(mechanical) ?
A='ride it' the more miles the better it will run

6 ride it lots and have fun

[Drew]

DAVID THOMPSON is quite right on a lot of things here. I'll see what I can add...

on 1), I'm with David- the SM comes with a 49-tooth, the SX with a 52-tooth. If you want some real fun, a 60-tooth is available here.

For 2)- why?!?! The bike already gets fantastic mileage, and runs fairly lean stock. Going smaller will only make things worse. You're better off making a restrictor plate if that's what you really want to do.

As for 3), if your hub is still good, replace the rim. Excel and Morad both make 3.00x17 rims (Morad's come with no holes drilled). I'm not sure if the Excel is 36-hole, which is what you need. The 2.75x17 (stock rim) or 3.00x17 (most easy to find replacement) will accept nothing larger than a 110/70/17- a 120 will deform so much that it won't be putting the optimum amount of rubber on the road. If you're in Europe, take a look at these. I'd go for them myself, but I can't get them in the US (probably never will, sadly). Personally I'm going with a Dunlop Qualifier 110/70/17 front, 140/70/17 D208 SM on the rear, but I'll be taking it to the track (hopefully a lot), and the Qualifier is on back-order until May. For a low-cost long-range option, my suggestion is Bridgestone BT45's.

To continue on point 3, The stock width is great for the weight savings. Rubber is heavy, and you already have a lot of unsprung weight, so no need to add more. Plus the narrow front tire gives a great turn-in you can't beat on the tightest courses.

Handguards in 4): I have Acerbis on mine, but I don't recall which ones. There is very little extra room, but they work (track-tested!). Note that the anti-vibration damper in the stock handlebar will hinder your install, so you'll probably want to replace that too (I went with a black-anodized Tag unit). And of course new grips (don't forget the grip-glue!). All-in-all, a job to put on a set of $70 handguards exploded into a 4hr task that cost over twice that amount.

Mech upgrades really requires us to know how much mechanical skill you have on your own, mixed with how much you're willing to spend (for parts and labor). The simplest set of mods is adjust your timing, get a pipe, and jet your carb. From there you'll have a solid performer. Suspension bits can be upgraded with Wilbers bits (fork springs cost ~$100 USD, rear shock ~$600). I'm personally not planning to do any more than this, as anything above and beyond is not cost-effective (i'd rather spend that money on a bigger SM).

The little MZ SM comes with some real trick bits already, so don't fret about upgrading everything on it.

[DAVID THOMPSON]

the 125cc mz's were designed with a plan

item 6 in my post above says it all

6 ride it lots and have fun

they are a lot like a honda ct70/dax also called trail 70
most people call them a toy bike but Damn there fun to ride

http://oldmanhonda.com/MC/NewArchive/Pics/CT70(2)_full.jpg

[Ezzelino!!]

Sry for replying late but I was quite busy lately. Yesterday I bought a new front tyre, Michelin, it has slighlty a larger diametre but surley it is much better especially in bends. Regarding the sprocket, my mechanic told me not to change the rear one and not to increase the tooth no as it would stress the engine a lot ! Is it true ? rear or front ? More teeth or less ?

Sry drew but I got stuck how I can jet up the carb.... any help ? will it increase revs ? and any front fender suggestions I can replace with ? I think I will replace the original one with a shoter acerbis whilst I bought `cheap` pollisport black handguards

1 last question.... what sort of products do u use in order to keep ur machine spick and span ? any secrets ?

V.Thanks

[DAVID THOMPSON]

SPROCKET SIZE IS VERY LIMITED FOR THESE BIKES

MY AREA HAS HILLS AND SPEED LIMITS OF 55MPH OR ABOUT 88.51KPH

I USE 16X52 AND WOULD DO SAME ON A SM

ON A SX I THINK 16 X54 OR 15X52 ON SX
BUT SPROCKETS HARD TO FIND FOR THIS BIKE

SOME YAMAHA USE THE FRONT IN A 15 TOOTH