125cc 2stroke Tuning Guide.

jamesknowles1991 · Aug 22, 2010

MiNoR cOnFuSiOn said:

125cc 2stroke Tuning Guide

First things first, you need a good engine, as in no cracks and if you can't fit them yourself good crank bearings/oil seals (water pump where applicable).

The power listed on this guide is from experience not claims.

For sheer power for money and driveability the best setup would comprise of:

Malossi 172cc kit
Dell'Orto 25mm Carb (best match for the standard reed window anyway although gains and losses are present with any other carb fitted)
Gear up kit
Aftermarket Carbon Reeds
Runner 125 standard exhaust if you have a Typhoon

This package is really good for your money, it utilizes the stock pipe so it's pretty much stock looking and will still see a reliable 15+bhp in any fitment. It gives for over 75mph true speeds and will start first time every time. It should also last a long time as there's no real strain on the engine.

Upping the ante a little we can start looking at utilizing the transmission for best performance, also how to shift the power band of the engine to a taller peakier curve, power doesn't always make for a faster bike.

Next few things on the list would be:

Piaggio 180cc variator (Malossi MHR if you're looking to take things further)
Aftermarket Exhaust (matched stub goes without saying but is ALWAYS forgotten by amateurs)
Aftermarket Stronger Clutch Springs
Malossi straight inlet manifold
Stronger Aftermarket Reeds
Malossi CDI swap/similar timing advance

With the new pipe the engine will produce it's power all at once in a certain rev range. This means we set the clutch to bite past the flat power at low revs and drop the roller weight slightly. This setup on top of the previous will see powers of up to 23bhp with correct setup although this is dependent on mainly the exhaust/match of the stub and setup.
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if i did these will the bike still have rliablity??

bertie · Aug 30, 2010

Yes as he said, it'll start everytime and be a reliable runner providing everything is fitted & setup correctly.

Ive been on a few rides where Ive seen bolt-on 172's travel over 100 miles in 1 day. Constantly riding too none of this fag break shit.

They only start becoming un-reliable once you start to break the 30bhp barrier.

Gilly Boi Mike 70 · Jan 1, 2011

Brilliant guide

samaroo44 · Jan 2, 2011

25mm carb or 172 kit first ?? would a 172 be alright with standard typh carb ??

yellasei · Jan 2, 2011

samaroo44 said:

25mm carb or 172 kit first ?? would a 172 be alright with standard typh carb ??
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does'nt the kit come with the carb?? a mate of mine runs an SR and his came as a kit. i would have thought that the bore kit would still be ok with standard carb though?

samaroo44 · Jan 2, 2011

urm okay i haven't seen a kit with a carb but ill have a look and cool ill probably 172 it first then and just jet like a bitch till its right

tErr0 · Jan 2, 2011

Use the search and then if you don't find the answer you are after post a new topic in the relevant place. This isn't the right place to ask questions.

MiNoR cOnFuSiOn · Aug 26, 2013

Always grab a kit first... Wasting time otherwise, its the biggest gain... Then carb, then pipe, then trans... Biggest gains first if installed in this order..

Stock carb is fine.. Don't even have to upjet tbh.. Nor change transmission.. Maybe go up a size or two just to be on the safe side, but most don't need it

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