10th Nov 2006, 04:26

Actually your second view is closer. Maybe I abuse the engine too much. The power-band for this bike is over 6000rpm. Not much before that. Pushing the engine over that point is just amusing. It's a 2-stroke engine. I use semi-synthetic 2T oil. comparable oil as use for bigger bike. For me it seems OK. just some 'tak tak' sound.. I need some advice ;)

18th Nov 2006, 09:05

An RPM of 6k is nothing for 125Z, they are good to go up until the rev limiter kicks in at 10k.

Personally have had tuned versions running almost to 12k quite happily. Anything over that, well the engine just seizes.

25th Nov 2006, 09:00

Calm down a bit, a 125 is not Super Fast.

19th Dec 2006, 12:19

I think the 125z was the fastest in its class. Better than the rxz135.

Top speed for my 125 is 165km/h. 2nd gear can go as fast as 80km/h at 8000rpm.

When the engine is still cool, I have problem to speed more than 6000rpm in any gear. Why is this happening?

29th Dec 2006, 15:27

With regards to the second commentator, the "tak-tak" sound you describe that the engine makes is a common characteristic of the two-stroke. This is due to the sound waves emanating from the cylinder into the exhaust system, due to the combustion process. You can think of the exhaust port on a two-stroke as a sound generator. The down pipe then harnesses these sound waves. These sound waves can then be used to pulse-tune the engine using the correct expansion chamber. A marvellous theory that was discovered in the 1950s by a German named Walter Kaaden, which in turn, opened up a whole new theory in the field of two-stroke tuning.

With regards to the fifth commentator, these two-stroke engines perform much better once you have warmed it up thoroughly and deactivated the choke. On the other hand, if you start it up from stone cold and ride away with the choke activated, the engine will rev to about mid-range and then hesitate.

4th Apr 2007, 00:08

The top speed of my Yamaha 125z is 150km/h... but before it reaches top speed, it makes the troubling sound `graummmm` or something like that... so what is my 125z problem?

7th Jul 2007, 00:22

I've ride my 125Z for 3 years. It's my main transport to work. I've kept up a strict practice of maintaining my bike, and it gave me no problem at all to ride at any speed I want. I change my piston, rings, needle bearing and pin every 6 months. I do all the necessary cleanings procedure of other part related to my top end rebuilding. Smokes and sound are unavoidable for 2-stroke bikes, but certainly you can clean up the carbon in the exhaust to minimise the smoke.

Clean cylinder, clear exhaust and correct tuning of the carburator should make your 125 run smoother and cleaner. I've ride my bike in 150 Km/h. It's not a problem for stock 125Z, but if you want to experience smoking Aprilia 125? I suggest you change your sprockets. 15 on the front and 39 on the back. Stock 125Z will install a standard 14 on the front and 43 on the back. You will feel the bike torquey, but you'll not get 150 Km/h. On 15/39 ratio, you'll lose some pick ups, but on your top rev... you'll smoked an Aprilia 125 easily. This ratio will get you to 170 Km/h in a single ride. At this moment you'll attract some bigger cc biker from behind. So beware.

Check the brakes often. The oil level and the pump too. I've experience some dragging problem, which cause my bike to slow down. It's dangerous. The last time I've found that I was speeding and when I finally stopped, my rear brake unit was glowing RED! I wasted my brake pad and not to mention about the pump. The seals for the pump melted and I have the brake oil bathed on my rim and tyre. It end up pay almost a hundred for replacing the parts. Well.. that's all for the speed and maintenance tips.

26th Aug 2007, 08:21

I'm the original author for this page..

Now for the time being I've modified my bike a little bit with huge results..

Now using RX-Z carburetor (that's 135cc 2stroke), shorter head clearance, new non-catalyser exhaust and that's it!

The acceleration now could beat any other bike in its class, and even 135 cc and 150cc 2 stroke bikes..

Top, duh, not so much.. only 165km/h..

But now an Aprilia 125rs never got a chance! (if it's standard..)

27th Aug 2007, 00:41

I use a Yamaha 125z. It is fun to drive and I never think about replacing it.

25th Sep 2007, 00:05

I'm also a 125ZR user. I want to know, how much is the cost if I want to overhaul my bike?

29th Sep 2007, 08:56

Hi, I've read all the comments about the 125z. To tell the truth, I love this bike.

I've made a lot of changes; tyres, wider sport rims, you name it. Modified block, ekzos, but one thing is still bothering me; the carb adjustment is still not perfect. Jetting combustion just nice by the look on plug. Going at normal speeds, there is a perr sound all the way, but push the throttle and you get great acceleration. This perr sound is what's bothering me. Guys help me please.

29th Sep 2007, 17:51

I think the 125Z needs a slipper clutch, because when I ride at 190KM/H and trying to slow down using the engine for cornering, some times my tire locks up... And I broke my hand once before because of the lock-up and I was in third place... so what I need to know is would there be a slipper clutch for these type of 2-stroke cupchai (small bike)?

25th Nov 2007, 13:52


I'm also 125z user, I just want to share my experience. Just now my bike can reach about 190-195km/h after I made some modifications.

After one year, I had a ride, and my bike only could go about 145-150km/h. I had it inspected, and the result the block, rings and piston are out. Finally my mechanic advised me to make some modifications to my bike, because the stock will not last if you ride it at high speeds every day.

First I lathed my block to 0.75mm, used new high temperature piston, high quality rings.

Second I increased the diameter of the hole of the carburetor and increased the injection of the 2t oil.

Third I had used the chamber exhaust and finally make some tuning of oil and air intake to the carburettor; to avoid my engine collapse the oil should be more than the air.

After that I change my sprocket ratio to 15,36.

The result are, in 1st gear I reach 60km/h, 2nd gear 100km/h, 3rd gear 140km/h, 4th gear 160km/h, 5th gear 175km/h and final gear 195km/h.

For 400m my bike can reach 160++km/h.

My advice, if you want to be at this speed, better for you to know to control your bike.

4th Jan 2008, 00:55

I have a 125z right now.. my bike is only just 2 years old.. but my 125z performance is greater than ever.. My top speed limit can reach to 180 km/h and more..

Always love your motorcycle..

9th Jan 2008, 03:45

I'm from GREECE and the reason I wrote for is "Where can I find a new YAMAHA Z-125 (2005 OR NEWER) TO BUY". Please answer me. Thank you at all.

Now I own YAMAHA F1-ZR (2002 MODEL). I'm waiting your reply. Manos, from Greece.