8th Sep 2009, 12:20

I have a Kawasaki AR 1984, and most of the time it runs fine, but it is when I hit nine thousand revs that it does not give any more power. Is that a fault as I am new to bikes of this age. However I find it does the best part of 85-90 mph, handles great in the dry, and is a bit dangerous in the wet.

13th May 2010, 13:38

Hi, I have owned my AR125 B1 for about 3 months, and it eats any Aprilia RS on the road around my area. They will do a ton with the right tuning and bearings. Mine going in to have the bottom end rebuilt, as the geezer I bought it off had bodged everything on the bike; everything was loose, it was a right mess, but up jetted the carb, put on a Micron racing pipe, new tires, a good clean, and it looks great. I hit 85mph two up.

25th Aug 2010, 02:37

I got an AR 125 when I was 16 to commute to school and back. I think mine was restricted, as in the manual it said it only had 12hp and not the 21hp of the unrestricted one. The bike went very well and only had to replace the piston once and re-bore the barrel. I must say in the rain the handling was shocking; I had two accidents in the rain where the back end just slid out. I see now on other forums that it was a common problem. My bike had a top speed of about 80mph / 120kmh.

18th Oct 2010, 16:40

To all you would be mechanics out there, here's how you really increase the power of your ar125:

First of all... source the disk valve from the ar 125a model, then change the main jet to 100, the needle jet (emulsion tube) to p-2 and the jet needle (throttle slide needle) to 4c01. Also having the barrel ported, plus raising the compression to 7.0:1. Of course you will need an upgrade in exhaust (Micron, Allspeed). All these modifications should increase the power to 21bhp.

Or you could just find the engine from the ar 125a model, as these come unrestricted from the factory.

Good luck.

Watch your speed!!

14th Jan 2011, 11:31

Hmm, to do the above is more like 18bhp. However getting hold of an unrestricted disc valve, a 26mm carb (as the unrestricted carb is 26mm) and an expansion chamber may be an easier approach.

These are the differences that the unrestricted AR125 have:





Again, if you owned an unrestricted version (that's me), then you may know that the micron expansion chamber held it back. That's because it was never developed for the 21bhp. However, I was lucky enough to talk to the guy who designed the pipe, and he told me to cut an inch off the defuser, and it does make a difference. You need to take the circlip out of the end of the baffle that holds it in place, take it out, and the long narrow pipe, mark an inch and cut. Be warned, you will loose slight bottom end, but it will go like a scolded cat LOL.

14th Jan 2011, 12:11

The thing is, the restricted AR125 will never match a standard 15.4kw (21bhp) AR, They look the same. But Kawasaki as usual made it very very expensive to de-restrict; in fact when the bike was new, costing around £860 in 1984, IT WOULD HAVE COST YOU IN THE REGION OF £600 to de-restrict it USING THE UNRESTRICTED PARTS.

Performance Bikes did a feature on tuning the restricted AR, and it was 26mm carb (restricted was 24mm) unrestricted disc valve, micron and K&N filter, which gave it around 18bhp.

The unrestricted AR125 was a very rare beast in the UK, but it beat the unrestricted Yamaha RD125LC in the top end shoot outs. Till Suzuki came in with its unrestricted RG125.

26th Mar 2011, 13:29

I have this Kawasaki AR125 1984, but I was confused with the A and B model. I live in Indonesia. With the standard engine and its equipment, this bike is hard to get 120km/h. Lucky for me, I got this B3 cylinder (there is a B3 mark under the exhaust port on the bottom of the cylinder), pairing with a Mikuni VM 28 (mainjet 95, pilot jet 27,5), Thailand made exhaust and a little work with the rotary valve, my AR can reach 165km/h at sixth gear! With the standard cylinder, although it's max over sized, I only could reach 120km/h. But with the B3 cylinder : 1st gear reaches 70km/h in redline, 2nd-90km/h, 3rd-120km/h, 4th-140km/h, 5th-150km/h and the top gear 165km/h! But it was in 1992, I still have the bike, but the CDI and stator was burned out! It's very difficult to find the replacement in my country.

But truly this is very great bike...

16th Apr 2011, 14:49

Hi all...

Just got my AR125...

Everything is good except for my wheel... I want to paint my wheel... the colour is green... Can anyone help me getting the colour code please??




28th Sep 2011, 12:37

Hi, I just bought an AR125 1985, and I'm about to change the oil for the front suspension, and I don't know what oil should I put in there, and how much. So if someone has the manual and knows this, I would appreciate it very much.

16th Jul 2012, 14:22

Hi, I'm new here. I want get a wheel for an AR50, AR80, AR125, KH100 or Kawasaki GTO... so just email me at safuanshahbudin@yahoo.com

Please can everybody help me to find it :)

18th Jul 2012, 20:21

My mate had a tuned RD125LC (33bhp) and was riding hard and fast, reaching 100mph, when this AR125 just shot past him. Quite understandably, he was shocked. I had an AR125 in 1998, and although I had already got my full licence, my AR125 was restricted to 12bhp. I just wish I had kept it and had it derestricted. It would have been interesting.

25th Apr 2015, 10:22

I have over 10 AR125s... Fantastic little bikes.

30th May 2016, 10:27

What jets did you use in the carb? I have a AR-125 B2, it has a 24mm Mikuni carb.

I think the bike needs rejetting since the Micron exhaust system is causing a flatspot. Could you or anyone else help on jet sizes?

30th Sep 2016, 23:40

Keep the airbox and fit a 110 main jet.

25th Jan 2017, 16:09

Hi all, I'm hoping you can shed some light on a Kawasaki 125AR with a rotary disc engine. The one we have has no radiator so it's not water cooled... I cannot find anything on a 125AR rotary disc engine. Thanks.

11th May 2017, 16:54

The AR 125 was never made as an air cooled engine; you must have a replacement engine.

22nd Jul 2017, 15:44

Hi, this is more aimed at the guy who has various ARs in the Mansfield area.

You seem to have good knowledge on tuning these great little bikes and I hope you can help me.

I have a 1990 black and red model, which i keep in great condition. I've de-restricted the engine, cut the disk valve, emptied the exhaust of restrictions, tuned the barrel to your dimensions, skimmed the head and 26mm carb. Done various plug chops and settled on a 110 main jet and needle on the middle clip.

Now the bike has a fantastic power band after eight and a half thousand, in fifth it will top 80, but only if no head wind can I reach the powerband in sixth. Any thoughts would be greatly received on how to overcome this. I've just ordered a front sprocket with a tooth less to see if this helps any.

By the way the barrel is on standard bore!

Regards, Kevin.