17th Mar 2005, 07:48

I also have an AR125, however I have not found any of the problems the original poster mentioned. I have not stripped the carb in 6 months, and even with the stock exhaust, my little beauty runs fine.

Road holding is impressive in the dry, although in the wet it leaves a little to be desired. The main issue I have is the weight of the back end; when riding into the wind, it has a tendency to weave.

All in all, an amazing little bike, and I might add that I have left many newer 125's in my smoke.

26th May 2005, 14:50

I recently had an AR125-B6 and it flew along nicely. Only slight problem was a flat spot between 5 & 7000rpm, but after this, acceleration was excellent (for a 125 with a Micron exhaust). Think I managed about 77mph (scary on a bike of this size).

Good value for money.

20th Jun 2005, 03:48

Fitting a micron pipe, with no carburettor alteration, will cause a flat spot at approximately 6000 RPM. The machine will still pull reasonably well low down, but before the power band, there will no throttle response for a few seconds, then the machine will go mental. This is the problem I had with my AR125, until I re-jetted the carb.

I could not believe the difference. I was grinning from ear to ear.

This can be overcome by fitting a different main jet, which will give more low end power, especially around the mid range. Also that notorious flat spot will be history and the exhaust note will be throatier.

22nd Apr 2006, 17:12

My AR 125 has had a few problems, it's been rebuilt 3 times! Fitted a Ginelli race exhaust and a race jet in the carb, and it goes off the clocks! A rapid little 125.

26th Apr 2006, 15:01

With regard to the comment above, an AR125 doing approximately a ton (100mph), the engine must be producing roughly 30 bhp. With reference to a bit of research I did some time ago, the AR engine can`t cope with power above 25bhp, because anything higher than that, the engine will blow.

This probably explains why you have had to rebuild yours on three occasions.

A good 125 for tuning is a MK2 RD125LC. These little beasts can easily achieve the magical ton with the correct tuning, and yet retain its reliability.

My AR, I tuned to about 20bhp and it was fine and did just over eighty mph maximum.

The AR 125 is excellent for reliability if left standard to the manufacturer's specification. The only item that may raise concern, is a noticeably loud rattle at idle. No need to worry, every AR125 I have dealt with, has had this. This is play in the clutch drum and doesn`t cause any problems.

With regards to horse power and speed, the two are related.

As a general rule of thumb, to double your bike's maximum speed, you have to quadruple the engine power because wind resistance is a large problem with increased velocity.

29th Apr 2006, 02:42

My first road bike back in 1990 was a little black and red AR125B7 I can still remember it being delivered!

It cost next to nothing to run, and only needed the engine stripping once in 30,000 miles, and that was to replace the main bearing, which had become noisy.

I only ever ran it on good quality 2 stroke (mostly putoline) and she returned around 75 to the gallon if commuting. I will always have fond memories of the bike, because it was very reliable and great fun to own. Everything remained standard, as I liked the midrange pull it had with the standard exhaust.

My friend had one too with a Micron exhaust and Dynojet kit. It was no faster, and mine would leave it for dead due to mine keeping its midrange.

A fantastic bike that costs nothing to run and will go on forever (unlike the ns125r that I replaced it with... big mistake!)

13th Sep 2006, 11:01

I have just got a 125cc AR sport 1990 model. It's a great runner, starts first time.

The only problem I have had with it was the back tire was leaking air, but other than that, everything is fine.

The top speed of my AR 125cc is 90mph. You probably won't believe that, but it's true. You have to see it with your own eyes, it's nippy little thing.

13th Oct 2006, 02:36

I just got such a bike from someone who had it behind the barn since 1992. I am looking for any type of documentation available. Hayne's manual don't have the book anymore.

I need to know:

What to feed that bike, octane, oil mix?

Gear oil type?

Any web link to mechanical information?

14th Oct 2006, 15:11

With regards to the above comment, I have a Haynes manual, in good condition for an AR125.

You can run the bike on basic unleaded (95 octane) that is most commonly available as the engine is designed to run on 91 octane. There are no advantages or disadvantages of using higher octane fuels, apart from the extra cost.

You can use 10W/40 engine oil in the gearbox, preferably semi synthetic and be sure to change it at the prescribed intervals to ensure smooth clutch action and gear change.

Engine oil should be a good quality two-stroke engine oil, again preferably semi synthetic at least. Avoid using cheap mineral oil, as this will cause reliability problems and create masses of exhaust smoke. The more synthetic the oil, the better it will burn thus ensuring better reliability and much less smoke. Semi synthetic is adequate for the Kawasaki AR125.

31st Oct 2006, 05:38


My name is Fredrik, from Finland, and I have built a crosscart with an Kawasaki ar 125 engine. The toy is almost finished, but I have a problem. the engine does not rev up! We guess it is something with the ignition, but are not sure. So PLEEEEEEASE if someone has a wiring diagram of the bike, will you please send me?! My email address is: crozz_freddi@hotmail.com

It would be of such unimaginable help, I havenĀ“t found it anywhere on the net!

11th Dec 2006, 15:00

I recently brought a 1990 ar125, it was a non-runner when I got it, but a new generator and flywheel soon had the little bike running again.

Soon after this, I took it for an MOT, it passed first time and was a cracking bike for about a week, then it blew a hole in the exhaust. I repaired this with exhaust paste, but this was short lived (about two days) then I tried a bandage, but this also blew after about two days, even chemical metal failed to do the job, but a welded plate and the exhaust is fine.

Now the bike lacks performance, it has no pull and has trouble running, idle is non-existent and the revs stay high when you blip the throttle. The bike doesn't want to know 6th gear and 5th is no fun either. I don't know what to do, so if any one has any ideas or has had the same problem, can you please leave a comment (or answer) on this website, or my e-mail at evilmidjit@yahoo.co.uk

Please help, pleeeease!

21st Feb 2007, 12:47

I have recently got a 1983 AR125 back on the road. The bike had been stood for 7 years and all it took for an MOT was basic work and a new disc valve. However, I've had to fit a K & N style filter due to it being cheaper than replacing a broken filter box. This has caused a problem with the carb set up. Can someone please give me some pointers such as jet sizes etc.