27th Feb 2007, 09:02

When fitting after-market airfilters, exhausts, etc, always check with the manufacturer of these components what the recommended jet sizes are for the carburetor.

If not, a trial and error method might be the only way to cure the problem. Try increasing the size of the main jet.

Alternatively, seek the advice from a tuning expert such as Stan Stevenson or even your local motorcycle shop whom will probably have unimaginable levels of knowledge.

20th Mar 2007, 11:13

Have recently just got hold of a AR 125 b2 version, bought as a non runner. Carb cleaned and de varnished, new petrol and a spark plug, and she seems to be a good little runner. Waiting to take her out and giving her a good run, but this will have to wait for a tyre, battery and an MOT..

Mine is missing its fairing. Anybody that has one or knows where to get one, could you post details of how much and where to get?



3rd Apr 2007, 10:23

I bought my ar125 in 2002 and loved it immediately. She has subsequently fallen into disrepair as I have nowhere to keep it and it is kept in my garden. She runs great, but I passed my driving test 2 years ago, and had a family and couldn't afford the bike, but didn't have the heart to sell it. The chain is rusted and the brakes have siezed on. I live in Ayrshire in Scotland and I would appreciate if anyone could help out with either buying her or recommending somewhere to take her to get sorted. My number is 07756062928. Ask for Stephen.

21st Jun 2007, 16:58

I brought my AR 125 couple years ago, and love going out on it, except the flat-spot between 5 and 7 thousand revs. But when it warms up, it is OK.

I don't believe people saying theirs does a ton, as I have done some research, and the engine wouldn't be able to cope. Mine only does 75-80.

The only thing that has gone wrong is I had to put some new friction plates in it. but what a fantastic little bike...

24th Jun 2007, 13:07

Hi, I have got a lovely AR 125. It was a good runner, but I had to change the engine because it was throwing out engine oil from the back of the engine, right where it joins, so I got a bottom end off eBay, and changed all my top end from mine to the one I just bought. I put a new gasket kit on it, changed the engine oil, and it started first time. But as soon as you rev it, it dies so I put a K&N air filter on her, and it is still the same. If you put your hand on the carburetor, it revs fine and goes well.

Can anybody please help me? If you had the same problem and sorted it out, then please help me.

Many thanks


4th Jul 2007, 16:19

I bought a 1987 AR125 B4 about 6 months ago.

It had a chrome micron on when I bought it. I took it on the bypass with my brother on his Gpz500; he clocked me at 105 mph.

A week later it had to have the engine rebuilt; main bearings, con-rod, clutch, barrel, piston. Now it runs a lot better, but only does 80-85mph.

Old piston was 1.5ml oversize; new one is only 0.5ml oversize.

17th Mar 2008, 13:23

I have just brought an AR125 B7 off eBay 3 days ago. Quite basically, it was a crotch rocket all the way back from Mansfield to Belper.

Then, I took it out an hour later, only went a few miles and she just wouldn't get into her powerband. This was really annoying. I carried on at a steady 40mph, low revs, then there was an almighty bang and my back wheel locked up.

Anyway, after being picked up in a van by my local bike mechanic, the guy who sold it me botched the clutch and it had exploded. Someone must be looking out for me and my family, because if it had happened doing 85mph down the a38 I'd be dead, leaving my wife and baby twins behind.

They've fixed her and I'm just waiting for the gasket, then should have my dream bike back tomorrow. Get one, but be careful. They're very old and rare, and you will do well to find a decent one.

Oh yeah, they are a bit faster and more powerful than the Rd125 if fully derestricted. Happy thrashing.

31st Mar 2008, 11:53

I've also just bought a AR125 off eBay. I'm picking the bike up tomorrow; can't wait to get it and have a thrash! The bike's in Crawley and I'm riding it back to Derbyshire; I just hope it survives the journey!

12th May 2008, 18:24

I bought an AR125 (reg K771BJB) in April 1998 and had her for two years. My one was black and red. I bought it to replace the KH125 I had. I have fond memories of both bikes. If I still had the AR, it would still be on the road. It has been scrapped to my knowledge. Great little commuter.

18th Jun 2008, 15:05

Well I picked up an AR 125 1986. It starts nicely on the kick. I know nothing about bikes, and have just started as an apprentice mechanic, so it's all fun.

After reading about our mateys rear wheel locking up, that's well put me off thrashing it around haha. No laughing matter; I'm glad hes OK.

The bike sounds so good, and as soon as I have my protective gear and have got my CBT out the way, it's all good. I drive my car like an elderly lady, so on my motored stallion I will stay steady and sensible.

4th Jul 2008, 02:49

Just sorting out my son's AR125 and came across this site; some useful comments on AR125s, I hope to eermm test it for him soon; looks like fun!

Lads, don't worry about back wheel locking up, just enjoy yourself; other road users are more likely to kill you than your bike! So enjoy and keep your wits about you, and always have two fingers over the clutch lever (in case of a lock up); it's a two stroke thing you know?

6th Sep 2008, 17:29

Two days ago I bought an AR125 on a G-reg, it took me 200 miles before refusing to run. I spent this eve cleaning out the carb and sorting out a few bits where the previous teen aged owner had played without knowledge, (the whole front end was held together with cable ties) Now she's a dream and is a rapid wee thing. Very impressed.

25th Jan 2009, 14:01

Bought a 1990 AR125; fantastic bike, but blip the throttle and it revs its nuts off on its own. Have to turn it off and start it again. Any ideas? Thanx.

20th Apr 2009, 17:27


I have an AR125, which I'm fixing up, but I need a wiring diagram for it because I need it back on the road, and I can't afford the Haynes manual at the moment, so if anyone has a copy which they could send me of the wiring diagram, it would be great, my email is rizzlaman@hotmail.co.uk

But yeah, cracking little bike, mine does about 85/90 when it's working, but I have had it stripped down due to an accident and need a wiring diagram to sort it again! (bike only had cosmetic damage) haha.

Thank you.