AR125

[Top-shaggy]

Hi TSI
Had a look at the exhaust at the flange and the dimensions are 36 x 31mm - see pictures:

It is not oval, more circular with a reduced area at the top.
This can be seen in a previous picture of the head.





As for the clutch springs for the AR125 A1-A7/B2-B8; 82-91
(Kawasaki Part Nr 92081-1492)
These are the same part for the Kawasaki KX85, KX100, BN125 eliminator and may well fit others.

Looking at the EBC tables the CSK41 H/Duty Clutch Springs which correspond to the AR125 part number also seem to fit:

h***a CG125 M1/1/ES4-ES8 01-08
h***a XL185 SZ/SA 79-81
h***a CX500 CA/CB/Z/A/B/C/EC 79-85
h***a GL500 Silver Wing 82-84
h***a CB750 KZ 79-82
h***a CB750 FZ/FA/FB 78-82
h***a CB750 FC/F2C/FD/F2D 83-84



These EBC springs have worked ok for me with tuned AR engines.
However always keen to try different kit if you know of something better?

Cheers
Shaun

[TwoStroke Institute]

Just gets better and better.I'm happy to defer to your AR knowledge, os if the clutch slips badly a 5 or 6 spring KX85/100 clutch might swap or failing that h***a 4 heavy duty 'man clutch' springs.

I'm twisting my mates arm about the pipe

[ar125josh]

Did anything ever come from this ?
I just joined this forum after reading this thread.
I have a couple of ar125s and very interested in how this works.

[Top-shaggy]

Welcome to the forum ar125josh.

I think TSI is still looking at the most innovative method of porting and piston/rod/timing configuration. I'm sure he is on with this in between doing his other stuff. He was waiting for engines from Japan.

In the meantime I'm sorting out a couple more engines and looking at alternative porting/timing using Standard piston/rod configurations. I should have something to show on the forum over the next couple of weeks. Hopefully with some testing results / dyno runs

If you have any questions ask away - some great knowledgable people on here.

Which model AR's do you have?
Oh and pictures always go down well

[ar125josh]

thanks for replying. Sounds very interesting, Im new to two strokes and tuning in general but its something I am trying to learn about.

I have an old A1B engine that i'm in the process of trying to rebuild, I just have to order in all the seals and bearings.

I also have to learn how to modify the kickstart assembly to take the later model assembly.

I have an A-2 on the road but it has been fitted with a restricted engine but has the micron exhaust, I need to source some decals for it. This is the bike the A1B engine will be put in.

I also B-8 in the shed in bits that I will be trying to restore this summer if all goes well. I just need to get to know a couple of good machinists.
Will try to upload pictures at some point.

[Top-shaggy]

Good stuff ar125josh, You have noticed something that not many seem too - their are two types of AR engines (subtle but this can catch you out with some parts being different, some significantly so)

And having an A1B engine and A2 / B8 bikes you will have spotted it's not just restricted and full power models that are different.

AR engines from 1982 up to 84/85 approx have differences from the 1985-92 models. Not limited to barrel, head, oil pump, exhaust etc

Why don't you keep the original kick start mechanism? Not sure you will benefit from using the later type?

All the best
Shaun

[ar125josh]

I have been trying to get hold of the original kickstart shaft as mine has been sheared in half on the outside of the casing. The only reasonable alternative I have, if I can't find a replacement, Is to put in a later model shaft.

Any alternative ideas are greatly welcomed as i have been scratching my head on this one.

I have read alot about the differences although I am yet to find some side by side comparisons, will be something I look into when I am a bit more confident with the engines.

What are the main differences in the barrel? Is it just more aggressive porting to make the most of the timing ?
Thanks josh

[Top-shaggy]

Josh
To be fair I would have to do the same as you to spot the difference with the kick start shaft. As you have both engine types why not have a look and post some pictures to make it more fun.

Your right part numbers differ but part diagrams look the same:

First A2 1984 - this is the same as the A1/A1A/A1B (haven't bothered showing this but I have checked as have the parts diagrams for these too)



Second A2/A3/A4 diagram - you will note only real difference in the 1985 on A3-A4 is the kick start shaft and kick start boss (parts 13061-1101/1142 and parts 13066-1016/1057 respectively)



Therefore it looks like all you need is the later shaft and matching later boss and it should work fine?

Like I said the rest will be trial and error unless anyone can answer more specifically.

Barrels between A and B models ?
This puzzled me for ages. I have a number of barrels off both A (unrestricted) and B (restricted) models.

Lots of magazines and write ups talk about the barrel and head being totally different and this makes the full de-restriction 'very difficult and expensive'

Well the really boring answer is they are not that different! KHI charged £160 in 1984 and over £400 in the mid nineties for the unrestricted barrel. What an expensive red herring!

Differences:
Barrel - unrestricted exhaust port 2mm (at most) higher than restricted and width very slightly smaller. Transfers no difference.

Head 2cc less volume unrestricted head and slightly higher compression ratio 6.5-1 std to 7-1 unrestricted

Also the barrels suffer from massive tollerence differences from casting that means that some restricted barrels fair as good as restricted ones:









Therefore best bet - pick a good barrel whether restricted or not and ensure it flows well. Porting is not the easiest with the CI barrel but you really don't need to do much to make it better than KHI's unrestricted one.

Hope that's useful
Shaun

[Top-shaggy]

Doh - just read back and spotted errata - meant to say half way through some restricted barrels fair as well if not better than unrestricted ones due to casting tolerances (flaws)

[ar125josh]

Thanks for that, that was a wealth of knowledge and gives me a bit to think about.
I will attempt the kickstart as soon as a guy on ebay lets me know if he has one.
I am going to be attempting to rebuild the engines in the b8 and the alb engine in a few weeks, I have never done it before but am confident that I can do it. I just have to clear space in the shed.
So to get the best from a restricted barrel just polish off the imperfections?
Would it just be a case of getting the head skimmed to raise compression?
Sorry for all the questions but you have more info than google haha.

[Top-shaggy]

Firstly im no expert tuner like many others on here. Learnt most of this over time together with more than my fair share of trial and error with AR's

I'm assuming you want something that's more powerful, remains reliable and you don't want to spend a wad of cash?

Suggestion: choose a good barrel. By this I mean one in good condition and with smooth open flow on the ports as standard. Raise the exhaust port to 27mm from top of barrel (you can go to 25mm exhaust and from 42mm to 40.5mm from top of barrel for transfers but that makes engine a bit too highly strung on the road in my opinion)

Use a base gasket as a template and this shows metal you can remove, polish up the ports. Match to crankcase.

Raise Compression - if you skim 0.3mm from head to get 13-14cc chamber it should give just over 7-1 compression ratio, almost the same as the unrestricted head which should be fine for road use. You can go higher than this - but I'm staying on the safe side / keeping reliability.

Use unrestricted disk valve and better than STD exhaust, typically micron / allspeed / Nikkon etc (even better if you adjust timing cutting the disk and get exhaust made up to match but again more money so not included my thoughts on this here)

If your keeping cost down and sticking to the Vm24mm carb on the b8 model then with micron/allspeed the starting point for main jet will be 100-105 with airbox and 105-110 with Ramair type filter. Using Vm26mm gives a couple more HP (this should be STD on your A1B engine)

These very basic mods should give you approx 25-28bhp from a STD B model engine and no reliability problems which isn't bad when STD B is only 12bhp.

Don't worry about oil pump sending enough through, just set on highest setting and use top quality synthetic 2stroke oil (I use the same as in the KR). Never had a problem yet with this.

Similar CDI - STD is fine.

Hope this is helpful.
All the best with the engine rebuilds
Shaun

[ar125josh]

Once again thanks for replying. Even if if your not an expert tuner, you seem to have an enormous amount of info on the ar.
Your suggestions sound perfect, my main aim is reliability.

I am looking to invest in a porting kit so will have a play with an old barrel to get the hang of it.

I dont mind if I have to spend a little more for the right parts, as they are going to be ongoing projects and I am not planning on selling either.

I already have a micron exhaust with the vm24 jetted to 105 but I am just waiting on the vm26 to arrive after being serviced, this will then be fitted.

I will have to speak to a few of my mates about the head to see if i know anyone who can do it for me.
How do you upload pictures to the site ? I just tried posting one but no luck?
Also do you know anywhere to buy spares?
Thanks for all your help.
Josh[/img]

[ScottaKR]

How do you upload pictures to the site ? I just tried posting one but no luck?

Sadly, the days where you could just put a pic straight from your hard drive onto a site are long gone.
Have a read of this. viewtopic.php?t=6004

[ar125josh]

cheers will create a photobucket account
thanks josh

[Top-shaggy]

Also do you know anywhere to buy spares?

Hi Josh
Unfortunately I can't give you a straight answer on that one - over the last couple of years I've found that AR parts are gradually getting harder to find and in many cases NLA

Simple maintenance bits are easily obtained from Ebay, Kawasaki, Wemoto, Sutton etc. Harder to find bits try CMSNL see:
http://www.cmsnl.com/kawasaki-ar125_model12112/
They are expensive and dont always have stuff in even though its listed- however the site is good for looking at parts diagrams!

Over the last six months ive bought AR bits from USA, France, Germany, Singerpore, Finland, Sweden, Japan etc - maybe if you need something send me a PM and I will see what I can do