Tuning the AR

[John]

Just thinking.

Since I got the AR it's always had funny problems with the power.

With the air filter cover on the bike pulls fine from stopped, but at around 7,000rpm the bike totally loses power, and won't go over that RPM. It happens in each gear.

With the air filter cover off the bike, it has little power before around 7,000rpm, but pulls well until about 750rpm into the red.

It's running a 100 jet, with a micron exhaust. I think it's the standard carb but am not 100%. I tried using a few smaller jets (97.5 and 95) but that didn't seem to make it better.

Is there anyone (G ) that would be willing to help me get it running propperly? I can't get it working right myself. :/

Also any way of getting more power out of it, without spending more than £50 or so?

Ta

[Smoto Bob]

i have had a few goes at tuning but never had any luck, if the manufacture has done it then you proberbly wont be able to make it any better for the MPG.

any way if the air box cover is off it would get MORE air so would need a larger jet.

could drill some holes in air box to get a bit more subtle adjustment.

but i would just ride it, until ya can get a bigger bike
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[John]

I have been for a few months, but I'd just love it to be that bit better.

It's also incredibly loud with the air filter cover off, and attracts a bit more attention then i'd like.

[Bendy]

Rebook your test for 2 weeks time and don't worry about the AR.

[cagiva gezzer]

If it runs better with the filter off, it is running rich, as removing the filter leans it out. Check youve got all the correct jets in there. Check the needle aswell.

You need some smaller jets as 5/2.5 decrease isnt much. Check the plug to see how rich its running.

£50? Cant do much with that - if its a steel bore you could give it a mild port job. You could skim the head to increase the comp and reduce the squish. It wont get to mito/rs power levels, but it might make it more fun.
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"because one stroke isnt enough and four strokes waste two"

[Kickstart]

Hi

Does sound like it is rich at the top end and lean further down the throttle openings. As such run a leaner main jet and lift the needle up a touch (try one notch).

However from memory you have fairly standard jetting, and I would expect it to need a richer main jet to go with the micron exhaust.

All the best

Keith
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[John]

What jet do ya think would work best?

Ta

[cagiva gezzer]

They cost less than a quid, buy some and try some.

If you are near a dyno , go there and explain that you dont want to spend much money, but you know the carb is messed up. Get a run and they will tell you what needs doing.

If you are near herts/ beds/ bucks i know a place which does runs for £10.
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"because one stroke isnt enough and four strokes waste two"

[John]

Where?

I'm in Reading.

[cagiva gezzer]

Aylesbury.

https://www.roadandtrack.co.uk/freestuff.html

I use him for my bike and hes a good bloke.

He should still do the runs for £10.
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"because one stroke isnt enough and four strokes waste two"

[stevo as b4]

Hi John, im guessing that your carb ahs probably been messed around with a some stage in the life of the bike, and in conjunction with the airbox lid. You would best be going back to totally std settings, on all the car jets,needles slides etc, for a restricted AR, and start again. The other thing to remember is that your AR is probably partially restricted now like many of them were. Its a very frustrating and expensive (if you buy all the new parts) 125 to fully de-restrict to 24bhp. Yours probably has a 24mm Mikuni carb, where as the full power ones (A version) have a 26mm. I dont know all the settings, but i know that the full power ones with the bigger carb run a 92.5 or 93 main jet as std. Your Micron pipe has removed the exhaust restriction, but the other restrictions on the AR are as follows:
1, Disc valve, the 12bhp one has a smaller cut away, for less inlet timing.
2, Exhaust restrictor
3, 24mm carb (12bhp) and 26mm carb (24bhp)
4, Cylinder porting is different, in terms of port sizes and duration.
5, Compression ratio is lower, dont know the exact figures, but its like about 0.2:1, so if its 7.8:1, it might be 8:1 on the full power version.
If i were you id get the A version disc valve brand new from kawasaki, and you can either try and find a 26mm AR carb in the breakers, (doubtful) or you can have your carb bored out to 26mm, and then fit the jets for the A version. that should balence the inlet and exhaust, so hopefully your bike will run better then. If you have problems with your AR's running id also fully service it, and check all the obvious things like Plug, coil, fuel tap and filter, and make sure theres no dirt in the tank. Your problems may well be down to a worn out or damaged carb, in which case a decent/new carb should sort it out. Full power AR's could reach 93mph, and most should do around 85ish if running ok.

[John]

Thanks.

Mine does an indcated 83 ish on the flat, maybe a little more if i duck down!

How much do you think the parts would cost? It's probably not worth spending any money on it TBH, but I dunno.

[stevo as b4]

Not worth spending money on it if its not running ok, before your start tuning. I doubt that a Disc valve will be too expensive, but if you go down the route of having your carb bored out, then you will probably want a new slide, needle, needle jet, main jet, pilot jet, and any gaskets, eg float chamber/ manifold etc. I dont know how much this would add up to? Keith probably knows more than anyone about what is worth doing or not on tuning 125's.

[John]

Sounds like a very dodgy slippery slope indeed.

I'll try to avoid it!

[Kickstart]

Hi

Probably not worth trying to bore the carb out. Too much else would need changing, at which point a new carb would probably be cheaper.

The AR was VERY difficult to derestrict, but it should manage better than 83mph indicated with a Micron.

That a full power AR uses a 100(ish) main jet on a 26mm carb tends to suggest that the jet in the 24mm carb should be a fair amount smaller.

All the best

Keith
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