ATAC system for ns125r-l

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi all,
anyone out there know anything about the honda ATAC system for the ns125(tc-01)?
is it a power valve, like on my aprilia rs?
can it be retro fitted, or does whole engine have to be replaced?
is it worth it?i have heard that engines with these things give out 30bhp, is that rite?
i beleive it was only fitted to the foreign versions of the ns, but if i could get my hands on either a complete engine or just the atac system, would it be an easy conversion?
cheers,
any advice/guidance welcomed!
GAZ

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Probably possible to retro fit, but not an easy bolt on part.

It is essentially a chamber on the side of the barrel that is open at low revs and closed at high revs. It is open and closed by a linkage operate by centrefugal force, which lives under the clutch cover. As such you would need the ATAC valve itself (think the barrel plug could just be taken out), linkage, clutch cover, rubber linkage cover, and the bits to operate it from under the cover.

A complete engine would be far easier (and probably cheaper these days).

No way would it make over 30hp. Honda claimed 24hp (26hp for the NS125RII), so reality would be somewhere short of that.

All the best

Keith
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stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

thanks, keith.
figured you would know about this!
seen an engine advertised for sale with this system on it,
& was wondering if it was worth going for?
but if it means changing engines, mite give it a miss!
thanks,
GAZ

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Think I know the engine you mean (and I just picked up an NS125F I have been given today).

Don't think it is that hard to change the engine on an NS, but for top end power the big problem is the exhaust. In theory you could rig the NS engine up to have the chamber in the close / full power position all the time and just say goodbye to some bottom end power.

All the best

Keith
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stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

mmm,
will think about it first!
at present i have the exhaust de-restricted, dunno wot top speed is, only ever taken it to 70!
but dont think it will go much faster, but it corners terribly at that speed in my opinion!
come to think about it, it doesnt corner well at any speed! & giving it more power would just highlight that!
but my problem is acceleration, so if the atac wont help or is not viable due to price/effort, i guess i should look at sprockets/gearing?
any idea what is standard set up?
cheers,
GAZ

TeddyCanuck · Nova Slayer Joined: 08 Sep 2007 Karma :

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

TeddyCanuck · Nova Slayer Joined: 08 Sep 2007 Karma :

bladerunner · World Chat Champion Joined: 09 Sep 2006 Karma :

a PS is a metric HP..

PS x .9863 = HP

So 200ps = 200 x .9863 = 197.26 HP

And as for the NS. Try rigging it for top end. It will help acceleration no end. With most of the 125 2 strokes it will be a little peaky for heavy town use but most of the time the trade off is more than worth it when it comes to hills,head wind,overtaking etc it will be far more user friendly
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

It is a chamber that is open at low revs for low power and closed off at high revs. Idea is that you bodge the chamber totally closed to get the full power effect.

All the best

Keith
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stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

You can do it yourself, but realistically not sure it gives you much extra at high revs to compensate for the loss at low revs.

The plug on the r/h side of the barrel is where the mechanism goes to open and close the chamber. It is that area that you would need to bodge.

All the best

Keith
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stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi,
thanks for the tips,
so if i open up plug & somehow manage to keep thing closed,
i should notice a difference?
might give it a go, if i break it it gives me an escuse to buy another engine,
a full power,atac one!
cheers,
GAZ

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Honestly don't know as nobody generally bothered. Decent exhaust, dump the airbox and an extension from the car to a single filter was about all most people bothered to do.

All the best

Keith
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stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi,
probably best leaving it as it is then?
will definately think about changing sprocket sizes as they are due to be replaced anyway.
anyone know the size/pitch of chain?
bike didnt cost much anyhow.
top speed i can live with, just wouldnt mind a little more acceleration!
guess i got too used to the rs!
time to get that back on the road.
mite just get rid of ns once i replace sprockets & exhaust.
speaking of exhausts,
mines is looking well tatty & looks like it has been welded in past.
so anyone any ideas where i can get a replacement?
will probably need the full system as i dont think i will get the can off due to rust!
cheers,
GAZ

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

I personally wouldn't bother, although if feeling rich I might be tempted to source a full power engine and do the job properly.

Standard I think is a 520 chain with 106 links on 13/33 gearing.

Micron used to do half decent exhausts but don't know if they still do.

All the best

Keith
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stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

HI,
will try & replace then soon,
mite as well try different size sprockets.
tried micron for replacement exhaust but no joy.
will keep looking on ebay tho!
think i might concentate on the rs!
seeing as its easier to get parts for.
that engines still there tho! (tempted)
cheers,
GAZ

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Well I just picked up most of an NS125R for spares. Decent exhaust and an engine with only 5k on it. Even the tyres are recent, battery almost new and the ignition switch isn't worn out.

All the best

Keith
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st3v3 · Super Spammer Joined: 16 Oct 2006 Karma :

I know this is a lil dated, but as I understand the power-valve on the NS is useless, the engine wouldn't for some reason handle the stress, I wanted one but was told I couldn't fit one on, Keith..... you got any advice? Karma

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Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

The power valve was not a great design. Think the basic problem was designing something that didn't infringe anyone elses patents!

Fitting the powervalve to a UK spec NS would be difficult and expensive. Loads of bits required.

All the best

Keith
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