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3/12/2014
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Edited Date/Time
8/7/2014 7:23am
A customer of mine at our local shop brought in a cylinder from and old CR80 that he is fixing up, it doesn't look like a stock Honda cylinder and it has ATAC stamped on the side of it, I measured it and its definitely a big bore. Anybody know who makes these and how to get a piston for it?
I believe the 84 through 89 CR80s had the ATAC cylinders.
Are you familiar with the Honda ATAC system?
84 and 85 had the butterfly valve version and through 89 had the ATAC label on the cylinder.
Check a Honda fiche if you want to verify.
Don't know why they kept the label after they eliminated the valve unless it was some sort of static resonance chamber. I'm not familiar with the post-85 ATAC.
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I seem to remember people saying they couldn't tell a difference with them removed and most aftermarket pipes did away with them since they spent their lives at WOT anyway.
I'd guess it was more of a gimmick to look like a replica of the big bikes but provided very little in the way of performance.
I wasn't sure if the later CR80s had the ATAC but saw the labels on the fiche, too. Maybe it's a mistake on Honda's part on the fiche?
Like I said, I wasn't familiar with them so I had to defer to the fiche, assuming it was a static system (sort of like the decompression eyebrows on CR500 ports).
If I had to guess, I'd go with the fiche being wrong.
Anyway, to the OP - if you have one with the exhaust manifold with the butterfly valve, it's an 84 or 85.
See, us old guys are good for something... when we can remember it!
Eric Gorr may be a good source for big-bore info if you need it.
And no this is the first I've ever heard of the ATAC system
Thanks for the imput guys
Cheers
Sounds like that's what you've got on your hands.
And Ace is right - that's why I was wondering if they had gone to something internal but the fiche didn't show any system parts after 85.
The CR125 went through different iterations of exhaust valves as did the CR250. Took them a while to figure out what worked best and was mechanically simple(r).
They did away with it on the 80/85 and never put one on the CR500.
I remember the original YPVS was simply a rotating drum that varied the exhaust port height.
I remember you could buy spacers for one of the systems that increased the chamber volume and added bottom end (according to those that used it).
Seems like the move was to a combination of variable port timing and volume which, depending on the design and what you define as a chamber, could be be classified as one.
Admittedly I haven't kept up with all the different manufacturers designs over the years.
However, it seems the move recently has been to put resonance chambers on thumper exhausts.
I do remember the YEIS system (that was called a "boost bottle" by most people) on the '81 YZ250 (and others) was able to make it run smoother and crisper by helping to smooth intake tract pulses.
Which gives me an idea for another thread in this forum...
BITD I had an 89 KDX200 and I seem to remember we made some spacers for it and another bike out of sheets of varying high-density plastic (PVC?) in an effort to gain bottom end.
We had used the same stuff to make reed spacers on old YZs (air-cooled) and such to experiment in the late '70s and early '80s.
Ah, the good old days of black magic along with youthful ignorance and curiosity!
THE FIRST ATAC HONDA USED ON THE 80 WAS 1984 THE LAST YEAR HONDA USED THE ATAC ON THE THERE 80'S WAS 1985. THE 1984 HAD A SQUARE HEAD.
86 through 2002 didn't have the ATAC system Just 1984 ,and 85. They only made 14 HP. In 1986 they done away with the ATAC system, and changed the porting bumping up the HP to 18 making them the most powerful 80 in the line up until Suzuki out did Honda in 89 I believe. Be4 that The KX 80 was king in 1984
I had the 1985 and the 1986 models as a kid.
The 1985 had a super dumbed down ATAC and the 1986 had nothing of the sort.
My guess is that Honda decided it was a bunch of extra cost for not much (if any) gain in performance.
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