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Reverse Shelfectomy

 

Let's say a "friend" has a de-baffled stock exhaust and performed the shelfectomy before he read Jon's notes on how useless it is. The mid-range isn't great now but the bike warms up nicely and is actually a bit smoother. This friend has shims lying around to slide on the needles.?


Without an expensive tuning, needle adjustment, and jet adjustment. Could the shims theoretically bump up the lean-ness in the mid-range and return the powerband to close-to-stock? Obviously the shelfectomy cannot be reversed.
 

Edward, would your "friend" like to purchase a used stock unaltered airbox?? My "friend" happened to buy a spare one and never used it for anything...

Ruari McLennan
Victoria BC

On Fri, Aug 12, 2016 at 6:44 AM, edward_watts@... [W650riders] <W650riders@...> wrote:
?

Let's say a "friend" has a de-baffled stock exhaust and performed the shelfectomy before he read Jon's notes on how useless it is. The mid-range isn't great now but the bike warms up nicely and is actually a bit smoother. This friend has shims lying around to slide on the needles.?


Without an expensive tuning, needle adjustment, and jet adjustment. Could the shims theoretically bump up the lean-ness in the mid-range and return the powerband to close-to-stock? Obviously the shelfectomy cannot be reversed.
 

Thanks Ruari would help, but have you had any experience shipping to Toronto, ON. I can't imagine it is cheap.
 

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Well, I'd ask $65 CDN plus shipping and I'll check what shipping is.?

Rusri


On Aug 12, 2016, at 9:26 AM, edward_watts@... [W650riders] <W650riders@...> wrote:

?

Thanks Ruari would help, but have you had any experience shipping to Toronto, ON. I can't imagine it is cheap.
 

The issue is not really with the shelf removal, which does little to enhance or hinder, but with the shape of the stock needles.

I believe Kawasaki recognised how important the signature sound of a 360 degree parallel twin was, especially as the bikes the W seeks to honour had much less silencing, so they allowed the exhaust note to be clearly audible.

The only problem was, as revs rose, the noise levels started to creep above any noise regulations so they had a dilemma...How to keep the crisp mid range sound, but muffle the ( rarely used by their target owners)?top end.

The answer was to force the bike's fuel mixture to get progressively more rich as revs increased. A rich mixture sounds duller and more muffled than a correct mixture and by effectively removing the high frequency component of the sound, they could stay under the noise regulations threshold.

To make it go rich they installed over-large main jets, and to make the mixture correct everywhere BUT the rev band above 6000rpm ( where the needles are fully out of the main jets) ?they created extra fat needles with almost no taper...They look more like roofing nails than carburetor needles!.?

Basically, the stock bike has perfect mixture right up until it hits 6000 rpm where the full enrichening effect of the over-size main jets is felt as the needles come fully clear.

The de-baffling allows a bit more exhaust to flow which makes the entire rev range lean while partially correcting the over-rich top end.?

Because the needles have very little taper, the shims do very little...far less than they would on a conventional tapered needle.

The answer to restoring the mid range is to purchase a Dyno-jet (or similar) Jet/needle set and fit the needles. these needles are adjustable, but more importantly, have a normal taper, giving the mid-range the correct fuel while the sharper, thinner tips still allow the top end to work.

Fitting needles is easy, requiring the removal of the four top screws holding each chromed carb 'top' down, lifting out the diaphragm and slide assembly, and simply pulling out the needle retaining clip.
it is A LOT less hassle than anything to do with the airbox!

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