Reducing Spring Pressure on Detent Spring/Ball

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Postby scheckaet » 06:51 pm Dec 13 2006

I'd be just as interested in what adjusting the opening at a higher RPM would "feel" like - more BOOM maybe ?! And maybe with some needle changes just to see . . .

Let us know how it turned out :wink:
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Postby tim » 07:40 pm Dec 13 2006

:pop: some( braver than me ) body try it already and let us know
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Postby Jeb » 05:59 am Dec 14 2006

I'm gonna order a stock spring and one of the little 5/16" balls today ('got some other stuff to get anyway). I was gonna measure and then acquire springs with less/more tension. Why a ball? Who knows, maybe slightly lighter and/or heavier balls are easier/cheaper to acquire - should impact in a similar fashion, right?

BTW - Dumb question: I see the word "ball" used - singular - rather than "balls", yet there are 4 of the 5/16" balls in the detent assy. Is "detent ball" descriptive of the assembly?
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Postby IdahoCharley » 10:08 am Dec 14 2006

>|<>QBB<
Jeb wrote:>|<>QBB<
IdahoCharley wrote:
. . . FWIW - On the KTMs changes in the power valve spring preload can make a noticeable difference.


There's quite a bit of discussion around the power valve adjustability with them orange bikes . . . that's why the comment about it being tried before on a KDX caught my eye.

I'd be just as interested in what adjusting the opening at a higher RPM would "feel" like - more BOOM maybe ?! And maybe with some needle changes just to see . . .


My experience with KTM adjustability on their power valves is basically an extended bottom end rpm range (holding off the hit longer with heavier spring pressure on the power valve) can be an advantage in woods or technical riding with the 300 and 380 motors. When the bike comes on the pipe the feeling is of a LESS dramatic hit because you are already up - rpm wise. Very predicatable and relatively smooth transition.

Dropping the spring pressure with an too early PV opening gives a motor 'sound' of coming on the pipe sooner - but from a seat of the pants feeling the acceleration seems a little slower and then "it there" if that makes any sense. Less predictable is maybe a better way to indicate the on pipe hit - noticed that if the pipe was really hot this feeling was minimal. This may be an advantage in the sand or desert type open riding - I really don't know.

A number of people with KTMs have adjusted how far down their power valves drop (beyond the stock setting) and at least one has limited how far his has opened in an attempt to get a longer over-rev. I just use the stock set-up clearances myself.

Anyone ever play with the 'range' of KIPS activation? You do have to be aware that getting too crazy with this can cost you an engine!! From people on the KTM PV threads they are talking about 1mm change or less.
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Postby hart125 » 10:52 am Dec 14 2006

the 5/16 balls are the ones that drive the centrifugal system in the crankcase. I think the 3/16 ball is the one we are talking about on the left side of the power valves on the cyl.
I had more pressure on mine by removing one washer and I noticed that the transition was more abrupt.. you could tell when the power valve opened. Obviously it opened at a higher rpm also with more pressure but also it closed at a lower rpm. more pressure means the valve stays in its position longer. More pressure means less predictability IMHO
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Postby Jeb » 06:59 pm Dec 14 2006

>|<>QBB<
hart125 wrote:the 5/16 balls are the ones that drive the centrifugal system in the crankcase. I think the 3/16 ball is the one we are talking about on the left side of the power valves on the cyl.
I had more pressure on mine by removing one washer and I noticed that the transition was more abrupt.. you could tell when the power valve opened. Obviously it opened at a higher rpm also with more pressure but also it closed at a lower rpm. more pressure means the valve stays in its position longer. More pressure means less predictability IMHO


Thanks for the clarification about "balls" . . . I was indeed discussing the system in the crankcase.

I put a little more thought into it then ordered one of the springs (the one in the crankcase). I'll use it for reference for a stiffer spring then either find a "weaker" spring or snip a tad off the new stocker.

Looks a little involved to make the change but I should be able to handle doing it twice. . . actually that would be three times unless I stick with the last one :grin:

Plan: after each "setting" is in place (stock, then stiff spring, then weak spring) I'll remove the cover off the left side of the main shaft for observation purposes, use a tach, and monitor KIPS movement. If I can manage to get the tach within the "view" of a video, I'll record the results. Then seat of the pants.

It's conceivable it ends up being a bunch of work with unexciting results, then again . . .

I must be crazy :rolleyes:
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Postby stringburner » 07:08 pm Dec 14 2006

You'll poke your eye out. :mrgreen:
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Postby IdahoCharley » 07:20 pm Dec 14 2006

Our own in-house testing program!! How great is that? :supz:

I better shut-up - someone will give me an assignment - back to the pew for me. :grin:
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