| Need piston to cylinder clearance measurement [message #517243] |
Thu, 17 November 2005 06:37 |
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I have a 01 ktm 300exc. I am wondering if anyone knows what the piston
to cylinder measurement is supposed to be for a stock piston and
cylinder. This seems to be a very difficult question for my local ktm
dealer, and I am trying to get rid of some piston slap..
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| Re: Need piston to cylinder clearance measurement [message #517248 ] |
Thu, 17 November 2005 12:34 |
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If the piston is slapping ( I'm guessing you hear it) , punch it out,
new piston & rings, have a nice day. Don't know if you are 2 or 4
stroke but the clearance is usually .002 to.003". The guy doing the
bore job should be knowledgeable enough to set you straight on the
exact numbers or the info may be included with the new piston. If not ,
buy a book, or better yet, find a dealer with a brain. I don't see any
reason why they can't help you out here other than just plain
stupidity. Good luck.
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| Re: Need piston to cylinder clearance measurement [message #517254 ] |
Thu, 17 November 2005 14:18 |
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"pater" <weavcowinory [at] aol.com> wrote in message
news:1132227250.753102.113540 [at] g14g2000cwa.googlegroups.com...
> If the piston is slapping ( I'm guessing you hear it) , punch it out,
> new piston & rings, have a nice day. Don't know if you are 2 or 4
> stroke but the clearance is usually .002 to.003". The guy doing the
> bore job should be knowledgeable enough to set you straight on the
> exact numbers or the info may be included with the new piston. If not ,
> buy a book, or better yet, find a dealer with a brain. I don't see any
> reason why they can't help you out here other than just plain
> stupidity. Good luck.
>
or a good machine shop (like an auto parts store that does machining in the
back). Was doing a rebuild on a small car engine & the machinist simply
measured the amount of irregularity in the cylinder walls (with his
fingertips!), measured the new pistons, and machined the bores to fit -- no
going by pre-determined book values but a custom fit.
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| Re: Need piston to cylinder clearance measurement [message #517264 ] |
Fri, 18 November 2005 23:07 |
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pater wrote:
> If the piston is slapping ( I'm guessing you hear it) , punch it out,
> new piston & rings, have a nice day.
Does KTM use sleeved or plated cylinders ?
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| Re: Re: Need piston to cylinder clearance measurement [message #517290 ] |
Sun, 20 November 2005 08:36 |
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"" wrote:
> pater wrote:
> > If the piston is slapping ( I'm guessing you hear it) ,
> punch it out,
> > new piston & rings, have a nice day.
>
> Does KTM use sleeved or plated cylinders ?
I am trying to avoid a bore job the cylinders are nikasil plated and
the cylinder is fine, i was just wondering what the clearance is. Yes
it is a 2stroke. just thought someone might know. It is easy enough to
dump jug off at machine shop and bore but why- when cylinder is fine?
Because you don’t!
--
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| Re: Re: Need piston to cylinder clearance measurement [message #517294 ] |
Sun, 20 November 2005 16:16 |
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"mcallan" wrote in message
:
: I am trying to avoid a bore job the cylinders are nikasil plated and
: the cylinder is fine, i was just wondering what the clearance is. Yes
: it is a 2stroke. just thought someone might know. It is easy enough to
: dump jug off at machine shop and bore but why- when cylinder is fine?
: Because you don't!
:
Boy have things changed! I had a motocross team in the '70's, you never
bored them newfangled nikasil jugs, but rather changed the piston and rings
every 4th race, the jug every 8th, and the crank every 16th. At the end
of the year you tossed the clapped out racer for the next year's model.
Nowadays, it seems everybody has a back yard alum-nikasil blaster -
at least on the internet.
This is the way it was: your results may vary. For a water cooled
2-stroke, your piston/cyl difference starts at .0025". If under hard
accelleration you develop cylinder scoring, it's because the piston
expands faster than the jug, so go to .0030". If there's chipping on
the bottom of the skirt, go to .0020" and watch for scoring. Pop
off the intake and take a peek.
BTW, the only piston slap I ever saw on any of the 6 bikes we
campaigned (Honda, Suzuki, Yamaha) turned out to be sprocket
and/or chain related and had nothing to do with the engines.
If you google KTM, nikasil and boring, you get a hatfull of companies
that do it - a telephone or email hookup would seem to be the
surest way to get a specific number set for your 2-wheeler.
Like others have said, toss your local guy.
Best o' luck
Dave
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| Re: Need piston to cylinder clearance measurement [message #527359 ] |
Mon, 21 November 2005 21:52 |
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mcallan wrote:
> "" wrote:
> > pater wrote:
> > > If the piston is slapping ( I'm guessing you hear it) ,
> > punch it out,
> > > new piston & rings, have a nice day.
> >
> > Does KTM use sleeved or plated cylinders ?
>
> I am trying to avoid a bore job the cylinders are nikasil plated and
> the cylinder is fine, i was just wondering what the clearance is. Yes
> it is a 2stroke. just thought someone might know. It is easy enough to
> dump jug off at machine shop and bore but why- when cylinder is fine?
> Because you don't!
I'd be surprised if the Nikasil was badly worn. My only experience has
been 4 strokes, but I'd probably just measure the piston and compare
that to spec. I'd expect most of the wear to show up on the piston and
not on the barrel.
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| Re: Need piston to cylinder clearance measurement [message #527368 ] |
Wed, 23 November 2005 01:09 |
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Hello, Rob Kleinschmidt!
This raises something that I've wondered about: It doesn't seem
likely that you'd hone a nikasil plated bore. How do you then
get the rings to seat? Are rings for nikasil plated bore a
different composition than for iron or iron-sleeved cylinders?
You wrote:
>
> mcallan wrote:
> > "" wrote:
> > > pater wrote:
> > > > If the piston is slapping ( I'm guessing you hear it) ,
> > > punch it out,
> > > > new piston & rings, have a nice day.
> > >
> > > Does KTM use sleeved or plated cylinders ?
> >
> > I am trying to avoid a bore job the cylinders are nikasil
plated and
> > the cylinder is fine, i was just wondering what the clearance
is. Yes
> > it is a 2stroke. just thought someone might know. It is easy
enough to
> > dump jug off at machine shop and bore but why- when cylinder
is fine?
> > Because you don't!
>
> I'd be surprised if the Nikasil was badly worn. My only
experience has
> been 4 strokes, but I'd probably just measure the piston and
compare
> that to spec. I'd expect most of the wear to show up on the
piston and
> not on the barrel.
>
--
Posted via Yanoff
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| Re: Need piston to cylinder clearance measurement [message #527369 ] |
Wed, 23 November 2005 04:06 |
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Wreckless Eric wrote:
> Hello, Rob Kleinschmidt!
>
> This raises something that I've wondered about: It doesn't seem
> likely that you'd hone a nikasil plated bore. How do you then
> get the rings to seat? Are rings for nikasil plated bore a
> different composition than for iron or iron-sleeved cylinders?
> You wrote:
> > I'd be surprised if the Nikasil was badly worn. My only
> experience has
> > been 4 strokes, but I'd probably just measure the piston and
> compare
> > that to spec. I'd expect most of the wear to show up on the
> piston and
> > not on the barrel.
Re nikasil cylinders
General advice I've seen seems to be that honing by the owner
doesn't help and may do harm. I believe they're factory honed. The
suggestion was to clean with soapy water and heavy scotch pads
when the rings were changed.
Four stroke nikasil cylinders can hit 6 digit mileage no problem.
Unsure about two stroke longevity.
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