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RE: [ST] Re: Any High Mileage Sprints Out There?



I am a engine reconditioner by trade and I will try to throw some light on
the situation

HMMMM What do you mean by tight


Tappet clearance or valve guide clearance
The tappet clearance is as David described but as for oil consumptiom this
is not related with burnt out valves or too little clearance unless the
engine is riden in this situation for a long period of time which would
likely do damage to the rings and other engine components and also the vave
stem seals as the valves are running a lot hotter which cooks the valve stem
seals ( but us sprint riders would not do this we love our bike too
much ).Running with too little clearance will cause the valves too burn out
by not letting the valve seat correctly with the valve seat in the head
which affects the cooling of the valve as this is importantant as the valves
rely on this contact to transfer the heat they generate to the head which in
turn is cooled by the coolant ( or air in aircooled engines).The other
problem with low tappet clearance is the exhaust gas escapes past the seat
and valve on combustion and usually picks the weakest point of the sealing
surface and causes a major temperature increase which causes the burnt out
valve situation by actualy melting the metal in the valve or the seat and
blowing a track out with the combustion pressure.

As for valve guides this is too little clearance will make the guides pickup
or seize causing damage to the bore of the valve guide letting oil down
between the valve stem and the guide. Same goes for too much clearance or
valve guide and valve stem wear and also fauly valve stem seals this will
cause oil consumption.

As for Petes problem I think there is a problem with the bottem end or the
valve guides as well as the valve problem . Pete find out exactly what the
valve guide clearance is as most mechanics do not check this from my
experience over here in aussie land unless they send the head to a engine
shop. Also Get them too check the valve stem seals before they remove them.
If all is ok i would be hitting them for the rings as well ( make sure they
measure the cyl bores and piston clearance as well).Also the honing of the
bore especially on late high performance engines is critical.If they use one
of those echeapo hones you are wasting your time and will do more damage
then when you started.If they do not have a correct hone take the cylinders
to a good reputable engine shop and get them to hone the cylinders it will
be worth the little cost to do this as modern rings rely on a good hone
finish.

I am alarmed about the valve seat problem and hope that it is not going to
be a major problem with all sprint engines when they get this milage on
them.

I have a few questions

What fuel have you been using
Are you sure the tappets where correctly adjusted (I would ask for a spec
sheet if i had someone adjust them for me )
Ask if the valves and guides they are replacing are the same as when the
engine was manufactured or have they been modified since.
what oil have you been using.
Has the engine ever been hot.
also that the tuning has been correct as a lean condition will cause valve
problems.
How many other sprints have had valve problems when they get around this
mileage on them.

If i can be of any other help please contact me

Cheers

and good and safe riding

Rob

Brisbane australia
01 Sprint Red the fastest ones




- -----Original Message-----
From: owner-st@xxxxxxxxxx [mailto:owner-st@xxxxxxxxxx]On Behalf Of Gaske
David G DLVA
Sent: Wednesday, December 05, 2001 4:23 AM
To: 'ST@xxxxxxxxxxxxxx'
Subject: RE: [ST] Re: Any High Mileage Sprints Out There?


I'm going to stick my foot into this one and hope it doesn't get bitten off.
The valves them selves aren't measured.  The distance between the Cam lobe
and the shim is measured.  The shim sits in a bucket which pushes on the
skinny end of the valve.  If it clearance gets to tight then I assume and
this is where I am guessing, is that the scavenging effect the exhaust pulls
oil up into the cylinder and thusly out the pipe.  That last part is a
educated guess so take as that and don't quote me.  Unless of course I am
right!!!

David "Lost Dawg" Gaske
'00 Sprint RS (yellow)
Fredericksburg, Va.  USA



- -----Original Message-----
From: Paul Reyes [mailto:plreng23@xxxxxxxxx]
Sent: Tuesday, December 04, 2001 1:12 PM
To: ST@xxxxxxxxxxxxxx
Subject: Re: [ST] Re: Any High Mileage Sprints Out There?


I would assume like an auto it is done at the valve seat. The other
question is are you talking about valve lash or valve seat? I am with
you on the other question, why do tight exhaust valves consume oil?

Paul Reyes
99 ST Blk



> OK, I'd like to show my ignorance and ask: why do tight exhaust valves
make
> oil consumption go up?  An even more basic question, where on the valves
are
> the clearances actually measured?  You can tell I didn't do my own 12,000
> mile service, can't you!
>
> Neil

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