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Join Date: Jul
Location: So. Calif.
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Quote:
FliegerOriginally Posted by
Go Viton.I would rather pay a little more in the increased oil consumption and put up with some smoke than over heat a valve due to lack of oil. The head could fall off and rattle around in the combustion chamber, messing the whole cylinder up.If it leaks a little oil, what's the big deal? You will eventually flush the oil by adding a little at a time and you will be aware that your top-end is getting lubrication.
A little oil is fine. Any more and the heat (on the exhaust side) oxidizes the oil until you have a fur ball-size chunk of carbon in the exhaust port and on the valve head. More than this and the oil starts to migrate into the combustion chamber. However, you'll also notice the smoke from the tail pipe at this point.Either one of the above scenarios isn't preferable. We seldom have a choice and instead should deal with the existing condition. Lube to the top end is good, but oil leakage into the chambers via the valve guides is hardly a consistent method of distribution.Sherwood
Had in mind to tart up one of the XS1 heads I have lying around. Picked up a set of Viton® valve seals for it. Reputed to outperform the originals. Got sidetracked and they sat on the shelf a while.
These are available with or without a metal jacket.
I am now sorting out a head for an extra SR500 motor. To go in the sidecar. Emphasis torque. Early 78/79 crankshaft and cases (larger crankshaft counter-weights), specially ground cam, larger valves, lighter valve springs, thinner spring plates, modified ports, carillo rod, O/S piston, modified/heavier flywheel etc. The XS650 and the SR500 use the same valve seals. No point leaving these sitting. Collecting dust.
Wonder how they will work.
Viton®. Flouroelastomer (FKM/FPM). A fluorocarbon based synthetic rubber. These contain 5% Teflon for reduced friction and wear.
Advantages:
have a wide and stable Temperature Range -30°C to 225°C (-10°F to 400°F)
resist hydrocarbons (fuel/oil)
have excellent dynamic properties (coeff. of friction,
tensile strength, range of hardness and resistance to compression set etc) &#; good abrasion resistance
have low permeation rates (esp. relevant to alcohols, hydrocarbons and biofuels (biodiesel, ethanol)
be solvent, mineral acid resistant (don&#;t really like ketones, amines or low mw esters,)
show low compression set
Disadvantages:
The fluorocarbon rubbers are used for special applications that require good heat, oxygen or corrosion resistance and hot solvent and oil resistance.
If you are looking for more details, kindly visit viton valve stem seal.
Applications:
Note: Viton® is a registered trademark of DuPont. It is often misleadingly used as a generic term for FKM/FPM flouroelastomers.
For the chemically-minded FKM&#;s thermal and fluid resistance are a function of 3 main features
Extremely strong bonding between the polymer backbone carbon atoms and the pendant (attached) fluorine atoms
High ratio of fluorine to hydrogen atoms bonding to the carbons (high fluorination levels tend to create stable compounds)
Full saturation of the carbon backbone .. no covalent double bonds between carbons minimizes attackable sites
Structures of fluorocarbon rubbers
Monomers Structural unit Type designation Commercial types VF 2 + HFPFKM
Viton A, AHV, A-35, E-60,FKM
Tecnoflon SL, SH VF 2 + HFP + TFEFKM
Viton B, B-50 VF 2 + HPFP + TFEFKM
Tecnoflon T VF 2 + TFCIECFM
KEL-F , , SKF-32 PFMVE + TFE + XFKM
ECD 006
An example of a structure of the fluorocarbon rubbers, VF2 / HPTFP / TFE -copolymer.
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