Rushour wrote:
Mon Feb 24, 2020 4:52 pm
Royal Enfield models were NEVER fitted with valve stem seals until 2005 with the Electra X - and in my humble opinion - if an engine was designed without stem seals - then they should NEVER be retro fitted. If you have to fit them then you have a problem which should be addressed - not disguised.
That problem might just be excessive clearances between valve stem and guide, even on new, OE parts.
I have stripped a few Bullet engines which had very worn valves and guides, but had not been smoking or using oil. Usually, when a Bullet uses oil or smokes, it is down to piston / bore / rings or breather and / or lubrication system issues, rather than valves and guides. I never use valve guide seals in my classic Bullet engine builds.
My experience is the same as BW.

Very rarely is excessive oil in the combustion chamber the result of oil coming down between valve stem and guide. It is almost always 'blow by' past the piston. Too great a gap between piston and bore, too wide a piston ring gap, worn or very newly fitted rings.

As Rushour says the use of valve guide seals only hides a root cause - even if they have their use.

Of course a 'wet sumping' engine will be most affected by this problem.

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