Valve Guide Seals – The What, Where, and How-To

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valve guide seals
Think of valve guide seals as the little hats that your valve guides wear to form the final “seal” between the valve guide and valve stem.  They are located on the top of the valve guide (i.e. on the non-combustion chamber side).

A little bit of oil is supposed to get past them, but too much oil and you have the dreaded blue smoke or exhaust puffing on startup, acceleration, or sometimes deceleration.

We spend so much time, effort, and money on valve fitment and valve seating, that we forget about our little friend the valve guide seal.

In fact, many early Harleys didn’t even have valve guide seals. I don’t think “Cal” came with them stock, but once someone has been into the top end of the motor, they are usually added.  In fact, if you find them, you know someone besides the factory has been there.  I found them when I broke into “Cal’s” top end.

They are typically added where not stock to reduce overall oil consumption as more gets past the valve stem and is burned without them.

So here are a few things that you should know about valve guide seals and a pointer or two.

-They are cheap and wear out quick, especially on bikes that sit around a lot, so a good culprit to look into if your bike is using a little bit of excess oil (and not peeing it on the ground).

-A question that is asked a lot and that I will answer here – You can change valve guide seals without removing the top end of the bike (that is, without removing the valve heads). That said, if you are going to go this far you should remove the valve heads and check the valves and valve seats.

-If you insist on changing the valve guide seals without removing the valve heads, you will need to stuff some rope in through the spark plug hole to prevent the valve from dropping down out of the guide when you remove the springs.

-Valve guide seals can typically be removed with a pair of needle nose or other small pliers. Grab the very top of the valve guide seal firmly and turn or wiggle back and forth. If it doesn’t turn or come loose easily, use penetrating oil for a few minutes. If that doesn’t work and as a last resort use a heat gun and heat things up before trying the next pliers.

-When installing the new valve guide seals, it is best practice to use a little bit of oil. Additionally, slide them over the valve stem and then seat them down on the guide.  

Big tip here. Use a little packing tape or other thin tape to cover the keeper groove on the valve stem. Otherwise you can get the new valve guide seal caught on the groove and damage the seal during installation.

-Generally, no special tools are required for this DIY project.  There are special tools out there, but they seem like a waste of money.

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