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Ken O'Connor Racing


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Cylinder Head Reconditioning

A good maintenance program is a crucial part of any off road bike or ATV's life span. Internal engine parts begin to wear the moment the machine is first started and continue to do so until they eventually break or wear out. Maintenance is all about finding these inadequacies and repairing, or replacing them, before they cause major problems. An often ignored part of your engine is the cylinder head. Let's face it, four stroke cylinder head and valve train maintenance is not going to be tops on the list when the sun is shining and you want to go riding. Unfortunately, poorly maintained valve trains have a way of ruining very expensive engine parts. When valve heads wear and start to mushroom, performance may not be the only thing you're loosing. Valve faces do not wear evenly once they begin to mushroom. Deflection will occur every time the valve face makes contact with the seat. This deflection causes rapid seat and guide wear and if not serviced, will eventually cause the valve head to snap off and fall into the cylinder. Ouch! That's going to leave a bruise. For this reason, your maintenance program should include cylinder head removal, disassembly and inspection at least once per year. Take short cuts and you could end up with something that looks like this!

What to look for:

A simple leak down test is a good start. Remove the cylinder head from the engine. If you don’t have a vacuum table, stand the head up on its side and fill the exhaust runners with kerosene. Now take a look at the exhaust valve heads. If you see any of the kerosene leaking by the valve, the valves and or seats are worn and it's time to service the valve train. Repeat the same procedure with the intake valves.

Can We Help?

Valve train service is nothing that can ( or should ) be performed by an amateur. OConnor Racing has the knowledge, equipment and experience to do the job right. After a complete inspection, we'll evaluate all serviceable parts, repair or replace them, and then perform an expert assembly. Valve seats are machined with extremely accurate tungsten carbide tooling to ensure a perfect seal.

Services Available:

Machine Seats

$25 Per Valve / $45 For Oversize Valves

Replace Valve Guides

$75 each (does not include parts)

Adjust Valve Lash

$65 Per Cylinder (does not include parts)

Disassemble Head, Inspect, Clean and Assemble


Cylinder Head Porting


Contact Ken