KPMI® does not advise reconditioning (re-grinding of the cam contact surface) of their tappets for re-use. KPMI® tappets undergo a proprietary heat treatment process and reconditioning can remove the hardened surface of the tappet. In the event the surface on which the cam-lobe makes contact is visibly free of wear and scuff-marks, then the tappet can be re-used with the same camshaft that it has been running against.
KPMI® recommends replacing tappets whenever a new camshaft is being introduced, or contact surface shows signs of wear. When replacing tappets KPMI® recommends the use of cam brake-in lube.
KPMI® valve shims can be ground as long as they are kept parallel and perpendicular to the outer diameter. "Professionally" lapping a shim or Blanchard grinding shims are acceptable options. Additionally, a device/fixture that has been designed to locate a shim to produce parallel surfaces that are perpendicular to the OD by way of a butt-grinding on a valve facer or similar equipment is also acceptable.
Many times this type of interference is created when the valves have been sunk into the head and the tips of the valves have been "excessively" ground (shortened) and thin shims are being used, to achieve recommended lash. In this condition KPMI® recommends either replacing the valve seats or using custom valves that are designed with the corrected overall length and the factory groove location. KPMI® does not advise retainer modification for this type of condition.
KPMI® makes both standard and custom guides that allow for more clearance for these types of conditions. KPMI® also advises moving any guides already in place further into the head, when a retaining ring or a guide shoulder is not present. Be sure to check all clearances when moving the stock guide into the port. Bear in mind that a valve job will be required when altering the guide location. KPMI® does not advise modifying the retainer for this condition.
KPMI® recommends that all valve guide hole(s) prior to guide installation be free of gall-marks and are round and parallel. Professional inspection devices are required to perform these determinations. Additionally, Honing, reaming and or boring a valve guide hole may be necessary operations when a valve guide hole needs to meet this criterion. The following recommendation(s) are for any combination of bronze or cast guides and aluminum or cast iron heads.
• .0015" to .0025" - Intake and Exhaust • KPMI® does not agree that an o-ring can allow for the necessary fit required to create optimum heat transfer and or fitment. Always consult with qualified professionals suited to inspect and repair your engine.KPMI® recommends honing the ID of guides prior to installation to a slip fit to the valve stem diameter, using the valve as a gage or a seat and guide machine pilot as your gage. Cast iron guides are easily reamed and KPMI® then recommends honing them to achieve a surface finish of RMS-32 or better. Bronze guides can be difficult to ream unless in well secured and accurately aligned conditions and preferably with the use of coolant. KPMI® recommends rigid type mandrel hones or diamond hones for controlled ideal results, when honing cast iron or bronze guides.
KPMI® only offers high quality long lasting valve stem seals. KPMI® believes that Teflon® and Viton® are the two best materials available for valve stem seals. KPMI® has developed a proprietary line of Red-Viton® seals and offers black Viton® and Teflon seals as well. The only difference in the red and black Viton® is the physical outer seal dimensions.
Tipping a valve to achieve factory stem protrusion can create an undesirable effect. KPMI® recommends that a trained and experienced professional determine the amount of material that can or should be removed.
KPMI® builds valvetrain system(s) based on a system approach. KPMI® evaluates cam profile(s) and given harmonics when engineering spring forces, heat treatment and materials for a given application. The weight of each component in a given system is as important as the cam dynamics and engine RPM(s). KPMI® recommends using the complete system approach when converting from titanium to stainless steel valves.
Lash caps are used for a series of conditions. Lash caps can be used to correct valvetrain geometry. They can be used to allow a greater wiping area for aggressive type cam profiles. They can also be used on titanium valves that are paired with a rocker arm. Lash caps are also used in some applications to adjust the valves. When using lash caps always make sure that there is ample clearance between the keepers and the cap. KPMI® recommends a minimum of 0.030" for this type of condition, unless the cap was designed to mate with the keepers.
KPMI® does not advise partial conversions on race bike and/or engines that have reached factory advertised service limits. In the event that your engine has reached or exceeded factory service limits, then KPMI® recommends installing a new complete valve spring kit and all new valves. However, on a low hour engines with apparent intake face recession and exhaust components that meet factory specifications, consider a KPMI® Intake Only System, when performing necessary service. Always consult with qualified professionals suited to inspect and repair your machine.
KPMI® does not recommend making any changes that affect the valve spring contact areas. Modifications that do not affect the valve spring contact areas are allowable. However, each KPMI® basewasher has been designed to a minimum cross sectional area, and any changes could adversely affect the strength of the basewasher. KPMI® recommends basewasher modifications only be performed by experienced engine builders.
KPMI® recommends our nickel aluminum bronze seats for maximum performance with titanium valves. The unique alloy blend; 80% copper, 5% nickel, and 10% aluminum, give these seats excellent thermal characteristics, resistance to wear (impact and chemical) and the proper expansion coefficient for use in aluminum heads. For two years KPMI® tested and recorded results with titanium valves. In every one of our tests the machinability, thermal conductivity, and resistance to wear of this nickel aluminum bronze material surpassed the high standards company set for success.
In order to maintain a safe cross-sectional area KPMI® recommends using a seat OD 2.0mm (.080") larger than the head diameter of the valve.
Yes, if the seat is iron based.
It is common in performance builds to use a longer duration cam with more overlap in combination with oversize valves. This combination reduces the valve to valve and valve to piston clearance at overlap. A shorter valve allows the builder to "sink" the valves to regain clearance, without creating excessive valves stem protrusion, poor rocker geometry, and other problems associated with excessive valve stem protrusion.
When guides are installed into a cylinder head, they distort due to interference fit. All KPMI® guides are designed with undersized IDs to allow the builder to true the ID and set the desired valve to guide clearance.
KPMI® designs certain springs with a progressive wind (closely spaced coils on one end) in order to achieve a variable spring rate. This makes the spring less likely to become excited by the harmonics of various camshafts, reducing the chances of spring surge. If your springs have this feature, the tightly spaced coils should be installed down on the basewasher to reduce reciprocating mass.