In an effort to improve the overall action and noise of their piston valves, Yamaha has begun using a plastic valve (Part No. G0141092). Previously, they used a metal valve guide (Part No. G0141090) that was rather noisy in typical valve operation. While the new guide is much smoother and quieter, it presents a number of unique problems. Please note: if you have the old metal-style guides you cannot convert to the plastic guides without replacing your valve cores.

      The valve guide sticks out only a millimeter or so from the side of the valve and can be easily shorn off. Exercise extreme care when replacing the valve in the casing after oiling or cleaning. If you force the valve into the casing while the guide is not properly lined up, it will be shorn off. Once this happens the valve will spin freely in the casing and not stay lined up. You will need to replace the plastic valve guide.

      If you use a Yamaha low brass instrument with this style guide, I highly recommned ordering and keeping a few of these guides on hand or in your case. You never know when a guide might get shorn off and need replacing.

Assembly Tips for Plastic Guides 1. Locate the guide pin on the bottom of the valve guide. 2. Make sure the guide pin on the bottom of the plastic guide fits into the smallest hole on the top of the piston. The other larger hole is an air vent. Almost half of the problems that occur with Yamaha low brass valves have to do with a person lining the guide pin up in the air vent. 3. Notice that the air vent is still partially visible when the guide is in place. If you cannot see the air vent you have picked the wrong hole! 4. Put a very small drop of Lock Tight on the threads (in the top of the piston) before installing the valve stem. This will help keep the stem from coming unscrewed causing the guide to come loose and spin around on top of the piston. 5. Just before tightening the stem, push the plastic guide with you thumb so that the guide sticks out over the piston as far as possible. 6. After oiling or cleaning, place the piston very carefully back into the casing aligning the guide tip with the guide channel inside the casing. Make sure the piston is all the way in before screwing down the top valve cap. [END]