Engine Rebuild

1985 RZ350

1985 California RZ350

The power valves in the engine I dismantled looked to be in pretty good condition so I cleaned them up and replaced any seals and O-rings that could be replaced.


Above is a shot of both barrels and both power valves which differ slightly from each other. This section focuses on rebuilding the right barrel valve (shown on the left above) but the left is very similar.


The power valve is removed from the barrel in two pieces with two small dowels to align them when reassembled At the end holder of each valve is an O-ring and an oil seal. The O-ring can simply be hooked out of the groove and replaced.


The end holder and oil seal will slide off the end of the valve half but may be a little sticky due to carbon and oil build up.


The oil seal can be pushed out of the end holder and replaced. Once replaced use a little grease on the seal and push the end holder back on the valve shaft. While the valves are out it is also a good idea to remove any carbon deposits around the cleaning groove. The cleaning groove is in the face of each valve running parallel to the rotation axis. It basically acts like a scraper when the bike is first turned on and the valve cycle through their full rotation.


Rub a little two stoke oil on the valve surface and then install it with both dowels into the right hand side of the left barrel.

Follow with the other half of the valve with the replaced oil seal, holder, and O-ring from the other side of the barrel.


Carefully align the dowels in the valve halves by looking through the exhaust port. When they are aligned push the two halves together until they are flush.


On the inside of the barrel there is a retainer that holds the valve in the barrel. It is a small piece of metal which fits into a groove in the end holder of the valve. It is held in place by a single Allen head bolt. Use Loctite or something similar on this bolt to make sure it stays in place while the engine is running.


To tighten the two halves together, insert the long Allen head bolt and washer through and tighten it up. The valve will try to turn as you tighten it, so using a piece of wood as a wedge in the exhaust port is a safe way to lock it in place while tightening. Now flip the barrel over slightly grease the exposed end of the power valve and fit the blank cover to the right hand side


The other barrel is similar but the end plate which faces to the left of the bike. It has an adjuster body, pulley, and cover. Again, I installed the adjuster body with Allen head bolts instead of the original Phillips head screws.