RD500 Powervalve Joints

[Captaincosmos]

I’m trying to put together a Powervalve pulley mechanism for an engine I’m building. I have bought two valve joints/clamps which came as two pieces each, but have found that they’re missing a third piece that sits on top of the joint, which serves as the connecting point for the control arms. I’m working blind on this because I’ve never seen the mechanism, nor can I find an image on the web, and my book has no reference to the part. Could somebody post a decent image of the joint and also the control arms if possible, as It looks like I’m going to be making some form of replacement.

[jackson.40]

[Captaincosmos]

Many thanks for the quick response. I’ve noticed that the pieces that bolt to the top of the clamps are offset and the rods are different lengths, nothing about this engine is easy.

[jackson.40]

nothing about this engine is easy.

That's why i like it

[Captaincosmos]

Looking at those rods, I’m thinking along the lines of the gear change rod from something like an R1. I could cut it in the middle, add or remove a piece to get the approximate length and then use the adjusters to dial in the valve openings. This means I won’t need to be as accurate when fabricating the brackets. I should also be able to polish them up for a bit of unseen bling. I’m sure the brackets will be a different story but I’m new to this so my enthusiasm is high.

[lost1750GTV]

Adjustable is a good thing. If memory serves, the original centrifugal powervalve on tz's had such an adjuster.

[Speed Freak]

The PV timing is adjustable at the connecting wheel where both rods come together.
It's a 2 piece design and when you loosen the 2 screws you can rotate them against each other.

For the overall timing there is an adjuster in the cables.

Only thing which is not adjustable is the rotation between the 2 cylinders which are next to each other.
My RD350 has a big deviation - one is open, the second one has a 1mm step at the outlet port.
I solved it with an adjustable center piece.
Or more simple solution: You can also grind down the one with a step.
Or another solution: Make them independent and put another 2 cables to the PV motor for the right PV

[silverstrom]

Or another solution: Make them independent and put another 2 cables to the PV motor for the right PV

That is what I did with my 350. 4 cables for 2 valves. Left and right valves are completely independent from each other.

[wolfgangh]

Thats what I did on my RD500 - each power valve independantly controlled with 2 separate cables - so 8 cables connected fo the servo motor. Had to machine a new drum of course to connect 8 cables.

[Captaincosmos]

I’m trying to visualise the eight cable set up, how did you connect the eight cables to each of the valves?

[wolfgangh]

I have added a picture in above post, will try to post more details. Basically each power valve has its own pulley with 2 cables attached to

[Captaincosmos]

Now I understand. I had visions of you connecting the cables on the right side of the cylinders using the pulley system from a 350 ypvs. For now, I’m going to try the gear change rod approach as the parts are readily available (cheap), the trickier bit will be making the brackets to a reasonable standard with something close to the right offset at the connector pins. Before I can even start making the rods, I need to, source a set of rear cylinders, without them, I won’t be able to estimate the length of the rods.