Took the NSR out again today, and I noticed when I turned the key on I didn't hear the powervalve make its usual noise. When the bike was warmed up I revv'd it to 7,000rpm and didn't see the powervalve move at all! Supposedly it is meant to go to full open at about 3,000 rpm, but I did not witness this. I'm wondering what is going on... Where do I start with the troubleshooting?

Also, I'm not sure if it's related at all, but the tacho randomly drops out when riding the bike giving no reading. It usually comes back within five seconds, but it's disconcerting.
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MC21 Honda NSR250. TYGA 300 conversion.

So I tried the standard test to see if the servo cycles with the cables disconnected and TPS disconnected but nothing happens. So I'm guessing it's either the servo motor itself or the PGM 3. My questions are, how do I test the servo motor? Which wires do I connect to power? How do I get the PGM 3 apart to have the transistors replaced?

Here is a schematic I made from the MC21.

There is a guy in Greece that repairs PGM3s


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Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom

Thanks. Applied power to the W and W/R wires and initially the servo motor moved a little. After that I could not get it to move any more, so I think it may be the suspect part. Hoping it's not the PGM.

Try and disconnect the cables to the RC valve. A common problem is that they are stuck in the cylinder.
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Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom

Nope, that's not it. The power valves themselves are free, the problem is the motor does not operate.

I ordered a second hand power valve motor from Japan and just installed it today. I'm still having issues with it, as it only wants to go to the HI position, it does not return to the LO position with the TPS reconnected. Am I correct in that it should return to the LO position with the TPS connected and the ignition switched on? It does not. Wondering if one of the transistors in the PGM III blown could cause this?

If you blew one of the transistors, it would only go one direction.

Yes, I think it may be a blown transistor. I started the bike and it did not return to the LO position when it reached 3,000 RPM as it should.

How do I go about replacing the blown transistor? Is there a way to get the back of the PGM III unit off? I took a look at it and can't see how.

The black plastic cover just pops off, but it's easy to crack it. It's held in place by a few small raised points that clip into recesses in the alloy housing.

With the cover off, you will see the tops of 4 transistors peering through the epoxy. You need to clean away the epoxy and replace the failed ones.

You should be able to get the transistors from somewhere like Maplin/Tandy/Radio Shack. They are NEC transistors, but I can't remember the number.
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Andy.
NSR-WORLD.COM

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