Hi all,

My 1990 MC21 RC servo will only move anti clockwise from the settling position to the “Lo” position. It will not move clockwise at 2000 rpm to the “Hi” position.

Any checks to determine what it could be other than the PGM III ?

Sami

First off, ensure the battery is fully charged. The RC Valve operation can be affected by a poor battery, or even a lower state of charge.

1. Turn the ignition off, set the run switch to "OFF", and disconnect the TPS.
2. Turn the ignition back on, and set the run switch to "RUN".

Does the servo cycle to the HI position when you disconnect the TPS?
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Andy.
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Hi Andy,

I’ve removed the servo and cables to check if any rc valve shafts were opening/closing freely.

I put a battery to the servo terminals as per testing suggested in the workshop manual and the servo does a full rotation and when reversed, rotates the other way.

Shouldn’t the servo rotate to high at around 2000 rpm on a standard loom and even with a restricted PGM III?

Yes, it should cycle to HI at around 2000-2500rpm, and then return to LO at around 3000rpm.

Hate to say it, but it sounds like the PGM needs looking at, if the servo runs both ways under artificial conditions.
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Andy.
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Does anyone know if a mc18 rc servo will work on an mc21?

I seem to recall an MC18 servo will work, but the pinouts are different. You will [I think] need to re-pin the plug. However, if you can get the servo to move both ways by directly injecting power into it, I don't think it's your problem.

What you really need to do, is try your PGM on someone else's bike.
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Andy.
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As per the mc21 section of the workshop manual, it states to gradually increase the engine speed to 2000 rpm and check the RC valve pulley moves COUNTER clockwise and stops in the low position.

Also states to reduce rpm from 2000 to 1600 rpm and RC pulley should move clockwise and stop in middle between low and Hi.

My RC servo is doing exactly this. I should have mentioned in my initial post that my RC servo will begin to move from Lo to Hi at around 7000 rpm.

Is this behaviour normal and due to a standard wiring loom without the de restriction and a restricted PGM III?

Research tells me that there are 5 variants of the PGM III.

Sami