Hi Guys,

On the home stretch putting my 88 2J MC18 back together, but I have run into an issue with the power valves. After an extensive search through forums on this issue, I didn't have any luck so here goes.

With the ignition off and the RC valve pulley manually turned toward 'high', it sweeps to the 'lo' position when the ignition is switched on as it should. I have also removed the cables from the servo motor to make the troubleshooting process a little easier, however when I fire the bike up, the RC valves do nothing until about 7-8k RPM, then the pulley rotates counter-clockwise (the wrong way) back past 'lo' around to the pulley stop.

Being a PGM1, I have tried 3 different RC servo motors, 2 different RC valve controllers, and even another PGM1 but they all do the same thing.

Has anyone seen anything like this before?

Many thanks,

Andrew.

If you have tried 3 different servo motors, then most likely that one of your rc valve controllers is faulty. The 2j has a rc valve controller and sub controller.

My rc valves would work sometimes and stop working so after changing the unit on the side(the one without the rubber case) , they were working fine.

Sami

Thanks for the response. I have tried a couple of different controllers and sub-controllers that came in the parts boxes with the bike and they do the same thing as well unfortunately, although I have no idea if they worked in the first place.

I was hoping that someone else had seen the servo pulley behave in the same way and had a definitive solution. It seems that when the controllers give up, everything stops working rather than it behaving oddly? Maybe the TPS could be the cause or something else that feeds an input into the control units?

Cheers

There are a number of different servo motors, If using a late style MC21 the wiring is reversed and will run backwards. Easy fix is swap the pins over. You may find youre not using the correct servo which is whats causing your trouble.
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If I have to take the carbs off once more...

Thanks Stephen. I had thought the same thing, but if the pins were opposed, I thought the servo pulley would still modulate at 2000-3000rpm as normal, but just in the opposite direction. If anyone has a part number for the correct motor, I can cross check, but the wiring is consistent with the loom it plugs into.

I also tried a spare TPS i had lying around today with no joy so it looks like the saga continues.

Also, has anyone heard of bypassing the secondary RC valve controller? I hadn't until I found this... http://88nsr250rsp.web.fc2.com/88rc.html but unfortunately I am unable to convert the web page from Japanese into English.

Thanks again for taking the time to respond guys. I am almost at my wits end.

Cheers,

Andrew

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