Hi all,

I am a newbie on this forum. I have a mc18 and 2 mc21 track bikes. The mc 18 is an absolute stonker. One of my mc21 has problems at high rpm(8500-10,000). It has a HRC jet kit and runs open carbs. I have spent four days at the track playing with the jetting but cannot get the top quarter throttle/ high rpm to run properly. I have been up and down the main jets and used A,B and C needles but no joy. Low and mid are nice. I had a slight air leak around one exhaust gasket and fitted new gaskets but it made no difference. It has the wire splices done. (the other mc21 has the proper HRC wiring kit) Has anyone got an idea of where to look? Has anyone else had a similar problem and have any wisdom to impart? Should I be looking at the wiring, power valves or what?

Hello Damian, and welcome to the Forum.

If the bottom and middle are clean, and you have tried all assortments of MJ and needle, then there is a possibility there is a problem with the RC Valves. You need to make sure they are opening fully. There could be some debris preventing them from opening fully, or maybe one/both are slightly out of adjustment.

If you want to discuss jetting specifics you will need to do it in the Members Area, as it is not allowed in the public area.
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Thanks Andy,

Pretty sure its not the jets. Whats the deal with the members area then?

Damian

Hi all,

Did a check on the power valve and while it cycled to the low position it would not cycle to the high position after the TPS was disconnected. What would cause this? Anyone else had this problem?

if you manuall turn the rc servo to the high position, with the TPS connected and turn the ignition on, does the servo move to the low position, suppose this would indicate the servo does work. I can only imagine if the servo does work, and the cables allow it to do then perhaps the TPS if faulty?? Without looking at the wiring diagram i can only imagine its a simple two way switch and perhaps you could simulate the TPS operating by shorting out the correct pins on the TPS connector to see if it operates the servo or prob better, check the resistances with the throttle open and closed at the TPS end of the lead.

I'll be working on my bike tomorrow night and have the carbs off so could do some comparrison measurements for you to check against.

cheers
Brendan

Hi Brendan,

Well it was the TPS. You were absolutely correct. After messing around with power valves, exhaust pipes, cables etc I plugged in my spare carbie and the valve cycled to hi and lo just fine. So new RULE No.1 for me when problem solving is to try the simplest problem first. Looking forward to track day now to give her a run. Thought I might have to take out the mc18. Blisteringly quick but the suspension needs a lot of TLC which is what I would need if I tried to outbrake anyone while riding it.

Thanks all for the help,
Damian

hey thats brilliant, glad it all sorted