More work on the infamous MC28 TYGA 300. Got the dead tacho to talk again so we could gauge where the power was coming on and off. Sadly the tacho stops at 5,000 and the Servo Motor is not activating the RC valves. We find the controller is actually a PGM3 off a MC21and following the wiring diagram from this website (thanks) we traced the circuit including operating the carb throttle sensor as well. No joy.

Next, took Neal's advice to twist the servo open by hand (ignition off) and then ignition on to expect it to return to the default position. Nothings happening. Revving the bike hard on the stand shows no movement at the RC valves, so whilst Simon the pilot sits on the bike holding the revs up, I wind on both RC valves at the cable plate, and the engine note evidently changes as one would expect. So we then resorted to pit mechanics desperate solution and cut 2 bits of stiff cardboard, folded them and jammed them into the cable plate at the full on position. Test ride - great response up top, pulling wheelies in 1st instantly under acceleration. The bike is going to Phillip Island in 2 weeks, and whilst that is a fast track, we are unsure of how the low end is compromised. A new MC21 servo motor is priced at $550 plus postage. 2nd hand ones, may be yes, maybe no. Anyone got any experience on bypassing the RC servo and running full bore?

There is NO airfilter assembly on this bike, just open bellmouths on the Keihin TB32s. Given we may have to run with the RC valves in the full open mode, has anyone tried tuned length induction to moderate the low end response so that we get a better linear acceleration? I was thinking of emulating the rubber tube lengths from the OE airbox. Anyone got any reference length for that hose to carb distance?

Thanks, Mike

I think you'd do better in the short term to just remove the cables from the RC Valve assembly, and pin the pulleys to the backplates with a couple of 5.5mm knock pins. You may need a little clutch slip in places, but it works perfectly well on a well set up 250 as a "get you out of trouble".

Frankly, you're wasting your time trying to "tune" the inlet to recover what you've lost with a failed RC Valve system. You'd be better off spending the time and effort fixing it.
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Andy.
NSR-WORLD.COM

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Look for another pgmiii to test on your bike , if the powervalves work then you know yours is faulty . You can try and have it repaired by twostroke race lab .
You should be riding between 8-12k so mid range shouldn't be too much to worry about .
Ps : jet up for the long straight !

It would maybe be better/safer to try your PGM on another bike, just in case something is wrong with your bike that caused it to blow.....no point in risking a fully working one until you know your setup is ok.