Hi Hans,
It has always frustrated me that the throttle cable bracket was not threaded, it would make any form of balancing easier.
I don't know what material the original Rotax locking nuts are made from but you cannot weld it, it just disintegrates :(
I had some new nuts made from mild steel which can be welded. It was an unusual thread, M6 x 0.75mm, so make sure that you have a suitable tap.
I did think about making a simple spring clip to keep the original nut in place. This would make it easier to use the SafeSync on another engine. I couldn't work out how to easily fit & remove the plastic gear wheel that fits on the adjustment screw. Unfortunately to fit this gear requires the throttle cable to be removed from the carb linkage.
My experience with motorcycle vacuum gauges, such as the ones I used in my video, is that they are not terribly accurate. If you connect them together with a T-piece and use a hand vacuum pump you will see that they do not track accurately over their entire range.
There is an adjustment screw on the front of the gauge to control the offset, this can be used get the gauges to agree in the region of most interest.
I know that there are other forum members who advocate the use of analogue gauges because they offer benefits when diagnosing problems. However for simple synchronisation I would say that one of the electronic differential pressure monitors would be easier to use.
I think that the purpose of using long hoses containing fluid would be to damp down the pressure oscillations so that the gauge readings are stable. The gauges I have use simple adjustable restrictors to perform the same function. They are not brilliant.
It is my experience that when synced correctly the gauges will match to within about 1 inHg over the entire rev range.
Kevin
