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I have been involved over the years with two stroke Rotax engines and in a former life as a level two (Aus) maintenance holder and as such have noticed a common problem with 582 503 and 447s, it is the black oil leaks comming from the exhaust manifold flange which are all slightly warped or mis aligned, and as a result every engine I do a service on I draw file both the exhaust manifold flanges and in the case of single carby engines the inlet manifold then finish them off on a glass plate with fine paper to get rid of file scratches and confirms a flat finish, this always cures the oil dribble from the exhaust.

Receantly I noticed that one cylinder on my 447 was running hotter than the other both EGT and CHT were higher just outside the acceptable imbalance range and this was on a new engine straight from the box, by raising the needle one notch it lowered the temps but not the imbalance, checked everything and found the inlet manifold had a warp in it the flange surfaces were not true.

Remember the factory tells you to align the cylinders/jugs with a straight edge bar when reassembling or torqing the heads so the port surfaces are straight and true but fit a warped manifold and you have leakage problems.

As mentioned I always file true the exhaust and inlet manifold flanges then use the manifold bolted up to the cylinders without gaskets and lightly torqued up (about 10nm), then I torque down the heads, even if there is the slightest misalignment the cylinders and manifolds will always be true to each other.

Just a note with a single carby 447 503 use the inlet manifold as a straight edge.

So folks don't assume a new engine is without faults.L

Finally this is my opinion and procedure take it on face value.
  • Re: Warped manifolds and exhaust oil leaks.

    by » 10 years ago


    Lots of good advice there Anthony....also worth reminding users of single carbs if you don't do as you do in Aligning the inlet manifold....that the inlet manifold cracks $$$$$ very easy with the slightest misalignment,

    You didn't say Anthony...did that cure you temp prob???

    Nick.

  • Re: Warped manifolds and exhaust oil leaks.

    by » 10 years ago


    Hello Nick yes it did improve the imbalance in temps I still have a variation between cylinders but now in the acceptable range.

    Interestingly up until a few weeks ago I was using a single EGT/CHT gauge on my single carb 447 assuming both cylinder temps would be almost the same, I have now fitted a MGL Stratomaster dual EGT/CHT with the good sensors, what a supprise it was to really see what is going on in the little Rotax and the rapid response of the gauges to load and throttle variations, gives you a very much healthier respect for balancing throttle settings and engine loads especially on decent.

    Anthony

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