Magnum 91 4stroke valve adjustment
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Magnum 91 4stroke valve adjustment
My magnum 91 was starting to run poorly 1/2 way during a 10min flight sometimes even dead stick. Land check it out start right up same thing. When it got hot the valves were tightening up. Just needed a valve adjustment. Simple I set them with .002 ok- .004 not ok.
But this is what I found the exhaust adjuster had a crack in the threads need a new adjuster. Ok but Magnum only sells rockerarm assembly 30something dollars. I used OS adjusters #45061202 tappet screw F40-300 from Tower $5.80 and it worked better than stock as it features an allenhead for adjustment instead of screwdriver slot.
But this is what I found the exhaust adjuster had a crack in the threads need a new adjuster. Ok but Magnum only sells rockerarm assembly 30something dollars. I used OS adjusters #45061202 tappet screw F40-300 from Tower $5.80 and it worked better than stock as it features an allenhead for adjustment instead of screwdriver slot.
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Join Date: Jan 2003
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Thanks for the part numbers. They are good engines, I have several, but the parts availability is not good. A few months ago I broke an intake valve spring and couldn't find any anywhere. Rather than put the engine away I bought a new head assembly for an ASP .91, it fits perfectly and runs just great. The head was much more than a valve spring, but now I have some spare parts from the old head. I think the new head was around $35 or so, as far as I can remember.