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A while back I mentioned some modifications that we are doing to Simonini starters. What happens is that the starter turns over too slowly to start the engine and the pilot thinks that his battery is flat or dead. People sometimes think that oil has built up in the cylinder giving the starter too much work, but this is rarely the case. In fact the problems are caused by poor design and material selection at manufacture. The starters are available from Simonini are and there is a UK representative.. But they can be modified as a more cost effective solution.


I was going to write this up as an article with photos, but am clearly never going to get around to it! So here is what we do.

Get a completely clear table as you are going to be dropping very small parts.  Mark the can, as although it looks symetrical, it is possible to reverse the direction of the motor if you put it back in the wrong place. Take the can off the motor. It will come off in one of two ways, either with the armature remaining in the can, or leaving the armature connected to the gearbox. If the armature has stayed attached to the gearbox try moving the brushes. This is one of the main design flaws. The brush brackets are made from plastic which grows when it gets hot. The brushes then seize in the holders and the motor doesn't work. I ease the holders with a Swiss file so the brushes are fairly slack. Brushes nice and free? OK next stage, and this is the bit where you need the clean bench. Take the cover off the gearbox. Careful! there are going to be loose bits and you need to find them and count them! You will probably see two loose C shaped bits made from laminations of steel. They should be held in by very thin rivets. The rivets break and fall into the gearbox. You need to find the four rivets laying loose in the gearbox and you want to simply remove the C shaped bits. You MUST find the FOUR rivets or they are going to f**k your motor. Now.. I simply discarded the C shaped bits and the four rivets, put it all back together and everything has worked better than new ever since. Jabba replaced the rivets with bits cut from pop rivet nails (the same diameter) and riveted the C shaped bits back into place. These things stop the pinion from sticking out and engaging the big starter cog, but either mine never does or the motor throws it back.

One last thing, lost the tiny springs pushing on the brushes? Look in the can - its magnetic and they always fall in there! Yes I panicked too! Its a good test of your dexterity getting the brushes back on the armature without damaging them, but its the sort of thing we have all been doing since we were kids isn't it? Or am I and Jabba the odd ones out?

Jim Carolan <>


Black Devil M25Y engine &  Simo

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Simo Starter Mods