When you get round to playing with the starter motor there are a couple of sensible precautions and tips.
The shell of the starter is divided into two bits, the "can" and the front end with the drive pinion protruding.
The armature inside has a bearing in the can end(oilite type bush) and the other end has a ball bearing held in place by circlips.
The brushes are held in the front end unit.
When you separate the can and front end the armature is held in place by the magnets in the can, which tends to slide the brushes off the commutator and jam in the space between the commutator and bearing. A certain amount of swearing may follow, more if the brush springs leap out of their mountings. The brush springs are made out of darkium, the metal that seeks out the darkest, shadowiest part of your workspace, even if this means making an impossible leap from your well lit workbench and under a table, into the tiniest crevice.
So it is advisable to clamp the pinion end before separating the can and front end, so that it draws the entire armature out from the can before dealing with the brushes.
Then it is useful to have a couple of clamps, bent up from , say, a paperclip, to hold the brushes back against their springs while you slide the front end of the armature, including its bearing out of the front end.
Then, cautiously remove the clamps one at a time while preventing the brushes / springs from leaping free.
To change the brushes you have to remove the spray cap on the starter wire, disconnect the starter cable, slide the contact plate through the rubber gland (or take it out first) on one side and simply unscrew the contact plate on the other.
There are two main faults with the starter, either the cable comes out of the graphite brush and I'm told that you can reglue that back in with a conductive instant glue, or the braided copper between contact plate and brush frays and breaks due to a harmonic vibration at 15000+ rpm. Use a silicone adhesive (eg: aquarium glue) to reinforce the braids and stick them down but leave enough unstuck to permit the brushes free range. Again, some motors fail because the braids have been shortened by the glue and it stops the brushes going all the way forwards.
A repair kip contains brushes and front bearing, the rear bearing is presumably oiled for life (oilsoaked sintered bronze). I've known a rear bearing wear so that the armature touches the magnets in the can.
Several people have reported that the magnets in the can have broken up or come loose. Probably wisest if you don't hit the can with hammers (you often see this on the dummy grid to either make a contact or encourage a sticking brush to slide forward)
Other times you will see people lift the rear of the kart to allow the rear wheels to spin, which indicates a problem with the clutch. The starter won't overcome a sticking or jammed clutch, but will sometimes work for a partial jam.
You can use an external starter if all else is right with the ignition system, as used by TKMs. But be aware that they are attractive items, the Southern Blues used to have a Starter left on the grid, often with the grid marshal, but someone nicked it at Clay Pigeon. There's a dispensation from the MSA for a hole to be cut in the side pod, as with TKMs, so it remains legal even if you start MSA racing.
Also, if you find, as some do, that it is difficult to operate the carburettor jets with them on the inside, between seat and engine, you can mount the whole carb upside down (ie with the fuel pipe connection on the bottom) but remember to check that the reed block pulse hole / gasket pulse hole is at the bottom too, otherwise the diaphragm pump won't work. (the carb was actually designed for a chainsaw and when mounted on the chainsaw is "upside down", so it is karters who are different. However this does make connecting, adjusting and checking the throttle cable connection more difficult and hand throttling when the cable spindle wears through ( a failing on the carb and something you have to check for)much more difficult.
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formula blue mechanics by 'Matty42' (17 May 2014 @ 9:51)
