Thursday, October 16, 2014

Starter Motor Issues?

Slow to turn over? Doesn't even attempt?
The little GSX saga continued when I wanted to turn it over on the starter motor just to see if everything was doing what it should.
I knew the cams were turning when I turned the crank with a spanner, but there's nothing like spinning it over on the starter to listen to any clonks, or other death blows.
With a charged battery at the ready, I used a pair of jump leads to try and get it to spin, but nothing, just sparks. It's worth noting that you don't want to hold the leads on for too long, in the hope it'll start to turn. Just flick the lead quickly to earth on the frame, or engine, and see if it begins to spin. 

The method.
My starter solenoid is probably shot, so I'll bypass that and go to the starter terminal itself. Connect your battery to the jump leads, and then the other positive to the live terminal on the starter (that's the bit where the lead is attached). If the starter is still fitted to the bike, flick the remaining earth connection on to the main earth lead from the engine, or the frame, or even the engine itself (sparks will arc between the lead and whatever you're connecting to, so don't do it on a freshly polished engine case!). 
Note: never flick the leads at the battery terminals either because the sparks may cause an explosion (Hydrogen is released from a battery when it's been charging).

That's the safety stuff done!
So, what did you get? Sparks, a growl, an attempt at turning? With help, mine actually began to spin, but felt rough and noisy. At that point I felt I should take a look inside and, as luck would have it, these things are nice and simple to pull apart.

The rusty cover on top of the crankcases, fitted right behind the barrels is where you'll find the starter. Two screws on this engine and it's off. The starter itself is held by two M6 bolts at the back of it. On the GSX250, you will need to remove the cam chain tensioner first - on the bigger versions it should come out without. With the starter bolts removed, it usually just requires a bit of wiggling backwards, and upwards, to get it out. This one came out easily because the O-ring was missing from the front.

Here it is, the old Nippon Denso 31100-11410 starter motor. Two long screws hold it altogether. Remove those and the front cap will come off easily (tap the side of the cap with a rubber mallet or block of wood).

Note the shims inside the cap to prevent end float. They rest up against the circlip you can see on the armature.

Time to be careful. The rear cap contains the brush holders. One brush will go to earth so that will remain with the cap, but the live side is connected to the bolt sticking out the side. I removed the wire first, then slackened the nut and finally used some aluminium flat bar as a drift to push it out of the main body.

Just like that! Now the cap can be removed along with the armature if need be. The magnetic force from the starter body will try to prevent you pushing this out.

Corrosion around the magnets.

But not as bad as what's going on around the brushes. It's not looking good.

One more shim on this end.

Part of the problem, the commutator is shorted out with what looks like carbon build-up. This needs to be clean, with good gaps in between each segment.

A hacksaw blade can be used to undercut if needed, but here a small screwdriver was ideal for cleaning out each slot.

Next I used 600 grit wet&dry around it to remove old stains/corrosion, followed by 1000 grit to clean it up. 600 grit was also use on the very end of the shaft too (this is essentially the bearing surface). Finally a light polish with Autosol has it looking pretty good again. 

Which is more than can be said for this end - the brushes are seized solid within the steel holders. The springs can be unhooked from behind the brushes and taken off altogether at this point. Next I gave it a wash in the sink with Jif and a toothbrush to get rid of most of the corrosion.
Then it was the time consuming process of trying to release the brushes from the years of rust build-up. Plenty of WD and a small piece of aluminium, that fitted in the slot at the back, was used to gently tap them. It took a while but the grip was eventually relinquished. 
Carbon brushes are fragile, and I didn't want to try and find replacements. A quick clean up of the rest of the end cap and it was ready for reassembly. Obviously I'd spend more time on it if it was a restoration, but all I want to do for now is make it work properly.

A tiny amount of grease was placed on the end of the shaft, springs were refitted, brushes held back and the armature slipped back into place - don't forget the shim! Release the brushes, or springs, and turn it to make sure nothing is fouling. All good so far.

Then the armature and end cap can be refitted into the main body, along with the plastic insulator that holds the live terminal. It can be a bit fiddly especially when the magnets try to pull the armature back out of the end cap.  

With that done, refit the shims on the front, apply a tiny bit of grease on the shaft and refit the cap (there is a seal in here so be gentle). Then refit the screws to hold the whole thing together (these will be attracted to the magnets and can take a bit of lining up).

With that done, grab your battery and leads, and give it a spin. This one sounds great! I found an O-ring to suit the front and plonked it back it back in the bike. With camchain tensioner refitted, it was ready to whirl.