Last time, we discovered the cause of the VFR’s battery eating habit. According to the workshop manual, the stator coil was no longer functioning correctly. As you may have surmised, I left out most of the charging circuit tests that passed. There is beauty in brevity and my posts are rarely that!
The stator coil on the VFR is on the left hand side of the engine, mounted to the inside of the alternator cover. This means it is submerged in the engine oil. (I’m guessing that most four stroke motorcycles would be the same). So, to replace the stator, you will also need a new alternator gasket and an oil filter (as you end up doing an oil change).
As usual, you should read my disclaimer, if you feel inspired to give this work a go. As a comparison, this is probably the trickiest procedure that I have blogged about. – You have been warned!
Start by removing the two side cowlings and the connecting front piece from the bike. These require a 5mm Allen key and patience as you struggle with the plastic clips that go together easily the first time and then deteriorate, get jammed up with road grime and go brittle with time.
Once the panels are removed, warm the bike up for a minute or two. The idea is to not make the engine too hot to work on, just to raise the temperature of the oil enough to reduce its viscosity. Stop the bike, do what you need to do to stop yourself from absent mindedly starting it with no oil and remove the oil drain plug.
While the oil is draining into an appropriate receptacle, unbolt the radiator overflow bottle. The workshop manual suggests removing it all together, but I found that by using a zip tie, I was able to access the alternator cover without needing to drain it or disconnect the hoses.
The astute reader may have noticed by now that while the stator is located on the left side of the bike, its connector is plugged in on the right hand side. This means the wiring is threaded through, from one side to the other. Pulling the old cable out is always going to be easier than threading the new one through… The workshop manual instructs you to remove the fuel tank, airbox and the throttle bodies to gain access to the wires. Removing all these parts would undoubtedly make routing the new stator cable easier, at the cost of making the overall job much harder! Instead, I tied a piece of string to the stator’s plug and carefully pulled the cable through the bike, such that the whole wire ended up hanging on the left side of the bike. The string is then left in place, to guide the new stator wiring back through.
Once the wiring is clear of the bike, the bolts holding the alternator cover in place can be removed. Even once they are removed, the alternator cover is held in position by the strong magnets that generate the current as they spin around the coils of the stator. There is a lug on the alternator cover that, with a bar and mallet, I was able to tap on the back of to break the magnetic seal.
Despite what the workshop manual suggested, I found that the stator on my bike was held in place with Allen key bolts, rather than Torx head bolts. I have no idea whether this is common or not, but it meant my purchase of the torx head keys was unnecessary… One day I will have a use for them… You will probably find that the bolts holding the stator in place are on pretty firmly, so take care not to do this :-). If I had any good suggestions on how to avoid sudden knuckle/cover contact I would not have injured myself, so good luck with that!
Carefully note the positioning of the stator so that you can correctly orientate the new one and then remove the dud piece.
While you have the stator removed, take some time to remove as much of the old gasket as possible without gouging the alternator cover. Remember that the cover holds the engine oil inside, so a good smooth surface is important to avoid leaks.
Once you are happy with your handiwork, use the dowel pins to hold the gasket correctly aligned and refit the cover. As per the workshop manual, the cover should get some gasket sealer in certain parts. Remember that the magnets in the generator will pull the cover on with a certain amount of force, so be careful to position wiring and hoses clear of its flight path!
Reassembly wasn’t quite as straight forward as I hoped. Although the string helped, I still ended up lifting the tank and airbox, as the wiring connector fouled on various bits and pieces. Still, I managed to avoid removing the throttle bodies with my mad-cap idea… For details on removing the tank and airbox, see this post from when the bike was newer and cleaner.
Fitting the oil filter is one of those few exceptions where I used my torque wrench. I am pretty good at not striping bolt threads – working on the 24 year old RGV teaches you to be careful with such matters, but the oil filter was too critical (and fragile looking) to warrant a careless approach.
The only other point to draw to attention is with refilling the bike with oil. Once the engine turns over, oil will be dragged around all the places it had drained from, so after a quick run, let it settle and recheck the oil level. You may find it needs more to reach the desired level.
Once I was happy that I had put everything back together properly, it was time to try the charging circuit. I didn’t have enough hands to take a photo when holding the engine at 5000 RPM, but as we can see, there was a healthy 13.80 volts at idle.