start with me ...
|What exactly is that grinding noise coming from the engine?|
That's what most owners of older Viragos end up saying to their steeds as they repeatedly depress the starter button. Unfortunately the button pressing only produces a godawful grinding noise but not much engine cranking. Most owners quickly (and wrongly) assume the starter is at fault and either head off to the dealer to have the repairs carried out, or pick up a new starter and do the job themselves.
If the shop is doing the work, hopefully they will identify the problem as not being the starter and just replace the malfunctioning pieces. However, if the owner is doing the job themselves they could be in for a costly mistake. If you walk into a parts store and tell the person you want a starter motor for your bike, they'll be more than happy to oblige. It's not their job to educate you on what you do or do not really need. The best part of it all is once you've bought the new starter, only to discover it's not the problem, you can't take it back because most stores have a no returns policy on electric stuff. Not to worry though, it only runs about $459.00, plus taxes. Heh, heh, heh. Sucker.
FINDING THE CULPRIT
|Exploded view of the XV750 starter assembly|
In many of these grinding starter cases (in fact, every one I've ever seen), the starter is not at fault. The culprit is the starter gears and the gear assembly that the starter is coupled to. The Virago system is very archaic compared to most starting systems found on motorcycles. I'm going to look at the 750 Virago, but the others do operate on the same principles, and also have the same problem components.
As the starter motor and gear (3) begin to spin, they in turn spin a reduction gear (9) that is coupled to a spiral idler wheel (4). On the spiral idler wheel is a throw gear (8), which, when the spiral idler wheel begins to spin, travels down the Idler Shaft (6) towards the crankshaft gear on the end of the rotor (not shown). This throw gear has a unique horseshoe shaped clip (7) that is fitted around it. This clip holds the gear tightly to prevent it from spinning as it travels down the shaft. Once the throw gear is completely mated with the teeth of the crank, the spinning motion of the shaft overcomes the friction of the spring and the gear spins with the shaft and subsequently turns the crank. When the engine fires and the starter button is released, the compression spring (5), pushes the throw gear back away from the crank.
The problem is as this horseshoe clip wears, (and they do), it allows the throw gear to start spinning before it even reaches the teeth on the crankshaft. Imagine for a moment, a spinning gear being that is being forced against another much bigger gear that is stationary and has quite a load behind it. The smaller, quickly spinning gear bounces off the bigger one as it tries in vain to mate up. Thus the noise.
|Worn throw gear to the left (side of teeth worn away)|
When the wear first begins to happen you will get the occasional grind until the gear finally manages to mesh up and the engine starts. But as the clip wears and the gear continues to bump and grind, the teeth of the throw gear begin to be wear away. As the wear becomes greater, it becomes almost impossible for the throw gear to properly engage with the crankshaft.
It appears that Yamaha had anticipated this problem when they originally conceived the Virago. They engineered it so the throw gear would be the gear to wear (softer metal, easier to replace) and not the rotor gear of the crankshaft (harder metal, very difficult and expensive to replace). They also placed a magnet directly beneath the starter gear assembly to catch all those metal fillings that are ground off the gears by this meshing action.
THE FIX IS IN
|Components from the starter assembly.|
Now in order to fix this little grinding matter you must first get at the problem. This necessitates draining the engine oil and removing the left side engine cover and the bits and bites that surround it. Once the cover is removed the starter assembly is clearly visible - It may even fall out as the cover is pulled away. The cover can be placed against the bike while the repairs are carried out to avoid having to disconnect the alternator, neutral, and pick up leads, which are all bolted or run through the engine cover itself.
If the starter assembly does not fall out at the time of cover removal, then the center guide pin will have to be pulled out first in order to allow enough clearance between the engine case and the rotor. With everything now out, take a moment and remove the magnet from the engine and thoroughly clean it of all the metal filings gathered to date.
Now for the reassembly, you should have the following new parts;
|Engine with alternator cover and starter assembly removed.|
L.H.S. ENGINE COVER GASKET
The reassembly process is the reverse of the removal, although it is a bit fiddlier, so don't be in a rush. Once all the workings are back in and everything looks pretty much as it did when it all came out, install the new cover gasket and close up the engine.
It would be a good idea to replace the oil and filter at this point in time, don't use the stuff that's been sitting in the pan while you were effecting repairs. All sorts of things can wind up in unprotected oil, even in that ultra clean workshop
There you're done, give that starter a spin! What a difference, eh? And much cheaper too.
Thanks for reading,