All I know is on Madness (a high comp 750 if that makes a diff) the starter would wind up pretty high before kicking out when I removed the relay. Possibly a foible of that particular drive.
Thought that extra high RPM spin wouldn't be good for bearings or commutator so put it back in. I've never had the starter out of that bike. And a few times while working on carbs it got a lot of exercise.
It's helpful to look in the earlier manuals when Yamaha thought to explain why they incorporated features and design, operation principles , the later manuals started the trend towards "shut up and replace parts" type mechanic relations. A sad trend.
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I've got a more cynical take on it.
Yamaha saw the need to add an electric starter to their flagship 4 stroke. Honda by gawd has one, we need one too.... set aside the fact that Honda designed theirs in from day one. Not wanting to completely redesign the cases, they tucked it up under the engine. Now, the problem is there isn't room on the clutch side.... so lets mount the motor facing the wrong way... yeah, now it fits.... with the drive on the
No matter, we can still have the bendix engage the crank... 'cept the only way to put a gear on the crank is to cut it into one of the flywheel cheeks. It's gotta be the right one though or we'll need to move the alternator.
Well crap, now we need a gazillion little shaft's and gears to connect the starter output... which is on the wrong side, to the bendix... which is also on the wrong side.... what could possibly go wrong....
So one of 'em goes to the boss and sez... "we can do it, but we just robbed a shitload of power off the starter from gearing and direction changes. What we need to do is decompress one of the cylinders to make sure we have enough power to actually start this thing."
So while the boss is doing a face palm over the absurdity of it all, one of the other engineers pipes up and says....
"We're also concerned that this overly complicated system could grenade on us due to the pent up nature of all the gear slop and direction changes and such. I think we need to put a relay in there that automatically kicks the starter out when the engine fires."
And so a monstrosity is born..... backwards, overly complicated... and noisy as fuck.... but sumbich if it didn't work just fine. So well in fact that the decompress feature was later deemed unnecessary.
The safety relay was never deemed unnecessary because marketing got wind of it..... this marvelous "safety feature"..... that nobody else had.
Did ya ever ask yourself why nobody else had one?
3+ years now without it on my SG.... it doesn't need it.