#Electric starter problems on the XS650 are very common, and almost always due

to a non-functioning #4 gear, the one that slides down the bendix helix and

engages the ring gear on the flywheel. Symptoms are a starter that does not

engage, a starter that just grinds ineffectually, or a starter that kicks out if the

engine does not start immediately. The usual remedy is to replace the gear

complete with it’s spring clip, but there is an easy way to fix erratic and non

functioning starters without changing the #4 gear, even if the gear is showing

signs of severe wear.

When people remove the offending gear it is often badly worn, and they

assume that is the reason the starter does not work. But exactly the converse is

true.

IT IS NOT A CASE OF THE STARTER NOT ENGAGING BECAUSE OF A

WORN #4 GEAR. THE #4 GEAR ONLY WEARS BECAUSE THE STARTER IS

NOT ENGAGING.

One will find in removing non-functioning #4 gears from an XS650 that there is

still lots of tooth left. Now the bendix on a car will continue to engage till the

teeth are completely snapped off, and even then will turn the engine jerkily.

One usually changes them to avoid damage to the ring gear on the flywheel,

rather than because they won't engage. It’s not the worn teeth on the #4 gear

that prevents engagement. The reason the starter does not engage is because

of the spring clip on the #4 gear losing it's tension. The manual calls for about

5 lbs tension required to rotate the clip in it’s groove on the gear. The tension

found on the new ones can be up at about 8 lbs. You will invariably find that

the tension required to move the clip on non-functioning starter gears will be

down to about 2 lbs or less. This can be measured using a fishing scale.

What happens is this.

Because the # 4 gear is light and does not have enough

inertia (resistance to being rotated from a state of rest), Yamaha designed in the

spring clip to increase the inertia. This restrains the gear from turning on the

bendix when the bendix shaft is initially rotated by the starter motor. So, as the

bendix rotates, the helix on the bendix shaft forces the gear down the shaft and

into engagement, because the gear will slide before it will turn. Once it gets to

the end of the bendix, by which time it is fully engaged with the flywheel ring

gear, it has no option but to turn, it has nowhere further to slide. When the

spring tension in the clip is too weak, there is not enough restraint, so instead

of the gear resisting turning, it just spins with the bendix shaft, does not move

down the shaft fully, and is not forced into engagement. It goes down just far

enough to grind off it's teeth against the flywheel ring gear.

All that is necessary to get a starter gear working, no matter how worn the teeth,

is to bend the clip so it gets back to a minimum of 5 lbs required to move the

clip.

All that is needed to do is drain the oil, remove the kickstart lever, brake lever,

foot rest, and disconnect the tach drive cable at the side cover. Then remove the

right hand side cover. The best way is then to remove the clutch basket and

dismount the #4gear from the bike. I haven’t yet tried to do this fix with the

clutch still mounted on the bike and the #4 gear in place, but this may well be

possible. I am pretty sure that on the newer units where the loop of the spring

clip bears against the floor of engine case the that the loop will be visible just

under the forward lower edge of the clutch assembly, and you will be able to

reach in and do the following without further disassembly. On the older units

with the clip with the skinny loop inside the recess in the crankcase, the clutch

will definitely have to be removed and the gear dismounted. In any case, either

way, just use a heavy pliers, like a linesman's pliers, or a Visegrip, to squeeze t

he loop of the clip closed so it bends a little and the clip then grips the gear

tighter. If you do remove the gear from the bike, lever the clip off the gear

using a screwdriver, squeeze the loop of the clip in a vise, and remount it on

the gear. Check the tension with a fishing scale, if it is less that 5 lbs squeeze

the loop a little more.

You can test it immediately, even before remounting the clutch. Pull the spark

leads so the oil-empty engine does not start, and hit the starter button. I bet your

starter will now work, no matter what the wear is on the #4 gear's teeth.

Farrell