4.09. Electric Starter

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Electric starter fix without gear replacement

Farrell Hope

Farrell's articles


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.


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


Lay the bike down in a 45 or so degree angle, and you don't need to drain the oil....of course, you can't really test it before closing it back up, and you have to remember to shut off your gas before laying it down...(this works for changing clutch components/oil pump components too...), and is better to do with low level of fuel in the tank...

Chris Tulloch


Safety relays

The electric starter is originally equipped with a 'safety relay' which prevents you from switching on the starter motor when the engine is running. The yellow wire from the stator (where the three coils join) operates this relay. Clymer 'XS2 & TX650' page 216 shows how it works. --herbs 20:49, 10 Jun 2005 (CEST)


Starter motor to case seal

If you have a persistant leaker, don't drive the seal all the way in, let it stick out of the case about 3 to 4 mm and run a bead of silicon sealant around the base of the starter housing neck prior to installing the starter.

CR (Chicago Rawhide) or SKF number 13388 / 34x46x8 in metric sizing (mm).

They can be ordered from Bearings & Drives or Motion Industries. http://bdindustrial.com/index.php https://www.motionindustries.com/motion3/jsp/mi/index.jsp



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