Starter Gear Fix!

garyr

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Below I documented the fix for the slipping 4th starter gear. I want to add the original poster/author is below. All I did was test and post pictures to what he is writing about. I applied this fix years ago to a kick starter spring the same way with success.

The reason why the starter slips and spins out because the spring has lost it's tension or was never set properly. This is what I found.

The spring has to be at 6 pounds. I found when it gets to 4 pounds it slips. I tested this on 3 other bikes. They were all at 4 pounds that slipped, new aftermarket-used aftermarket OEM or otherwise. Just takes 2 pounds difference.
xsscale.jpg


This is what happens to the gear when the spring is at 4 pounds pressure.
xsgear.jpg


This is a fish scale I bought at Walmart for $15.00. I'll keep it and use it to adjust the steering head.
xsscalle.jpg


Here is the factory spring tension rate
xsinfo.jpg


I have gotten two of Mikes stater kits for 2 of my bikes and one worked fine and the other just spun. This is what I've found on the adjustment. You can only squeeze the spring in a vise. No matter how hard you squeeze you only achieve 6 pounds. So if you don't have a scale you will be in spec. Just don't over squeeze on the vise and disform the spring.
xsvise.jpg


Here is what I've also found. On the left is Mikes spring. Notice the flat sides to fit the new gear. To the right is a OEM NOS spring, it's fatter-just not grinded flat. When I put a NOS spring on Mikes gear you only get 4 pounds. If you squeeze the spring you get 8 pounds so that is the best set up. *Note* if you put a OEM spring on a OEM gear you will only get 4 pounds, the spring has to be bent in a vise.
xsclips.jpg


You really can't bend it on the bike and not take it apart this this.
xspliers.jpg


OEM part #
xsclip.jpg


Below is a post from the author with his fix I just documented and tested. This will fix the dreaded starter problem. You could probably just remove the slipping gear and squeeze the spring and you would be fine.


#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

 
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Very nice. I knew about the tension but never saw it documented with actual measurements and numbers like you've done. A note on installing the drag clip. Lay it over the top of the gear and snap it down into the groove. Don't try to insert it from the side. That will spread it open too much and you'll lose the tension.
 
are you saying that it's IMPOSSIBLE to over tighten the clip spring? I'm nervous I may have done that, but I'm having the starter-won't-engage symptoms (which seems like there's not enough tension on the clip). What symptom would I have if it were truly overtightened?
 
are you saying that it's IMPOSSIBLE to over tighten the clip spring? I'm nervous I may have done that, but I'm having the starter-won't-engage symptoms (which seems like there's not enough tension on the clip). What symptom would I have if it were truly overtightened?

I found any amount of pressure with the vise leaves the correct spring tension. The idea is "snug" the vise NOT super,super tight. My guess is you can move the spring with you fingers when you take it out of your bike. Put the spring in the vise and snug it in the vise then take it out and if you can't turn it with your fingers it worked. When you sung the vise you will see the spring end loop move it's shape.. slightly. Note: like in the picture you bend the spring in the vise with the spring installed on the gear.

And "NO" it's not impossible to over tighten it if you tighten the vise as hard as you can you could deform the spring. For the hell of it I tested an old clip and did tighten the hell of of it and my test it actually held fine and the shape stayed but I can't guarantee that for everyone with every type of vise. My point was I tried different pressures in the vise on the spring and they all gave me almost 8psi of spring pressure so you don't have to worry about how much vise pressure you use to achieve 8 pounds.
 
Thanks! what's the reason they changed the position of where the bend in the spring sits in the case? Does it actually make a difference?

I don't know why. I know Yamaha changed that in the early to mis 70's. I would only put the spring in...in that grove. If you buy a Mikes gear and spring as stated above you need to also snug that spring in the vise.
 
Around 1975, the drag clip was updated and the new one was made from heavier wire. It wouldn't fit in the original groove any more so it was positioned just to the right of it.

3IUtXfv.jpg
 
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If the spring is TOO tight, will it get stuck engaged?

No you can't make it too tight no matter how hard you squeeze in the vise, the spring will disform first and loosen actually. The more tension the better it engages.

Just don't over think it. Just squeeze it in the vise and snug up the spring weather new spring kit from Mikes or OEM or the used spring itself.
 
Very nice. I knew about the tension but never saw it documented with actual measurements and numbers like you've done. A note on installing the drag clip. Lay it over the top of the gear and snap it down into the groove. Don't try to insert it from the side. That will spread it open too much and you'll lose the tension.

I see garyr isnt online and Im tearing mine down. If I may ask you a question 5Twins - I see that gary has the spring still on the gear in the vice. As Im going to re tighten my original spring, do I need to take it off the gear or do the same as the pic with the spring on the gear and tighten in the vice? Thanks
 
I've done it both ways, the last time just last week was with the clip on the gear, as Gary instructs. The time before that, I took it off. It works either way but leaving it on is easier. I now have a fishing scale too so I'm able to test the "fix".
 
It can't stay engaged because when the engine starts the starter stops spinning. This lets the return spring push the gear out of engagement. The engine spinning the gear faster screws the gear back on the splines as well.
Leo
 
hi guys i have done the starter gear fix,,,,,i actually removed the spring from the gear and clamped it in the vice... then slipped it back over the gear...my teeth were slightly chopped ,so while i had it apart ... i put the gear in the vice and stonned the teeth ... then i re-assembled it it works like a treat... .y bike is a 1976 frame with a 1983 motor in it regards oldbiker
 
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