Starter motor problems.

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tony.mon
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Starter motor problems.

Post by tony.mon » Mon Aug 22, 2011 8:45 pm

We have had a spate recently of starter problems; where the motor seems ok, but the engine won't turn.
This can only be caused by one of two things; sprag clutch rollers flattening or transfer gear failure.

This article addresses transfer gear failure.

Image
http://img9.imageshack.us/img9/7180/e0800.tif

The transfer gear is two steel sprockets on a common shaft, fitted between the starter motor and the sprag clutch (which is behind the alternator rotor).
Its job is to transfer rotary motion form the output shaft on the starter motor to the sprag clutch. Honda have designed this gear in such a way that the two gears are on a common shaft; one gear has a shaft cast integrally and the other gear is pressed onto it with a tight interference fit.
I assume that the design allows the two gears to rotate against each other under extreme stress, such as when the starter motor is turning the gears but the engine "kicks back" and tries to counter-rotate, which would lead to catastrophic failure of the starter motor shaft splines if the torque were not relieved in some way.
Unfortunately, after this has happened a few times, the gears pressed together become worn enough to allow them to rotate against each other under normal starter motor loads.
There is a loud squealing noise when this happens.

In order to repair this, there are three choices:
1. remove the gears and replace them with a new set
2. remove the gears, weld them together and replace, and
3. remove the gears, drill and pin and replace.

Solutions 2 and 3 are easy and cheap, but if one assumes that the gears are meant to allow one to move relative to the other under extreme forces, it might not be the most effective solution, assuming that the situation causing extreme forces may reoccur.

However, the options are quite simple, either weld the two gears firmly together, or drill at an oblique angle and fit a roll pin which again will effectively lock the gears together.

In order to remove the gears it looks at first as though a large amount of disassembly is necessary, but it can be done fairly easily.

Firstly, set the engine to front top dead centre in the position (front cam lobes facing upwards and away from each other- see Sirch's excellent thread to set this) ( tip: set the engine to the rear position first, then rotate the engine one and a quarter turns anti clockwise to get to the front position needed) then remove the front CCT.

Now remove the alternator cover, and the alternator coils, around the rotor.
You can now see the rotor. Remove the rotor (you'll need a puller, or a rotor removing tool- (Benny Hedges has the specs to make one- search in Workshop threads) and remove the rotor, and the sprag clutch behind it.

Once that's out of the way you will be able to see the lower fixing bolt of the front cam chain tensioner, held on by a star drive bolt.

Then, using the correct star drive socket, remove the lower tensioner blade bolt.
The gears themselves are mounted onto an axle pushed into the crankcases; this can be simply pulled out using a magnet. Removing the starter motor, if not already done, makes this easier.

Now, by careful use of a couple of large screwdrivers, the two gears can just about be squeezed past the lower end of the tensioner blade, and removed.

Replacement is the opposite of removal.
Check for any flat spots or wear on the sprag clutch rollers, if there is any visible wear they must be replaced.

Don't forget to carefully re-check that the cam timing is correct before reinstalling the tensioner itself.

Now, assuming that you're completely confident, press the starter button-
and the engine will start.
:thumbup:
Last edited by tony.mon on Mon Aug 22, 2011 9:05 pm, edited 2 times in total.
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tinysmall
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Re: Starter motor problems.

Post by tinysmall » Mon Aug 22, 2011 8:52 pm

Ta very much for this mate :thumbup: I'll get on it in my next set of days off.
Never argue with idiots. They drag you down to their level then beat you with experience!

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Leachy
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Re: Starter motor problems.

Post by Leachy » Thu Sep 08, 2011 3:10 pm

Cheers for this thread Tony.mon, if i ever see you i owe you a :beer:
Absolutely Sodding Bloody typical!!!

tony.mon
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Re: Starter motor problems.

Post by tony.mon » Thu Sep 08, 2011 8:12 pm

It's only this if there's a screeching sound when you press the button, and you pull the alternator cover off and can see the motor turning but the alternator isn't!

If this isn't the case it's a dodgy lead to the starter motor and/or connection bolt on the motor itself.
It's not falling off, it's an upgrade opportunity.

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darkember
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Re: Starter motor problems.

Post by darkember » Thu Sep 08, 2011 9:11 pm

WOW Tony you are an encyclopedia of information :thumbup: :thumbup: Makes Valve clearance a boring task :D :D

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sirch345
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Re: Starter motor problems.

Post by sirch345 » Sat Sep 10, 2011 9:41 pm

Good write-up Tony :thumbup: well done :clap:

Chris.
A closed mouth gathers no foot. :thumbup:

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dkt1376
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Re: Starter motor problems.

Post by dkt1376 » Fri Sep 12, 2014 2:28 pm

ive recently done this repair for a friend of mine, i did set the timeing and remove the tensioners as i was doing the stopper mod at the same time.
it says in the origional post you can remove the gear by prying it gently past the cam chain guide 8O, that may be the case but it was to tight for me to try that on someone elses bike.
because i had the tensioners out it was just as easy to undo the blade.
as you can see in the second pic the gear will come apart when they are knackered.
Image

Image
a landrover d2 and a ktm, i had to have a honda to restore relability in my life.

tony.mon
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Re: Starter motor problems.

Post by tony.mon » Sun Sep 14, 2014 5:31 pm

That was properly loose; I haven't see them come apart before.
It's not falling off, it's an upgrade opportunity.

rhys0019
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Re: Starter motor problems.

Post by rhys0019 » Thu Oct 02, 2014 7:03 am

Hi I need help! I tried to start my bike and all I get is a clicking from my starter relay. If I push it to start it goes ok when I pull the front brake while riding the speedo drops to zero and the trip clock goes off . If anybody has any ideas?

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sirch345
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Re: Starter motor problems.

Post by sirch345 » Thu Oct 02, 2014 9:56 am

Your problem sounds more like either a charging problem or the battery is on the way out. Also don't rule out bad connections, especially the main power lead to the started motor. If you need to remove the main power lead on the starter motor to clean up the connection, make sure the bolt doesn't turn, if it does you can damage the insulator inside the starter motor. Also check battery leads are done up tight at the battery terminals, including the earth lead that bolts onto the back of the engine connection, and the connections on the starter solenoid (that's the thing you can hear clicking, which I think you already know).

I would check the starter motor power lead first, and check (with a multi-meter) the charging rate at the battery terminals with the bike running, no lights on. You should be getting somewhere between 13.5 and 15.5 volts,

Chris.
A closed mouth gathers no foot. :thumbup:

tony.mon
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Re: Starter motor problems.

Post by tony.mon » Tue Sep 22, 2015 7:05 pm

I have some spare transfer gear sets in stock if anyone needs them- just pm me for a price.
It's not falling off, it's an upgrade opportunity.

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fabiostar
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Re: Starter motor problems.

Post by fabiostar » Sat Sep 26, 2015 10:04 pm

tony.mon wrote:It's only this if there's a screeching sound when you press the button, and you pull the alternator cover off and can see the motor turning but the alternator isn't!

If this isn't the case it's a dodgy lead to the starter motor and/or connection bolt on the motor itself.
do you mean as in the starter motor turning or the engine. forgive my thickness lol
the older i get,the faster i was :lol:

tony.mon
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Re: Starter motor problems.

Post by tony.mon » Sat Sep 26, 2015 10:09 pm

You can see one transfer gear turning, driven by the starter motor, but the second transfer gear doesn't turn the crank.
The two transfer gears should turn together; if one turns so should the other.
With the alternator rotor removed you can see what's happening.
It's not falling off, it's an upgrade opportunity.

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fabiostar
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Re: Starter motor problems.

Post by fabiostar » Sat Sep 26, 2015 10:23 pm

tony.mon wrote:ou can see one transfer gear turning, driven by the starter motor, but the second transfer gear doesn't turn the crank.
The two transfer gears should turn together; if one turns so should the other.
With the alternator rotor removed you can see what's happening.
ah rite i see said the blind man. yeah they are turning togther when i had the starter clutch gear on but not the flywheel itself :thumbup:
the older i get,the faster i was :lol:

Triad
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Re: Starter motor problems.

Post by Triad » Tue May 24, 2016 1:05 pm

Hello! Sorry to resurrect an old thread but... I'm having troubles with the starter clutch/sprag.
The starter motor is fine, turns but some gear slips and the bike won't start. The teeth of the next wear (where the motor engages) look fine too... so which part could be worn?
My mechanic still has to open the carter to find out but I wanted to save time and fine the parts to get back on the street asap. Any advice?

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