Suzuki RF900 "Cush" drive needs fixing? Please help

[chadnz]

Hi all,

My RF900, 1998, has 35000miles on it, and the battery doesn't charge... one place said I needed a new alternator generator, costing $1400 brought over from Japan, and another mate said that its a common occurence at these miles on RF900s... and its just the "Cush drive". Can anyone give me some info on where to get parts and how to fix it please? Any ideas would be wicked. Thanks, Chad, chadnz@gmail.com

[ManDownUnder]

Riffer is your man for this detailed stuff. I have sent him a message so he knows to look in here

[chadnz]

Yeah I don't know what a cush drive is or where to get one or how to fix, i got a mechanic mate that cna do it all, just need to know WHAT to do heh

[Warr]

If its like any other motor cycle (permanent magnet rotor) alternator. Chances are its the Rectifier/Regulator that has cooked.
Look at 2nd pic (http://www.1stconnect.com/anozira/SiteTops/energy/Alternator/alternator.htm)
That shows stator coils which feed to the Rect/Reg 3 wires. Yellow in colour, the expensive bit to replace is the stator. With a multimeter on resistance find these 3 yellow wires, you should have the same resistance between any 2. On open circuit / zero ohms will indicate the stator is burnt out.
This is NOT the most likely cause of your troubles.
If you do have similar resistance .. then very likely you need a new regulator/rectifier.
No need to buy OEM just make sure the one you get has decent heatsink fins on it. A mod some of have done is to mount a cooling fan over the top of the fins just to ensure it will last a little longer.
Best of luck :)

Bend-it below has alerted me to that I have written a load of Bull...t
Looks like the RF uses a propper alternator - Good on Suzuki !!

As Bend-it states most likely is the brushes which feed the control voltage to the rotor via the slip rings.
Hopefully easy to replace. When I did mine on my XJ900 I took the old ones down to a local auto Electrician and he found/modified some to suit.

[Bend-it]

Yeah, 've heard about this problem as well, but *touchwood* it hasn't occurred on mine... Apparently gsxr750 alternator units are the same and it's easier to find 2nd hand ones of them... Would love to read riffer's comments.

[Bend-it]

This what you need?

http://shop.wemoto.com/pictures.dyn?u=1915519qqq5828373

[chadnz]

Mean as, thanks for the info, will pass on to my mate... now to see what Riffer says too!! Thanks for such fast replies everyone!!

[xwhatsit]

Cush drive shouldn't have anything to do with your battery or alternator or anything electrical. All it is, is some rubber inserts in your rear wheel, that act like little shock absorbers to take up the `thumping' that comes from the engine through the chain. They are there to minimise chain/sprocket wear and make for a smoother transmission.

[Ixion]

Yes, rear wheels have them. But so do some alternator drives. Sort of mini versions of the rear wheel ones, for the same purpose. BMW has one, so too, apparently , do RF900s.

[xwhatsit]

Yes, rear wheels have them. But so do some alternator drives. Sort of mini versions of the rear wheel ones, for the same purpose. BMW has one, so too, apparently , do RF900s.

Would that cause the alternator to fail, though?

[Ixion]

Well if the drive fails, alternator rotor, him no go round n round n round n... Then , no lecktrickery.

[Blackbird]

If there's a chance that it's your alternator, look at the following post and get in touch with Ken Cairns in Hamilton. http://www.kiwibiker.co.nz/forums/showthread.php?t=47720&highlight=alternator

[crazybigal]

sure will, these bikes do them at around 60,000km mark so sound about right.
dodgy mechanic telling him he needs new stator bla bla for $1400 bucks:angry: should know better.
from mem you can get cush drive sorted for under $200 bucks. battery may be poked as well.


Would that cause the alternator to fail, though?

[crazybigal]

pm madmal64 he did his old rf900 a while ago, he will give you some ideas

[Grahameeboy]

If the motorcycle will only run when the battery has charge then there's most likely a problem with the alternator cush drive which can shear. This is an easy one to spot as, once the battery is flat the motorcycle simply won't go. Once again, this is a problem that, while it's probably possible to do it yourself, getting someone who knows what they're doing usually saves a lot of time and stress in the long run.

This happened on my RF..........

[riffer]

Okay, I've found the link.

Yep. It's the alternator cush drive.

You see, when these bikes came out a few Americans had the alternator drive shear on them. Lawsuits were threatened. Suzuki changed the design of the unit to incorporate a cushioning mechanism in the drive to the alternator. The trouble is, this $20 part fails very easily through wear and tear.

From what I know, its an easy fix, and a cheap part.

The trouble is, getting at the bastard. The labour costs are what causes the expense. And IIRC you need to split the crankcase to get at it, though I'd have to look at the manual to confirm.

Unfortunately, I've never done the fix, as my bike's an RS and therefore pre-cush drive.

How are your skills mechanically? Its apparently not too hard to fix.

[xwhatsit]

Ho, my apologies. Not everything is built like a Honda single :D

[Mental Trousers]

With those miles it's pretty much guaranteed to be the alternator drive.
In the pic below parts 38-41 are the alternator drive that is in your bike. Earlier bikes had parts 34-37. Ironically, 38-41 were meant to cure an occassional failure in parts 34-37 but instead of curing the problem they made it 100x worse!!
It's virtually always part 40 that fails. It's the single biggest problem with the RF900. Most reliable way of fixing it is reverting back to using parts 34-37.

http://andreas.warby.org/E4Alternator.gif

Have a read through the 2nd half of this thread too - http://www.kiwibiker.co.nz/forums/showthread.php?t=37435

[Colapop]

I know for damn sure there's another thread on here with comments from someone who's done this job... and it cost him $20... and a little effort - not too much from memory.... Hmmm shall get sleuthing on that one....
Found a couple of bits and pieces...
Hi all
Well I now have everything going on the bike. :scooter:
Found out the problem with the rev counter was a cooked resistor. Replaced this and all is fine.
I now have intimate knowledge of most of the electrical system on an RF.
For those that are not aware, if your volage regulator craps it self it can casue quite a bit of damage to other electrical components due to overvoltage.


Hi all,
Thanks for your replies
Got a price for one from a genuine part - $321.00 + gst ex Japan
Talked to an Auto Sparkie and came up with a suitable replacement for $36.00.
Uses a standard Bosch regulator mounted remotely with fly leads into generator.
Cheer

http://www.repairmanualclub.com
and the one I was refering to...

this one (http://www.kiwibiker.co.nz/forums/showpost.php?p=794372&postcount=23)
I should get a prize for finding that! Very Sniperish....

[Warr]

With those miles it's pretty much guaranteed to be the alternator drive.
In the pic below parts 38-41 are the alternator drive that is in your bike. Earlier bikes had parts 34-37. Ironically, 38-41 were meant to cure an occassional failure in parts 34-37 but instead of curing the problem they made it 100x worse!!
It's virtually always part 40 that fails. It's the single biggest problem with the RF900. Most reliable way of fixing it is reverting back to using parts 34-37.

http://andreas.warby.org/E4Alternator.gif

Have a read through the 2nd half of this thread too - http://www.kiwibiker.co.nz/forums/showthread.php?t=37435
Very good links on that thread MT, and worth repeating http://andreas.warby.org/photos/2003/0728.html

[chadnz]

Man you are all so helpful thats wicked... I'll get to work contacting these genius people!! Thanks a million, now where do I start... No mechanically I have no tools and pretty much suck, but have a contact who can do it... I just need to print all this off and go from there... that bit mentioning rev counter, mine, was shooting up and down on the motorway prior to it dying, maybe that was voltage stuff.. guess I'll find out soon enough. SO glad oyu guys know all this, Mt Eden Motorcycles guys just said it was $1400 ex Japan, not sure if thats plus labour?? Anyhow, I will print this off and decide what to do next...

[SARGE]

Hi all,

My RF900, 1998, has 35000miles on it, and the battery doesn't charge... one place said I needed a new alternator generator, costing $1400 brought over from Japan, and another mate said that its a common occurence at these miles on RF900s... and its just the "Cush drive". Can anyone give me some info on where to get parts and how to fix it please? Any ideas would be wicked. Thanks, Chad, chadnz@gmail.com

have a sparky build you one of these ...(applies to the FJ1200 in this instance but will work on anything ..) i have installed this on my FJ, complete with the adjustable voltage mod ..


Semi-legal stuff first ----

This design may be distributed freely with my consent (I'd like to know
where it goes). It may not, under any conditions, be sold.

================================================== =================


As you have undoubtedly discovered, the price that Yamaha is asking
for it's OEM voltage regulator is outrageous.

The circuit described here works as a replacement at a fraction of
the cost. It also allows the voltage regulator to be relocated to a
cooler location on the bike, such as adjacent to the battery.

The circuit is based on a Texas Instruments TL594 pulse-width-modulation
control IC. The internal oscillator, in this case set at approximately
20 kHz, generates a sawtooth waveform sweeping between Vcc and ground.
That waveform is fed to some logic to create a square wave of variable
duty cycle. The duty cycle is controlled by the output of the error
amplifiers. In this circuit, the voltage sensed from the motorcycle
battery is divided down and compared against a precision 5 volt
reference. If the battery voltage drops, the output of the error
amp drops and the duty cycle decreases. Vice versa should the battery
voltage rise too far. The voltage divider is calculated to give a
divided output of 5v with a nominal battery voltage of approximately
13.8 volts. This corresponds to the battery charging at about 2/3
potential max charging rate.

The variable-duty-cycle square wave is fed through more logic and
then drives two independent output transistors. Only one is needed.
In this circuit, the output is used in an emitter-follower configuration
so that the waveform is inverted. That is to say that as the
battery voltage decreases, the waveform duty cycle is increased so that
is spends more time at the 'high' voltage.

This output drives the gate of a heavy-duty MOSFET which energizes the
alternator rotor field windings and in turn produces a charging current
from the stator windings. As the duty cycle of the MOSFET driving
waveform is increased, the average voltage across the rotor windings is
increased and therefore the average stator output current is increased.

(The catch diode between the drain on the MOSFET and the battery
voltage connection (i.e. across the stator brushes) is for protection.
Any good moderate current (the 1N4004 is rated for 1A continuous,
10A peak) rectifier diode will work here.)

*** Update: 8/23/95: Use a beefier diode that the above stated as the
catch diode. I think the 1A rating here is too light. ***

In slightly more lay terms, as the load on the electrical system
is increased (high beam turned on, grip heaters on, etc), more
energy is drained from the battery. The voltage regulator senses
the lower battery voltage caused by the drain and increases the
alternator output current to match the load and maintain battery
charge.

As I, and other FJ owners, have experienced, riding an FJ for a long
distance on a hot day can cause the battery to overcharge and boil
dry. Over time, this can become a permanent condition. What has
happened is that the IC in the stock regulator has succumed to the
heat (of both the big air-cooled engine and the air temperature) and
failed such that the driving transistor (in the OEM regulator, it's
a bipolar Darlington) is stuck on. This causes the average stator
voltage to rail high and the alternator just pumps out as much
current as possible continuously. Hence batteries overcharge and
boil dry in short order.

This replacement circuit can be constructed and wired to the
alternator using the stock IC regulator bracket. i.e. the
replacement regulator can be placed anywhere on the bike, within
reason, instead of in the stock position which is subject to
excessive heat.

When I called for a quote on a replacement voltage regulator for
my '89 FJ1200 in October '94, my local Yamaha shop told me it would be
$190. Mail order prices were barely less. The components in
the replacement circuit should be easily had for less than $10 or
$15. The TI TL594 IC is only about $1.

And OBTW, yes, it does work. ;-) It works very well indeed.


Jeff Earls, Portland, OR and by mail: <jearls@rdrop.com>
Old adress: Beaverton, OR
Old emailadress <jearls@teleport.com> <jearls@mdhost.cse.tek.com>

[ManDownUnder]

Man you are all so helpful thats wicked... I'll get to work contacting these genius people!! Thanks a million, now where do I start... No mechanically I have no tools and pretty much suck, but have a contact who can do it... I just need to print all this off and go from there... that bit mentioning rev counter, mine, was shooting up and down on the motorway prior to it dying, maybe that was voltage stuff.. guess I'll find out soon enough. SO glad oyu guys know all this, Mt Eden Motorcycles guys just said it was $1400 ex Japan, not sure if thats plus labour?? Anyhow, I will print this off and decide what to do next...

Get in touch chap... I might (MIGHT) be able to ease your pain... PM sent.

[Warr]

...... From the text "MOSFET which energizes the
alternator rotor field windings"...

I thought you may have found a circuit that could be used on other bikes, but it will only work on an alternator that does not have a permanent magnet as its rotor.
The Permanent magnet type usually runs in oil directly off the crankshaft where as the FJ1200 and the RF's alternator run dry.
A 'dry' system allows the use of a coil for the centre (rotor) magnet which can be controlled. ie Need more output - increase the voltage on the rotor.
The permanent magnet type alternator used on a large number of bikes these days allows no control. The alternator is producing maximum output all the time, meaning a very robust output regulator / rectifier must be employed. Heat is the by product of this arrangement and failure is more a case of 'when' not 'if'.

[SARGE]

I thought you may have found a circuit that could be used on other bikes, but it will only work on an alternator that does not have a permanent magnet as its rotor.
The Permanent magnet type usually runs in oil directly off the crankshaft where as the FJ1200 and the RF's alternator run dry.
A 'dry' system allows the use of a coil for the centre (rotor) magnet which can be controlled. ie Need more output - increase the voltage on the rotor.
The permanent magnet type alternator used on a large number of bikes these days allows no control. The alternator is producing maximum output all the time, meaning a very robust output regulator / rectifier must be employed. Heat is the by product of this arrangement and failure is more a case of 'when' not 'if'.

sorted ... ya .. i figured the RF would have the same type of system but i wasnt sure .. i had a mate of mine whip this system up for me .. cost $30 and a box of beers to do it and it works great ..remote mounting is do-able also so i have mine mounted inside one of my air ducts for cooling

[chadnz]

Ok great, well my mate has his wedding next week so can't do it for a couple of weeks... if your mate wants to do it again then i will happily pay more than that!!!!