Starter Clutch....

I bought a parts bike from a wreckers last year and he said it wasn't running because the starter clutch was gone in it....

What's a starter clutch?

I know what a starter motor & the clutch are, and how they work, but have no idea what a starter clutch is.

 

HI,

Starter clutch...from the starter MOTOR, a gear connects the starter motor to the starter CLUTCH. The starter clutch is connected to the crankshaft and is a link in the process to turn the engine over when the starter motor turns over.

When the starter motor turns it engages the mechanism in the starter clutch (i.e. it grabs) which then transfers the rotational energy from the starter motor to the engine. Once the engine is running the mechanism inside the starter clutch disengages - basically it works on friction when the starter clutch is sent spinning in a particular direction on start-up.

On the XJ's it sits directly behind the alternator housing, inside the engine. There's the hard way to get at it to repair it or there's the really hard way to get at it.

The HARD way is to dismantle the alternator and its guts, open the plate at the back of the alternator housing (torx bits required) and then delve carefully into the cavity (instructions have been posted a few times elsewhere on this site).

Or the REALLY HARD WAY (which you might have to do anyway if you drop a small piece into the engine doing it the HARD way) is to split the crankcase (requires removing engine from frame) and doing open heart surgery - once the engine has been opened the operation itself is fairly simple.

Does this help...?

 

A starter clutch uses rollers to lock the idler gear and the starter sprocket which drives the crankshaft via the primary chain when the stater clutch is turned in one direction and freewheels when turned in the opposite direction. These rollers are pushed out of the starter clutch housing at a slight angle by small springs and this allows the starter to lock up solid when starting the engine, and then to release when the engine starts. If you picture how a socket set rachet works then you pretty much have it.

 

I thought as much... Thanks.

So what typically goes wrong with these?

Hey Kiwi... Hows that 750 going?

 

If anyone knows where to find these I'd appreciate knowing where to look or what to search on... did a search before I posted this and for 400 odd results from "Starter Clutch".

 

Below is a post from Bike-Man-Man who like me has performed open heart surgery to replace starter clutch springs and rollers. There's been a couple of posts on this lately so it may be useful to those in need:

"Yes, it is possible, however if you drop the rollers, springs, or spring caps in the crankcase, you going to have to do it the "right" way anyway...Be prepared....The keys are some patience and go slow...

I'm doing this from memory so if I left something out or you have a question, please let me know....

First I took off the starter assembly off and the alternator cover and positioned it aside...Next you must remove the stator (the big copper thing inside the cover that spins w/the engine) there's a bolt in the middle to remove, but the stator has to be pressed off the shaft, you'll have to have a special tool...I've seen them on ebay, but I modified an old harmonic balancer removal tool (the threads were the same)...If you look at the stator it has threads cast into its housing, thread the special puller bolt into that, and while turning the puller, the stator will slide off the shaft....Next, remove the three torx screws that hold the retainer plate to the case....Then, the oil spray tube can be removed...Now the tricky part, pull the shaft out of the case (the starter clutch unit will fall down) using long screw drivers separate the two halfs of the clutch mechanism....The half closest to you will have the chain wrapped around it, and half farthest from you will contain the rollers, springs, and spring caps....Using the long screwdriver, hold the farther section up higher than closer, using another screwdriver you can manipulate, and rotate the clutch/roller mechanism around to remove the three rollers, springs, and caps....A telescoping magnet will help alot...Reassemble the opposite of removal, go slow, make sure both halves of the clutch mate together properly, use a dab of grease to hold the springs, and caps together....

I will also add as a side note, as it may or may not be required to do so, but I did have the trans clutch removed while doing this, and I also unbolted the idler gear that goes between the starter and the starter clutch(this is done from the trans clutch side)....The idler gear will fall down an inch but can easily be manipulated with magnets and screwdrivers...

 

typically the rollers get nicked or the springs in them die
pretty fragile

if it dies at old age i would say that the rollers have become to small and will not jam like they are supposed to

 

Thanks Red & Turtle... Very helpful

 

The starter "clutch" due to its design is also susceptible to getting gummed up, and thereby not engaging. It is also sensitive to too "slippery" an oil (friction-modified synthetics, for instance) that doesn't allow the rollers to "grab" and lockup properly. A lot of members have "fixed" apparent starter clutch issues with an oil change, or an engine flush and oil change.

 

The XJ750 is on the road and I've been putting some miles on it, currently the focus is building up the second set of carbs (I bought from you) as although the original set are OK I'm not convinced they are 100%. I am still interested in the spare set of XJ900 pipes you have if they are still for sale. Can you send some pictures?

I've not had the pleasure of visiting the starter clutch on the XJ but it does look very similar to the model fitted to my XZ550 (83) which suffered from at least three problems (all design flaws or Yamaha assembly issues) and I had them all.

1. The starter clutch housing cracks, the cause of this cracking coulds be related to the other issues below. The cracks open up under load and effect the rollers and springs, causing them to either pop out completely or effecting the contact angle and poor contact (skipping without rotation).

2. On the XZ the retention of the starter clutch housing was by cap screws and these would loosen off as the factory had not used loctite (or if they had it wasn't up to the job). The fix was to use slightly longer cap screws and peen over the thread ends.

3. Flat spots on the rollers and weak springs.

Fortunately the XZ was such an undesirable bike and there many XZ400's for sale here in NZ, I had plenty of spares.

 

I'm doing a garage cleanup as we speak so I'll haul them out and take some pics

 

cracks like this

 

I'm beginning to think "clutch" is an oxymoron in this case.

This thing is nothing more than a giant, primitive sprag clutch, (one-way clutch) except every sprag clutch I ever saw had MULTIPLE rollers to grip with, not just three.

From Wikipedia: A sprag is used in the electric starter motors of modern motorcycle engines to replace the "bendix" common to auto starters.

Let's hope they're using more than 3 rollers now.

Those cracks follow the drillways for the springs, don't they? I wonder if they were more heat than impact generated?

All XJ's have this crappy design, don't they?

 

Lovely picture, exactly what happens. It could almost be out of my long lost (but not forgotten) XZ550.

Sprag clutch was the exact term I was searching for!

 

I've just finished a Clutch replacement too, and decided as I did it the right way ... to go all the way .. total overhaul! If it's an older high mileage bike chances are it will need a good clean out, and a new set of bearings/rings anyway... thanks to this site, and a heap of experience from many members you pretty well have all the know-how right hear to do the job.

 

Right in the middle of a starter clutch-ectomy on
an '82 XJ750RJ, doing it the 'harder way'. Figured
it'd be a good idea to go ahead and replace the
chain guide as well, sure enough it was pretty well
worn out, after just under 30K miles.
Starter clutch body was cracked in three places,
like many others.

 

I'm not sure how you would actually accomplish this procedure as described.....that starter clutch assembly on the 550-900 engines is a "2-piece" unit, but the "halves" don't need to come apart because the idler gear just pulls off the back of the clutch assembly.....the "halves" that you are referring to (one side is shown in the picture above by NCJ56) are held together via three socket head cap screws.....adn there's no way that you're going to loosen those screws while that unit is inside the engine case and you're working through the alternator shaft cover plate opening.

In theory, you might be able to get the major clutch assembly unit (the side nearest to you) rotated/tilted "upwards" enough to use a telescoping magnet to retieve the rollers, caps, and springs out of their sprag "holder", but my gosh, I just don't know how you'd ever get all those little Humpty Dumpty pieces back into the sprag again (actually, the springs and pushrods you MIGHT be able to manipulate back in, but trying to put the rollers back in requires that the springs be compressed, and THAT task seems like it would be the really impossible part of this procedure).

Mind you, I haven't attempted to do this myself, but I have fiddled around with an "empty" engine case and a starter clutch assembly, and tried to manipulate it about as described, and that was with the engine cases sitting on top of a workbench.............and I finally gave up.

If anyone DOES attempt to do this task with the engine still together, PLEASE document it with photographs! I promise I will nominate you for a Guiness Record Book award!!!

 

In searching for a way to repair the starter clutch - hopefully
without having to remove the engine -- I came across the
post that chacal has quoted just previously.

The Haynes manual I was using also referenced the starter
clutch as an assembly that could be removed from the
engine without removing the engine itself, so at the outset
I endeavored to as much, to no avail.

The apparent problem with accessing the assembly through
the opening behind the alternator was (in my case at least)
that although the Hy-Vo chain and the idler/drive gears could
be fairly easily removed, I found the three (loctited!) socket head
screws holding the assembly together inaccessible, thus
preventing separation of it into two 'halves' and eliminating
the possibility of rotating the resulting subassembly around
to access the rollers/caps/springs.
And, as stated previously, losing any of those items - cap screws,
rollers, spring caps, springs, or rubber cushions - presented
itself as such a high probability that I scrapped the idea of
possible repair by this method.

The other route that appeared possible was perhaps by
removal through the underside of the motor, accomplished
by removing the oil strainer (sump) plate, removing the
oil pump (all easy enough), removing the alternator
stator/rotor/jackshaft, and gaining access to the starter
clutch once released in that manner.

Problem there, though, was that the transmission input shaft
blocked removal of the starter clutch from above it
(I realized this once the cases were separated later),
thereby negating repair by that method. This was what
the manual (assumedly) was suggesting, I think.

Once it was revealed that trying to effect repairs
with the engine in place was going to be a greater headache
than just biting the bullet and working the problem
from the bench, the decision to do so became clear,
with the added benefit of being able to make a general
inspection of engine internals (looking for galled bearings, etc.)
as well as being able to replace the primary chain guide,
which had worn beyond limit.

Hope this info has been of some assistance - removing
the engine, once everything was said and done, has not
been that big of a deal.

 

Now we're talking....

This is what I originally expected the fix to be... Pull motor out, strip down to get to it.

Thanks for the photo's guys... Makes a huge difference to be able to see what they look like.

Seeing as this is my parts bike I doubt I'll embark on this mission anytime soon (have an XS11 to restore first) but it means that I will most likely rebuild this entire engine as a spareafter the XS is done.

 

OK, a few months ago I tried the method through the alternator hole on my Seca 750. I'm pretty good with a wrench having worked as a commision paid technician at a major Yamaha Suzuki stealership for over 9 years. After getting the alternator shaft out, I gave up trying to separate the two clutch 'halves'. There just didn't seem to be enough room to do it, since the halves could not be removed from the drive chain through the alternator hole, nor could the halves be separated with the chain on. With the engine removed, cases split and trans shaft out, it would drop out the bottom. So, I put it back together and dread starting it when hot. It still starts fine when cold. I'm using 10W-40 oil, and I suppose I'll go to a heavier straight weight once it gets worse. By the way, it has 37,XXX miles on it, and I don't plan to put overhaul money into it. I don't like it that much :roll: . So I've got a set of the starter clutch springs, cups and rollers for sale. Anybody got a 1990-93 FJ1200 for sale?