Saturday, 2 August 2014

Sprag Clutch Removal

Hi there,

Here is a step by step process to remove the sprag clutch. The sequence of disassembly is as follows:

1. Remove Left side rider's foot-rest
2. Remove Gear clip
3. Unplug the wiring coming from the clutch-case (/dynamo)
4. Remove Clutch case
5. Remove magneto's center nut
6. Remove clutch plates
7. Slide out (carefully!) the main sprocket connected to crankshaft along with primary chain and clutch plate holder assembly
8. Remove center nut in the clutch assembly
9. Remove allen screws and bolt holding the clutch case
10. Remove the remaining part of the clutch case
11. Open the allen screws to expose the sprag clutch

Unplug two connectors linked to the wiring loom coming out of the clutch case. You may need to remove the battery cover for this. Also ensure that the clutch oil drains into the pan, else it will be a mess, especially if you are doing it at home.

Not recommended though: Mech is using a rod to lock the primary chain/clutch assembly from rotating, so that the screws can be opened. Use specialised tool if you have access to.

Clutch plates are removed already. Remaining part of the clutch assembly will only come out only when the primary sprocket comes out. This may take time, if its very tight (thanks to RE's quality of manufacturing/assembly) like mine. Be patient at this stage, as any damage due to rush will be costly and painfully time consuming.

Special spanner to removed the center bolt holding the magnet in place.

Magneto comes out.

Now is the pain-part of this whole process. Didn't know it would be so tight. I was happy that its been untouched till date and was bit grumpy that the mech didn't had any specialised tool to removed a tight sproket.

It hurts to watch him do this to my bike ;(

Arrrgghhh had enough. Asked him, and got an obvious answer, that there is no specialised tool and it is actually supposed to be easy to pop-out. Well..whatever!

Finally after the visual torture and few scuffs inside my clutch case, the damn thing came out. Along with the main sprocket came out the primary chain and other side connected to the clutch assembly

One more bolt to go before the remaining part of the case can be removed.

3 allen screws around the crankshaft and one bolt on right hand side of gear shaft

It may need a soft head hammer to loosen the case from all sides, especially around the crankshaft and starter motor area.

Bit of crowbar method. Make sure not to over-do it.

Comes out finally.

All the chain lubrication and dirt been piling up around the drive sprocket which stays outside the case.

Inspect the case for any signs of unusual marks, etc.

Remove all the allen screws on the sprag clutch case.

Again a light use of soft head hammer would loosen the case.

The sprag clutch assembly is visible now.

Take out all the 3 sprockets and a stainless steel axle rod.

These two make the sprag clutch kit. One on the right hand side slides inside the sprocket kept on the left side.

Notice the tooth structure of the bearing visible here.

In a completely damaged sprag clutch, the bearing looses those metal teeth (pieces) inside the clutch case. That's bad and it will cause further implications. Imagine the primary chain rotating at a high speed and these metal pieces fall all over it. 

This is the damaged part. The area near my thumb supposed to be smooth, but it was developed grooves in the shape of the tooth seen inside the other bearing. Hence it doesn't slide, during reverse rotation of the sprag clutch. 

NOTE: After removed the complete sprag clutch set along with the main gear connected to the starter motor, the case remains completely hollow with no parts in it. So every time the start button is pushed the starter motor spins freely inside this case.


As its not everyday that you get to open the clutch box and get to see the primary chain, sprocket, etc, take this opportunity to inspect every part that you can. For example, I could notice the following:

1. My primary chain adjuster has run its best life and now there is a small packing underneath. May be the next overhaul I need to replace the set.

2. Sprocket internal locking thread on my bike is too tight (even after grinding it a bit). I need to compare it to a new spare if its a odd one that came from the factory, then this also needs to go.
Note: Being tightly connected to crankshaft is actually not a problem in the bike's operation, its just difficult to remove when needed. Which is again once in a blue moon.

3. My main sprocket is in decent condition for the now but I better replace it (along with chain-sprocket set) sometime after the ride.

4. My clutch assembly looks spankingly new :D Just bragging!!

Now while at it, I would prefer to clean up the areas visible. As once all parts are put back in place, certain areas of the bike (like the front drive sprocket) wouldn't be accessible from outside. So do the necessary clean-up at this stage.


Follow the same process in reverse. Additionally you may use a glue (mostly fevicol) on top of certain washers to ensure there is no chance for oil leakage. In my case, we used a little bit on the washer around the crankshaft.

Fill 400-500ml of 20w50 oil once the clutch case is assembled.


After the bike got ready I did a test-ride and riding was fine, but I found the kicker was not working properly. Kickers basically felt kinda spongy. For this I had to get the clutch cable adjusted. Then it was all fine and I could feel the kicker rotating the crankshaft (/piston) inside. After few attempts of kick starting the bike successfully I called it a day.

Sometime in the coming months, I am planning to put the new sprag clutch myself. This guide will come-in handy for sure.

Hope you enjoyed going through this photo-guide  and it helps you not only to understand the mechanics of the bullet better, but also to perform DIY jobs at home garage.

Keep Rolling,


1 comment:

Unknown said...

Thanks very much for this great info and pictures, due to a failure of my sprag clutch l'll be using this info to work on mine now.