[Possm_23]

I purchased my bike a couple months ago and I love it. The sprag clutch has gone out on it. If I replace it, will this be a recurring problem. I can use the kick starter for now but I am having knee surgery done so I will need to use my ES.
Thanks

[Arizoni]

The starter sprag clutch on the older Bullets is known for its failures.

IMO, it was under-designed and when used on a big single such as the Royal Enfield, several things can lead to its destruction.

Some say, "using it" is one of these things but I'll skip that one for right now. 

Sprag clutches as you may know consist of a number of elongated, "dog bone" looking steel sprags located between a hardened steel shaft and ring.
In this case the shaft is the crankshaft and the ring is inside the starter motor gear that surrounds the crankshaft.

With the shaft rotating faster than the ring, the sprags allow the shaft to turn freely.  If the ring rotates faster than the shaft, the sprags rotate slightly and bind up between the ring and the shaft temporarily locking the ring and shaft together.  This transmits the power from the starter motor which drives the ring to the crankshaft.

The usual cause of the sprag clutch failure is when the crankshaft rotates backwards.  This backwards rotation is usually caused during shutdown by the piston starting its final "compression stroke" but the crankshaft not having enough momentum to get the job done.  That can cause the compression to blow the piston back down the cylinder resulting in the crankshaft rotating backwards.

The sprags treat this as though the ring is rotating faster than the crankshaft so they lock up.  This causes the ring inside the starter gear at the crankshaft to accelerate the currently stationary starter motor reduction gears and the starter motor to a high speed.
This basically overloads the sprags and causes them to break.

To minimize this problem, the new UCE engine uses an automatic decompression system to prevent the reverse crankshaft rotation.

On the older Iron Barrel and the AVL Lean Burn engine, using the decompression lever to kill the engine instead of just turning off the ignition switch will reduce or eliminate the problem.
The engine suddenly dying when it is idling can also cause the crankshaft to reverse its rotation. 
There's not a lot that can be done to totally eliminate this except to increase the idle speed a little or to blip the throttle when the engine sounds like its about to die.

Another thing that can kill the sprags is a weak battery or poor electrical connection to the starter motor.

[dginfw]

FWIW, once these motors are set up properly and tuned up, it is VERY easy to start them.  There are videos of people in India starting them by hand

[Kevin Mahoney]

Very good advice from Arizoni. I own the prototype ES bike and have never had trouble but.....among his good advice about the decompressor I use it for the first couple of revolutions when starting just to make sure the engine has a bit of inertia in the right direction.

[Possm_23]

Two questions... Is it nessasary to replace the sprag and if so any one know of a good video showing it done.

Thank

possm_23

[heloego]

https://www.youtube.com/watch?v=ckiQN_i-buE

Another of singh's great videos!
Actually about removal only, but good enough to get you through it if you feel you must replace it.

[Blltrdr]

I'm assuming the motor in question is a classic iron head and not the newer UCE motor. Maybe I'm wrong but I thought Singh's UCE was the first year production.

[Possm_23]

I don't know one from the other. It's a 2008, the starter is in front of the cylinder not behind it like in the video. I am kinda ignorant when it comes to the jargon used about bikes.

[ace.cafe]

That,s either an Iron Barrel Bullet or an AVL Electra X model.
If you provide a picture, we could tell you which one.
 It is not necessary to replace the sprag, if you will use the kicker only, which most people do anyway. But you should take out the intermediate gear cluster to prevent any trouble from the sprag.

[Possm_23]

I went ahead and ordered a new sprag, Im going to attempt to put it in just so I can have it. I think I can do the work, usually if I tear something apart I can put it back together. I've learned a lot about how to use the ES so maybe I wont destroy this one. Thanks for all the help guys. I still intend to use the kickstart now that I learned how to use it.

[Arizoni]

A quick way to tell which engine your motorcycle has is to look at the rocker arm covers.

If the joint where they meet the cylinder head is running parallel with the ground you have a "Iron Barrel" engine.
If the joint is canted at an angle of about 40-50 degrees to the ground you have a AVL Lean Burn engine.

The AVL engine was the replacement for the older Iron Barrel.
The new Unit Construction Engine (UCE) replaced the AVL engine around 2009 and is the only currently made engine.

Parts for the older Iron Barrel and the AVL in the United States are readily available from Nfieldgear.  1-800-358-0938

[creaky]

Im going to attempt to put it in just so I can have it. I think I can do the work, usually if I tear something apart I can put it back together.

Good luck changing the sprag. I did mine and it was easier than I thought. My only advice (wish someone had warned me) Be careful refitting the stator and make sure you have clearance all round from the rotor. I stuffed up here and it cost me a new alternator. But the sprag clutch works fine. Richard