Unofficial Royal Enfield Community Forum
Royal Enfield Motorcycles => Bullet Electra & AVL => Topic started by: Buckeroo on February 04, 2014, 06:34:38 am
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I have read many topics on this crummy piece of engineering called a sprague clutch. But I have not seen any real solutions short of just removing it. There does not seem to be a replacement primary case that eliminates the starter motor or even a cover plate that allows removal of starter. So what I end up with is an ugly unusable starter hanging on the front of the motor? I've been out of the loop for a while. Anybody come up with any new solutions in the past 6 months?
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Yes. Take care of your sprage .
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I too, was unhappy to hear about the fragility of the sprag (after I bought my bike!). I thought I could manage by just using the kickstart but I find that too strenuous. So, I bump-start down the hill where I live (after first getting it over TDC and in third gear) - always starts easily this way. If I ever do need to use the electric start, I make sure I get it over TDC and with the valve lifter pulled in I hit the starter, let it get up to speed and then release the valve lifter. This takes the stress off the starter motor and prevents a kick-back. I always stop the engine with the valve lifter. I also have 800cc of ATF in the primary. Finally, always ensure the battery is fully charged. I hope with these simply precautions that the sprag clutch will lead a long and happy life.
I think we should have a competition to see who can remove their starter motor assembly and replace it with something more useful and attractive. Perhaps a coffee grinder, a smoothy maker, pencil sharpener etc
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Sprag failure is more common on the AVL engine due to the higher compression ratio. From my own experience (4th sprag... or is it 5?), I can offer the following points of wisdom:
1. Sprags fail, not on starting but specifically on stalling. When the engine doesn't have the required momentum to get past TDC, it can backfire. The sprag is designed to stop the engine driving the starter motor once it's running; sort of a one-way clutch. A backfiring engine (engine going backwards) was not taken into account in the design.
2. Given these facts, it can be seen that the method of starting has no bearing on Sprag Clutch Failure. It is the method of stopping the engine that is important.
3. The best protection is to ensure that your tick-over is not low but comfortably high (but not racing).
4. Stop the engine either on the Ignition Switch, Kill Switch or on the Decompressor (valve lifter). Each method prevents a stalling and possible backfire which must be your aim to save the sprag.
4. Stalling is the enemy and must be avoided at all costs
Adopting these tactics has (thus far) proved to be the saving grace of my sprag clutch.
Watch this space!
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Electric starting on a weak battery could cause the engine to turn backwards if it can't get it past the firing point fast enough. Spinning the engine up to speed first with the valve lifted has to be the healthiest option for the starter, battery and sprag. Similarly, a half-hearted kick could cause a bounce back. Stopping the engine by turning the ignition key (or kill switch) will cause the engine to 'bounce' back when it has lost enough momentum to get over TDC. Stopping the engine via the valve lifter has to be the safest option as it is impossible for the engine to bounce back on no compression. So, I would argue that starting and stopping methods have an equal bearing on sprag failure.
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Hi,
There does not seem to be a replacement primary case that eliminates the starter motor or even a cover plate that allows removal of starter.
Actually there is an inner primary case meant for the Indian home market 4 speed Electra 350 which can be adapted, have a look at THIS: ???
http://www.ebay.co.uk/itm/251021647790?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
You will need to re-drill and tap the three holes in the crankcase drive side where the E/S inner primary bolts on: as this is a K/S inner the holes are in a different position, but the good news is that the E/S drive side crankcases still have the metal in place in the right position to drill and tap (8mm or the 5/16" thread of your choice) for the K/S inner case.
If your Electra-X/AVL Classic is still running with the stock left foot gearshift you will also need an accurately drilled hole for the gear change shaft (a good reason for a right-foot shift conversion, if you ask me :-X ) You might also need the engine sprocket from a K/S model and definitely a K/S inner primary to crankcase gasket.
The alternative is to cut off the "blob" for the E/S portion of the stock inner primary and have (for example) a very good ally fuel tank shop weld a piece of suitably shaped 16 gauge ally sheet into the hole. I have seen a fairly rough attempt at this which didn't look so good, so get someone who really knows what they're doing.
Any use?
A.
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I had read about the 350 case replacement, but I'm not so confident of drilling holes in the correct place. I have also read about a free replacement of the ignition module that eliminates the backfire or at least firing on a back fire stroke. And I suppose I will replace the sprag and use the decompression switch to kill the motor. I was hoping the issue did not carry over to the electric starter. I have also read that I shouldn't use ATF in the primary when using an electric start. I have a liter of Castrol w20-50 in the primary currently. The sprag is damaged it seems to the point of not letting the engine even roll over. I had hoped I could just ignore it, but guess not. Can the rotor and clutch be removed with air tools? Is it necessary to buy the special tools to remove these items?
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I have read many topics on this crummy piece of engineering called a sprague clutch. But I have not seen any real solutions short of just removing it. There does not seem to be a replacement primary case that eliminates the starter motor or even a cover plate that allows removal of starter. So what I end up with is an ugly unusable starter hanging on the front of the motor? I've been out of the loop for a while. Anybody come up with any new solutions in the past 6 months?
The main things for people who insist on using the starter all the time is a fully charged, powerful battery, a well tuned engine & NEVER shut the engine off with the key!
Kill it with the decompressor. Turning the key off after the engine dies soon becomes a habit.
If, like me, you avoid the starter like the plague, the most important thing is getting the engine in the right place & then giving a full, smooth, powerful kick all the way down. Pretend you want your foot to make a hole in the driveway. A half-assed kick can give you a kick-back. It's the kickbacks that break sprag teeth.
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Just found an alternative to the oem RE sprag. It's on eBay, out of Australia... it appears to be a borg warner part.
http://www.ebay.com/itm/160995951012?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 (http://www.ebay.com/itm/160995951012?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649)
I'm asking a couple of questions about the part and will see what response i get...
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Yes, the same sprag lives in Borg Warner transmissions.
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Yes, the same sprag lives in Borg Warner transmissions.
Ace, do you think this is any better than the oem sprag? Know of anyone use the borg warner part? My thinking is the application in the bullet (or any single prone to kickback) and the design of the sprag will result in the same demise; regardless of who marks the part.
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Ace, do you think this is any better than the oem sprag? Know of anyone use the borg warner part? My thinking is the application in the bullet (or any single prone to kickback) and the design of the sprag will result in the same demise; regardless of who marks the part.
It doesn't matter who makes it.
I just remove it and kick start it.
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I will say this, I use the E-Start occasionally, and it isn't broken yet. But nothing has racked my nerves more than when I was tuning the carb after an up-jet and having to start it over and over especially when it would sputter out. Couple of times on a sputtering out and stall I would hear the 'click-whirrrrrrrr' afterwards. The tell tale sound that the sprag just took a hit.
It seems that a healthy bike, with a strong battery, and letting out the decomp when you turn it off will keep the sprag in shape. God forbid you stall the 'wrong way' or have to fine tune a carb or sort out some other problem where you could get a bit of a kick-back while tweaking and tuning.
When mine finally goes, I have resolved to just go ahead and remove it.
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Never shut AVLs off with the ignition key & only use the ES in emergency traffic situations if you must. Girls in India kickstart these bikes.