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| A sprag clutch was used in early electric-start Bullets. |
A reader named Tom recently asked this:
"David, I have a 2005 Military Bullet. When I try to kick start the decompressor does not work, but cable seems OK. Electric start will not work either. The kickstart is always hard to push and seems engaged with turning over. Any ideas?"
I pointed him toward the Yahoo Group, where he soon got this very complete answer from member Rick F:
"Most likely the sprag clutch in your starter drive has disintegrated and jammed, forcing the crankshaft to turn the starter gears. Been there, done that. Is your engine now very difficult (virtually impossible) to turn over? If so, you may need to replace the sprag. It's a simple mechanism designed to allow rotation in one direction but not the other. Looks sort of like a large diameter ball bearing found in the starter gear train.
"To get at it you must remove the primary drive including clutch, then remove the inner primary case to get access to the compartment that houses it. Nothing terribly complicated but it is a tedious disassembly/reassembly; not a 15 minute job.Hitchcocks Motorcycles has a good exploded diagram in the parts section of their website.
"If you've heard a loud 'clang' when the engine kicked back on starting or stopping, that's it trying to turn your sprag backward. Doesn't take too many of these kickbacks before the sprag is broken."
Tom replied:
"Thanks Rick! Sounds like you have really hit the nail on the head. I have heard the 'clang' on a number of starts, when I switch from kick starting to using the electric start. Sounds like time to order some parts and dive in."
There is more information about the sprag to be found on the Royal Enfield USA Community Forum, where one of the members is president Kevin Mahoney. He told his readers there that, at some point in production, Royal Enfield began equipping AVL (Lean-Burn) Bullets with an updated ignition control box that protects the sprag from kickback. He urged his readers with Lean-Burn powered Bullets to make sure that the Transistor Controlled Ignition (TCI) box on their motorcycles is green in color.
"I want to remind all of you Lean-Burn owners to check the TCI (ignition) box underneath your seat. It should be green, which is the newest model. If yours is black either call us with your VIN number at 800-201-7472 or go to your dealer and get a free replacement. The new one may help save you from a sprag clutch repair somewhere down the road."
These concerns don't apply to the new Unit Constructed Engine models (C5, G5 and B5 as they're called in the U.S.). They use a different design.
Now and again I get horrible noises when I try and start my C5, electric start only, I am far from impressed with only 8000 miles on the clock. piece of shite no wonder India ia and always will be a 3rd world country.
ReplyDeleteI agree with you. the parts from this bike sucks
ReplyDeleteI just bought an '08 bullet with only 6000 miles on it a month ago. The sprag clutch has already failed me twice. I've tried starting it several different ways, but cant seem to avoid the terrible "clang" sound when it turns over. I'm thinking to just letting the e-start go and using my kickstart only. Do I need a working sprag clutch to kick start my bike?
ReplyDeleteThe reply I received from experts I asked: "It needs to be removed. It is always engaged at all times with the front primary gear. As it disintegrates, it will drop metal parts down into the primary, and they can end up jamming into the chain and sprockets."
DeleteAnd this: "One doesn't need a working sprag clutch to kick start an e-start bike -- but if one has a jammed sprag, it can lock the electric starter gear train and motor to the crankshaft so that the whole plot turns with the crank. This could make kick starting and running virtually impossible. Mine failed this way once. The replacement, installed a couple of years ago, has never given trouble since I began using the compression release for starting and stopping the engine, taking care to avoid kickbacks. So the answer to the question I think is being asked, is, it depends on how the sprag fails. If it fails in a manner that leaves everything free, no problem kick starting. If it jams and cannot be freed, the sprag must be removed or repaired to enable starting, kick or otherwise."
DeleteAnd this: "With the possible exception of the likes of Gina Lollobrigida, foreign bodies and motorcycles are not compatible. Take out the bits before they cause more trouble. Not a difficult job, and the resulting peace of mind is well worth the time and effort.
DeleteI got about 30K kilometers on my original sprang and the replacement is doing OK using the decompresser for starting and stopping although I did experience a sort of clattering sound the other day."
David, your advice has been invaluable. I cannot seem to kickstart the bike, so im assuming its jammed. im replacing the sprag next week. is there a specific technique used for decompressing while starting and stopping. Thanks for your time!
ReplyDeleteThe advice concerning the decompressor is simple. The motor can not run without compression. When starting with the electric start activate the decompressor briefly to allow the motor to get spinning past the point where it could ever kick back and then let it go to create ignition. When stopping, don't use the kill switch or turn off the ignition: activate the decompressor and let the motor happily spin its way to silence with, again, no possibility of kick back.
DeleteOne sprag clutch desintegrated and damaged, can damage the starter motor? Please I need help! Thanks, David
ReplyDeleteI must say the sprag clutch is basically junk, the little flat cage that holds it together is a poor design. It really cannot hurt the starter motor itself, The good news is just pull out the sprag unit and just go with a kicker. However it is wise to get the proper pullers for magnito, clutch, and primary gear, about 100 bucks on ebay, total time to fix about 3 hours. Unless there is a better sprag clutch out there, I think just kickstarting is the best way to go as replacing the srag is just going to fail in a short period of time anyways. Mike
ReplyDeleteHi David, Please can you tell me how much it roughly costs to replace the sprag clutch? Thanks,Pradeep
ReplyDeleteI'm sorry, I can't. Best of luck.
DeleteRs. 4100/- for the Sprag Clutch Assembly and Rs. 300/- labor charge at the company ASC. This for the UCE model.
DeleteHi dose anyone know if you can just replace the old version sprag with the newer design without having to replace the whole assembly too? I.e. just buy the sprag bearing?
DeleteMy ampere meter failed twice in the past one month..i replaced it twice because otherwise the neutral light wont turn on and the bike wont start.. And now today almost a month after the 2nd ampere meter change..the bike wont self start with clutch applied..
ReplyDeleteCan someone please help me regarding why my ampere meter failed twice nd the newest problem regarding self start and clutch
Thanks for posting this, David. I've just had my 2008 AVL primary off to fix a leaky cover on the e-start/sprag housing from when the sprag was replaced early on its its life.
ReplyDeleteOh dear, what's this I spy? Yes, pieces of sprag everywhere, and the second one has gone at just 8600 miles. I have the green TCI, up uprated battery, and have been stopping using the valve lifter.
At this rate, it's essentially a service item, and not a cheap one at that. I've messaged Royal Enfield Sevilla to see if they are still making a retrofitted version of the upgraded EFI sprag:
https://www.facebook.com/royal.enfield.1800/photos/?tab=album&album_id=814036478690354
Hai sir I have a royal enfield bullet 500 and while applying self start a metallic cracking sound is observed after that the engine starts what is reason for this sound and what are the remedies
ReplyDeleteYou don't state what era your Bullet is from but if it has the modern unit constructed motor the sound you hear may be the automatic decompressor clicking. Some find it annoying but it apparently does no harm.
DeleteSir whether sprang clutch will affect engine of royal enfield bikes
ReplyDelete