Forum

[612cc]

I have had a few clashing sounds from the primary case recently whe starting EElectric start, , thought it may have been the Sprag however the issue is when the decompressor is down i seem to be turning gears around not just the piston and very difficult to turn, the sound sounds very drive chain ,sh i hope that all makes sense ..
any ideas what this could be ?
thank you

[Beezabryan]

Why not open up the primary drive?......... But knowing BA about these modern Enfields I may not be giving the best advice

[Norm]

I'm surprised any sprag would survive on a 612

[612cc]

Well as i suspected a minced up sprag , as regards to the comment on a 612 well it lasted a few years 15,000 miles and everyday starting ,
anyway to anyone in a similar postion i fitted a new one in an hour/half cost £55.00 borg warner sprag fitted spot on , and instead of ATF which is what i was using went for a good 20/50 runs a lot better ,stopping with the decompressor really is a good trick , makes starting better due to pistion postion ,
hope this is of some use to anyone, out to Scottish borders @ the weekend (:

[MadMike]

Stopping with the decompressor? That means that the piston will come to rest in almost any random position in its four stroke cycle. Stop by using the key or a cut out and it will generally stop on compression as that is where it will meet massive resistance as it slows. This means that the piston is in almost the correct postion for re-starting, and both valves will be closed thus sealing the combustion chamber whilst taking all load off of the pushrods etc etc. Of course I could be wrong and am happy to be proven so. Discuss.

[Norm]

Mike,
not stopping with the decompressor is when most damage to the sprag occurs, piston coming up on compression and it gets pushed backwards if it can't go over TDC. You never notice this situation on a non E/S bike because it doesn't matter, but with the sprag unable to go backwards you get one very sickening band and expect to look down and see smashed cases

[612cc]

Nicely put Norm !

[apparently lucky eddie]

Both valves closed and engine on the compression stroke is exactly where you do not want the engine for kickstarting as the engine will need to rotate twice to come back to the same position with a fresh petrol/air charge for firing. This could well result in a kick-back as it is unlikely there will be sufficient momentum to turn the engine through compression on the second rotation. A similar thread came up recently.

[PeteF]

I've heard of this before but I can't see that the piston "bouncing back" would harm the sprag. If the thing can stand pushing the engine over compression it can stand catching the piston on the (unpowered) rebound surely. It's a powered reverse (kickback) that does the damage isn't it? I don't have an ES but still stop the engine with the decomp. Why? 'cos I like the sound it makes

[Norm]

Peter, as you don't have an E/S you can't make comment as to wether the piston kickback could cause a problem or not but ask anybody who has suffered this problem and they will tell you about the gut wreching sound that the kickback makes. I have no idea how the cases stay together, they must be tough. The other way to help save the sprag is to open the decomp, spin the motor and then close the decomp so that the flywheels have some momentum to prevent it kicking back on starting