280 Pro Flywheel Torque

[steam]

I have to replace the woodruff key between the flywheel and crank on my 2004 280 pro as it has sheared. Does anyone know the correct tightening torque of the securing nut? The engine has a flywheel weight fitted.

Also, I have been advised to lap the flywheel and crankshaft together with course grinding paste and a little WD 40. Any thoughts on this?

[jse]

I have to replace the woodruff key between the flywheel and crank on my 2004 280 pro as it has sheared. Does anyone know the correct tightening torque of the securing nut? The engine has a flywheel weight fitted.

Also, I have been advised to lap the flywheel and crankshaft together with course grinding paste and a little WD 40. Any thoughts on this?

The flywheel fastener goes to 40Nm, or about 29.5 Ft lbs.

Don't lap the flywheel unless there is severe damage to the tapered shaft and flywheel hub and it's a last resort before replacing the crank and flywheel. The Woodriff key does not hold the flywheel tight to the hub and is only used for alignment during installation. What holds the hub to the crank is that the tapers of the two parts are not a perfect fit. One taper is bored/machined at a 1 degree +- angle of the other one and it's known as a "one degree interference fit" or more accurately a "Morse Taper".

Jon

[geordabroad]

Jon

I live overseas with long delays to get parts. I've just examined my bike after it revved out FOT to find the flywheel very loose and the woodruff key sheared. If the woodruff key is only used in aligning the flywheel when re-fitting it, then it should be feasible for me to replace the flywheel without it (or with just the broken edge ofthe woodruff key sitting proud (but securely) to ensure the alingment. After all, the bolt holding the two tapers together should ensure the flywheel sits securely.

Would you agree, or is the woodruff absolutely necessary to get an exact alignment? Would you receommend I wait to get a woodruff key delivered?

Ian

[b40rt]

Jon

I live overseas with long delays to get parts. I've just examined my bike after it revved out FOT to find the flywheel very loose and the woodruff key sheared. If the woodruff key is only used in aligning the flywheel when re-fitting it, then it should be feasible for me to replace the flywheel without it (or with just the broken edge ofthe woodruff key sitting proud (but securely) to ensure the alingment. After all, the bolt holding the two tapers together should ensure the flywheel sits securely.

Would you agree, or is the woodruff absolutely necessary to get an exact alignment? Would you receommend I wait to get a woodruff key delivered?

Ian

As an absolute last resort, I heard of people using a bit of a small spanner cut and adjusted to fit.

[jse]

As an absolute last resort, I heard of people using a bit of a small spanner cut and adjusted to fit.

I just sent Ian a reply to him PM'ing me this question, but could not find it to copy to the general forum. I essentially said that the key could be left out, but there was a possible problem with static ignition timing being off. In the "old days" we often made them from scrap metal if necessary, but in a pinch, you could tap one end of the embedded Woodruff piece in the crank snout with a pointed punch, which, due to the rounded shape, will cause the other end to pop up slightly, enough to use as a guide if the flywheel hub was carefully slid on the crank.

Jon

[geordabroad]

Jon et al

I have an update for you on my woodruff key exploits on my TXT 300. Yes Jon, I put the fairly sizeable part of the broken woodruff key back in the groove and bedded it in with an end sticking up. Located the flywheel and tightened it up. All back together... started after a few kicks with chock. Was chuffed to bits.

However, flooded it later on when I got out to the hills and it wouldn't start after that. Kicked for a long time to no avail. Had a look tonight, after further advice from Jon and the flywheel had moved and totally anihilated the portion of woodruff key I'd used.

Now I think I know why... I live in China and they only use 1/4 or 1/2 inch sockets sets. My torque wrench is a 3/8 so I tightened the bolt on the flywheel as tight as I could with a normal 1/2 socket wrench but I'm sure it was nowehere near 40 kn. So WHEN I get my new woodruff key I'll also get a 3/8 socket sent out.

A question that springs to mind is: How to you stop the flywheel rotating when you're tightening the flywheel centre bolt? A thought would be to have the bike in gear and loads of back brake. Am I right? There are a couple of allen key bolts on the front of my flywheel (I'm guessing that means it's got a flywheel weight) I could also use them to hold the flywheel steady, eh?

Anyway, Jon, yes part woodruff keys do the trick, but I guess without properly torqueing the bolt up (which I doubt I did) I was asking for this to happen.

I also looked at the shaft and the snout. Scored but not badly... worse (scored and slightly pitted) near the very tip of the snout of the shaft. Does that sound bad to you? Should I be looking to use grinding paste between them?

Anyway, will now order new woodruff keys (will get spares) along with new 3/8 socket and domino black throttle and see how we go.

Cheers and thanks for all your help.

Ian

[b40rt]

Wouldn't use the method of stopping the engine you describe. You can get flywheel holding tools, not sure whats available for yours. You should buy a good quality torque wrench, will always come in useful.

A method for stopping the flywheel rotating I use is - an old leather belt, one end vice gripped to the foot rest or similar. Wrap the other end round the circumference of the flywheel, overlapping the free end. Hold the belt and revolve the flywheel, this will tighten it up till it grips, then torque to the setting. Various people recommend tapping the bolt and rechecking.

[jse]

Jon et al

I have an update for you on my woodruff key exploits on my TXT 300. Yes Jon, I put the fairly sizeable part of the broken woodruff key back in the groove and bedded it in with an end sticking up. Located the flywheel and tightened it up. All back together... started after a few kicks with chock. Was chuffed to bits.

However, flooded it later on when I got out to the hills and it wouldn't start after that. Kicked for a long time to no avail. Had a look tonight, after further advice from Jon and the flywheel had moved and totally anihilated the portion of woodruff key I'd used.

Now I think I know why... I live in China and they only use 1/4 or 1/2 inch sockets sets. My torque wrench is a 3/8 so I tightened the bolt on the flywheel as tight as I could with a normal 1/2 socket wrench but I'm sure it was nowehere near 40 kn. So WHEN I get my new woodruff key I'll also get a 3/8 socket sent out.A question that springs to mind is: How to you stop the flywheel rotating when you're tightening the flywheel centre bolt? A thought would be to have the bike in gear and loads of back brake. Am I right? There are a couple of allen key bolts on the front of my flywheel (I'm guessing that means it's got a flywheel weight) I could also use them to hold the flywheel steady, eh?

Anyway, Jon, yes part woodruff keys do the trick, but I guess without properly torqueing the bolt up (which I doubt I did) I was asking for this to happen.

I also looked at the shaft and the snout. Scored but not badly... worse (scored and slightly pitted) near the very tip of the snout of the shaft. Does that sound bad to you? Should I be looking to use grinding paste between them?

Anyway, will now order new woodruff keys (will get spares) along with new 3/8 socket and domino black throttle and see how we go.

Cheers and thanks for all your help.

Ian

Hi Ian,

I would try tightening the flywheel fastener once more before bedding the parts together with grinding compound as that will destroy what is left of the interference tapers that allows them to stick together. I'd slightly overtighten the bolt, say about 5 Nm and that might help. You probably can get an adapter that will allow the 1/2" sockets to be used on the 3/8th" torque wrench (I have a couple in my toolbox so I know they are available).

To keep the crank from turning, take the plug out, take a few feet of about 3/8th inch cotton or plastic rope, bring the piston up about an inch before TDC (you can feel the piston with the rope end) and stuff the rope through the plug hole to fill up the combustion chamber, then move the piston up against the rope to stop the crank. When finished, back the piston down a little and pull out the rope and put it in your toolbox till the next time you need it.

Jon