CW woodruff key
Posted: Fri Aug 16, 2013 6:24 am
hodakarider1973 - 05/05/08 at 1:25pm
Apparently during the winter off season maintenance, I have lost the woodruff key used to align the flywheel on my 73 Combat. Anyone know what size the key is? My local hardware store has all sizes, but I don't remember how small it was. They are pretty cheap and I can buy several and do a trial and error until I find the right one, but thought you guys might know! Thanks
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hodakaronwa - 05/05/08 at 8:51pm
I cannot tell you the dimensions of your flywheel key but I can tell you that it is of a metric size not easily bought locally. I have purchased keys close enough to patiently file the width down until it will work. I would suggest that you contact Paul and very possibly your key may have been sucked onto the magnets of your flywheel? I have had that happen more than once.
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joebat - 05/06/08 at 5:33pm
It is 3mm wide for sure and I think x 13mm dia. They are very hard to find locally--Even the the MC store I tried wanted the bike make and model just to find one--(Of course HODAKA is NOT in their computer!) Paul sells them. Or I found that McMasterCarr has them if you want to buy in quantity.
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hodakgem - 05/08/08 at 5:12pm
Do not buy a key from a hardware store for general machinery. the steel is too hard, they are not designed soft to shear if the flywheel nut comes loose.
If you do not use the exact size, you will find the flywheel may wobble enough to throw your ignition timing a few degrees, enough to make the bike run weird.
There is another brand bike that uses the exact same key.
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KirkN - 05/08/08 at 5:37pm
Interesting discussion, and I have nothing to add that's Hodaka-specific, but....
On older Honda SL / XL models, I know that the flywheel key is not, strictly speaking, necessary at all. It is there merely to hold the flywheel's rotational position while you tighten the flywheel nut. It is the friction at the tapered fit between the crankshaft and the flywheel (friction created by the clamping force of the flywheel nut) that holds the flywheel in place, NOT the key. There is very little load on the flywheel - it's not being used to drive anything but push some electrons. The clamping force is more than adequate to hold it in place during use.
Is that a true statement - that the key is designed to shear if the nut comes loose? What forces would cause it to shear?
If you had the wrong sized key, but somehow otherwise managed to hold the flywheel accurately while you tightened the nut, would you have any problems?
Do Hodaka's even HAVE a tapered shaft like the Honda's I'm familiar with?
My 250SL has a tapered fit at the flywheel, and so it is likely to operate like the Hondas, but I don't know about the other models.
Good luck with it.
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hodakarider1973 - 05/08/08 at 7:25pm
Hodakas do have a tapered shaft and the key doesn't hold anything it is merely a tool to set the timing, but they will shear if the nut is not tight enough. I have been told that if I mark the flywheel and a corresponding spot on the case (with the flywheel in proper position of course), that from now on I won't need a woodruff key. However since I didn't do that, I do need a key. My local bike mechanic supposedly has one that will fit. (fingers crossed)
___________________________________________________________________________________________
Bullfrog - 05/09/08 at 6:05pm
This post is for Hodakarider1973.
Note that your Hodaka came from the factory with marks on the OD of the magneto flywheel and on the cases which identify TDC (Top Dead Center) and the proper ignition firing point BTDC (Before Top Dead Center) but those marks are useful ONLY (this is important) repeat, ONLY if the magneto flywheel is installed in the proper "clock position" on the crankshaft . . . which the woodruff key assures.
ie, with the woodruff key in place, there is only ONE way to install the magneto flywheel on the crankshaft. When the flywheel is installed in that position, the ignition will work well and the timing marks should be pretty darn accurate.
However, if the woodruff key is not in place, then the flywheel can be installed in any one of 360 (rotational) positions (and that is counting only the full one degree positions). Without the woodruff key, the flywheel can be installed in the RIGHT place (rotationally speaking) on the crank taper only through the use of the most careful, time consuming, skill demanding, "eyeball alignment" methods known to man. . . . and there is no assurance that things won't shift as the flywheel nut gets tightened. All-in-all, not a recommended situation. It is MUCH better to get the proper woodruff key and use it to assure the flywheel gets mounted in the proper position.
OK?
Additional comments
1. Yes, it is completely true that the mating tapers are what "locks" the flywheel to the crankshaft. The woodruff key is NOT there to handle torque loads.
2. If your woodruff key has sheared off, the following faults are likely the cause:
a. Flywheel nut did not get properly torqued. 170 in-pounds is recommended. If the nut was not torqued properly, the tapers were never properly "mated" to hold against the torque loads.
b. The taper inside the flywheel hub or the crank taper has been damaged. "Paint" the crank taper with a blue Sharpie and install the flywheel (with no woodruff key) by hand and firmly press it in place by hand then gently twist the flywheel back and forth while keeping the crank from turning. Remove the flywheel and inspect both tapers for "high spots". Buff/grind off high spots. Re-check fit of tapers as necessary till there is uniform contact all the way around on both tapers.
c. The woodruff key slid/rocked back as the flywheel was installed. This would result in a "cocked" flywheel which wobbles when the engine is kicked over - and no "seating/mating" of the tapers. Always check for a true running flywheel when it is reinstalled . . . BEFORE putting the shift cover back on.
d. Grunge on the tapers. Clean and reinstall.
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mrmadmoto - 05/09/08 at 7:25pm
I have used lapping compound and lapped fly wheel to crank to get a good seat.
___________________________________________________________________________________________
END OF THREAD
Apparently during the winter off season maintenance, I have lost the woodruff key used to align the flywheel on my 73 Combat. Anyone know what size the key is? My local hardware store has all sizes, but I don't remember how small it was. They are pretty cheap and I can buy several and do a trial and error until I find the right one, but thought you guys might know! Thanks
___________________________________________________________________________________________
hodakaronwa - 05/05/08 at 8:51pm
I cannot tell you the dimensions of your flywheel key but I can tell you that it is of a metric size not easily bought locally. I have purchased keys close enough to patiently file the width down until it will work. I would suggest that you contact Paul and very possibly your key may have been sucked onto the magnets of your flywheel? I have had that happen more than once.
___________________________________________________________________________________________
joebat - 05/06/08 at 5:33pm
It is 3mm wide for sure and I think x 13mm dia. They are very hard to find locally--Even the the MC store I tried wanted the bike make and model just to find one--(Of course HODAKA is NOT in their computer!) Paul sells them. Or I found that McMasterCarr has them if you want to buy in quantity.
___________________________________________________________________________________________
hodakgem - 05/08/08 at 5:12pm
Do not buy a key from a hardware store for general machinery. the steel is too hard, they are not designed soft to shear if the flywheel nut comes loose.
If you do not use the exact size, you will find the flywheel may wobble enough to throw your ignition timing a few degrees, enough to make the bike run weird.
There is another brand bike that uses the exact same key.
___________________________________________________________________________________________
KirkN - 05/08/08 at 5:37pm
Interesting discussion, and I have nothing to add that's Hodaka-specific, but....
On older Honda SL / XL models, I know that the flywheel key is not, strictly speaking, necessary at all. It is there merely to hold the flywheel's rotational position while you tighten the flywheel nut. It is the friction at the tapered fit between the crankshaft and the flywheel (friction created by the clamping force of the flywheel nut) that holds the flywheel in place, NOT the key. There is very little load on the flywheel - it's not being used to drive anything but push some electrons. The clamping force is more than adequate to hold it in place during use.
Is that a true statement - that the key is designed to shear if the nut comes loose? What forces would cause it to shear?
If you had the wrong sized key, but somehow otherwise managed to hold the flywheel accurately while you tightened the nut, would you have any problems?
Do Hodaka's even HAVE a tapered shaft like the Honda's I'm familiar with?
My 250SL has a tapered fit at the flywheel, and so it is likely to operate like the Hondas, but I don't know about the other models.
Good luck with it.
___________________________________________________________________________________________
hodakarider1973 - 05/08/08 at 7:25pm
Hodakas do have a tapered shaft and the key doesn't hold anything it is merely a tool to set the timing, but they will shear if the nut is not tight enough. I have been told that if I mark the flywheel and a corresponding spot on the case (with the flywheel in proper position of course), that from now on I won't need a woodruff key. However since I didn't do that, I do need a key. My local bike mechanic supposedly has one that will fit. (fingers crossed)
___________________________________________________________________________________________
Bullfrog - 05/09/08 at 6:05pm
This post is for Hodakarider1973.
Note that your Hodaka came from the factory with marks on the OD of the magneto flywheel and on the cases which identify TDC (Top Dead Center) and the proper ignition firing point BTDC (Before Top Dead Center) but those marks are useful ONLY (this is important) repeat, ONLY if the magneto flywheel is installed in the proper "clock position" on the crankshaft . . . which the woodruff key assures.
ie, with the woodruff key in place, there is only ONE way to install the magneto flywheel on the crankshaft. When the flywheel is installed in that position, the ignition will work well and the timing marks should be pretty darn accurate.
However, if the woodruff key is not in place, then the flywheel can be installed in any one of 360 (rotational) positions (and that is counting only the full one degree positions). Without the woodruff key, the flywheel can be installed in the RIGHT place (rotationally speaking) on the crank taper only through the use of the most careful, time consuming, skill demanding, "eyeball alignment" methods known to man. . . . and there is no assurance that things won't shift as the flywheel nut gets tightened. All-in-all, not a recommended situation. It is MUCH better to get the proper woodruff key and use it to assure the flywheel gets mounted in the proper position.
OK?
Additional comments
1. Yes, it is completely true that the mating tapers are what "locks" the flywheel to the crankshaft. The woodruff key is NOT there to handle torque loads.
2. If your woodruff key has sheared off, the following faults are likely the cause:
a. Flywheel nut did not get properly torqued. 170 in-pounds is recommended. If the nut was not torqued properly, the tapers were never properly "mated" to hold against the torque loads.
b. The taper inside the flywheel hub or the crank taper has been damaged. "Paint" the crank taper with a blue Sharpie and install the flywheel (with no woodruff key) by hand and firmly press it in place by hand then gently twist the flywheel back and forth while keeping the crank from turning. Remove the flywheel and inspect both tapers for "high spots". Buff/grind off high spots. Re-check fit of tapers as necessary till there is uniform contact all the way around on both tapers.
c. The woodruff key slid/rocked back as the flywheel was installed. This would result in a "cocked" flywheel which wobbles when the engine is kicked over - and no "seating/mating" of the tapers. Always check for a true running flywheel when it is reinstalled . . . BEFORE putting the shift cover back on.
d. Grunge on the tapers. Clean and reinstall.
___________________________________________________________________________________________
mrmadmoto - 05/09/08 at 7:25pm
I have used lapping compound and lapped fly wheel to crank to get a good seat.
___________________________________________________________________________________________
END OF THREAD