Jump to content

flywheel install trick to tighten to 47 ft/lb

Recommended Posts

i have an old 2003 crf450 and i came up with this little trick so i thought i would write it up as my memory is starting to fade away and i won't have to re-learn it.  i have never had luck using a strap wrench on the flywheel to hold it.  I've always ever used a aluminum chock inserted between the primary gear and the clutch main gear on the right engine side.  The latter method is a hassle since you have to remove the right side engine cover and all that.  So this morning i looked closely at the flywheel, it has three holes close to the center and then this one hole on the outer flat part.  This hole will accept a 1/4 inch or M6 bolt.  When this hole is aligned on the crank shaft at the 3 o'clock position there is plenty of room behind the flywheel to accomodate the rest of the bolt and a nut and even to get a wrench on the nut on the back side.   I had a snapped piece of 1/8 inch spring steel that meaured about 16 3/4 inch to act as a chock against the head of this bolt.  I bought a bolt that was stainless steel 1/4 inch-20 X 3/4 inch length.  I have a kick stand on my bike so the bike was layed over a bit anyway.  The steel bar was chocked up under the bolt head which was inserted in the flywheel and the concrete garage floor.  Then i could tighten the flywheel nut to 47 foot pounds with a torque wrench without any issue.  Saved me like an hour of having to tear everything off the other side to do a gear chock.  After it was done, just unfastened the bolt and nut and done.

I dont think you even need a stainless bolt just any old bolt since 47 ftlb is not a big deal of sideload.  

flywheel tool 005.JPG

flywheel tool 007.JPG

flywheel tool 008.JPG

Share this post


Link to post
Share on other sites

I've always used a couple pennies shoved into the gears on the other side to lock up engine rotation(no need for the special gear holding tool). I agree, strap wrenches are junk.  This is a pretty good idea if you don't already have the right side and clutch apart though!

Edited by Jdunn217
  • Like 1

Share this post


Link to post
Share on other sites

I just installed a flywheel on my 06 the other week and it didn't have a hole like that.  I used a strap wrench, it sucked.

Share this post


Link to post
Share on other sites
1 hour ago, filterx said:

Ya I put the bike in gear and had a buddy hold the bike with the rear brake on

I have a strap wrench but probably will do this too,:thumbsup: I've never torqued a FW or clutch nut to spec. I always go under so the bearing doesn't get notchy. I figure I've Loctited the FW nut and the clutch has a bend over washer so maybe 5 or so less than spec.

Edited by HRC27
  • Like 1

Share this post


Link to post
Share on other sites

I tried the putting it in gear method and immediately didn't like how it felt. It felt like I was twisting something so I resorted to the strap wrench.

Share this post


Link to post
Share on other sites

I also have a 2003 crf450r and my flywheel doesn't have a notch like that! If i could give you a good piece of advice, Always clean the bike before working on the motor!

Edited by ThrustWasher

Share this post


Link to post
Share on other sites
On 5/29/2017 at 2:04 AM, filterx said:

Ya I put the bike in gear and had a buddy hold the bike with the rear brake on

That will not work: the clutch will slip before you reach the required torque, hence the need for the special tool. Were you using a torque wrench or were you going by feel ?

What I do is put a few loops of rope around the flywheel tighten one end of the rope on the footpeg and have a buddy hold the other end taught. The rope will tighten on the flywheel as it begins to rotate and it will hold it still.

 

 

Share this post


Link to post
Share on other sites
5 minutes ago, jnk said:

That will not work: the clutch will slip before you reach the required torque, hence the need for the special tool. Were you using a torque wrench or were you going by feel ?

What I do is put a few loops of rope around the flywheel tighten one end of the rope on the footpeg and have a buddy hold the other end taught. The rope will tighten on the flywheel as it begins to rotate and it will hold it still.

 

 

I think this would fine in 5th gear.

Edited by Eddie8v

Share this post


Link to post
Share on other sites

The gear the bike is in is in makes no difference. It just makes it easier for you to hold the rear wheel still.

The problem is this: the rear wheel holds the chain, the chain holds the gear box and the gear box holds the clutch. On the other side of the axle the clutch is on you are trying to torque a nut to a force higher than the clutch discs can withstand and they will slip.

And I talking from experience: I also though that I could hold the flywheel using the rear brake but the flywheel was turning with torque wrench before it would click.

Edited to add: now that I think of it the clutch and flywheel are not on the same axle but you get the idea: between the flywheel and the rear wheel there is the clutch and the clutch will transfer that match torque before it starts to slip.

 

 

Edited by jnk

Share this post


Link to post
Share on other sites
6 minutes ago, jnk said:

The gear the bike is in is in makes no difference. It just makes it easier for you to hold the rear wheel still.

The problem is this: the rear wheel holds the chain, the chain holds the gear box and the gear box holds the clutch. On the other side of the axle the clutch is on you are trying to torque a nut to a force higher than the clutch discs can withstand and they will slip.

And I talking from experience: I also though that I could hold the flywheel using the rear brake but the flywheel was turning with torque wrench before it would click.

 

 

The gear it's in makes a HUGE difference! It's a leverage thing. If you leave it in 1st, you're likely feeling the rear brake slipping, not the clutch slipping. Your clutch shouldn't slip with only 47lb-ft of torque applied to it, that's about what the 450 motor makes at the crank.

5th gear affords the most leverage for the rear brake to hold, have someone sit on the bike and hold down the rear brake pedal while you tighten the flywheel nut.

  • Like 1

Share this post


Link to post
Share on other sites

I did a quick google search on the torque the bike produces and I found it is somewhere in the mid 30 lb-ft. So the torque you are applying to the nut is well above what the engine applies to the axle.

But look at it this way: if the clutch could hold the flywheel still then what would be the need for the special tool everyone is using ? :thumbsup:

 

Share this post


Link to post
Share on other sites

I could have sworn I did it years ago. I always use my trusty impact on that nut and on clutch center hub nut so I guess I shouldn't be giving advice, sorry.

Share this post


Link to post
Share on other sites
6 hours ago, Eddie8v said:

I could have sworn I did it years ago. I always use my trusty impact on that nut and on clutch center hub nut so I guess I shouldn't be giving advice, sorry.

I've done that w/my 3/8" butterfly Impact Ed. Just turned It down some.:rolleyes:

Share this post


Link to post
Share on other sites
19 minutes ago, Chrisy Wright said:

I used a 2p and jammed it in the main drive and counter balance bearing easy peasy never had any problems rebuilt many 04 07 09 engines and never seen a flywheel like that haha

Well if you have access to the right side then you have no problem to begin with. The problem is how to keep your flywheel from turning without taking the right case off.

 

  • Like 1

Share this post


Link to post
Share on other sites
This topic is now closed to further replies.

×