Can you reduce engine braking? 2008 yz 450f


59 replies to this topic
  • kx450f63

Posted September 19, 2012 - 04:33 AM

#21

So I was installing a new rear tire and checking the bearings today for a race this weekend and it got me to thinking about this post. Some of the more experienced mechanics on here can confirm if my thoughts are correct. An over tightened rear axle nut and or rear axle bearings that are going bad making the decelleration is greater? I guess the front bearings and axle nut could also do that? Maybe a dragging rear brake?

I have an 08 YZ450 and the engine breaking doesn't seen extreme.


An over tightened axle nut... likely not a problem. If you look at how all the pieces of the rear wheel go together you will notice that all the pieces (axle head, swing arm, spacer, inner race of wheel bearing, inner spacer, second inner race, second spacer, other side of swing arm, and nut) basically form a solid piece that does not move within the mounted assembly if all is in proper working order. Basically once you begin to over torque the nut you will need to deform a piece before it will cause a binding issue.

Failing wheel bearings could certainly be a problem, but they would need to be drastic before you would notice it while riding or on deceleration.

A dragging rear brake could certainly be a problem. If there is not enough free play for the master cylinder to allow the fluid to return you will have an issue. A failing caliper could induce excessive heat from excessive drag and therefore heat. This could also cause a non-return issue with the fluid and resulting brake drag.

All this you would notice during pushing the motorcycle, which he did not mention.

  • KJ790

Posted September 19, 2012 - 04:53 AM

#22

An over tightened axle nut... likely not a problem. If you look at how all the pieces of the rear wheel go together you will notice that all the pieces (axle head, swing arm, spacer, inner race of wheel bearing, inner spacer, second inner race, second spacer, other side of swing arm, and nut) basically form a solid piece that does not move within the mounted assembly if all is in proper working order. Basically once you begin to over torque the nut you will need to deform a piece before it will cause a binding issue.

Failing wheel bearings could certainly be a problem, but they would need to be drastic before you would notice it while riding or on deceleration.

A dragging rear brake could certainly be a problem. If there is not enough free play for the master cylinder to allow the fluid to return you will have an issue. A failing caliper could induce excessive heat from excessive drag and therefore heat. This could also cause a non-return issue with the fluid and resulting brake drag.

All this you would notice during pushing the motorcycle, which he did not mention.


Over torquing the axle nut will crush the aluminum spacer between the bearings and will cause the wheel to bind up and turn hard. This is a pretty common problem (there are tons of threads on here with people that have this problem). However just like a dragging brake, as you mentioned, you should notice this when you try to roll the bike or spin the wheel with the bike up on a stand.

  • kx450f63

Posted September 19, 2012 - 04:56 AM

#23

http://motocrossacti...f96b82cfcc.aspx


Yes. I think Gray touched on the BTL.

  • KJ790

Posted September 19, 2012 - 05:12 AM

#24

Yes. I think Gray touched on the BTL.


Yes, and the BTL clutch is commonly known as a "slipper clutch". Just trying to answer your question from earlier.

  • kx450f63

Posted September 19, 2012 - 05:21 AM

#25

Yes, and the BTL clutch is commonly known as a "slipper clutch". Just trying to answer your question from earlier.


Yes, you did help to educate me, thank you. I guess I over looked the commonly know part (slipper clutch) as I have not investigated the slang until now. Thanks for the link. I guess it just makes more sense to me to call it a back torque limiting clutch. (BTL clutch)

  • kx450f63

Posted September 19, 2012 - 05:27 AM

#26

Over torquing the axle nut will crush the aluminum spacer between the bearings and will cause the wheel to bind up and turn hard. This is a pretty common problem (there are tons of threads on here with people that have this problem). However just like a dragging brake, as you mentioned, you should notice this when you try to roll the bike or spin the wheel with the bike up on a stand.


I guess I have not run into this problem, for that matter I have not noticed many bikes with the inner spacer being aluminum. I know many of the little bikes are but is it aluminum on the big Yamaha's?

  • KJ790

Posted September 19, 2012 - 06:24 AM

#27

Yes, you did help to educate me, thank you. I guess I over looked the commonly know part (slipper clutch) as I have not investigated the slang until now. Thanks for the link. I guess it just makes more sense to me to call it a back torque limiting clutch. (BTL clutch)


Yeah, I'm not quite sure why it's called a slipper clutch, but that's what it has always been called. It started in the road racing world and made its way to the MX world a few years ago.

I guess I have not run into this problem, for that matter I have not noticed many bikes with the inner spacer being aluminum. I know many of the little bikes are but is it aluminum on the big Yamaha's?


Yes all Yamaha mx bikes (and most other brands as well) use an aluminum spacer between the bearings that can be crushed if the axle is over-tightened.

  • grayracer513

Posted September 19, 2012 - 07:04 AM

#28

So you have never had your Rekluse have more of a loose feel to it where it softens up?


I don't understand what you're asking, but the Rekluse in my bike does not alter engine braking from about 3000 RPM up in any way.

  • kx450f63

Posted September 19, 2012 - 07:06 AM

#29

Yeah, I'm not quite sure why it's called a slipper clutch, but that's what it has always been called. It started in the road racing world and made its way to the MX world a few years ago.

After reading a little about Hinson's design I can see why one would call it a slipper clutch but what I am more interested in at this point is if you guys have any good links to the various mechanisms the different manufactures are using to accomplish this BTL assembly.



Yes all Yamaha mx bikes (and most other brands as well) use an aluminum spacer between the bearings that can be crushed if the axle is over-tightened.


I just had my 11 KX450 apart and I didn't notice if it was aluminum or I don't remember the same with an 08 KX450 about a month ago I did for a friend.

If one were to crush (which I do understand you are telling me it happens) a bearing or inner race of a bearing would also need to be dislodged in order for this to happen. If I understand it correctly... the swing arm pushes on the spacers, the spacers push on the inner races, the inner races push on the inner spacer. I guess I just can't imagine the amount of force people are putting on the axle nuts to cause this problem.

I'm not sure the OP wanted to get this far off track but it sounds to me like the most effective way to solve his problem may be the BTL clutch or just find a work around like the majority of us do.

One more question. Does anybody incorporate the centripetal clutch and BTL into one assembly? I think that would be the ticket. You would be able to stop and start without using the clutch lever. Fall over and not need to keep the clutch lever engaged to keep the engine from stalling. You could lock up the rear brake and not need to worry about your timing with the clutch lever. You could fine tune engagement, disengagement, and the amount of slippage on the BTL side for a rider preferred amount of engine braking. Of course you would still be able to manually control the amount of engagement with the clutch lever. Now that I might be interested in.

  • grayracer513

Posted September 19, 2012 - 07:18 AM

#30

Yeah, I'm not quite sure why it's called a slipper clutch, but that's what it has always been called. It started in the road racing world and made its way to the MX world a few years ago.



I'm sure they existed before this, but Honda installed one as OEM equipment in the first V65 Magna (1100cc V4) they built in '83:

Posted Image

Posted Image


Yes all Yamaha mx bikes (and most other brands as well) use an aluminum spacer between the bearings that can be crushed if the axle is over-tightened.


That must take a ridiculous amount of torque to accomplish. I rarely tighten mine rear axle as far as the 90 ft/lb the book recommends.

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  • grayracer513

Posted September 19, 2012 - 11:08 AM

#31

If one were to crush (which I do understand you are telling me it happens) a bearing or inner race of a bearing would also need to be dislodged in order for this to happen. If I understand it correctly... the swing arm pushes on the spacers, the spacers push on the inner races, the inner races push on the inner spacer. I guess I just can't imagine the amount of force people are putting on the axle nuts to cause this problem.

Considering that spec torque is 90 ft/lb, it does seem a stretch, eh? The axle compresses the bearing and spacer stack as a unit. When the spacer gets crushed, the other elements, including the bearing races, move closer to the center. Trouble is that the outer races are already bottomed in their bores and can't move with the inner races. That puts the bearings axially out of line with themselves and they bind.

One more question. Does anybody incorporate the centripetal clutch and BTL into one assembly? ... Now that I might be interested in.


Not that I know of, but, semantics: It's "centrifugal", not centripetal. Centrifugal force is that which moves or tends to move out from a center. "Centripetal" is the opposite, forcing or holding something toward the center. The Rekluse operates on centrifugal force.

  • kx450f63

Posted September 20, 2012 - 03:33 AM

#32

semantics: It's "centrifugal", not centripetal. Centrifugal force is that which moves or tends to move out from a center. "Centripetal" is the opposite, forcing or holding something toward the center. The Rekluse operates on centrifugal force.


I guess I have a tendency to look more towards the effect of the force (centripetal) and not the cause (centrifugal). I suppose I take the cause for granted and look at the effect.

If I may dumb it down a little and use this analogy... Does the tire act on the dirt, or does the dirt act on the tire?

Without one force the other doesn't doesn't do the work we are asking to do?

I am also slightly disappointed in you Gray. No speculation or even hard facts on the overall awesomeness or lack there of on the idea of combining the two clutch assemblies?

Edited by kx450f63, September 20, 2012 - 03:34 AM.


  • grayracer513

Posted September 20, 2012 - 06:49 AM

#33

Effect is dependent on cause. Put a ball in the center of a round plate and spin the plate, and the centrifugal force flings the ball off. Centripetal force is not involved in the equation. Put an edge on the plate and the edge becomes the centripetal "force". It's true that the centrifugal weights in the Rekluse are stopped from flying out of the clutch by being forced to apply pressure to the plates (centripetal force), but that's only a resistance to the root causal force (centrifugal) created by the spinning clutch.

As far as overall awesomeness, a combo clutch like you described would probably develop a loyal following, but I'd imagine it would be fairly small. An obvious point of resisance would be the price something like that would have to bring just because of the cost to put all that technology in a single unit. But it would be exactly what some people would look for.

Me, I love engine braking. The engine will never lock the rear wheel.

  • KJ790

Posted September 20, 2012 - 07:23 AM

#34

Effect is dependent on cause. Put a ball in the center of a round plate and spin the plate, and the centrifugal force flings the ball off. Centripetal force is not involved in the equation. Put an edge on the plate and the edge becomes the centripetal "force". It's true that the centrifugal weights in the Rekluse are stopped from flying out of the clutch by being forced to apply pressure to the plates (centripetal force), but that's only a resistance to the root causal force (centrifugal) created by the spinning clutch.

As far as overall awesomeness, a combo clutch like you described would probably develop a loyal following, but I'd imagine it would be fairly small. An obvious point of resisance would be the price something like that would have to bring just because of the cost to put all that technology in a single unit. But it would be exactly what some people would look for.

Me, I love engine braking. The engine will never lock the rear wheel.


I can't resist... technically if you spin a ball in a circle on a disk and then let go of it it will fly away from inertia, not a force at all. The lack of a force is why it would continue on it's straight path. For there to be a force there must be an acceleration on the ball (either a change in velocity or a change in direction). Put a lip on the edge of the disk and it will provide a centripetal force on the ball towards the center of the circle, keeping the ball spining in a circular motion. The resulting force put on the lip of the disk from the ball could be considered the centrifugal force, but without a centripetal force there is no resulting centrifugal force. Just getting into semantics now though.

As for a recluse clutch that has a built in slipper clutch, that would be awesome, but I imagine it would be very expensive and sales would likely be low.

  • kx450f63

Posted September 20, 2012 - 08:42 AM

#35

We may need to contact Newton to solve this debacle!

I think we have it though... to solve your excessive engine braking problem you need a BTL Centrifugal/Centripetal clutch, manufactured by? You could just buy the Slipper clutch from Hinson so you don't need to wait.

Oh ya... No reverse analogy on the tire and dirt problem?

  • grayracer513

Posted September 20, 2012 - 08:48 AM

#36

...technically if you spin a ball in a circle on a disk and then let go of it it will fly away from inertia, ...


I assume it to be obvious that you mean if you put a ball in on a disc and spin the disk, not the ball. The "inertia" the ball has is static until centrifugal force acts on it to cause it to fly off the disc, so the kinetic inertia the makes in seek to continue in a straight line is provided by the centrifugal force. That force is created by the ball being "driven" in a circle on the surface of the plate. The driving force tries to move the ball "forward" in the direction of plate rotation on a vector tangent to the circle, concurrently trying to accelerate it laterally toward the center, which is where the original centripetal force comes from. However, the static inertia of the ball that enables and creates that centripetal force is the only thing operating against the centrifugal force in this example, so the latter force wins. Without that force, the ball would not be set in motion on its flight off the edge at all. Anything that holds it on the disc and causes it to circle around the center is centripetal force.

Centrifugal force can't be harnessed mechanically without centripetal resistance, but the root force involved is still centrifugal, nevertheless.

The two forces are intertwined and codependent to a degree, of course, but it gets to be one of those chicken/egg engineering arguments that wastes so much classroom time.

  • grayracer513

Posted September 20, 2012 - 08:51 AM

#37

I think we have it though... to solve your excessive engine braking problem you need a BTL Centrifugal/Centripetal clutch, manufactured by? You could just buy the Slipper clutch from Hinson so you don't need to wait.


You might have swerved into something here. Without seeing one, my guess is that you could drop an EXP ring into a Hinson (?) BTL clutch, and then you'd have it (for only $400 more than Hinson already charges :eek: )

  • KJ790

Posted September 20, 2012 - 08:54 AM

#38

Oddly worded; I assume you mean if you put a ball in on a disc and spin the disk, not the ball. The "inertia" the ball has is static until centrifugal force acts on it to cause it to fly off the disc, so the kinetic inertia the makes in continue in a straight line is provided by the centrifugal force. Anything that holds it on the disc and causes it to circle around the center is centripetal force. Centrifugal force can't be harnessed mechanically without centripetal resistance, but the root force involved is still centrifugal, nevertheless. Without that force, the ball would not be set in motion on its flight off the edge at all.


I guess I did word it oddly. I mean that to put a ball on a disk and spin the disk you would need to hold the ball in place initially to get it spinning with the disk (say that there was glue holding the ball to the disk). Once the disk is spinning, say that the glue lets go, the ball will obviously fly off of the disk. However, it is not a force at all that makes the ball fly off of the disk, rather a lack of a force. The force initially in action was caused by the glue, redirecting the ball into a circular motion (centrieital force). Once the glue breaks there are no forces acting on the ball, so the ball's inertia causes the ball to continue in a straight line away from the disk (an object in motion remains in motion until acted upon by an unequal force). There is no force propelling the ball away from the disk.

Centrifugal force would be the force opposing the centripetal force (the force the ball applies back onto the glue, equal and opposite to centripetal force). Once the glue breaks there is no longer a centrifugal force.

Edited by KJ790, September 20, 2012 - 08:56 AM.


  • shrubitup

Posted September 20, 2012 - 09:10 AM

#39

KJ said it earlier. Pull in that lever thingy on the left side of the bars during a corner or downhill descent. :busted:

  • grayracer513

Posted September 20, 2012 - 09:36 AM

#40

Centrifugal force would be the force opposing the centripetal force (the force the ball applies back onto the glue, equal and opposite to centripetal force). Once the glue breaks there is no longer a centrifugal force.

Then there would be no motion. When the glue breaks, the forces are put out of balance with each other (one is reduced to near zero), and the centrifugal force wins, propelling the ball off the edge.





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