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GOING TO TAKE 2LBS OFF OF THE FLYWHEEL

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...I want to take 2lbs off of the flywheel. Will this be ok? I do not want to sacrafice ANY bottom end torque or low speed drivability or reliability. You can take the flywheel out with the engine in the frame. Correct?........thanks

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A flywheel just adds a larger moment of inertia to an engine.  It doesn't create power; it just stores it.  So any reduction in weight will reduce the perceived low end power and increase the speed at which an engine revs.  That principle is why people add flywheel weights to MX engines.

 

I'm pretty sure you can remove the flywheel with the engine still in the frame.

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A flywheel just adds a larger moment of inertia to an engine.  It doesn't create power; it just stores it.  So any reduction in weight will reduce the perceived low end power and increase the speed at which an engine revs.  That principle is why people add flywheel weights to MX engines.

 

I'm pretty sure you can remove the flywheel with the engine still in the frame.

I have read that you can take off up to 2 lbs without any problems. I do not want to be stalling out when i am going under 5 mph in rocky or slippery trails....

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If you can even take 2 lbs off it, you will create low end stalling and "flame outs" that did not exist before. Make sure you do this to an extra flywheel, so you can switch back.

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If you can even take 2 lbs off it, you will create low end stalling and "flame outs" that did not exist before. Make sure you do this to an extra flywheel, so you can switch back.

This is what i need...feedback. Thanks. I am going to try and find the article that states you can take off 2 lbs safely from the xrl slug.Whats the maxium you would take off Zac?

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Years ago, I built a few xr 500 motors for 1/4 mile flat track. We took 6-9 oz off the flywheels, and they did rev a bit quicker. But, when the track got slick, the quicker rev caused traction to suffer. I am not sure what the difference between a 500 flywheel and a 650 is. I would say that if the 650 is much heavier, you could safely take it down to the weight of a 500 wheel. I'm not sure if our machinist messed them up, but they did vibrate a little more as well.

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Been there, done that. I ended up taking a pound off of mine. As you can see int he pictures below, I only had the shiny silver piece shaved down. You could get more aggressive and have it undercut and you could also have some shaved off of the OD of the bowl itself. I wanted to start small and work my way up.

The difference between and XRL and XR600R flywheel is tremendous. The stock XRL flywheel weighs in at 8 pounds while an XR600R flywheel weighs five pounds! I experienced no noticeable loss of low-end, but did see a small gain in terms of responsiveness. You can easily remove the flywheel with the engine in the frame. You will need new gaskets for the side cover and the starter cover. I hope you have an impact wrench and flywheel removal tool. If not, get them before you try to start.

[/url]

HEre are the XRL and XR6R flywheels:

Flywheels.jpg

 

 

The XRL flywheel. This is with the starter clutch which weighs a pound and a half.

 

P3050056.jpg

 

Stock XRL and shaved flywheels

 

IMG_0141_zps5996ae19.jpg[/url]

 

Mounted up

IMG_0144_zps9c48cfb2.jpg

Edited by ThumpNRed

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This is what i need...feedback. Thanks. I am going to try and find the article that states you can take off 2 lbs safely from the xrl slug.Whats the maxium you would take off Zac?

 

Is your concern a loss of low end, or actual engine running problems?  Any weight removal will cause a loss of low end, at least theoretically, and the increase in rev-ability will be proportional to the loss of low end.  There's no positive sum gain, only a trade off.  In terms of actual engine running problems, MX engines run with tiny flywheels. 

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Been there, done that. I ended up taking a pound off of mine. As you can see int he pictures below, I only had the shiny silver piece shaved down. You could get more aggressive and have it undercut and you could also have some shaved off of the OD of the bowl itself. I wanted to start small and work my way up.

The difference between and XRL and XR600R flywheel is tremendous. The stock XRL flywheel weighs in at 8 pounds while an XR600R flywheel weighs five pounds! I experienced no noticeable loss of low-end, but did see a small gain in terms of responsiveness. You can easily remove the flywheel with the engine in the frame. You will need new gaskets for the side cover and the starter cover. I hope you have an impact wrench and flywheel removal tool. If not, get them before you try to start.

[/url]

HEre are the XRL and XR6R flywheels:

Flywheels.jpg

 

 

The XRL flywheel. This is with the starter clutch which weighs a pound and a half.

 

P3050056.jpg

 

Stock XRL and shaved flywheels

 

IMG_0141_zps5996ae19.jpg[/url]

 

Mounted up

IMG_0144_zps9c48cfb2.jpg

What do you think Red? What would be the maximum you would try taking off if you had to do it again?

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Is your concern a loss of low end, or actual engine running problems?  Any weight removal will cause a loss of low end, at least theoretically, and the increase in rev-ability will be proportional to the loss of low end.  There's no positive sum gain, only a trade off.  In terms of actual engine running problems, MX engines run with tiny flywheels. 

My main concern would be losing too much bottom end. Right now with the gearing and weight reduction it wheelies very easy in 1st and 2nd without the clutch on level ground, and with a bump or crest off road and some body english it can be coaxed in 3rd. I dont want to loose this characteristic even if it means having a snappier throttle response. I had a bad flip over about an hour ago off road. I was wheelying up a hill that was hard packed. I was hitting about 30-35 mph and without time to react to tap the rear brake lever the pig threw me off hard and i came down hard on my back. I thought it was broken. I lay there in agony moaning for about 5 minuits unable to catch my breath for about a minuit. I managed to get up to turn the ignition off and to check for damage. This will be the 3rd bad crash with the pig in 2 years. I couldnt believe my eyes. My gear shifter was bent and the rear tail light cover came off without hurting the bulb! The xrs only exhaust tip was crushed bad which im guessing took most of the impact. Gas was pouring out. I lifted the pig up, put it in neutral, hit the e button and it fired right up!...crazy huh? Then i layed back down on my back for about 5 minuits. I have been charging hard off road lately and knew i was due for a spill....lol.I think if this pig had a lightened flywheel and a pumper carb it would wicked off road.

Edited by Thumper3

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Been there, done that. I ended up taking a pound off of mine. You could get more aggressive and have it undercut and you could also have some shaved off of the OD of the bowl itself. I wanted to start small and work my way up.

The difference between and XRL and XR600R flywheel is tremendous. The stock XRL flywheel weighs in at 8 pounds while an XR600R flywheel weighs five pounds! I experienced no noticeable loss of low-end, but did see a small gain in terms of responsiveness.

What do you think Red? What would be the maximum you would try taking off if you had to do it again?

id say u could safely mechine the flywheel down to the weight of an XR600 without too much drama's however i dont know how the "E-start" will like this, experts chime in here:

Edited by tassie jeeper

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id say u could safely mechine the flywheel down to the weight of an XR600 without too much drama's however i dont know how the "E-start" will like this, experts chime in here:

Bingo! That has been a concern of mine. I think you will probably hit a point where the starter begins to suffer as you go ever lighter on the flywheel. I am not sure (I wasn't in the room when Mr. Honda's smart guys were sorting out the XRL), but I think the heavier flywheel serves two purposes. First, it makes the big single easy for a noob to navigate around town. The darned thing is nearly impossible to stall and will climb anything that the tires can hang onto. Second, I think the heavy flywheel helps the e-start get the motor spinning. Both purely guesses, but they make sense in my engineering challenged mind.

 

Getting the XRL flywheel down to five pounds would be a challenge. The shiny silver piece that I carved down on mine would have to be removed altogether and replaced with something lighter (an aluminum spacer perhaps). Getting the piece out is no small feat. You can easily remove the torx bolts, but there are also a ring of rivets that you'd have to drill out. If you did not remove the ring in question, you'd have to shave down the bowl itself... a BUNCH. I took off a bunch of material and thought we had lost at least two pounds. I was surprised when I threw it on the scale and it was only one pound lighter.

 

It helped though... the bike does spin up faster. The stock flywheel is so heavy... I did not notice any loss of grunt.

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I got 1.5 lbs off mine thats about all you can do.

Do you mean thats all that can be taken off without affecting drivability or thats all that can be taken off physcially? Did you find your bike was more snappier, what about the bottom end torque?

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Does anyone have a xrl flywheel lying around that has already been lightened that they want to sell? Or a stock xrl flywheel that they have the knowledge of how to lighten it, can do it and sell me??

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Do you mean thats all that can be taken off without affecting drivability or thats all that can be taken off physcially? Did you find your bike was more snappier, what about the bottom end torque?

Ok FIRST off flywheel weight has NOTHING to do with hp or torque!!! It has to do with how the engine responds lighter flywheel quicker response! But lighter flywheel easyer to stall. Thats why say on a CRF450R they have dam near NO flywheel! they need the response to get out of corner and over that triple! Thats why a CRF450R off road need more weight to help stalling and make smoother power! With a lighter flywheel you get the OH S--T when to front wheel comes up! On the XR650L Honda made flywheel that heavy (also they had to add the mounts for starter BTW starter gear does not count on flywheel weight as it dont turn when engine is running) they put that much weight to keep new riders from stalling it or getting S--T scared of of them when the front wheel comes up from sloppy throttle control!! As far as 1.5 lbs that is all you can get off physcially!

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I had 2nd flywheel that my guy got it closer to 2lbs but had to mach it so it needs rebalincing but cant find anybody to do it Falicon wanted 300 dollar just to do balancine F that! so it is on shelf cant say its avl as we will get locked out from site!!

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