Rekluse vs Flywheel weight


14 replies to this topic
  • moon55

Posted December 11, 2009 - 10:41 AM

#1

I've got a 2001 YZ426f and was wanting to tame it down a lil and reduce stalling for woods riding/racing. Just wanted to compare effects of adding FWW versus installing rekluse auto clutch. Auto clutch is expensive and want to know if adding FWW will make a noticeable difference,while saving a few bucks.

Thanks.

  • grayracer513

Posted December 11, 2009 - 11:31 AM

#2

Both help, and although many users of the auto clutch will say they don't need the FWW, both do different things, and they work well with each other.

Understand the effect of a heavier flywheel: A four-stroke single drives itself only during the power stroke, and from a point just after the opening of the exhaust valve at the bottom of the power stroke through more than the next one and a half revolutions, it slows down, loosing some of the speed it generated, and because horsepower depends on speed, loosing some of the power it generated as well. Adding to the rotating mass of the engine allows rotating inertia to help carry the engine from the end of one power stroke to the beginning of the next with less loose of speed, and by doing so, actually increases the low RPM net power of the engine. For all its benefits, an auto clutch cannot accomplish that.

  • Chas_M

Posted December 11, 2009 - 11:37 AM

#3

If you can afford it, add the auto clutch first. I'll bet that it will solve all your problems, and more, without adding an extra flywheel weight. On top of the auto clutch many benefits, the auto clutch itself adds a small amount of extra flywheel effect. Use the Pro version or else spring for a Revloc clutch for about the same price.

  • grayracer513

Posted December 11, 2009 - 12:04 PM

#4

The argument that the Rekluse adds rotating mass is flawed in that the clutch rotates more than 2.6 times slower that the crank, and thus any weight added to it has exponentially less than 1/2.6 the effect that it would were it added to the crank.

And as I said, in spite of the benefits of the auto clutch, it can't add low end power as the flywheel weight can.

I don't use an auto clutch, and don't foresee buying one anytime soon, although I have been in some situations where it would have been really nice to have had one. But even if I did, I'd use the heavier flywheel, too. Great mod for the money.

  • crf450rider64

Posted December 11, 2009 - 12:20 PM

#5

I have an 09. I purchased and installed a Rekluse clutch. I was sorta cautious and did a lot of research and asked alot of questions. I race in a Hare Scramble series as well as Motocross. I have about 60hrs on the clutch now and can tell you it is exactly what I wanted.
It was super simple to install. The best thing is you can adjust it to what ever style you are looking for. From super soft never using the clutch......... to almost not having an "auto clutch". I set mine up as hard as possible (one spring) so I still have basically use the clutch. The big advantage is, it will not stall if you have to lock it up. I am 100% pleased with mine.

  • Chas_M

Posted December 11, 2009 - 03:42 PM

#6

The argument that the Rekluse adds rotating mass is flawed in that the clutch rotates more than 2.6 times slower that the crank, and thus any weight added to it has exponentially less than 1/2.6 the effect that it would were it added to the crank.

And as I said, in spite of the benefits of the auto clutch, it can't add low end power as the flywheel weight can.


The argument is not flawed at all. Your statements are true except that adding flywheel weight does not add power anywhere. The auto clutch adds about 8 ozs to the spinning clutch mass, and even though it's only about 1/3 as effective as flywheel or crankshaft mass, it nevertheless adds a small amount of flywheel inertia.

  • grayracer513

Posted December 11, 2009 - 04:25 PM

#7

First, because the flywheel prevents loss of horsepower through parasitic deceleration, it does have the effect of adding NET horsepower, but only at low speeds. Reread post #2.

Because the relationship of mass to inertia is exponentially related to speed, the mass added to the clutch is much less than one third as effective as when added to the crank. Furthermore, the inertia of the rotating flywheel is applied against the decelerating crankshaft through a 1:2.6 reverse reduction, which reduces its effect further.

An accurate analysis of rotating mass requires a lot of detailed information we don't have here, such as the 3 dimensional composition of the two masses compared. The distance of the center of the mass from the center of rotation is a factor, also, an in that regard, the clutch, being larger, does have some advantage. Since the diameter of the clutch is more or less twice that of the flywheel, then the inertial advantage of the larger clutch will be the square of two, whereas the speed advantage of the same mass rotating at the crank would be the square of 2.6, a 170% advantage.

In addition, in order for the rotating clutch to apply its inertia to the crank, it must do so through the primary drive gear which reduces the force by 2.6:1. So the inertia of the rotating clutch is .60 of that of the flywheel to start with, then the gear speed increase reduces that to .23 of the same force, so the inertia provided by a heavier clutch is roughly a quarter of the same amount of weight added to the crank.

I suppose you can still say that it adds some additional inertia, but it's not very much at all by comparison.

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  • keegan1014

Posted December 11, 2009 - 06:22 PM

#8

I have the same bike with the rekluse and I love it
but I cant speak for the flywheel weight

  • SparksXR426

Posted December 11, 2009 - 09:17 PM

#9

I ride mostly tight woods and love the GYTR off road flywheel weight. The Rekluse sounds nice but as far as I understand (correct me if Im wrong here) the motor freewheels with a dead engine in gear (this is a BIG deal to me sometimes) and the price is nothing to get excited about. Only well thought out and focused mods for me now, not a rolling parts wagon like some of my last rides. I am watching the autoclutches with interest though.

  • yz_for_me

Posted December 11, 2009 - 09:19 PM

#10

I ran both on my last bike ('03 YZF) and really liked it. I can say this, Gray is right, they really do different things. I had the fw weight on for over a year before adding the Rekluse. The main thing I noticed with the fw weight is it smoothed out the power. It did help with stalling somewhat but it wasn't a night and day improvement. The Rekluse on the other hand doesn't do a lot to alter the power curve (like Gray said, it's inertia effect is reduced by its slower rotational velocity), but it puts an end to pretty much all stalling.

I'd say if you like the challenge/fun of a clutch and just want to tame the power a bit to make it more managable, save your money and go for the fw weight only. On the other hand if you like the hit of your motor but just really hate stalling, get a Rekluse only. If you want smoother power and no stalling do both.

  • grayracer513

Posted December 11, 2009 - 09:29 PM

#11

... as far as I understand (correct me if Im wrong here) the motor freewheels with a dead engine in gear (this is a BIG deal to me sometimes)


If you have the bike in gear and let off the gas, you get engine braking same as normal. If you start the bike rolling at an idle, below the stall speed (engage/disengagement) of the clutch, it will coast free, as if in neutral, until you blip the throttle, which will speed the engine up and engage the clutch, after which you'll have engine braking again. But if the engine isn't running, the clutch will not engage, and you can't bump start, or stuff like that.

  • SparksXR426

Posted December 11, 2009 - 09:49 PM

#12

But if the engine isn't running, the clutch will not engage, and you can't bump start, or stuff like that.


Trying to dig in (go off on the left, shut down and jam the handlebars into the hill) on big hillclimbs would get a little more interesting. FWW cured 95% of stalling issues for me (rider error sums up the rest:rolleyes:) and greatly enhanced the low end manners of the motor with no real downside.

  • eazrider

Posted December 12, 2009 - 04:06 AM

#13

I'm not smart like some folks. I had a 10 oz weight on my '06 450. loved the way it tamed the power down. I then added the Rekluse Pro clutch, and found the motor too sluggish coming out of the corners. I removed the 10 oz weight, and man, I could steer with the rear wheel again. Guess I was wrong, but I thought any time you added rotating mass, it slowed down it's acceleration...?

  • Ray450

Posted December 12, 2009 - 06:38 AM

#14

The 2001 426 was a very good bike, and very well may have been better for offroad than the early 450s since it seemed to have more manageable power, more gears and more flywheel feel (not sure if it actualy did). But, it's 9 years old now, and isn't even close to the newer bikes. I'd have to say the investment alone in a Recluse would not be worth it. I'd suggest selling it, using that recluse money to upgrade to a 06 or newer (I just had to go down to $2,600 to sell a 2007), and just get the GYTR offroad flywheel weight. If you need to keep the 01, you can get some cheap weights for it as well, I just couldn't see spending alot on that old a model, plus the learning curve installing and riding with it. I had a early recluse (03 YZ 450F) and didn't like it that much, I still had to kick start it almost as much, because while it helped the low speed stalls, it still had some stalls and flameouts, but couldn't be bump started immediatley like without the Recluse.

  • Chas_M

Posted December 12, 2009 - 08:15 AM

#15

The Rekluse sounds nice but as far as I understand (correct me if Im wrong here) the motor freewheels with a dead engine in gear (this is a BIG deal to me sometimes)


This is one of the many places where the LHRB is helpful in conjunction with the auto clutch, although with an auto clutch there is little chance of a dead engine to cause a problem in the first place.





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