flywheel weight

[motonuts]

have 98 kx 250 and a 10oz. flywheel weight that i like in the tight stuff mountain riding...now i cant tell that its on there anymore. i'm racing local desert and i dont know if it will help or hurt the bikes performance. some steep hills in the des. and some fast stuff. leave it on or take it off? :bang:

 

[tyesai]

They aren't hard to remove and install, just take it off and see what you think.

 

[Britt Boyette]

I would leave it on. The only thing I know that a weighted flywheel does is make it not rev as quickly as a non-weighted one. You would only feel this on a tight Arena-Cross type track, I would think. It depends on your riding style too. Some people need the extra weight because they are prone to letting the revs drop to quickly and stalling the bike before they can pull in the clutch or don't downshift soon enough. In auto racing, you see lightened flywheels in drag racing and sprint cars. You see heavier flywheels in NASCAR and Salt Flats speed cars.

 

[motonuts]

next race is next weekend and i can't change it out there...no air impact, and i'm not riding till then. so i guess i can race w/out it and see, i know pro rider steve hatch runs a 8oz on his kx250, during GNCC's. i'll just have to toast the clutch uphills double clutching, passing guys who stall up the trail.
also.........?????...better dead engine start take-offs? with weight or without? start is usually sand.

 

[SpDyKen]

Leave it on. You are getting too worked up trying to make this decision. Increasing crankshaft mass DOES NOT reduce power in any way! Most experienced engine builders increase mass to their cranks to smooth out their power increases. Enjoy everything you have and work on the things that really improve your power & performance, like jetting, gearing or other, more in-depth mods. Bottom line, you'll go faster with more flywheel weight, I'm sure you'll find.

 

[motonuts]

thanks for the info, i was worried about making a 2 stroke feel like a small 4 stroke
by installing a flyweight, losing that snap.

 

[Rcannon]

Leave it on. I believe a person would lose snap if they added several pounds, but honestly, 9-13 oz is hard to feel. The biggest difference , for me, is that the bike does not stall. The snap is still there.

 

[christopher in tam]

Flywheel weight will make a snap feel more like a solid hit. But peak power will still be the same.

 

[Rcannon]

Flywheel weight will make a snap feel more like a solid hit. But peak power will still be the same.

That description is excellent. I meant to say that! LOL

 

[bikepilot]

I played with a 12oz weight on and off on my KX250 and found that I did better with it on in every type of terrian except serious sand dunes (where it didn't really matter much). Even on a loamy MX track I did better with the weight. The big difference I noticed was that when accelerating through a really bumpy section it would stay hooked up better rather than rev up and bounce off the ground as easily. Also seemed much better when skimming whoops.

 

[rodH]

I played with a 12oz weight on and off on my KX250 and found that I did better with it on in every type of terrian except serious sand dunes (where it didn't really matter much). Even on a loamy MX track I did better with the weight. The big difference I noticed was that when accelerating through a really bumpy section it would stay hooked up better rather than rev up and bounce off the ground as easily. Also seemed much better when skimming whoops.

How does one figure out what weight to get??

 

[motonuts]

ok, i'm convinced. i'm leaving it on. thanks guys...more traction=more power=more tire life....

 

[2-stroke diehard]

Having more flywheel mass makes you a smoother (i.e. faster) rider. If you have very advanced riding skills, the stock super lightweight flywheel may be an advantage on fast MX, but in basically every other situation, you will be quicker with a bit more mass.

I went through this decision process with my car a while back and decided to stick with the stock (heavier) flywheel also, same principle. You have two cars or bikes with a given peak HP, but one acts like a jittery race horse at low speed (lightened), while the other is easy to control at all speeds and ultimately faster for most drivers (heavier) .

 

[rodH]

Having more flywheel mass makes you a smoother (i.e. faster) rider. If you have very advanced riding skills, the stock super lightweight flywheel may be an advantage on fast MX, but in basically every other situation, you will be quicker with a bit more mass.

I went through this decision process with my car a while back and decided to stick with the stock (heavier) flywheel also, same principle. You have two cars or bikes with a given peak HP, but one acts like a jittery race horse at low speed (lightened), while the other is easy to control at all speeds and ultimately faster for most drivers (heavier) .

Hmm, I always prefer a lighter car (within reason), I would much much rather drive a porsche 911 than a cadillac, i would MUCh rather drive an F1 car than a Nascar, I much rather drive a honda S2000 than a Ford Mustang, I would much rather drive a bullet bike than a Harley, and I'd much rather ride a SX/MX bike than a dual sport. I am thinking about getting a Wt for my bike, but now I am starting to wonder if that is the right moved based on my preference.?????

 

[Rcannon]

The heavier flywheel will not turn your 911 into a Ford diesel truck. The difference is not that dramatic.

The biggest difference is the bike does not want to stall. It is also much easier to ride at a slow speed.

 

[darringer]

rodH, your comparing apples to oranges. The motor characteristics are not changed that drastically. The only real difference I have felt with my 12oz. weight when on the track is much better hook out of corners and on slippery sections of the track. In the midrange and top end of the powerband, there is no feeling of sluggishness from the weight. They really shine at very low rpm making the motor almost stall-proof. It's not a major investment, and you can remove or install it in minutes to feel the difference for yourself. I don't know anyone that has removed the weight once installed, though.

 

[2-stroke diehard]

Hmm, I always prefer a lighter car (within reason), I would much much rather drive a porsche 911 than a cadillac, i would MUCh rather drive an F1 car than a Nascar, I much rather drive a honda S2000 than a Ford Mustang, I would much rather drive a bullet bike than a Harley, and I'd much rather ride a SX/MX bike than a dual sport. I am thinking about getting a Wt for my bike, but now I am starting to wonder if that is the right moved based on my preference.?????

I was of course referring to flywheel weight with cars, not vehicle weight. I have a MKIV Supra Turbo with 735 HP, it drives just like any "normal" car out of turbo boost and pulls away smoothly from stoplights with a 900 RWHP-worthy clutch, since I have the stock flywheel (32 lbs!!). You can buy a lightweight flywheel (9 lbs), but then the car suddenly becomes prone to stalling on hills/at lights unless you watch it, i.e. it becomes like a jittery race horse. It's harder to drag race with a lightened flywheel, although road course performance is better. The heavier flywheel makes the car easier to drive, although it doesn't rev quite as quickly.

Relating this to bikes, my CR doesn't like picking its way through tight trails too much, and a heavier flywheel would help out, but I haven't decided if I want to compromise its ultimate MX ability either. A nice enduro bike would fill that need, which may be the answer for me.

 

[rodH]

thanks for the comments guys, that makes me feel better, I need to get one now.

a Supra with 735 HP, WOW, that is freaking amazing. I have just over 300 in my 350Z, and can't get much more than that unless I want to go FI, which I don't. I am trying to make it as fast and as light as I can (they came a little heavy right out of the box) and still be NA.