Other Pro's n Con's of lightweight flywheels.

Freakrider

Freakrider

X247
Location
Tampa Bay area
Lighter flywheels spool up faster at what cost ? How does this affect crank bearing life/ engine longevity ? The flywheel acts as a crank harmonic balancer to help with vibration. Does any of this matter because you have run a lightened msd TL FW for several seasons without issue ? Anyone care to discuss ?
 
hink320

hink320

Location
sask, canada
I'm not too worried about the flywheel having a detrimental effect on crank bearing life because I'm running a +16mm crank and know that I'll have to rebuild it every 50 hours or so anyways.
 
MADMAT

MADMAT

Location
Ohio
No you said to change the change rings on a stock SJ every 2 season...lol. :)

I think you HAVE to rebuild a crank like that every 50 hours (INSANE!!!) or risk blowing a very expensive set up. I will never own one again! That 8mm I had needed rebuilt waaaaaaaaaay to soon for my liking!!
 
Freakrider

Freakrider

X247
Location
Tampa Bay area
hink320 said:
I'm not too worried about the flywheel having a detrimental effect on crank bearing life because I'm running a +16mm crank and know that I'll have to rebuild it every 50 hours or so anyways.
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Wow talk about cherish every hour you ride that motor. Will the front/ most expensive bearing need replaced after 50 hrs ?
 
wanderer1

wanderer1

Location
Cruising Around
MADMAT said:
No you said to change the change rings on a stock SJ every 2 season...lol. :)

I think you HAVE to rebuild a crank like that every 50 hours (INSANE!!!) or risk blowing a very expensive set up. I will never own one again! That 8mm I had needed rebuilt waaaaaaaaaay to soon for my liking!!
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Derail- I said every season and stand by it for a 2 stroke. ever check a service manual for a 2 stroke? Most call for piston replacement every 25 hours. Having a loose piston/ring clearance issue will definitely decrease crank bearing life and is easily avoided by simple maintenance. I like to avoid catastrophic failures and such. On topic-light weight everything, crank-rods-pistons,driveshaft will not adversely affect bearing life. If anything it will help.
 
CARBONX2

CARBONX2

Location
South Africa
Kyle(DASA) recommendation on DASA 1200:
We recommend top end at 60-70 hours and bottom end at 120-130 hours.
On the 89mm bore we can get a little more time on.
 
MADMAT

MADMAT

Location
Ohio
I would think lighter would only help too...but I don't understand why. It seems like it would just be exactly the same to me....or at least un-measurable differences.
 
Freakrider

Freakrider

X247
Location
Tampa Bay area
I use to think a lighter flywheel would help with crank bearing longevity until I posted it here and Tom21 corrected me regarding harmonic balancing. I went internet searching at the time and found my instinct was wrong. The 3.5 lbs 701 flywheel that Yamaha engineers came up with was for a reason (4 lbs on some bigger motors). Don't get me wrong, I run a lightened FW but just discussing this topic. This thread is about flywheel weight crucial to engine harmonic balance ?
 
CARBONX2

CARBONX2

Location
South Africa
A heavier flywheel will absorb a lot of vibrations from the rest of the engine, but affects response. Someone knowledgeable/experienced needs to balance a typical FW engine to tell how good/bad the balance is.
 
Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
On the flip side, I heard zero has some fancy balancer he uses to check every flywheel he works. I don't think yamaha does that. I wonder how much difference in balance there is before and after he gets his hands on one. A lighter balanced flywheel is surely better on bearings than a heavier unbalanced one.

@#ZERO
 
Freakrider

Freakrider

X247
Location
Tampa Bay area
Vumad said:
On the flip side, I heard zero has some fancy balancer he uses to check every flywheel he works. I don't think yamaha does that. I wonder how much difference in balance there is before and after he gets his hands on one. A lighter balanced flywheel is surely better on bearings than a heavier unbalanced one.

@#ZERO
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Yamaha does balance flywheels, if you compare them you will see that they drill several partial depth holes close together in outer flywheel and some have less holes than others depending on their original balance. If you do a Google search you will see that Tom21 is correct about why a flywheel has intentional weight to it and how it controls harmonic vibrations from the crank.
 
H

Half flip95

Formerly pondracer95
Location
Lake Havasu City AZ
Freakrider said:
Yamaha does balance flywheels, if you compare them you will see that they drill several partial depth holes close together in outer flywheel and some have less holes than others depending on their original balance. If you do a Google search you will see that Tom21 is correct about why a flywheel has intentional weight to it and how it controls harmonic vibrations from the crank.
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Yes, they are designed for longevity, but im pretty sure that all went out the window when you added the pipe, porting, high compression and +16mm on the stroke. we're already doing everything we possibly can to shorten engine life, why stop at the flywheel?
 
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