Flywheels / Inertia / Momentum/ Energy

This could be a MASSIVE topic.... But I can only light the fire before I get pulled into my work day....

Where to start??

On 450 class machines... The rule of the day when modding a monster is: "you are going to need more flywheel or you are going to waste a lot of power" 

Whether it's in uncontrolled wheelspin , or in too much power to make your riding rythm work.... You can build a monster that you CAN'T ride... Flywheel it up and all that power becomes controllable and useful...

There are plenty of stock machines that are known for having too small an amount of flywheel mass right from the factory...  Prone to stalling and lighting up tires with abrupt hit...

Also... Thumpers, by virtue of single cylinders , wreak havock on valve trains and timing chains... With all their intermittent snap and slack between power pulses... You watch one strobe light study of a thumper timing chain and you will wonder why they don't just all snap on the first ride...

I have experienced many crazy built 2 strokes that have personalities that order on pathologic ...lol... More flywheel makes the power and traction and a whole lot of things work...

I am , of course , talking about the control of very strongly built engines with a wretched excess of power....  Not putting a big fly on something that is nutless to begin with....

Quick bit about what makes sand drag quads run at the top of the heap.... I have been involved in quite a bit of sand drag quad building... Even though I'm not a fan of drag racing myself I have done a lot of head work etc for the drag race crowd....

They spend a lot of money on VERY heavy tungsten weighted cranks and heavy flywheels.... The biggest step in our gearbox is the step from 1st to 2nd...biggest numeric hike.... They gear as TALL as you possibly can to still launch HARD in first gear... And shift ONLY ONCE during the race.. taking all that inertia and banging it at high rpm into the big jump to second gear... Unreal what one of those setups pulls like with a killer engine.... Unreal...

Sooooooo...

After all that... Time to talk about something I have not experienced...  Too much flywheel mass initially...and making everything better by reducing flywheel weight...

Adnohguy has mentioned big benefit, and no trials tractability loss, by dropping a lot of flywheel mass on our 230s...

Who has done it?

How much can be dropped? 

Who does the work?

What's it cost?

What are the results?

There might be some big variances between the type of motor build and type of riding. 

I don't have a stroker mine is a bore only. I also ride in some very tough technical stuff including some big screaming power hills. I haven't touched the flywheel in mine. I like what it does now. However that doesn't mean it might not be better with a few oz. shaved off? 

I do prefer bikes in general with more flywheel and have tried both on other models. 

Thanks for the input Steve... I am in 100% agreement ...

I love my setup so far.... One more round of doing the BBR piston and I'm sure I will be done....

But.... I can't help but wonder about the flywheel... Wouldn't want to miss out if it's something easy to setup...

This could be a MASSIVE topic.... But I can only light the fire before I get pulled into my work day....
Where to start??
On 450 class machines... The rule of the day when modding a monster is: "you are going to need more flywheel or you are going to waste a lot of power" 
Whether it's in uncontrolled wheelspin , or in too much power to make your riding rythm work.... You can build a monster that you CAN'T ride... Flywheel it up and all that power becomes controllable and useful...
There are plenty of stock machines that are known for having too small an amount of flywheel mass right from the factory...  Prone to stalling and lighting up tires with abrupt hit...
Also... Thumpers, by virtue of single cylinders , wreak havock on valve trains and timing chains... With all their intermittent snap and slack between power pulses... You watch one strobe light study of a thumper timing chain and you will wonder why they don't just all snap on the first ride...
I have experienced many crazy built 2 strokes that have personalities that order on pathologic ...lol... More flywheel makes the power and traction and a whole lot of things work...
I am , of course , talking about the control of very strongly built engines with a wretched excess of power....  Not putting a big fly on something that is nutless to begin with....
Quick bit about what makes sand drag quads run at the top of the heap.... I have been involved in quite a bit of sand drag quad building... Even though I'm not a fan of drag racing myself I have done a lot of head work etc for the drag race crowd....
They spend a lot of money on VERY heavy tungsten weighted cranks and heavy flywheels.... The biggest step in our gearbox is the step from 1st to 2nd...biggest numeric hike.... They gear as TALL as you possibly can to still launch HARD in first gear... And shift ONLY ONCE during the race.. taking all that inertia and banging it at high rpm into the big jump to second gear... Unreal what one of those setups pulls like with a killer engine.... Unreal...
Sooooooo...
After all that... Time to talk about something I have not experienced...  Too much flywheel mass initially...and making everything better by reducing flywheel weight...
Adnohguy has mentioned big benefit, and no trials tractability loss, by dropping a lot of flywheel mass on our 230s...
Who has done it?
How much can be dropped? 
Who does the work?
What's it cost?
What are the results?

You can get approximately 1 lb +\- from a 230f crank and flywheel with out a re-balance. (Depending on year of bike)

No room on a Terry Miller stroked crank to get any weight off of it with out a re-balance

230f crank weighs 15 lbs Stock

IMO:
1 lb removal is far from enough weight removed to make any real noticeable difference on a stocker. But with the high compression ratios that I run , 12.5/13.5-1
It is more noticeable.
AND with the right battery, your bike will weigh over 4 lbs less than a stocker.

I get $75.00 each for doing either.

Oh yeah!!

Exactly the GUY I was hoping would chime in on the topic....

I was hoping for a bigger sales pitch on the difference it makes though...lol... I want to think it's going to make friends start looking for the hidden nitrous tank... Same as I always want from every mod... Dream big...

A pound off the perifery makes the biggest difference in inertia since that weight carries the most velocity/inertia...

Now to stalk eBay for a decent price on a flywheel...

I'm not going to pull the crank until it needs replacing... Too lazy for that...

Flywheel isn't out of my lazy threshold yet...😎

Edited by mixxer

I turned 12.9 oz. off my 230 flywheel since I have access to a manual lathe. Mine is still 223cc, but has most every other common mod done. What I noticed is that it did rev a little bit quicker off-idle. Mid-high RPM didn't feel much different. This was even before I did the PWK carb swap.

I like having the stall-resistant-luggability and was afraid I'd lose some of that even though the engine weighs a metric ton. Well, I will honestly say that if I'm riding it like a trials bike in my yard (slow balance riding/standstill) it does stall just slightly more often if I don't keep a finger on the clutch. With that said, when I'm actually out trail riding I rarely stall due to the less reciprocating mass. I think the only time I notice it (negatively) is when I ride over a big log and let off the throttle and the rear wheel stops spinning enough to kill it just as I'm getting over the log. Although that is probably more due to my poor technique...

Overall, would I do it again? Definitely, especially since it was free for me, haha. While I do like a broad, torque-y power-curve, this bike needed some more 'snap' on the low-end, IMO. The more off-idle grunt the better, without being too abrupt to rip the rear tire loose on any soil.

Excellent info! Thanks for adding in!

Frank Nye told me years ago lightening the CRF230 flywheel is a must-do and very noticeable when riding.

After building the 8mm stroker and added comp. I feel NO need to lighten the flywheel on my bike. It rev's insanely fast! Now on other bikes I have removed the flywheel all together :) My Honda SL350/450 vintage twin flat tracker I even cut the end of the crank off! Also on my 74 XL350/450 flat tracker we removed the flywheel. Both bikes use a small 6v battery to the ignition. Any ways both of those benefited from NO flywheel for the racing I was doing. For the riding I do with the 230 the stock flywheel mas feels perfect. In fact I went to a crf450 throttle housing on my 230 to get a quicker pull and will be putting the stock one back on for better control of the new found torque right off idle :) If I could just find a in between feel..............I have to imagine Guy's bikes are very exciting to ride! Just not the kind of power delivery I need on the edge of cliff's that I ride on ;) 

Ricky, I remember the "total loss ignition systems"

I did one on my Rupp RMT80 minicycle... And I hated it!! Lol... Silly kid...

That bike still had a point ignition system and you could cut down the entire flywheel outside and just leave the hub that triggered the points .... I can't attest to a performance increase, but I can attest to the pain in the arse of needing a charged battery or your ride was done...

Lol.... Hated it....

After building the 8mm stroker and added comp. I feel NO need to lighten the flywheel on my bike. It rev's insanely fast! Now on other bikes I have removed the flywheel all together  My Honda SL350/450 vintage twin flat tracker I even cut the end of the crank off! Also on my 74 XL350/450 flat tracker we removed the flywheel. Both bikes use a small 6v battery to the ignition. Any ways both of those benefited from NO flywheel for the racing I was doing. For the riding I do with the 230 the stock flywheel mas feels perfect. In fact I went to a crf450 throttle housing on my 230 to get a quicker pull and will be putting the stock one back on for better control of the new found torque right off idle  If I could just find a in between feel..............I have to imagine Guy's bikes are very exciting to ride! Just not the kind of power delivery I need on the edge of cliff's that I ride on  



You (all) know, or at least should by now, how my stuff runs. I’ve posted about it many times.
There is absolutely no “out of controll” Power band on any of my bikes. Every one who has ever ridden my bikes would not be afraid to ride it/them on trails that are on the “edge of cliffs” any more than a stocker.

No surges, no “on the pipe”, no “out of controll power band” that would require a slower turning throttle than a stocker. Very easy going if thats how you chose to ride them.
It/they will crawl along in first gear like a stocker or accelerate from right off an idle or any gear. No screaming or high rpm revving required unless you want to ride it that way for some reason. I never run it up to the limiter, no fun up there. Short shift and feel the pull, or let off the throttle and cruise. But it’s really nice to loft the front wheel over obstacles with just the throttle when needed.

My bikes are not for terrorizing oneself, they are for the enjoyment of smiling from ear to ear.

IMO:
Clark Kent would probably really appreciate riding my sleeper bike because none of the bling shows.
Oh yeah!!
Exactly the GUY I was hoping would chime in on the topic....
I was hoping for a bigger sales pitch on the difference it makes though...lol... I want to think it's going to make friends start looking for the hidden nitrous tank... Same as I always want from every mod... Dream big...
A pound off the perifery makes the biggest difference in inertia since that weight carries the most velocity/inertia...
Now to stalk eBay for a decent price on a flywheel...


Look for an 05 or older flywheel.
5 hours ago, mixxer said:

Ricky, I remember the "total loss ignition systems"

I did one on my Rupp RMT80 minicycle... And I hated it!! Lol... Silly kid...

That bike still had a point ignition system and you could cut down the entire flywheel outside and just leave the hub that triggered the points .... I can't attest to a performance increase, but I can attest to the pain in the arse of needing a charged battery or your ride was done...

Lol.... Hated it....

Yes that would be silly on a play bike but a race bike that only see' s 15-20 min at a time 3times a night was fine on the battery. The performance increase was huge on my bikes for acceleration. 

 

1 hour ago, adnohguy said:

 

 


You (all) know, or at least should by now, how my stuff runs. I’ve posted about it many times.
There is absolutely no “out of controll” Power band on any of my bikes. Every one who has ever ridden my bikes would not be afraid to ride it/them on trails that are on the “edge of cliffs” any more than a stocker.

No surges, no “on the pipe”, no “out of controll power band” that would require a slower turning throttle than a stocker. Very easy going if thats how you chose to ride them.
It/they will crawl along in first gear like a stocker or accelerate from right off an idle or any gear. No screaming or high rpm revving required unless you want to ride it that way for some reason. I never run it up to the limiter, no fun up there. Short shift and feel the pull, or let off the throttle and cruise. But it’s really nice to loft the front wheel over obstacles with just the throttle when needed.

My bikes are not for terrorizing oneself, they are for the enjoyment of smiling from ear to ear.

IMO:
Clark Kent would probably really appreciate riding my sleeper bike because none of the bling shows.

 

 

Sorry guy I didn't mean it to sound like your bikes are peaky or something but knowing how strong my 251cc all stroke no bore engine is I can imagine that a 270+ monster with more head work and more cam and more carburetor would be (exciting) to ride with ALL that thrust of torque! :) and with a lightweight flywheel/crank combo WOW is what I think. Yes I also ride mine just like my xr628 :) short shift and smile. Lol

In fact I went to a crf450 throttle housing on my 230 to get a quicker pull .....


I’d really like a faster throttle. Can you please provide information on exactly which throttle/cable/etc. you used?

Thanks a lot.
17 minutes ago, motrock93b said:

 


I’d really like a faster throttle. Can you please provide information on exactly which throttle/cable/etc. you used?

Thanks a lot.

 

Quick FYI here.... Faster throttle on non accelerator pump carbs = faster bog...

Quick FYI here.... Faster throttle on non accelerator pump carbs = faster bog...

Understood. I’m interested in “judiciously” getting faster throttle opening so I can more easily get it wide open. I rarely experience bogging, and would definitely benefit from an easier full throttle position.

I'm still thinking of doing this but big but JAAAAA.  I use for tight hard trail steep trail 14/ 45 gear the stroker  does this with ease just above idle.  So the only way I can report is buy a used flywheel send to guy and try it. All the reporting from ADN about light flywheel on his bike. Does not count as anything he does to his bike wont slow it down. Keep up the great mods GUY, hope one day on dirt bike travel to. Washington to try your monster 272 plus.

Also report on heavy add on flywheel on other bikes. Useless info but here it goes on my CR500 two smoke 13oz great mod. KTM 200 two smoke great mod. Wr450 bad mod to add heavy fly wheel mod. On friends big bore ported  Cr500  killed all low end heavy fly wheel helped, but he wished he left it stock. On other built CRF450X with r cams heavy port work very fast but now useless trail bike. Heavy Wt fly wheel helped but still bike only good for racing useless trail bike. Be careful what you ask for unless you want to cultch it like a 125 two smoke. Also you don't want off idle zap so quick you slide off 12in wide trail. Like my Ex xr300 xr250 / Ex xr440  xr400 , for racing open riding make it fast as you can. Ok all useless info over.

49 minutes ago, motrock93b said:

Understood. I’m interested in “judiciously” getting faster throttle opening so I can more easily get it wide open. I rarely experience bogging, and would definitely benefit from an easier full throttle position.

Makes perfect sense

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