Author Topic: Lightened Flywheel Opinions  (Read 7590 times)

Online canuck750

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Lightened Flywheel Opinions
« on: April 26, 2015, 08:33:45 PM »
I am considering installing a lightened flywheel in the 750 S3 I am rebuilding. My Eldo is stock and my V7 Sport has a RAM clutch, both are unique and I enjoy the feel of them both.

I am thinking of Ed Milich's lightened flywheel and ring gear.

Anyone have any experience running an early big block with Ed's kit?

The only other mod is a B10 cam I am going to run, otherwise stock 750 heads, pistons and heads.

Thanks

Jim
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Offline mtiberio

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Re: Lightened Flywheel Opinions
« Reply #1 on: April 26, 2015, 08:35:31 PM »
Might go well with the short stroke crank. Doesn't help smoothness however.

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Re: Lightened Flywheel Opinions
« Reply #2 on: April 26, 2015, 08:41:42 PM »
Might go well with the short stroke crank. Doesn't help smoothness however.

Does a lightened flywheel add to rough running and/or harsher shifting? or do you mean a lightened flywheel will just maintain the 'unique' Guzzi rhythm?

Thanks

Jim
1949 Guzzi Airone
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Offline mtiberio

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Re: Lightened Flywheel Opinions
« Reply #3 on: April 26, 2015, 08:58:10 PM »
Lighter flywheels make bikes easier to stall off the line. They make life tougher on engine components (rods, pistons), and easier on down stream (trans, ujoint, rd) components. They allow quicker revs, but you lose some low rpm smoothness. I dont like them per-se in street bikes

Online oldbike54

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Re: Lightened Flywheel Opinions
« Reply #4 on: April 26, 2015, 08:58:24 PM »
Does a lightened flywheel add to rough running and/or harsher shifting? or do you mean a lightened flywheel will just maintain the 'unique' Guzzi rhythm?

Thanks

Jim

 Jim , a lightened flywheel allows the reciprocating mass to speed up and slow down more during each revolution . I have read some engineering treatises that made the claim that with single and twin cylinder engines that a lightened flywheel actually decreases an engines ability to rev to high RPMs due to this .

  Dusty
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Offline Triple Jim

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Re: Lightened Flywheel Opinions
« Reply #5 on: April 26, 2015, 09:08:17 PM »
I have read some engineering treatises that made the claim that with single and twin cylinder engines that a lightened flywheel actually decreases an engines ability to rev to high RPMs due to this .

I would like to read those treatises.
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Re: Lightened Flywheel Opinions
« Reply #6 on: April 26, 2015, 09:31:08 PM »
I would like to read those treatises.

 Probably Kevin Cameron . He DID build lots of really fast MC racing engines . Memory tells me that the idea is , at higher RPMs the lighter flywheel allows the engine to speed up and slow down more in each revolution , thus using more energy to accelerate the reciprocating mass after each power stroke . Remember , IC engines do not maintain a constant speed between power cycles .


  Dusty

 Edit , also , by maintaining a more constant crankshaft speed , the cam timing will stay more accurate . Cams have a really hard time keeping up with crank speed variations , especially with chain drive instead of gear drive . I'm thinking that those monster twin cylinder Hondas that Todd Henning raced , with Cameron built engines , used stock weight cranks and flywheels , and this is my reference .

 
« Last Edit: April 26, 2015, 09:50:42 PM by oldbike54 »
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Offline rodekyll

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Re: Lightened Flywheel Opinions
« Reply #7 on: April 26, 2015, 10:00:49 PM »
In my experience, the more 'snatchy' or abrupt things are when rolling on/off the throttle, the less life in the components.  It's a tradeoff, for the fun factor, but sometimes max life isn't the point . . .

That being said, I just replaced my light flywheel in the trike with a stocker.  Who needs a performance land yacht?

But to get to the question -- my only advice is to have whatever shop operate on YOUR stuff.  I read a lot of dissatisfaction in all sorts of forums about the 'exchange 'method, regardless of the shop involved.  Some folks feel that the ring gears and such that they submitted as 'cores' were in better shape than what they got back.

 . . . and generally speaking -- I've got a local machinist who did a flywheel for me to-order for $40. 

Offline Triple Jim

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Re: Lightened Flywheel Opinions
« Reply #8 on: April 26, 2015, 10:04:48 PM »
Probably Kevin Cameron . He DID build lots of really fast MC racing engines . Memory tells me that the idea is , at higher RPMs the lighter flywheel allows the engine to speed up and slow down more in each revolution , thus using more energy to accelerate the reciprocating mass after each power stroke .

Energy isn't used when the parts speed up and slow down, it's stored and released.  That's the sort of argument that makes me suspicious.
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Re: Lightened Flywheel Opinions
« Reply #9 on: April 26, 2015, 10:20:24 PM »
Energy isn't used when the parts speed up and slow down, it's stored and released.  That's the sort of argument that makes me suspicious.

 My understanding is that the flywheel is the storage device . Now , in a multi cylinder engine , or a 2 stroke , the acceleration/decceleration is greatly reduced .

  Dusty
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Offline NCAmother

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Re: Lightened Flywheel Opinions
« Reply #10 on: April 26, 2015, 10:47:32 PM »
I would just contact Ed, and tell him how you want to ride, he's very personable

Offline Triple Jim

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Re: Lightened Flywheel Opinions
« Reply #11 on: April 26, 2015, 11:30:30 PM »
My understanding is that the flywheel is the storage device . Now , in a multi cylinder engine , or a 2 stroke , the acceleration/decceleration is greatly reduced .

All the rotating parts share in the flywheel effect, including the "flywheel".  No energy is lost due to acceleration of the rotating parts, either in the positive or negative direction.  Things like friction lose rotational (kinetic) energy to heat.  16 cylinder 2-stroke, single cylinder 4-stroke, it doesn't matter, energy isn't lost as the parts speed up and slow down during the cycle.  But with a big flywheel, there is less change in angular velocity.

I don't mean to derail the thread, but I do like to promote correct physics.
« Last Edit: April 26, 2015, 11:32:55 PM by Triple Jim »
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Re: Lightened Flywheel Opinions
« Reply #12 on: April 26, 2015, 11:34:17 PM »
All the rotating parts share in the flywheel effect, including the "flywheel".  No energy is lost due to acceleration of the rotating parts, either in the positive or negative direction.  Things like friction lose rotational (kinetic) energy to heat.  16 cylinder 2-stroke, single cylinder 4-stroke, it doesn't matter, energy isn't lost as the parts speed up and slow down.  But with a big flywheel, there is less change in angular velocity.

I don't mean to derail the thread, but I do like to promote correct physics.

 Hey , I'm just going by what Cameron said . Not an engineer , sometimes the terminology confuses me , but I stand by the theory based on his research .

  Dusty
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Offline Triple Jim

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Re: Lightened Flywheel Opinions
« Reply #13 on: April 26, 2015, 11:41:03 PM »
OK dusty, I understand that you're only relating something you read, but this really isn't based on Kevin Cameron's research, it's based on physics.  I assert that if you did a dynamometer run of an engine, then lightened its flywheel and repeated the run, there would be little difference, particularly at the high end of the curve, as long as the run was long enough to not bias the results toward an engine that accelerates quickly.

edit:  I can envision a situation in which an engine, after lightening its flywheel, exhibited a lot of vibration, which could lose power to heating its surroundings, and this would show a lower power output.  In this case, the flywheel would reduce power lost, but not simply because the crankshaft had less angular acceleration.
« Last Edit: April 26, 2015, 11:47:05 PM by Triple Jim »
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Offline blackcat

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Re: Lightened Flywheel Opinions
« Reply #14 on: April 27, 2015, 06:19:27 AM »
I have Ed's work and the B10 cam in my CX with no head work from the rebuild I did a few years ago. It occasionally stalls if I'm not thinking specifically about letting out the clutch so in some sense it is no different than before I made the change. It gets up to speed much faster than before and I noticed no difference in shifting,etc.



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Offline mtiberio

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Re: Lightened Flywheel Opinions
« Reply #15 on: April 27, 2015, 08:36:24 AM »
try to remember that even when lightened, a guzzi flywheel/clutch assembly is still quite heavy...

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Re: Lightened Flywheel Opinions
« Reply #16 on: April 27, 2015, 08:40:53 AM »
Thanks for the input guys,

I am going to give Ed a call and discuss my project.

Cheers

Jim
1949 Guzzi Airone
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Offline PeteS

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Re: Lightened Flywheel Opinions
« Reply #17 on: April 27, 2015, 08:44:09 AM »
Manfred Hecht lightened the flywheel on my 850 Lemans 20 years ago. Winds up like a two stroke. Can't say the vibes are any worse nor has longevity been shortened. This motor is no stranger to redline and beyond having done about 20 track days and mountain road blasting. You've got an early cafe racer. Treat it like one. Guzzis can take it.

Pete

Offline agoldfish

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Re: Lightened Flywheel Opinions
« Reply #18 on: April 27, 2015, 09:10:21 AM »
I went from a 2.5Kg Flywheel down to 800gm on my Ducati 900SS, in combination with a a lighter Alu clutch basket (another 900gm albeit rotating at roughly half the speed of the crank).

I know its not a Guzzi but still a large capacity aircooled twin.

NO DOWNSIDES. Idle was NOT affected (it went up a little on its own by 2-300rpms). It never stalled (more than before) and drivability was GOOOOOOOOOOD! Motor span up much quicker and was smoother. The effect of engine braking was somewhat reduced.

A mod i would do again. And look forward to doing to my MONZA.

Like most things i guess it is a matter of how far you go. If you tuner of choice knows his onions then there shouldn't be much to worry about.
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Offline motoguzzibill

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Re: Lightened Flywheel Opinions
« Reply #19 on: April 27, 2015, 01:36:14 PM »
I lighten the flywheel on an 83' 850 Lemans. Seat of my pants evaluation is that it spins up and shifts much quicker. Downside is you loose the Guzzi inertia, roll-offs are much more abrupt and the engine did not idle as smoothly. Would I do it again, probably only on a high performance (Guzzi rating!) setup. I wouldn't consider it for cruiser or other easy rider. Sure like that slow idle on my Eldo, all flywheel.
Bill

Offline Stevex

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Re: Lightened Flywheel Opinions
« Reply #20 on: April 27, 2015, 02:21:22 PM »

I've just lightened my LM2's flywheel and the bike is so much better for it.
After putting the Guzzi back on the road last year, I was so disappointed with the way it ran; now, it's the bike I always hoped it would be.
It winds up quicker and responds to the throttle much better.
Engine braking is brilliant.
No extra vibration at all, and it idles just fine, in fact it settles down to smooth idle after starting, far quicker with the light flywheel.
Gear changing is still a relatively slow affair, but noticeably smoother.
Doesn't stall...why would it?
Probably the best mod I'll ever do to the bike, and I'd never go back to a boat anchor flywheel.
Steve
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Re: Lightened Flywheel Opinions
« Reply #21 on: April 27, 2015, 05:40:59 PM »
I have Ed's work and the B10 cam in my CX with no head work from the rebuild I did a few years ago. It occasionally stalls if I'm not thinking specifically about letting out the clutch so in some sense it is no different than before I made the change. It gets up to speed much faster than before and I noticed no difference in shifting,etc.





Wondering if you changed the connecting rods in this engine? The CX engine and it's soul mate the SP of that time have weak rods compared to the LeMans and other factory built high output bikes.
I only mention it because the only 2 Guzzi big blocks I have seen let go on a street bike were hopped up versions of that engine.
Hunter
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Offline pressureangle

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Re: Lightened Flywheel Opinions
« Reply #22 on: April 27, 2015, 06:24:25 PM »
Probably Kevin Cameron . He DID build lots of really fast MC racing engines . Memory tells me that the idea is , at higher RPMs the lighter flywheel allows the engine to speed up and slow down more in each revolution , thus using more energy to accelerate the reciprocating mass after each power stroke . Remember , IC engines do not maintain a constant speed between power cycles .


  Dusty

 Edit , also , by maintaining a more constant crankshaft speed , the cam timing will stay more accurate . Cams have a really hard time keeping up with crank speed variations , especially with chain drive instead of gear drive . I'm thinking that those monster twin cylinder Hondas that Todd Henning raced , with Cameron built engines , used stock weight cranks and flywheels , and this is my reference .

 

It's well documented that Bonneville speed trial engines perform better with heavy flywheels. Light flywheels improve acceleration, simply because they don't store as much energy; more to the wheel off the corner, less to brake going in. Dynomometer contest engines often have heavy flywheels as well.

FWIW Henning's big "450" Hondas had Ron Hamp heads. http://ronhamp.com/
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Re: Lightened Flywheel Opinions
« Reply #23 on: April 27, 2015, 07:04:16 PM »
 I sent Ed a message and got a prompt reply to my questions, I am mailing him my ring gear and flywheel for lightening, nothing ventured nothing gained. I will be able to compare it to the 72 Eldo, 73 V7 Sport (with Ram clutch) and the new to me 77 Le Mans, should prove interesting.
1949 Guzzi Airone
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Offline centauro

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Re: Lightened Flywheel Opinions
« Reply #24 on: April 27, 2015, 07:35:57 PM »
I have Ed's work and the B10 cam in my CX with no head work from the rebuild I did a few years ago. It occasionally stalls if I'm not thinking specifically about letting out the clutch so in some sense it is no different than before I made the change. It gets up to speed much faster than before and I noticed no difference in shifting,etc.





When I bought my used 1984 SP 1000, I was not aware that the flywheel had been lightened; but when I took the gearbox off to replace the clutch, I found the same exact arrangement in this photo- lightened flywheel and starter ring gear, probably done by the same machinist.

I replaced the flywheel due to notched teeth with a standard T3 flywheel, and weighed them. The set up I had weighed 6.5 lbs, and the standard flywheel + ring gear was 3 lbs. more.

After reassembly and test ride, I have to honestly admit that I don't see any difference whatsoever in shifting, idle speed, or acceleration. I ride very conservatively and rarely exceed redline, but I would surmise that consistently staying above 5000 RPM might make it easier to spin up, but at the expense of the clutch center hub and flywheel teeth. (YMMV)......
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Offline Triple Jim

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Re: Lightened Flywheel Opinions
« Reply #25 on: April 27, 2015, 08:34:04 PM »
It's well documented that Bonneville speed trial engines perform better with heavy flywheels.

Well, it's also documented that Guzzis that hold records at Bonneville have light flywheels.   There's a lot of mystique in racing.    :)

http://www.mgnoc.com/article_land_speed_record.html
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Offline blackcat

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Re: Lightened Flywheel Opinions
« Reply #26 on: April 28, 2015, 07:41:54 AM »
Wondering if you changed the connecting rods in this engine? The CX engine and it's soul mate the SP of that time have weak rods compared to the LeMans and other factory built high output bikes.
I only mention it because the only 2 Guzzi big blocks I have seen let go on a street bike were hopped up versions of that engine.
Hunter

The engine was rebuilt because the rod bolts loosened up on one of the rods while I was going about 25 mph. Both rods were replaced along with the crank.
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Offline NCAmother

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Re: Lightened Flywheel Opinions
« Reply #27 on: April 28, 2015, 08:48:25 AM »
Great call Canuck.  I've bought some stuff with Ed, and his word and work is good.  I wanted to go with a Millich flywheel, but due to money constraints picked up a ram clutch on eBay for a good price.  I think you'll be super stoked.  PS, how do you like that ram clutch in your other bike?
Best, Nate

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Re: Lightened Flywheel Opinions
« Reply #28 on: April 28, 2015, 08:54:15 AM »
I have only a 100+ miles on the V7 Sport, the road sweeping will be done around here in a week or two and the bikes will get back on pavement. My initial impressions are I really like how easy the pull is and the bike revs up so much quicker than the Eldo.

Cheers

Jim
1949 Guzzi Airone
1958 Guzzi Cardellino
1972 Guzzi Eldorado
1972 Benelli Enduro
1973 Guzzi V7 Sport
1973 Laverda SF1
1973 Benelli 650S
1974 Guzzi 750S
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1975 Ducati 860 GT
1978 Moto Morini 500
2015 KLR 650
2016 BMW K1600

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