Effects of a lightened flywheel

[Scooterdude]

Just curious as to the effect a lightweight or mid weight flywheel would have over my standard one, I'm guessing a bit sharper off the bottom but am I going to loose mid/higher range torque as a result of the lesser weight?

[ToBoldlyGo]

I've done a few hundred miles running in a motor with a mid weight flywheel, and I was interested to see if I noticed any difference. It's quite nippy for a little 175 and I suspect you do lose a tiny bit of inertia. The end result of that seems to me to be that you have to stay on the revs a little more. It doesn't seem to have the momentum to get up hills if you let the revs die off. The secret seems to be to keep it revving and it will fly. I don't know if you lose any top end as yet, for obvious reasons. But it pulls surprisingly well.

[holty]

ive used lightened flywheels for years, a worthwhile upgrade, probably aimed more at at tuned engine, gives better acceleration through the gears and makes the engine more responsive, a good side effect is the reduction in weight puts less strain on the crankshaft, downside is the tick over has to be raised slightly as the lack of inertia makes the engine want to stall at very low speeds, but overall a good upgrade.

[Martin s]

My stage 4 200 with 22mm and clubman was transformed. A cheap upgrade, seems to pull better up hills and faster acceleration etc. This is an Indian electronic.

[Scooterdude]

Ok guys you've convinced me. I'm ordering one of Rayspeed in the morning.

[holty]

with the af flywheel you might have to check your alignment of pick up and the triggering fingers on the flywheel to make sure they line up correctly mark with tipex and check through the window in the flywheel, bgm need packers somtimes.

[Scooterdude]

Cheers Holty, yes I've got a BGM v3 that I presume must have developed a faulty lt coil as the scooter still ran but it was virtually impossible to see a spark, I've still got the shims and didn't know what they were when I bought it or what they did, however it's now fitted one of Anthony Tambs stators so it's this that will be used with the AF flywheel, now I'm learning a bit about the subject I now know to check the pickup height.

[holty]

your other option is to fit an external pick up as well, if one fails you can connect the other, belt and braces.

[Scooterdude]

Yes external pick up, casatronic ignition etc etc, were does it all end though I wonder? No I'll stick with the normal stator for now and when I go to Brighton on Friday I'll take a spare + tools and a spare piston and rings just in case mind!

[Fast n Furious]

Pro's and Con's............. How about a variable inertia flywheel? Now there's a challenge with potential benefits!

[Fast n Furious]

ive used lightened flywheels for years, a worthwhile upgrade, probably aimed more at at tuned engine, gives better acceleration through the gears and makes the engine more responsive, a good side effect is the reduction in weight puts less strain on the crankshaft, downside is the tick over has to be raised slightly as the lack of inertia makes the engine want to stall at very low speeds, but overall a good upgrade.

All very true. Magneto driven CDI makes a very low voltage spark at tickover level further exacerbating the problem of getting a reliable and even tickover on ported engines with light flywheels. A battery DC supplied CDI makes a good powerful spark right through the rev range. This help enormously with low inertia tickover and resists 2 stroke plug fouling. It also overcomes reliance on the shitty LT stator coils.

[Norrie Bodge]

I've gotta Ducati flywheel sat on shelf !
Just wondering weather I'll get any further benefit by fitting it ?
Replacing the mid-weight flywheel currently fitted on my GP???

It's running a LTH Reed manifold with 30phbh & JL3

[holty]

probably the way forward would be something like an ignitech ignition box or zeeltronic, its just powered by a battery thats charged by your lighting coils, a trigger would be needed, maybe one of anthony tams might do the trick, and they are mappable for any amount of advance of retard, and will give a perfect spark all the time. no more low tension coil that will give up the ghost when needed most. the system that i have on my lammy 350lc is the yamaha one it has 2 coils inside the flywheel for the ignition, low speed for starting and building up the revs a bit, then the high speed coil takes over as the revs rise higher, controlled by the cdi.

[gaz_powell]

I've gotta Ducati flywheel sat on shelf !
Just wondering weather I'll get any further benefit by fitting it ?
Replacing the mid-weight flywheel currently fitted on my GP???

It's running a LTH Reed manifold with 30phbh & JL3

I've got one on my ever sagging shelves .... I have only previously used these flywheels with the matching stator.
In this day and age i`m sure there will be stator alignment and height issue to allow it work with a SIL, pattern, BGM etc but give it a go.

Ive machine the internal face (a Taffspeed mod) to try and help with this but wont know until I use it - ive got a spare stator so will get round to setting it up in the closed season.

However I like welded and lightened SIL ones, at about 1950g

The Standard Indian Electronic Flywheel weighs about 2650g and the AF type weighs about 1400g - so the mid/lightened standard type sit comfortably balancing weight and inertia.

Wish I could get a genuine Ducati stator !

I see there is a new Ducati kit out now

[rossclark]

The original AF Ducati flywheel had very little clearance and sometimes rubbed on the pickup.

The 'standard' mod was to machine 1mm out of the mag flange. This obviously had the potential to cause alignment issues between the pickup and the flywheel triggers.

Taffspeed came up with machining the inside of the flywheel- a band about 3mm wide on the outside edge if the inner face.
This did not affect alignment. I have done this with a couple of nthese I have.

The later AFR flywheels are supposed to have addressed this problem, but I've had rubbing on one of these so it pays to check carefully.

[Adam_Winstone]

Yes, there is a pickup height issue with these, for which there were various fixes:

Machining the mag housing so that the stator sat deeper - fine until you looked to replace with a different ignition or different engine build, which then resulted in any other stator sitting too low.

Machining the inner face of the flywheel - fine in most cases but I know of more than 1 flywheel that then cracked through and sheared!

The best and IMO correct way is to cut of the required number of laminates so that the pickup sat lower, which is exactly what the clever people at Scooter Center did when designing recent versions of their stator, supplying them with an already reduced pickup height but with spacer/packer laminates in the box so that you can simply add packers (or not) to suit your flywheel... well done Scooter Center

Adam

[coaster]

...................A battery DC supplied CDI makes a good powerful spark right through the rev range. This help enormously with low inertia tickover and resists 2 stroke plug fouling. It also overcomes reliance on the shitty LT stator coils.

I suspect the reason this isn't adopted on a Lambretta will be down to the current draw on the battery. I have no figures but do know that many years ago when the dynamo on my mini packed up I had a flat battery within 20 miles or so I daresay it would be fine for open road use but slow town riding might soon flatten the battery

[Scooterdude]

The original AF Ducati flywheel had very little clearance and sometimes rubbed on the pickup.



The later AFR flywheels are supposed to have addressed this problem, but I've had rubbing on one of these so it pays to check carefully.

Well I got the lightweight flywheel from af. First thing I noticed was the fan fins were of a much smaller diameter and when I put the fan cover on the fins sat far to low so wouldn't have been of any use anyway, secondly the pickup despite having no shims was sitting higher than the flywheel contacts and was almost rubbing on the inner edge of the flywheel, started it up and as has been said before it wouldent tick over so took it off only to find the lighting coils had rubbed the inside of the magnets so sent it back. What a complete waste of time.

And the best bit was loosing the flywheel washer, I spent nearly two hours looking for the blighter in a very small garage, in the end I gave up and as I was packing my stuff away there it was stuck to the magnet on the back of my work light!

[rossclark]

There are AF and AFR flywheels , outwardly similar, the former were built by Ducati and the latter for AF in India. Both can work but they are different and the AFR ones have their own issues related to the means of attaching the magnets, which sometimes cause spurious triggering and sometimes come loose. Early AF Ducati ones I've seen had a knurled ring on the inside outer edge - it is this that was often machined out - only 0.5 mm or so. I can believe that taking more could case weakness in this area.

They are based on the Luna line flywheel and are of a smaller diameter than the standard size flywheel. The fit inside the inner lip of the magneto flange entirely which inevitably means that they face of the flywheel is further from the cowl than a standard one. The fins, being the same length as standard are also that much further from the cowl.

You can either slot the cowl holes or fit a packer inside the cowl to lessen this gap.

[Fast n Furious]

...................A battery DC supplied CDI makes a good powerful spark right through the rev range. This help enormously with low inertia tickover and resists 2 stroke plug fouling. It also overcomes reliance on the shitty LT stator coils.

I suspect the reason this isn't adopted on a Lambretta will be down to the current draw on the battery. I have no figures but do know that many years ago when the dynamo on my mini packed up I had a flat battery within 20 miles or so I daresay it would be fine for open road use but slow town riding might soon flatten the battery

If the right critical component fails, then a ride home with the AA is the nature of the beast. It's all about detecting and improving the weakest link.
I use a DC powered, computer programmable race CDI on my Jet. It consumes 200mA of current. That's 2.5W near as damm it. (they all consume around this figure for single cylinder applications) Even with my puny 2.1AH battery to power it, without charging, I reckon I'd easy get a thousand miles before it quit.
Charging a flat battery overnight, at some roadside garage, in the pissin rain, in some godforsaken place that doesn'y speaky the Queens, is much easier than trying to fix a knackered stator.
During the day, I could run my ignition from a solar cell!