Flywheels Again II

[koko64]

My flywheel testing is pretty much complete for carbed two valve 900/750 models.

Flywheels Tested include:
 OEM 1.9-2kg
Machined OEM 0.9-1kg
DP 650-700gm
Kamna DP copy 500-535gm
Kamna/Nichols "Pie Tin" 285-325gm

My stubbornness relates to wanting more acceleration but trying to avoid too much engine braking without having to resort to a slipper clutch . To describe the process as a PITA is an understatement. The lighter flywheels gave addictive acceleration akin to an 1100Evo but with annoying levels of engine braking messing up corner entries. They also gave quick handling and immediate steering which I like very much. The bike felt lighter than it was. The OEM flywheel let me flow thru a series of esses gaining momentum, but you needed to have that momentum early. Minimal engine braking.
The DP carbed and machined OEM flywheels were in the sweet spot with only a moderate increase in engine braking but providing a significant improvement in acceleration. Steering effort was also reduced and I could get by without a slipper clutch.

I have settled on the machined OEM flywheel which was one of my first mods to the M900. The bike was still smooth with the machined and DP flywheels although a little more clutch work was needed in the tight slow stuff. The very light flywheels did increase vibration and I actually felt some nausea from the resonance thru the bike with the two lightest wheels. A younger person may have felt nothing .

I think the threshold for not needing a slipper clutch was about700-900gms depending on your riding style with these motors. Of course hi comps pistons increased that effect greatly and the threshold appears lower in weight with stock low comp motors as evidenced in my M750. The motor balance of that model coped with the light flywheel quite well as a hi comp M750 also coped well. The 900 motor really feels it as the compression rises and the flywheels get lighter as a combination with greater drive and more engine braking as a side effect.

Speeddog correctly predicted that I would come a full circle with my testing and settle on the machined OEM flywheel at about 950gms. It was good to learn what flywheel weights work well with different engine combinations for different purposes.
Cheers.

[koko64]

There have been some changes in our fuel here, particularly higher octane pump gas. The lighter flywheel highlighted a lean issue well dampened by the stock flywheel. Pilot jets in the FCRs up to 55 now. Change happens.

[Howie]

There have been some changes in our fuel here, particularly higher octane pump gas. The lighter flywheel highlighted a lean issue well dampened by the stock flywheel. Pilot jets in the FCRs up to 55 now. Change happens.

Alcohol poisoning?

[koko64]

No grog in it, but they're running less detergent and more upper cylinder lubricant This 98RON has less range but runs very crisp. You can feel the response as they've really improved the fuel from how it was. Less misfires and carburating smoothly and cleanly.
The other major brand has too much detergent IMO (98RON) , can trigger the CEL, fouls plugs and can cause rough running. Strangely the range is better.

[koko64]

Unwittingly spun the rear coming out of a corner on cool tarmac. Gotta watch that. . Bike is angry again and so much fun. Shows how various tuning components change an engines character.