Topic: 750 flywheel/rotor weight differences

[DH]

I read that there is an early type rotor (up to around the k3 or so) that is
heavier than the later version. Part numbers seem to all be the same. Why is
this? Curious to see if there are disadvantages or advantages to either, and
if they are interchangeable, bolt, washer included. also interested in how either makes the engine act. tia.

[scottly]

The early alternator rotors had a raised flange on the OD, and weighed about 5.7 pounds, while the later rotors didn't have the flange and weighed about 4.5 pounds. The lighter rotors have less flywheel effect, and allow the engine to change RPM more quickly, although this is mostly only noticeable in nuetral. There have been cases reported of the heavier rotors causing the end of the crankshaft to shear off. The rotors are interchangeable.

[DH]

The early alternator rotors had a raised flange on the OD, and weighed about 5.7 pounds, while the later rotors didn't have the flange and weighed about 4.5 pounds. The lighter rotors have less flywheel effect, and allow the engine to change RPM more quickly, although this is mostly only noticeable in nuetral. There have been cases reported of the heavier rotors causing the end of the crankshaft to shear off. The rotors are interchangeable.

Scott I'm thinking of getting a spare to have balanced. Will there be an increase in smoothness if I do this? I'm guessing the light version would be a better candidate for this ? Or do you think it's worth the trouble? Bike is stock k5. /just looking to make a really nicely mannered street bike.

[Don R]

 Cycle X claims to find out of balance rotors often. Since they are not keyed to the crank I doubt they are balanced to the crank when manufactured. I'd like to know the difference too, I know RC engineering lightened them and even those have been found to be out of balance.

[scottly]

I don't know when Honda changed the rotor design; my K1 had the flange, and there were no balancing holes. The K7 rotor I have does have balancing holes, and I've seen a picture of an early flanged rotor with a balancing hole. The rotors should have a neutral balance, like an internally balanced 350 Chevy flywheel, instead of the externally balanced 400. How well were the stock rotors balanced? Who knows? I would recommend the lighter rotor, in any case. I seem to recall someone recently selling balanced rotors?

[DH]

Cyclex is where I got my information as well. Think I;m going to try the balance and the lighter version rotor. Shooting for no more fuzzy mirrors at hiway speeds. Makes sense to have less weight hanging off the end of the crank too, altho I probably don't ride it hard enough for that to matter. Thanx for pics scottly

[754]

It will revup quicker..easier to save the day if you start to bog on the launch...when racing..