Flywheel weight

[Jens Eskildsen]

Desided to start a new topic for debate.

My original post:

800gram removed from the flywheel/starterclutch, was done over 2 times, but heres the final product. Still more weight to be removed, but we stopped here.
Hopefully this will remove some of the felling of dragging an achor in a bungy cord behind the bike


[/QUOTE]

Originally Posted by jjrider

Good carbs with an accelerator pump gets rid of that bog/lag/hesitation a person feels on these bike . Higher comp helps as well .

The 660 Raptors have a considerably lighter flywheel(and smaller dia) , they rev to 9k easily (but won't live long if let there ). These motor aren't tight enough tolerances to spin like that , but the heavy flywheel is what lets them sit at 60-70mph effortlessly , something I can notice the 660 doesn't do as well .
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Thanks for the input Hope other will chime in aswell, we could gather some good info, and hopefully some more personal experiences.

Yes, better carbs will help much, much more. I've tried several carbs in the past, even double flatsides. But I have grown to like the stockers, for no special reason. I guess they work fine for me, are easy for me to work on, and everything fits intake-wise. I have several trips each year outside this country, so it doenst hurt when things like that are stock.

I've never felt the difference in cruising ability when riding fx. a TT600 which have a lighter flywheel, and it has no sprage/starter-clutch and associaated sprockets ect ect which also weighs a ton. So quite a few lbs less rotating mass. My wr250r beeing a totally different bike, has the same cruising speed as the Xt, but has next to no flywheel weight. I've ridden it geared down for hours straight on the interstate (well, stopping for gas, but otherwise straight for over 250 miles at 65mph)

I really dont think the flywheel affects the cruising speed much, if any. Its more the change in engine rpms, where you have to spin up/slow down the heavy flywheel that makes a difference. The flywheel on the XT is still superheavy, and heavier than most other bikes, even when reduced of 800g. I remember a friend and I once compared my flywheel to his on a ktm 640 enduro. His felt like the cap of a bottle in comparison.

I removed 550g the first time, and could barely tell a difference. To this day im still not sure if I could feel a difference. 550g is so little percentage-wise, compared to how big the total rotating mass of the flywheel, crank, counter balancers, rod and piston ect is.

Im not doing this for performance. The first time was just to do it, I paid a friend of a friend a case of for the machinework, so just about free.

This time I needed to repair the wire for the neutral swich, so I was inthere anyway, and there was talk about different pullers in another thread and I wanted to show/tell how efficient a good puller is.

A friend offered to put the flywheel in lathe free of charge, so we removed some more weight. So less weight, and as you say, smaller diameter.

Sometimes you do stuff just to do it. This is one of theese times. Couldn't find many other who have done it, so I figured why not =) I enjoy my time in the garage aswell.

Anyway: Which tolerences are "looser" on the Xt, compared to the raptor? Small end, crank and piston seems the same? My guess is the cam ect has the same tolerences aswell. (could only find specs for Xtz660, but theyre the same specs as xt600)