Lightened Flywheel Owners

[Wheelie]

I've been thinking about sending my flywheel off to be lightened during the off season and have a few questions.

About 75% of my riding is dunes or track, the remaining is trails or woods.


Questions:

Was it worth the money, and who did you have do it? Cost?

Performance gain or loss?

Dune riders---was it easier to launch in 2nd gear from a tight spot, and was it quicker to pull into the meat of the power?

It seems like 8oz is the norm, can more be taken off? What is the weight of the stock EX flywheel?

Thanks,

Jeremiah

[drew416ex]

I dont know how much it weighs, but I took off what another guy on here did to his. Its a thread about him doing the kick start mod. I did it myself at work so im not sure how much it would cost. As for performance, it helped. It revs quicker than it did before. I ride mx and in my opinion it was worth it especially since it was free. :D

[1krazyquadridr]

I had Steve #7 who wrote the article on converting over to kickstart do mine, and it made a quite a difference on how quickly the bike revs. I love it for MX. He took off over a pound on mine. However for the dunes I would think you would want that extra weight and torque to get your paddles moving in the heavy sand.

[400exrider707]

Talk to member Cals400ex if he's still around. He tried it against Laz's advice (Gt Thunder owner and operator) and said it lost power with the lighter flywheel. Laz told him not to, but he tried anyways and verified what Laz had told him. I've since heard a few other people agree with that.

So the consensus was, do NOT lighten them on the 400ex's.

[sc400ex_rider]

well i totally disagree, first off steve said his torque jumped like 30%. 2nd gt thunder used to lighten the ex flywheels, 3rd you are just taking the engine back to factory specs since the ex is just a xr400 engine that was desinged without electric start and the 2 extra lbs is alot for a 400cc engine that is why they dont run like the xr400. 4th i have seen 6 cylinder bmw car racing engines and the flywheel was only about 12 inches in diameter with a tiny multiplate clutch. and what do they know about racing?
FACT THE LIGHTER THE RECIPROCATING MASS THE QUICKER IT CAN ROTATE WITH LESS INERTIA
why do you think all the 450 cranks look so different from the 400ex's
why do you think they sell +4,+6,+8oz flywheels for dirtbikes ....to mellow out the power on muddy tracks. WOW you guys dont know chit
P.S. ya it sucks........... ill race you anytime LOL PWND

[brokenmike]

I have a 8oz lightened flywheel and it does make it rev quicker. I love it.i bought it off e-bay.

from converting to xr400 kickstart and shaving the flywheel one said it was a 35% increase in power which is a lot. You cant shavethe stock one too much otherwise you wont be able to start your quad. Thats why there is so much more because of electric start. A heavier flywheel makes it harder to stall. Maybe thats why the 400ex is such a good all around quad you can putt if you want.

[Ruby Soho]

we do this on 110's all the time.

basically, the less mass on your crank, makes the engine able to rev up and down quicker.

you look at a 250f flywheel, its like half the size of a 400ex flywheel. and if you've ever heard a 250f compared to a 400ex you'll notice the difference (theres more to it but its a good example)

some of the problems with the less mass is its easier to stall the bike, especially coming into corners when the bike revs back down and you pull your clutch in, some people say its harder to start, but i have a tiny flywheel on my 110 and it still starts first kick..

the main problem people see with the less weight is you loose mass, so the flywheel doesn't have the weight on top end to keep it going. for example, my 110 has all the bottom end in the world, but when i go wide open down a straight it doesn't last long becasue theres no mass to keep it going.

it really depends on how you want your power delivered.. if your on tight mx tracks lighters probably better, if your into lugging trails or riding really fast youll probly want to keep it

[yfzfelix]

TC Racing did mine, don't know if it helped any because I did a 6 mil stroker at the same time, I do know the 6 mil stroker helped !! Steve

[ae13291]

Originally posted by sc400ex_rider
well i totally disagree, first off steve said his torque jumped like 30%. 2nd gt thunder used to lighten the ex flywheels, 3rd you are just taking the engine back to factory specs since the ex is just a xr400 engine that was desinged without electric start and the 2 extra lbs is alot for a 400cc engine that is why they dont run like the xr400. 4th i have seen 6 cylinder bmw car racing engines and the flywheel was only about 12 inches in diameter with a tiny multiplate clutch. and what do they know about racing?
FACT THE LIGHTER THE RECIPROCATING MASS THE QUICKER IT CAN ROTATE WITH LESS INERTIA
why do you think all the 450 cranks look so different from the 400ex's
why do you think they sell +4,+6,+8oz flywheels for dirtbikes ....to mellow out the power on muddy tracks. WOW you guys dont know chit
P.S. ya it sucks........... ill race you anytime LOL PWND

a lightened flywheel will make a car alot harder to launch and will loose power when u are putting pressure on the motor in low rpms for instance a hill. its inertia that will keep the flywheel spinning

[sc400ex_rider]

i just didnt like the way the stock flywheel felt, it just didnt rev like a honda...............

[Tofu.Man]

Does lightening the flywheel have any adverse affects on engine balance in these motors?

[born2ride14]

not if they are put an a lathe and lightened

This is really interesting. I've been thinking about doing this when I do my 416.. Im more concerned IT wont climb hills as good. That's what a local guy said...

I have a lauve in my basement because of my dads shop. If I put it on the lauve and use that to cut the flywheel, will it become unbalanced? Or would it work?

[kingdingaling]

As long as the flywheel is neutral balanced (no weight off to one side to make up for an unbalanced rotating assembly) then it wont throw it off balance if you turn it on a lathe. And I may be wrong, but most ATVs have neutral balanced flywheels.

As far as power goes...it takes power to rotate the flywheel, so the more weight you remove the easier it will rev and the more PEAK hp you will see. However, removing mass reduces the inertia, so the fourwheeler will be more likely to stall at lower RPMs. Especially pulling out! If you ride trails it is usually not recommended due to its tendency to bog down if you let off the throttle and try to get back on the gas too quick, but once again, thats at lower RPMs!

[Ruby Soho]

how could be it be unbalanced on a lathe... if you don't know what your doing don't bother.. have a shop do it.

and the only difference it will make is that it will rev quicker, and hit a little harder, and loose some topend

[drew416ex]

Originally posted by Ruby Soho
how could be it be unbalanced on a lathe... if you don't know what your doing don't bother.. have a shop do it.

and the only difference it will make is that it will rev quicker, and hit a little harder, and loose some topend

Why would it loose top end, mine didnt.

Originally posted by Ruby Soho
how could be it be unbalanced on a lathe... if you don't know what your doing don't bother.. have a shop do it.

and the only difference it will make is that it will rev quicker, and hit a little harder, and loose some topend

I know what I'm doing, my father uses these machines for a living also. But I remember someone saying a while back that even on a lathe you need to send it out to be balanced. Just wondering if that was true.

And I know that's all it will do, if you remember the convo we had when we didn't hate each other we both agreed that we like quicker rev'ing quads/bikes. lol

[sc400ex_rider]

You need to cut it and then balance it when I did mine he cut through the holes drilled in the side to balance it. so it was totally unbalanced again. also after i built my motor there was a funny vibration in the footpegs at about 2500 rpm's. after i had it cut and rebalanced it was gone. the guy even said before he balanced it he would do better than the factory balance. it cost me $45 to cut it and $45 to balance it. i love the way it revs now but it will not climb hills at idle now LOL

[Ruby Soho]

i have a lightened flywheel on my 110. same thing pretty much..

its such a little difference depending on how much you take off, but we take like 8 ounces i think off the 110's and you can't really notice a loss in top end but i used to run an IRK which is basically a flywheel about 2" in diameter and extremely light... that was a very obvious loss in topend cause it has no weight to keep the inertia going.

think i said that right... ha

[400exrider707]

I'll lighten up a 400ex flywheel for free if anyone wants to try it. I just want to verify its the same arbor that we use on the 450 flywheels.

We balance to tighter tolerances than factory Honda as well...:o

Email me at mtdewman015@hotmail.com for info or questions.

I will take off whatever weight you want off of it. All you have to do is let us know how it turns out either way.

[400exrider707]

Originally posted by Ruby Soho
i have a lightened flywheel on my 110. same thing pretty much..

its such a little difference depending on how much you take off, but we take like 8 ounces i think off the 110's and you can't really notice a loss in top end but i used to run an IRK which is basically a flywheel about 2" in diameter and extremely light... that was a very obvious loss in topend cause it has no weight to keep the inertia going.

think i said that right... ha

The 110 motors use a heavier flywheel than the 450R's do.... think about that for a minute...

I'm doing my 110 flywheel very soon.

Originally posted by sc400ex_rider
i just didnt like the way the stock flywheel felt, it just didnt rev like a honda...............

they wont ever rev like a Honda unless they get some VTEC lol seriously though if Honda quads had VTEC no doubt they would just kill the competition. Its the perfect setup your cam is smaller to give you the low end and mid then the VTEC lobes are used and its now like an aftermarket cam without the low end loss if you just had a huge cam. Just watch it:
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