Un balanced flywheel?

Got questions? We got answers....
mwoj
Supporting Member
Posts: 103
Joined: 04:34 pm Mar 24 2016
Country:

Un balanced flywheel?

Post by mwoj »

So I am rebuilding my 1985 kdx200. Almost done. the original flywheel was stuck asf onto the crankshaft. I tried welding a nut and making a puller, both didnt work. Anyway, finally got it off(supported whole engine by the flywheel and hit the end of the crankshaft until the engine dropped). Anyway, the welding messed up the surface of the flywheel. I had ground down the welds, and actually ground alot of material. I tried to even out the surface of the flywheel but theres no way I can make it perfect without some lathe or special tool. I was thinking about the damage it can cause if I ran the bike like this. Would it ruin the crank bearings? Would it be so insignificant that it doesn't matter? What would happen?
JL4049
Member
Posts: 86
Joined: 06:25 pm Jun 04 2016
Country:
Location: Eastern Victoria, Australia

Re: Un balanced flywheel?

Post by JL4049 »

A bit of material removed right at the centre of the flywheel will not have much of an affect on the balance, if it is further out towards the rim, it could.
mwoj
Supporting Member
Posts: 103
Joined: 04:34 pm Mar 24 2016
Country:

Re: Un balanced flywheel?

Post by mwoj »

Like half way from the center of the flywheel, and half way to the outter most edge. Like its right in the middle, between it being close to the center, and being on the outer edge. You feel? Is this still okay?
pumpguy
Gold Member
Gold Member
Posts: 821
Joined: 10:00 am May 29 2012
Country:
Location: Spring Grove, Illinois

Un balanced flywheel?

Post by pumpguy »

The balance of a single cylinder crankshaft (and its flywheel) like used in the KDX is always a compromise. It is balanced for all of the rotational weight plus a certain percentage of the reciprocating weight. Might be 40%, might be 50%, might be more. In the end, it is a trial and test sort of thing.

As far as the balance goes, I would try it and see how much vibration you get.

Now, the truth of the crankshaft alignment, that's another thing altogether. I can't imagine with all that banging and knocking around you did that the shafts are still true to one another.

To check the alignment, you need to pull the crank out of the cases and put the shafts on V blocks or between lathe centers. Then use a dial indicator to see how much the main shafts are out from a true zero runout.

This crankshaft alignment procedure is described in detail in the manual, and can also be found in every other single cylinder 2 stroke motorcycle service manual.
mwoj
Supporting Member
Posts: 103
Joined: 04:34 pm Mar 24 2016
Country:

Re: Un balanced flywheel?

Post by mwoj »

Id rather risk it for the biscuit on this one. I hung the engine maybe 3 inches of the ground, supporting it by the flywheel (hung hooks under the lip of it). I had someone hold the hooks, and then I put a rod on the crankshaft and hit it maybe 3 or 4 times. Could that really cause the sides to be unaligned?

i'm just wondering if the flywheel itself could somehow wreck the crank bearings. If I feel any vibration is it bad? Is there regular vibration?
mwoj
Supporting Member
Posts: 103
Joined: 04:34 pm Mar 24 2016
Country:

Re: Un balanced flywheel?

Post by mwoj »

Actually just gonna have a machine shop lathe it down.
User avatar
Jaguar
Supporting Member
Posts: 590
Joined: 01:32 am Jul 03 2013
Country: Paraguay
Location: Paraguay
Contact:

Re: Un balanced flywheel?

Post by Jaguar »

those old KDXes aren't properly balanced anyway.
If you were riding it before then you should remember how much it vibrated.
A little error from welding will be as nothing compared to the original imbalance.
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/
mwoj
Supporting Member
Posts: 103
Joined: 04:34 pm Mar 24 2016
Country:

Re: Un balanced flywheel?

Post by mwoj »

Didn't get past 10-15mph and maybe 1.5k rpm when I rode it..so not to much experience on this bike. Im having some other work done at the machine shop anyway so I might as well have them level it out.
User avatar
KDXGarage
KDXRider.net
KDXRider.net
Posts: 14047
Joined: 06:45 am Nov 01 2004
Country: United States of America
Location: AL, USA
Contact:

Re: Un balanced flywheel?

Post by KDXGarage »

Good luck with it.
Thank you for participating on kdxrider.net. :bravo:
To post pictures from a device: viewtopic.php?f=88&t=24128
mwoj
Supporting Member
Posts: 103
Joined: 04:34 pm Mar 24 2016
Country:

Re: Un balanced flywheel?

Post by mwoj »

Was that sarcastic? Or were you serious. Because if it was a sarcastic "good luck" then I would very much like to know why. Is there anything wrong with having it lathed down? Not trying to be aggressive or anything , I've never dealt with an unbalanced flywheel before. So any opinion is greatly valued.
ohgood
Supporting Member II
Supporting Member II
Posts: 925
Joined: 10:00 am Jan 04 2014
Country:

Re: Un balanced flywheel?

Post by ohgood »

there are two bearings for the crank, two fits in the cases for those bearings and two press fits on the crank itself. whopping the crank hard enough to unfit a taper that was shrunk into place will likely mess up some of that alignment. i would use a puller next time, and during reassembly use the heated slug method instead of force.

good luck is good luck here, very little sarcasm. Jaguar is the man when it comes to.... well just about everything in kdx land, straight shooter, etc

:-)
Fitterman24
Supporting Member II
Supporting Member II
Posts: 96
Joined: 10:28 am Jul 13 2013
Country:

Un balanced flywheel?

Post by Fitterman24 »

And so is Jason! There is no sarcasm here. I'd say if you don't have much in it, like you said, put it back together and have fun with it.
mwoj
Supporting Member
Posts: 103
Joined: 04:34 pm Mar 24 2016
Country:

Un balanced flywheel?

Post by mwoj »

I probably have $800 overall. Going to get it plated this weekend. So if I do need a new motor, oh well. The kid before me had absolutely no idea what he was doing so it was prolly messed up some before I got it. THE $800 into it is mainly for body, paint, suspension. Chain, fork savers. Chain guards. Small stuff that added up. We shall see tho. THANK YOU all for your input.
User avatar
Jaguar
Supporting Member
Posts: 590
Joined: 01:32 am Jul 03 2013
Country: Paraguay
Location: Paraguay
Contact:

Re: Un balanced flywheel?

Post by Jaguar »

I think that if the flywheel was left-right wobbly that it wouldn't cause a radial force imbalance just a slight unequal force on the shaft from the right end of it to the left end. Probably not enough to really matter. Here's my crank balancing page although I don't think your crank wheels use holes to balance it: http://www.dragonfly75.com/moto/vibes.html which is what my crank balancing spreadsheet requires. I started to make the software so it could also calculate for the "half moon missing section" of crank wheels that yours uses. Let me know if you want help balancing it.
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/
mwoj
Supporting Member
Posts: 103
Joined: 04:34 pm Mar 24 2016
Country:

Re: Un balanced flywheel?

Post by mwoj »

If I see that it virbarates or anything, il tear my engine apart, and give it a shot. If I were to send my crank to you, would you be able to balance it for a fee? Or does it have to be balanced with the rest of the engine?
jeswinehart
Gold Member
Gold Member
Posts: 63
Joined: 08:14 pm Nov 26 2015
Country:
Location: White Pigeon, Michigan.

Un balanced flywheel?

Post by jeswinehart »

Those Kawasaki flywheels are so out of whack from the factory it is unbelievable. 7 to 9 thousands out of whack.
When folks say a un-balanced motor,,,, it is a true understatement imo.
I am encapsulating a 84 kdx flywheel and I expect no different then all the kxt/kfx (3+4 wheeler tecate)
flywheels I have trued up on my lathe.

http://s1122.photobucket.com/user/jeswi ... html?o=199

john
mwoj
Supporting Member
Posts: 103
Joined: 04:34 pm Mar 24 2016
Country:

Un balanced flywheel?

Post by mwoj »

Those are some pretty flywheels ;). Got any for sale?
jeswinehart
Gold Member
Gold Member
Posts: 63
Joined: 08:14 pm Nov 26 2015
Country:
Location: White Pigeon, Michigan.

Re: Un balanced flywheel?

Post by jeswinehart »

What I do is rejuvenate flywheels that have all 4 and send back out to the owner who sent to me for $60.00 (shipped).
I do purchase old flywheels that have "issues",,, mainly for the magnets.
The flywheel in middle is the 84 kdx200 flywheel I am currently working on.
Bottom one is kxt about half way thru my process.
Top one is kdx something,,, maybe ? that is ready to bolt on when I figure out what it fits :)
http://s1122.photobucket.com/user/jeswi ... sort=3&o=0
jeswinehart
Gold Member
Gold Member
Posts: 63
Joined: 08:14 pm Nov 26 2015
Country:
Location: White Pigeon, Michigan.

Un balanced flywheel?

Post by jeswinehart »

And in getting back to your original quistion,,,, if you have the opporpunity to balance your flywheel I highly recomend to do so.
I will see if I can find a picture or two of how I found it best to chuck them up in a lathe.

john
User avatar
Jaguar
Supporting Member
Posts: 590
Joined: 01:32 am Jul 03 2013
Country: Paraguay
Location: Paraguay
Contact:

Re: Un balanced flywheel?

Post by Jaguar »

I'm in south america and so it wouldn't be feasible to send me your crank for balancing.
Once you get tired of the vibration and want to fix it then take it apart and give me all the specs and I'll tell you what size holes to drill where.
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/
Post Reply