Flywheel Weight?

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#1
I have been reading the forums (seemingly non-stop... I'm hooked) since joining last month and have read a lot about flywheel weights being installed on MX bikes for trail riding .

I took a long break from riding (about 24 years) and recently got back into it. I went out and bought 1991 CR250 in great shape and a totally rebiult engine and it runs very strong. Of course it has that 2-stroke breakneck surge when you hit the band (which is why we luv 'em!).

Is the stock powerband not good for trail riding or just something to just get used to? I originally bouth a 1991 KX125 (I'm 6'1", 195 lbs.) and as ya know you got to stay on a 125 to keep it going so I bought the 250 for better lows and mids.

How does the FWW smooth out the band and where exactly does it go? I haven't cracked a case or pulled a head on a bike for millenia and can't imagine putting a weight on the flywheel. Is this necessary for trail riding/enduro and if I wanted to do some track work would it be detrimental?

Also... is this year of CR250 (1991) a pretty good year?

Thanx for any replies in advance
 

BSWIFT

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#2
Modern mx bikes have very little flywheel weight and it allows for the fast revs in the simplist explanation. When trail riding, the high revs aren't always desireable. Added flywheel weight gives your engine some lugging power on the bottom and smoothes out the hit on top. I have used flywheel weights and they work great. I currently am no using one but there are log crossing that I tend to stall on. This is acceptable but a flywheel weight would help prevent it. BTW, adding flywheel weight is very simple. All that is required is removing the cover(left side) and removing the "nut". Probably take you 30 mins start to finish.
 

NVR FNSH

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#3
A 16oz(?) flywheel weight has made a huge difference on the trail manners of my '90 KX500. I dare say it will out lug my flywheel weight equipped '99 WR400 and the KX is running 14/46 gearing.

Brian
 
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#4
Thanks

Thanks a lot for the info guys. If it ever thaws out here I'll hit the trails and check out the behavior of this bike to see if a FWW is needed

Thanks again.
 

KaTooMer

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#5
Flywheel comparisons are not always equal from bike-to-bike, model-to-model, because it seems the manufacturers are always playing with the stock weight of the flywheel from year to year. I tend to go towards the heavier weight options, but not necessarily the heaviest. I run an 11oz Steahly on my woods-ready KX and I think it's fine (could have gone as high as 13oz, I believe). This is probably due to my past history with two Suzuki RMX's and two KTM 300's, which have fairly heavy flywheels compared to their motocross siblings. It's what I'm used to. Adding a flywheel weight is one of the easiest and most effective mods you can do to an MX bike that you want to ride in the woods.
 

motometal

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#6
I think flywheel weights also help a bit with starting...the engine has more momentum. Will you get used to the bike without it...sure, I guess it's all relative to your skill, the conditions, etc. You may notice less of that nice two stroke hit with the flywheel.

It's tough to go wrong with a CR. If there is a weak spot on the '91, it would be the forks. That was about the 3rd year of the inverted forks, and they were pretty harsh. In my opinion, it actually took until about '96 before Honda came up with forks as good as the '88 conventionals, stock-wise anyway. The good news is that the aftermarket companies have had more than enough practice with the re-valving. If you don't want to go that route, you could start with a fresh oil change, run the oil on the light side, and make sure the springs are proper for your wt.
 
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#7
Thanks Motometal

Thanks a lot for answering the year and make question. What is the supposed advantage of inverted forks anyway?

The guy who sold me the bike said that it was set up for someone who weighs 200 lbs... I'm about 195 so I'll check it out. If it doesn't feel right I'll be taking your advice. Is suspension work something better done by a professional or can it be learned pretty easily (at least changing the oil and such)?


Thanks again.






motometal said:
I think flywheel weights also help a bit with starting...the engine has more momentum. Will you get used to the bike without it...sure, I guess it's all relative to your skill, the conditions, etc. You may notice less of that nice two stroke hit with the flywheel.

It's tough to go wrong with a CR. If there is a weak spot on the '91, it would be the forks. That was about the 3rd year of the inverted forks, and they were pretty harsh. In my opinion, it actually took until about '96 before Honda came up with forks as good as the '88 conventionals, stock-wise anyway. The good news is that the aftermarket companies have had more than enough practice with the re-valving. If you don't want to go that route, you could start with a fresh oil change, run the oil on the light side, and make sure the springs are proper for your wt.
 

motometal

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#8
I guess whether or not you want to tackle fork oil changes etc. depends on your mechanical aptitude, time, patience, resources, etc. I really hate letting anyone else work on my stuff so I tend to dive into it and learn as I go. Occasionally, stuff gets broken, and I pay for the experience, but at least I know what not to do next time.

The actual revalving of the forks is best left to the pros in my opinion (although there are do it yourself kits available).