Flywheel Weight: 10oz vs 12 or 14

[dirtbikingdad]

I've got a 10 oz flywheel weight on my 01 CR250 and was wondering if it would be noticeable replacing it with a heavier one. The more I ride this bike (coming from a 400EX quad) the more I like it.... but still I am not riding his bike (never will) to its potential due to the hit. While most of the hit is gone due to the 10, a gnarly pipe and dual stage reeds, it still gets the back tire loose at a drop of a hat. Is it worth spending the $$ on a heavier weight? BTW, we only ride in the woods. Thanks.

 

[SQUIRLEYMOFO]

wish mine had a big enough hit that I had trouble riding it.

 

[mtk]

Try replacing all the aluminum clutch plates with steel ones. This will help a bit and also keep your tranny oil from getting fouled so quickly.

I put steels in my 2002 first, followed by a 10oz Steahly flywheel weight, and I noticed a difference with both mods. The weight was more pronounced, but the clutch plates helped a bit as well.

Beyond that, you could always try one and see for yourself. If you don't like it, you can sell it on e-Bay pretty easily.

 

[Lew]

Hows your jetting? A heavier fww I don't believe will take away the hit you are talking of. The steel clutch plates are nice, but most likely won't curb the hit either. Get you pilot jet dialed in and try some different needles and maybe fatten up the main one or two sizes.

 

[dirtbikingdad]

Thanks for the input. I didn't say I couldn't ride it, I would just like to smooth out the some....

As for the jetting, it is stock. Honestly, it feels fat. It spews spooge, but never, ever fouls a plug. And I putt around a lot since we are to learning and I ride with my 9 yo. Also, I'm running 50:1 on the oil. Motul 600 full syn. The guy I bought it from used just like that but never did the math. Initially, I was going to reduce the oil to reduce the spooge, but when I found it to be 50:1. I decided to leave well enough alone. I had considered dropping the needle. I guess I should do a plug check and see whats up and maybe do some tuning. I really hadn't done that yet since I have been spending most my time helping my son work the bugs out of his KDX. Again, thanks for input.

 

[NO HAND]

Retarding the timing also is a cheap and effective way to reduce the midrange hit.

 

[motonuts]

LEAVE IT. I TOOK MINE OFF TO TRY IT WITHOUT. DIDNT EVEN NOTICE THE GAIN. MAYBE IM USE TO IT. THAT WHEN I NEED POWER I JUST STAND ON IT AND TOAST THE CLUTCH, IT STILL RIPS GOOD ENOUGH FOR ME. I DONT THINK A COUPLE OF OUNCES WILL MATTER.
I RIDE A 98 KX250 W/10 OZ WEIGHT. RACE SO CAL DESERT.
ALSO HAVE A V-FORCE, IT HELPS. GNARLY PIPE. :yikes:

 

[Nevada Sixx]

what about taking a tooth off the rear sprocket? a moose reed spacer may help as well... after i put a dent on the insideside of my pipe using a hammer,, about where the cylinder is, that made my 125 smoother. I had to put a dent there cause the pipe was rubbing my cylinder head.. and that was the result in power.

 

[tyesai]

I have an 04 with a FMF Gnarly and Shorty Power Core II with a 12 ounce flywheel weight installed. I am a piss poor rider and I ride both trails and motocross. My bike is jetted rich, at least in the summer it still fouls plugs, right now it isn't so bad and I am a fat guy so you would think with all that in my favor the bike would hook up. Even I can get the back tire to spin at will be it muddy, or dry, or perfect tacky soil. You may notice a difference if you went to the 14 ounce weight but I don't think 2 more will help you. Playing with tire pressure may help some.

 

[NO HAND]

...Playing with tire pressure may help some.

Very true, it is quite impressive the difference a few lbs make in traction and plushness.

 

[mtk]

You'll never stop wheelspin; the bike makes over 40hp so spinning the wheel is a fact of life.

The weight WILL help with making it more controllable in the woods.

Proper jetting will also help a great deal. More than likely, you're bike is jetted poorly, which results in it pulling weakly and then suddenly clearing out and ripping. That is rarely fun, particularly in tight woods. I'd definitely recommend finding "Spanky's Jetting Guide" (it has been posted here dozens of times) and fixing your jetting problems, before you do anything, and see how it runs. I'd still recommend ditching the aluminum clutch plates as well because the only reason they're in there is to make the rotating assembly as light as possible. With a flywheel weight, that isn't needed so why put up with the additional oil contamination?

Get it jetted and see how it runs, then decide on the bigger weight.

 

[dirtbikingdad]

Thanks a bunch guys. I think I've got some direction to go now. Jetting is definately needed. Thanks for the Spanky's Guide MTK.

 

[Vic]

Retarding the timing also is a cheap and effective way to reduce the midrange hit.

:cool:

Try this before you spend any more money.

 

[motometal]

you might as well go back to the recommended 32:1 premix ratio while you are at it. Better for engine life.

I don't think you would notice a few ozs difference in flywheel weight. I went from no weight, to the biggest one Steahly makes (whatever that is), and could feel the effects but not to the extent that I thought I would. I should take the weight back off some time to see what that feels like.

Eric Gorr's port work would definitely tame the hit, if that's what you ask him to do. I got the mobetter job done on my CR, but haven't assembled and ridden it yet.

 

[dirtbikingdad]

Got the bikes in the cleaned up shop now and will start looking at the timing issue too. I also ordered a G2 throttle today. When I searched for flywheel weight, I found some posts about the G2 too. I also saw some good info about it on KTMtalk.

About the spooge. If it is not burning and its coming from the pipe, doesn't it already have enough oil? Also, if I go back to 32:1, that will lean it out. Which I think it needs anyway. Any comments?

 

[NO HAND]

... Also, if I go back to 32:1, that will lean it out. Which I think it needs anyway. Any comments?

Spooge problems reveal a jetting issue, not a problem with ratio oil/gas. 250s should run 32/1 and no leaner.

 

[Vic]

If you're running pump gas, you will likely have spooge even if the jetting is right.

 

[2wheels]

HIt

Erric Gorr porting for low end. It's not that expensive . It's only about the same costwise as an after market pipe. I am 70 years old and am riding trails on a 2002 CR250.

 

[magneto]

I recently bought an 01 CR250 that was completely stock and ran rich (spooged) as well. I put the bike on a diet of Premium pump gas and Golden Spectro Synthetic at 32:1 and changed the jetting in the Mikuni TMX to a 400 main (420 is stock IIRC), and a #30 Pilot (#35 is stock). I believe that I also moved the clip up one notch on the jet needle. Changing the pilot seemed to make the most difference in spooge reduction. This particular model seems to be pretty sensitive to the air screw adjustment as well.

Accessing the carb on this bike is a pain. Is it like that on on the new bikes?

 

[motometal]

About the spooge. If it is not burning and its coming from the pipe, doesn't it already have enough oil? Also, if I go back to 32:1, that will lean it out. Which I think it needs anyway. Any comments?

We could go into great details here regarding oil ratios, if you really want to learn about it then do a search. Otherwise, i'll break it down to this:

Jetting makes way more difference than oil ratio regarding spooge.

All else being equal, more oil will help your engine last longer. After all, that's what lubricates it.

Spooge is not just oil, it's unburnt components of the fuel, and carbon, and partial combustion products.

 

[dirtbikingdad]

....32:1 will make it run richer, not leaner.
.

Are you sure? My experience has been that when I mixed the oil in the fuel, it essentially makes the fuel thicker. Which makes it more difficult to be pulled through the jet. Which makes it leaner.

While I may be wrong, I appreciate all the help I can get... or my correction when I am wrong. Thanks.

Also, thanks for the jetting hints Magneto. What elevation are you at?

(I went back and checked your signature... I'm guessing near sea level like me.)

 

[magneto]

I'm about 500 ft above sea level.

The more oil that you put in the fuel the leaner the bike will run since the oil displaces the gas in the mixture (20:1 will run leaner than 32:1 etc...) Jet with carburator changes, not fuel/oil changes. I run 32:1 in both my CR250 and CR500 without problems after I got the jetting sorted out.

 

[SpDyKen]

We could go into great details here regarding oil ratios, if you really want to learn about it then do a search. Otherwise, i'll break it down to this:

Jetting makes way more difference than oil ratio regarding spooge.

All else being equal, more oil will help your engine last longer. After all, that's what lubricates it.

32:1 will make it run richer, not leaner.

Spooge is not just oil, it's unburnt components of the fuel, and carbon, and partial combustion products.

Ok, Mm, I agree with all you've said EXCEPT the "32:1 will make it run richer, not leaner" part.

Let's consider your theory.

For this discussion we have to agree that we are NOT talking about ANY changes in jetting, right? So, let's say our XYZ 250cc bike has a 100 main jet. So it meters in approx. 100 "units" of fuel/oil pre-mix into the carbs. airstream at full throttle. This is more than 50 "units" of fuel/oil premix and less than 200 "units."
So at W.O.T., when 100 "units" of fuel/oil mix are being fed into the air passing through the carb. and into the engine; let's discuss that "mixture" of fuel & oil.

A 50:1 fuel to oil mixture is 50 units of fuel to 1 unit of oil. 50 gallons of gasoline mixed with 1 gal. of oil is an example of this. This is 1 divided by 50, which equals 0.0200, or 2.00% of this mix is oil.

A 32:1 fuel to oil mix is 32 units of fuel to 1 unit of oil. 1 divided by 32 equals 0.03125, or 3.125% of this fuel/oil mix is oil.

This means if we have a 1000cc container of each of these mix, 2% (20cc) of the 50:1 mix is oil; 3.125% (31.25cc) of the 32:1 mix is oil. Please note that this means we have 980cc of fuel in the 50:1 container and 968.75cc of fuel in the 32:1 container.

SO, when your XYZ 250, with it's 100 main jet meters in it's 100 "units" of each of these different fuel mixtures into a given amount of air, which one contains more actual gasoline? Or in other words, which one is "more rich in fuel to air ratio?"

I'll be curious to read your conclusion to this hypothetical scenario, Motometal.

I do admit that a 32:1 fuel to oil mixture is "richer in it's oil to fuel ratio" when compared to to a 50:1 mixture. I think that this is what confuses many people. But we are referring to the resulting fuel to air mixture when we discuss whether a bike is "rich" or "lean," right? Let me know what you think. :ride:

 

[magneto]

After you change to the correct jetting you may still notice spooging for a while because excess oil residue will have built up in your pipe/silencer. When I bought my bike I had to clean the pipe and repack to silencer to get an accurate idea as to how much spooge the motor was actually putting out.

 

[motometal]

wow, sorry guys, I had that one backwards. ooops! didn't think it through. glad you were there to catch it :bang: