As far as i know a bigger fly wheel will make power delivery smoother and less aggressive, not give it more bottom end. It will be harder to stall and rev up.

Hey, great video. I think a lot of riders think the 125 can't make a good woods bike, but you just showed a simple mod plus a few others and you can have a great woods bike - especially for new riders or those who just don't want mega horses. Nice job.

I have used Steahly's off and on for 25 or more years, always worked great for woods and dessert riding. Also company owners ride and there kids ride. Thank you for the Info 🏁🏁👍🙂🏁.

Cheers mate! Helps to see other's experience. Going to do this to an RM250 and YZ400F!

Thanks for the video bud. I’m getting ready to install one on my 2015 200 (same bottom end as yours). I ride mostly woods and gnarly clay trails so I’m looking for more traction

Glad you like it! More bottom is always good!

Your collection of bike's is growing by the minute 😁🤣👍

DUal stage reeds and 6mm thick exhaust spacer gave me a lot more bottom end on my 89 YZ125.

thx for the vid. going to put mine on now. 2012 250 sx. also putting the green powervalve spring 🤘🏻

Nice video, I have a flywheel in my 250sx, I would say it just changes the engine character, makes the bike chug along better at low rpm, makes the bottom end power more usable while sacrificing some of the 2-stroke explosion, you don't loose hp it just slows the hit, less likely to stall is a huge plus for trail riding, not sure how it will be on a 125 but for trail riding its been great on my 250!! Cant wait to see more VFR and dirt vids!!!!! Keep it up man!

Thanks for the great video. I'm considering this mod for my 125.

The old flywheel add on haven seen that for years ... big for the old farmers.

Opened the casing on my bike and discovered it has one of these weights fitted, no wonder it was so sluggish and keeps dropping off the pipe in between shifts. I'd strongly suggest nobody fits it to a 125 unless you want your bike ruined. Even with 13 52 gearing it's awful. Also incredibly hard to remove if it's been on there for a considerable amount of time. Useful vid 👌

HeroRR, thanks for this vid. Hugely helpful, thanks!

Hey man great video and information your video is super clear is there a trick to this ..?

Heavier to rotate doesn't "add" anything. Its harder to rotate initially, but once its going the momentum will carry itself better. It will make the driveability better at low speeds better chugging without stalling because of inertia of the rotational mass. I hated a lightweight flywheel on my Subaru. Yes it revved faster but I went back to stock for better driveability

I have KTM SX 150 2014, I added 10 ounce flywheel, and since than my spark plugs where going out about approximate 7 hours ( i was riding really slow and technical staff) jetting was from manual and I even put smaller idle jet, but still spark plug was in oil, thats the reason why spark plugs died. I took off flywheel and rode same trails that I rided with flywheel, spark plug is clean and like new, no oil on it. Do you have noticed something like this? I guess I better sacrifice bottom end for spark plugs.

Very nicely done. Thanks for the information.

I feel 12oz on a 125 is overkill but it gives us a chance to see on a more realistic scale how power is improved so nice vid bro

Isk if you still have this bike but it sounds like your needle is too rich.

Vfr 800 is the winner for me ;)

A another good way for just pudding around ( not giving it full throttle) you can change the gas and oil ratio ( a little less oil )

Hi HeroRR. I am getting my 1991 YZ125 dialed in over the last year. I am having issues with lack of power on hilly single track, in particular on the bottom end. Did you notice additional torque to move the bike on hills? Thanks!

Might pay to check your jetting.

Would have gone the 250 myself. Or the 300 EXC if going street legal. Had the 300 and was a great bike. Rode a kwaka 125 motocross bike and just can't compare lol.

Any science on how these things perform?

Hey new rider here , I'm a smaller guy and got a 2 stroke cr85 , the powerband is insane and I'm wheeling 1 - 3 , do you think this would help keep the bike on the ground a little easier? Nice bike BTW 👍

Is that flywheel or clutch, sorta think that's clutch?

The Video is studdering a lot. Is that just for me? How many B-Frames do you use when you Export the videos?

replace to a small front Sprocket It is going to be perfect for low speed

U need to swap for a 250/ 300, both are easy to ride.

Where did u find that engine stop tool who makes it

Why didn’t you add the 2014 ktm sx125 to your bike list yet

Soooo you buying a Honda crf450l like you said you would in your “Honest conversation about the DRZ400SM” ?

Orr a beta 300rr

It's like a trials bike now

I'm amazed that horsepower isn't negatively effected. Torque is how hard something pushes. Horsepower is the rate of acceleration, how quickly an engine or electric motor, can spool-up. The Rev-limiter, is the top-speed of the engine itself. And the Red-line, is the suggested top-speed of the engine, because past that, you're more likely to break something. So with any vehicle. The point of making any rotating part, be it a flywheel, crankshaft, wheel, selected tire, whatever, the point of making spinning parts lighter, is to improve the rate of acceleration & deceleration. In other words, improving Horsepower and stopping distance. Reducing the rotating or reciprocating mass of a part, is more effective, then removing the same amount of mass, that's sitting on the suspension. Like replacing body panels, fasteners, and any batteries, with lighter versions, won't be as dramatic of a change, as removing the same amount of weight from the unsprung suspension parts, the wheels, the pistons, things like that. But I don't know if this should automatically apply to flywheels... Flywheels, crankshaft dampers, and weights like you added. The point of them, is to store energy, between the power strokes of an engine. So reducing the weight of the flywheel & damper, will improve the engine's ability to change speeds, but it maybe less smooth, may struggle climbing hills, and maybe easier to stall. A heavier flywheel/damper, should do the opposite of these things. Have you seen the machines that crush big rocks into pebbles & dust? Their flywheels are MASSIVE. They take a long time to spin up. But once up to speed, they easily pulverize rocks, because heavier flywheels store rotational energy, and they resist change. Long ago. When I was in automotive school, enthralled by Gran Turismo 4. I asked an instructor, what are the benefits of making a flywheel heavier, instead of lighter, because at the time, I didn't know. I forgot what he said, but he basically said, don't mess with anything. USELESS. I guess he wasn't into hotrods & Tuning. Understandable. Mechanics hate modified vehicles, because they don't know if a problem exists, because of something OEM, or because of some mod they don't know about. More reason to professionally repair & maintain your own vehicle, if you want to modify it. That's what got me into Tuner-car culture, racing, cars, and now motorcycles exclusively in real life. I adore modifying, because I not only personalize a vehicle's appearance, but also make it physically fit my needs. Which is exactly what you did, adding that weight, to your bike.

Never check it

If you had to check it every 10 hours i would have one fucked crank case

Add blue Loctite too *N U T*

Please buy a 250 or 300xc or xcw

The exc has more bottom end than sx. You should have bought that for trail riding.

Ok these do not give you more power it takes the hit away they normally put these on beginer bikes and yes trail bikes aswell this will make you less likely to stall make your bottom end power more usable for riders who are timid and dint like reving the guts out of the motor infact this will actually slow your bike down ITS A 125CC LEARN TO RIDE IT AS IT IS YOU WILL BE BETTER OFF YOU SHOULD OF SPENT THAT MONEY ON FUEL TO BECOME A BETTER RIDER