Going really old school here...

[csrozier]

So, I have a 2003 YZ250 as well as a 2004 yz450f, love em to death, but I am having one problem, lol. My good friend bought a used 2001 yz250 he took to a buddy of his 56 yr old ex-racer, and he did some modding to his 2001 yz250 and I have yet to be able to figure out exactly what they did, but I have a good idea about one thing in particular.

Anyone heard of "stuffing the crank"? What I mean is taking the motor and filling the lower bottom end by the literal crank with styrofoam I believe is what they actually used to do back in the day to get a lot more compression. I know it's illegal in motocross now to do that, but anyone ever done that, if so how noticeable was the affects? How did it make the bike run/sound etc? And lastly, if you really have done it and it was worth it, what exactly did you do?

Sorry for the long post guys, but I am really trying to do whatever I can to make this 250 fast without it being obvious to him I did it, it's sort of like a game we got going because at the moment, I can't outrun him on the 250, but I can get on my 450 and have my way with him. Any other tricks or mods that aren't really anything like big bore kits or anything like that I would definitely be interested in. Thanks for you guys feedback!

[steve18328]

Here is an example of crank stuffers. You can get them online.

[k.g]

Any other tricks

 

Yeah, practice more. It's a lot more effective in the long run.

[csrozier]

Steve, those crank stuffers that your showing there, have you used them and do they put excessive wear on the motor?

[dirtjumpordie]

How fresh is the engine in your yz250?  Best thing for these engines is a fresh top end if its been a while.

 

And only way to go is wiseco for me.  I have never had a wiseco piston fail. Ive shattered the best of the best cast pistons, but forged wiseco has never failed and Idk anybody that has shattered one under any circumstances lol

[steve18328]

I have only used the plastic ones. I have never seen any extra wear on the motor. They don't touch the rod or cases. They bolt to the crank. I have see plastic ones standard on new cranks as well. I can't remember if it was a factory crank or wiseco. Also be sure you can install them without pressing the crank apart before buying a set. I was told some stuffer require a crank press for installation.

Edited April 25, 2015 by steve18328

[csrozier]

Thanks for that information Steve and everyone else who replied. The topping and as well as bottom hand on his bike is absolutely fresh, I bought the wiseco bottom and top end kit for it, I am a full believer in Wiseco I love them to death lol actually just put a brand-new forged Wiseco piston in my 04 yz450f and it runs like a scalded ape lol. I think what my buddy has done to his bike is all basic things, we both have a really good friend that used to race two strokes back in the day and he can tune the carb better than anyone I know of, I think he just has the carb dialed in perfectly and a couple other things, I'm getting the impression his crank isn't stuffed lol, his bike has just been a solid YZ through and through. The only parts I know are different are the expansion chamber and silencer, they're both pro circuit and the silencer is the size of a coke can, no bigger and sounds like it's spitting freaking ball bearings out "pinging" at a normal idle , so the exhaust may have something to do with it but I've never heard a 2 stroke sound the way his sounds in my life. It literally will heart your ears it pings so loud.

If I can figure out to send a pic of it I'll post a pic of the exhaust and the silencer and see if anyone knows the model of the pro circuit silencer.

[C-P]

Good little crank stuffer mod in here, pretty cool YZ stuff overall.

Edited April 25, 2015 by C-P

[csrozier]

That video was pretty cool about all the stuff that guy would do to YZs, and his work looked REALLY nice. I was told by an old timer today something that I have been trying to make sense of all day and can't, maybe someone can enlighten me? I don't understand how this would work..

(Old guy rode bikes for like 15-20 yrs in races and was stupid fast and really nice with motor work)

He said guys would use crazy different things to stuff the crank ie. that stuff that comes in a spray can that sprays out as a wet foam but then will expand a bit and harden up after it is sprayed.

I immediately think he's talking about that spray sealer that is foam and is usually yellow that ppl seal places in the house with it, but that stuff it seems like if you sprayed it in the crankcase that it would harden until you started the motor, then I'd think you'd have a shit storm on your hands bc that crap would be in your case-don't see how that would possibly do anything to make an effect like stuffing a crank nor would it be safe for the motor..

[Excitable]

port work, proper squish and spot on jetting are all you need.