125 modded vs 250f

[Yzrider054]

will a yz125 with reeds, pipe silemcer and some porting keep up with a 250f stock ?

[TheShadyMilkman]

.... depends where you are riding altitude... and how much porting you do.. race fuel..... tuning carbureation...rider..traction..and other factors too numerous to list. the 125s are getting lighter also so the extra power of the 4stroke doesnt really give it the upper hand but in a drag race i would want the 250f in tight twisty sections i would definitely want the 2stroke. cough cough four strokes stall cough cough

[99kx250rules]

Originally Posted by TheShadyMilkman

.... depends where you are riding altitude... and how much porting you do.. race fuel..... tuning carbureation...rider..traction..and other factors too numerous to list. the 125s are getting lighter also so the extra power of the 4stroke doesnt really give it the upper hand but in a drag race i would want the 250f in tight twisty sections i would definitely want the 2stroke. cough cough four strokes stall cough cough

I have seen alot of four stroke riders lose races because when they fall they can't get them started quick enough.

[pwisz]

Just ask Bubba what he thinks!!!

[Aus_Rider_22]

Sad fact is that us 125 riders need all the help we can get against 250f's..

Generally, 2 equal skilled rider's racing on 125 and 250f, the 250f will win. It is easier to ride and keep in the power.

That's not to say that a 125 can't beat a 250f, it's just that it's easier on 250f for most people.

[Yzrider054]

to make it more fair the 125's should be upgraDED TO 150'S this way they would have more of a chance and everyone could just pick what they want.

[wamxp1mp]

It depends on more then just shear HP I would say yes you can on a 125. I had an '03 YZ250F I did not enjoy ridding it or racing it. You won't see me on a 4 stroke untill decomp braking is totally or nearly gone and it free coast's. I like 2 strokes for this reason it's easier for me to jump and recover. It's more flickable so it reminds me of being on a bicycle, so it feels more feathery in the air. I find that 4 strokes don't quite feel that way, they have this more solid/planted feel. Combined with decomp braking when you back off the gas you notice it more. 4 strokes have more initial torque right off the btm so they typical get better starts and sometimes better at doing jumps outta corners but 2 strokes are just as good, but skill is more important and preference overall.

I ride alot of open classes or age classes anymore so a 144 is totally legal, but honestly if your not like alessi or somebody like that I doubt you'd ever get protested at the track. My current ride is an '04 KX 125 that is mainly stock except for the v3 reed block. My friends I ride with all are like on 250's plus. My bike totally hangs all doubts I had where erased at this harescramble race that had us ripping down a mile of a road course totally wide open tapped out.

If I was going to get a new 125 it be an '05 YZ totally tricked out to a 144

[Yzrider054]

im thinking about getting a yz250 2 stroke and then just detuning it a little.

[Logik]

Originally Posted by Yzrider054

im thinking about getting a yz250 2 stroke and then just detuning it a little.

why?���

[MotoMan]

Originally Posted by Yzrider054

to make it more fair the 125's should be upgraDED TO 150'S this way they would have more of a chance and everyone could just pick what they want.

You know...the more I think about this the more I kinda agree with you. I like the idea.

[mtk]

I believe AMA amatuer racing allows the 125 class to go to 144cc and the 250 class to go to 265cc. AMA Pro, however, does not.

With that said, I've heard that even the 144s aren't a match for the 250 thumpers.

[souphmars]

yea a 125 can hang with a 250f- look at bubba- the 250f's couldn't hang with him- if u have a little bit of skill u shouldn't have a prob- i started out on a 125- it was great, i never had a problem with keeping up with anybody- if u r goin to get a 250, don't do anything to it to try and slow it down- just learn to ride it- i think a 250 is easier to ride than a 125 myself- not as much clutchin and work goin on- if u r considering a 250 2 stroke, just go ahead and get one- after a while on a 125, u will probably be ready for 1 anyways

[gonzo]

A new 05 YZ125 could hang for sure. You can pin it around corners like no other. Straight a ways run slim but just keep shifting. I am yet to wind out 6th.

Probably going to port it but not for the 250F thing for just more power period.

[mtk]

Originally Posted by souphmars

yea a 125 can hang with a 250f- look at bubba-

Exactly, look at Bubba. He ran a 250F at Steel City last year. His comments afterwards was something to the effect of, "That thing is so much faster than my 125 its almost like cheating." He clearly indicated that the four-stroke is the faster machine, given equal riders.

I checked the rulebook that Faded posted and, as always, he's right on the money. I thought you might be able to get away with a bit of milling and a stamping kit (i.e. the rule doesn't say it has to be factory stamped, only that it has to be stamped with the displacement. I can mill off the old numbers and bang on "144" pretty easily) but the class specifies 125cc as the upper limit for two-strokes.

Shifting gears is lost time. Every gearshift costs you time in a race. Every one.

[TurboV6]

I find it kinda hard to believe that a worked over 125 can't hang with a 250f. I guess it really comes down to riding style and skill level. You will lose time shifting, however, with the sequential gearbox you reduce the time shifting to an absolute minimum. If you don't chop the throttle or only just slip the clutch or dont' use it at all, then it takes virtually no time to bang an upshift. I'll take it a little easy on the shifts and let the shift forks live to fight another day however.

[mtk]

Sorry, but you DO lose time shifting, without fail, no matter how you do it. On the roadrace track, each shift is a tenth of a second. I'm quite certain you lose at least that much on dirt.

And there's also absolutely no question a 125, worked or not, is slower than a 250. There's a multitude of reasons for it, none of which I have the desire to type in at the moment, but the fact that it came right out of Bubba's mouth should be good enough as he's obviously ridden both. The complete domination of the "125" class by 250Fs is another bit of proof. If the 125s were competitive, folks would race them. They don't.

[tman88g]

Originally Posted by mtk

The complete domination of the "125" class by 250Fs is another bit of proof. If the 125s were competitive, folks would race them. They don't.

Sad but true...

[TurboV6]

Well, just for arguements sake, let's say that it does take a tenth of a second per shift. Really, that isn't going to amount to an appreciable gain. There are way too many other variables on dirt to single shifting out as a sure fire way to slow you down. Getting on the gas just a bit later out of a corner or two will slow you down more than a couple more shifts per lap. bmw's sequential box shifts in 80 milliseconds which is quite quick. On the bike when you shift it's not like you have to go through neutral wasting time, just gear to gear. Plus, the original post isn't comparing worked 125's to worked 250f's, it compares a modded 125 to a stock 250.

[Aus_Rider_22]

If you are at all worried about losing time while shifting, don't think buying another bike (250f) will help you gain sec because of not changing as much.

Save the money and get your suspension done for your weight/riding ability.
You will gain secs from the bike tracking longer in turns and rough bumps.

[land-down-under]

what if u had a 125 bored to like 167 with all the pipes reeds etc..i saw one on ebay, it said in the description 4 strokes dont stand a chance...i understand that he was exagertting a little tryin 2 sell his bike, but is there any truth to it if it was to 167cc?