CR250R......of doom. Testing positive for Beastmode

[scotty dog]

Preliminary research find me looking at a company called Eddie Sanders racing.  They use 92-01 CR250 motors for micro sprint cars.  They have a long rod stroker crank that they sell for not much more than a hot rods oem replacement crank.

rpm manufacturing does a 270 kit, with piston for not much more than a standard strip and re-plate job. 

I haven't done the math yet, but with the 3-4 options Eddie Sanders offers on rod length, something like a 300cc should be easy.   

My destroyed crank is a hot rods, so i am going to call them and find out about getting it rebuilt.  Supposedly those guys are "real", and by real i mean, not a warehouse in China, but rather a machine shop in the USA.

I just want to cheat as hard as possible for the 250 class.  Something like a 60hp 300cc two stroke against a 37hp 250 fourstroke.  I have to mention I am kidding, I forget sometimes that people take this seriously. But no, seriously, some 250F kid is going to take a shit in his pants.

I like your way of thinkin premixed,  who's gonna know how big it is? As long as it has "250" stickers  on it.
I liked the 98 a little better than the 99 , was a bit stronger mid to top I thought,  mine was s screamer, loved it

[Brap]

Looks sweet chad, good luck

[Formerly knownas Premixed]

I split the cases last night and the inside of that motor is THRASHED.  It must have broken a rod, spun the rod inside the crank case a few times and just shredded it.

At this point I am looking at it thinking, It needs nikasil, it needs new engine cases, it needs a crank, it needs reeds, it needs 80 dollars in powervalve parts. It needs radiators and an 01 pipe.  I just do not want to alter the crank case by grinding it to try and fix all the destruction in there.  I am sure someone can fix it, so I am going to inquire about that.

It's really starting to look less and less "worth it" as all my 03 motor needs is a piston.  So, we'll see.  I still want the HPP motor in there badly.

[Brap]

You have any idea as to what 250 motor was the strongest off the line?

[Formerly knownas Premixed]

You have any idea as to what 250 motor was the strongest off the line?

Honda?  97-01 were the best 250 motors they ever made, but the 97-99 and 00-01 chassis sucked.  in 03 they got the chassis right, in 04 they got the forks right, but from 02-07 the motor was weak.  it made 45-46hp like the 97-01 motor, but it made it like a 125.  no bottom, no mid, then a 2,000rpm punch, then it falls on it's face if you don't shift it.  It's hard to even ride the clutch.

[Brap]

Like in general, all brands. I was told the 2005 RM was a really good engine but i've never ridden any other 250 so i can't compare it

[Formerly knownas Premixed]

The best motor is the 04+ KTM.  It scared MC into retirement.

The 03+ KX, and 04+ RM are both clones of the YZ 02+ YZ. .  Honda did it's own thing in 02 with the RC valve motor, and like I said, it's got no low end because the crank case volume is too high and the intake on the case reed motor is too short.  It's like a road racing motor, which is no surprise as I am hearing the whole RC valve idea came from the NSR department.

[_X_]

low end is for trail riding.

[Formerly knownas Premixed]

low end is for trail riding.

oh.

[moto867]

mc retired in 02

[2T Institute]

The best motor is the 04+ KTM.  It scared MC into retirement.

The 03+ KX, and 04+ RM are both clones of the YZ 02+ YZ. .  Honda did it's own thing in 02 with the RC valve motor, and like I said, it's got no low end because the crank case volume is too high and the intake on the case reed motor is too short.  It's like a road racing motor, which is no surprise as I am hearing the whole RC valve idea came from the NSR department.

No such thing as too high case volume, servo pv operation is far superior to crank governed, if the  engine has no bottom end the pipe will be the culprit. Fitting a servo power valve control will iron out dips in torque curves in minutes.

[Formerly knownas Premixed]

mc retired in 02

Incorrect.  He retired in January 2003, on KTM, to get out of his 2 year KTM contract (retirement clause).  He had a gnarly off-season testing crash, the motor was so strong he requested to ride it in stock form, plus, KTM promised him linkage, and never delivered.  put all of that together and he said "fuck it".

[Formerly knownas Premixed]

The best motor is the 04+ KTM.  It scared MC into retirement.

The 03+ KX, and 04+ RM are both clones of the YZ 02+ YZ. .  Honda did it's own thing in 02 with the RC valve motor, and like I said, it's got no low end because the crank case volume is too high and the intake on the case reed motor is too short.  It's like a road racing motor, which is no surprise as I am hearing the whole RC valve idea came from the NSR department.

No such thing as too high case volume, servo pv operation is far superior to crank governed, if the  engine has no bottom end the pipe will be the culprit. Fitting a servo power valve control will iron out dips in torque curves in minutes.

How many RC valve CR250s have you owned/built/ridden/raced?

fitting a servo valve means nothing if the actuation point is wrong.

2T Institute, here is a guy who learned it by "doing it".  All of the flaws of the motor that I found were solidified here.  Give it a read, you might learn something.

Its a combination of things, starting at a TMX Mikuni carb with a slide that doesnt seal well, rolling in to a case reed induction that is too short, into a crank case that is too volumuous, into a cylinder head with way too much squish, and a poorly shaped band all together.  PArt of it could be the pipe, which could be why Scalvinis pipe for this bike is so radically different than the FMF and PC.

http://www.thumpertalk.com/topic/639710-diy-cr250-engine-porting/page__hl__%20cr250%20%20self%20%20porting

[_X_]

hey! wobbly is a hardcore biker, fn sweet. ok, resume thread.

[Super Trucker]

Robby  Renards  dad  had  his  02 or  03  cr250    running   strong  enough  that  Honda  wanted  to  tear  it down  and   duplicate   the mods.  Give,em  a call .   I   pull   the  pv  cover  off ,  then  fire  my  04 cr125 up.  Then   check   the  pv  to see  if  it,s  operating   correctly.  I   lube  the cables,  and   all   pv  parts  are   fine  tuned-  polished  to   get  the  pv  operating  as   smooth  as possible.   I  want  the pv  opening   asap,  with  the  bike  running  I   adjusted   the  cables  and   got  the pv  opening  quicker.