RM250 platform for Snowbike?

May 26, 2020
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Just will not rev the same

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Meaning the power delivery? They say the big bore kit brings more low and mid range power without sacrificing top end... That sounds like a good bet with snow bikes.

Would you prefer a stock bore 250 over a 290 or KTM/Husky/Beta 300?
 

wwillf01

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100 percent I own both... and to me the 250 is way better than the ktm 300 unless you get it set up like the mx bike... but even then still prefer the 250... you never use the low end... always 5 grand and up....

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May 26, 2020
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Interesting. I could see that. The 300s are built for lugging and most 250s are built to scream. But talking with Rodney at Millennium Tech, it doesn't sound like the 290 is necessarily a lugger...
 

wwillf01

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Could be the case just make sure they set it to scream....... see link and watch the 1st and 3rd video with a 125 pound 12 year old ... they just rev... the more even rev the bike can pull you have more options shifting and not loosing momentum... even more reving in powder....


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Jan 3, 2008
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100 percent I own both... and to me the 250 is way better than the ktm 300 unless you get it set up like the mx bike... but even then still prefer the 250... you never use the low end... always 5 grand and up....

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Have you rode a 300 sx side by side with a 250 sx by chance? Everyone claims they(300sx) are amazing but I raced one in sand and still had bike lengths more top end pull. But it was an older bike. 08 300sx build vs my 2013 250sx
 

wwillf01

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Maybe Eric can chime in but he runs a 380... did a lot of work to get it to rev... once he did that it is a blast to ride...

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May 26, 2020
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Here's what Rodney at Millennium Tech had to say "For all practical purposes the 290 IS a 250 MX. The porting of the standard 2 stroke 250 has a more linear power delivery than the KTM. The porting of your cylinder will retain and increase/improve the factory power delivery curve."

I'm going for it. Port / Powervalve work needs to be done regardless, as the PV had grooved the piston I just pulled out of there...
 
Jul 21, 2010
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Are oversized footpads necessary? Man they are expensive! I've read the posts about welding on extensions, but seems like the results are mixed - bent extensions and or icing/snow build up issues with the lack of open interior...
I ran these on a ktm 300 for a season and they worked fine after a little grinding to get them to seat nicely. 15 mins w a die grinder did the job.
 

needpowder

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I spoke with Millennium Tech yesterday and Rodney pretty much convinced me to go with the 290 big bore kit... I know a lot of you guys suggested just to run it as a 250, but this will be a dedicated snowbike and seems like a little more displacement would be a good thing.
I kind of thought the point of this thing was to run it cheap. If you wanna spend 1000 bucks justsell your rm and buy a 2014 through 16 YZ 450. It will crush your RM even with your silly big bore plus be way more reliable.
 
Dec 20, 2007
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I would not spend a dime to big bore it unless the cylinder is damaged. You could spend a ton of money on it and still not have the power of a stock 03 ktm. Whatever you do it will still be fun as any 2 stroke. My buddies cr250 is a total dog but seems to make him grin more than his ktm350.
In my group the 250sx are always leading the pack ahead of the 300s. I can make the 300s run better but stock the exhaust ports are a mm lower. It's Real Good for idle power with tires but I haven't figured out how to idle up a hill in deep snow.
 
May 26, 2020
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I would not spend a dime to big bore it unless the cylinder is damaged. You could spend a ton of money on it and still not have the power of a stock 03 ktm. Whatever you do it will still be fun as any 2 stroke. My buddies cr250 is a total dog but seems to make him grin more than his ktm350.
In my group the 250sx are always leading the pack ahead of the 300s. I can make the 300s run better but stock the exhaust ports are a mm lower. It's Real Good for idle power with tires but I haven't figured out how to idle up a hill in deep snow.
Exactly, low end enduro lugging vs MX high revs...
 
Sep 18, 2018
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I run a YZ250 with a Tom Morgan 300 big bore/balanced crank on VP110.....home made plastic skid plate, carbon pipe guard, Lectron and that's pretty much it. I use heated gloves when real cold.

Bikes rips, run with 450s at seal level and out west just fine.
 
May 26, 2020
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I run a YZ250 with a Tom Morgan 300 big bore/balanced crank on VP110.....home made plastic skid plate, carbon pipe guard, Lectron and that's pretty much it. I use heated gloves when real cold.

Bikes rips, run with 450s at seal level and out west just fine.
Sorry for the delay, Schwany. Do you run a carb heater and thermostat?
 
May 26, 2020
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What's everyone mixing premix at? Are you going 32:1 motocross ratios? Generally are you liking at the flashpoint of different brands? Hotter or cooler for winter?

I've had good luck running lower flashpoint temps on my summer trail rm250 - minimal spooge and no plug fouling.

Thanks everyone for the insight.

I've rebuilt the top end (295cc) and clutch with new basket (Wiseco), plates (OEM) and springs (OEM). Next will be plumbing the cooling system with carb and bar heaters and thermostat. Then rebuild the forks and put the kit on.

I'm sure I'll have some gearing questions when I get to it.
 

wwillf01

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I use redline without issue 32 to 1 on the yz250... just go with something thinner without bean oil in the mix. I would use a moto type oil because its pinned 99 percent of the time...

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