Lets talk ktm 300 xc
- Thread starter relentless rider
- Start date
Here is an excellent read. For the folks considering their 250 or 300 two stroke bikes on an ST or SX kit. The engine discussion is very interesting. The 4-stroke "torque myth" also discussed. Will put a smile on your face.
http://motocrossactionmag.com/Yamah...T-MOTOCROSS-ACTIONS-TWOSTROKE-VERSU-7117.aspx
They compare a 250f to a 250 two smoke.
Here we are looking at comparing 250 or 300 cc two smokers with 450fs
There is just no comparison in torque the sx450s are closer to the stock
Cr500 than any 250 or 300 smoker in fact you need to do a lot of work on a
500 two stroke to make it much better than the 450- 500 four-strokes.
Can you get 55 + hp out of a 250 or 300 smoker absolutely you can but
I would guess that someone is going to get real good at doing top ends.
If you are bend and determined on a smoker -- bigger is better - any two
stroke you will have to build it up to better a 450f .
450fs are plentiful and proven on the snow.
For most probably the best bang for the Buck -- that said I like a project as
much as the next guy just to see if I can make it work even if it is not better.
So have fun.
R
relentless rider
Well-known member
Just installed the MH on my bother inlaws 500 xcw, load it in the back of his truck that bike is a tank to the lite 300 , ya on paper they say its what 15 20 lbs more , but in real life its not! For what ever the 300 lacks in power to the 4s ill make up riding the hell out of it.pistons are cheap we can rebuild in the woods, how do we ride 2 stroke sleds? Wot all day .and two strokes smell good, sound good, haha .the way I look at snowbiking is just having fun, you dont have to have the best most powerful bike to do that,a least in the dirt its is the best bike ever and if anyone wants to fight out that one lets go hit the woods ,
, I picked 300 for that reason , if its a good snow bike thats just a bonus, as for rebuilding all the time , im not sure of hours or miles, but I did keep track of fuel and being close to 50 gals ran though it the piston and jug look like brand new, so if you smell a sweet aroma in the air, and a track mark that you cant poach its the 2 stroke ahead of you! 
Im just having fun now ha
, I picked 300 for that reason , if its a good snow bike thats just a bonus, as for rebuilding all the time , im not sure of hours or miles, but I did keep track of fuel and being close to 50 gals ran though it the piston and jug look like brand new, so if you smell a sweet aroma in the air, and a track mark that you cant poach its the 2 stroke ahead of you! Im just having fun now ha
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mtn-doo
Well-known member
Ha! 
I was afraid this might ruffle some feathers! Great article though. Most folks don't realize the 2-stroke engine facts. You're missing the point. This is "NOT" a 2 stroke VS 4 stroke discussion. I have a new 450SXF. It's not being "bent" on a two stroke. The facts are, they produce more HP and more torque per CC that a 4-stroke period. A small 250 two stroke produces close to what a 450F does. Just the physical facts. The 500 - 2's kill them. A "stock" 500 two stroke produces "TWICE" the torque of a 450F at only 3000rpm. A small 250-2 is almost equal to a 450F at about only half the size.. It's a fact, read the dyno charts. Also, they love to run WOT and will do it for days with no issues. Just like our sleds. Rebuilds are $200 and take two hours, and don't need one but once every couple of seasons. Compared to days in the shop and a couple grand for a 4 stroke. Rebuild's recommended 20 hours? ish? on a 450F. People need to know their options, the pro's and con's. For the benefit of the folks who have a 250 or 500 two stroke at home and are considering a snowbike, yes, they are lighter, more powerful, less expensive, and easier to maintain than the 450F's. So go out and have a blast. Your bike will work great! I have ridden and tested both. They are very capable of giving you a good time, with some added great benefits!
I was afraid this might ruffle some feathers! Great article though. Most folks don't realize the 2-stroke engine facts. You're missing the point. This is "NOT" a 2 stroke VS 4 stroke discussion. I have a new 450SXF. It's not being "bent" on a two stroke. The facts are, they produce more HP and more torque per CC that a 4-stroke period. A small 250 two stroke produces close to what a 450F does. Just the physical facts. The 500 - 2's kill them. A "stock" 500 two stroke produces "TWICE" the torque of a 450F at only 3000rpm. A small 250-2 is almost equal to a 450F at about only half the size.. It's a fact, read the dyno charts. Also, they love to run WOT and will do it for days with no issues. Just like our sleds. Rebuilds are $200 and take two hours, and don't need one but once every couple of seasons. Compared to days in the shop and a couple grand for a 4 stroke. Rebuild's recommended 20 hours? ish? on a 450F. People need to know their options, the pro's and con's. For the benefit of the folks who have a 250 or 500 two stroke at home and are considering a snowbike, yes, they are lighter, more powerful, less expensive, and easier to maintain than the 450F's. So go out and have a blast. Your bike will work great! I have ridden and tested both. They are very capable of giving you a good time, with some added great benefits!
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relentless rider
Well-known member
Thats the point what mtn-doo said, there are alot of guys, gals out there that have bikes( 2 strokes) and want to snowbike , just have been told that there isnt enough power so they dont put anymore thought into it, thanking I need to buy a efi 450 , the kit , well im 12,000 or more, into it to hit the snow,
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Quote: A "stock" 500 two stroke produces "TWICE" the torque of a 450F at only 3000rpm.
Yes it also falls on its face at 6000 rpm where the 450s just get going.
Was looking at building a cr 500 for the snow. First you have to port them to get the rpm and power up -- then a good crank job (balance) may be a good idea -- all of them are old so new clutch is fore sure a must so are carb heaters ( but no electrics) Now you are also back at jetting as altitude and temps change (remember the old days sledding) If you ad all this to the purchase price it becomes a expensive snow-bike only unit.
My point is simply that for most folks a used 450 EFI motocross bike is the cheapest option without any mods needed to work well.
There is no doubt that with some serious mods and know how you can make just about any bike work well enough on a snow-bike.
However that superb 300 single track woods bike will be wrecked for woods riding if you port it and get it set up for max power on a snow kit.
If you ever made a MX 250 into a single track / woods bike you will know that the mods you need for a snow-bike are not at all compatible with that.
In the end 2 stroke or 4 stroke single track/woods bikes are not well suited for snow-bike MX bikes are a whole lot better for that purpose.
I am looking for a dedicated snow-bike only keep my off road bike for just that.
May need a bigger garage as well and sell my sled.
Yes it also falls on its face at 6000 rpm where the 450s just get going.
Was looking at building a cr 500 for the snow. First you have to port them to get the rpm and power up -- then a good crank job (balance) may be a good idea -- all of them are old so new clutch is fore sure a must so are carb heaters ( but no electrics) Now you are also back at jetting as altitude and temps change (remember the old days sledding) If you ad all this to the purchase price it becomes a expensive snow-bike only unit.
My point is simply that for most folks a used 450 EFI motocross bike is the cheapest option without any mods needed to work well.
There is no doubt that with some serious mods and know how you can make just about any bike work well enough on a snow-bike.
However that superb 300 single track woods bike will be wrecked for woods riding if you port it and get it set up for max power on a snow kit.
If you ever made a MX 250 into a single track / woods bike you will know that the mods you need for a snow-bike are not at all compatible with that.
In the end 2 stroke or 4 stroke single track/woods bikes are not well suited for snow-bike MX bikes are a whole lot better for that purpose.
I am looking for a dedicated snow-bike only keep my off road bike for just that.
May need a bigger garage as well and sell my sled.
R
relentless rider
Well-known member
After the mods on the xc its even better in the tight woods, technical rocks more ridable. Can lug a gear higher.. next year id like a 450 for a SB only with boost .
Interesting stuff. I believe comparing the 500 to the 450 is closer than comparing the 450 to the 300. A 300 is more or less in 450 land as far as power is concerned which is pretty good considering its 150cc smaller. Add in the power to weight ratio factor and its more or less there.
The 300 when ported and head modded will not go through top ends any more than a stocker. I have friends with 300's with years of racing on this type of mod. The power increase is not that extreme, rather makes the engine come on sooner with a nice increase throughout the entire range, more efficient and allows for more consistent jetting. The porting one would do from say Slavens or Mike S would work fine in either situation i believe.
It is also more fuel efficient than the 450. I owned both in KTM trim and the 450 would be empty and my 300 would still have fuel left over in the single track.
As for comparing a 450 to a CR/KX500 the motor in the 2 stroke is more powerful period. Its 50cc bigger and will kill a 450. In the sand with taller gearing and 5 more paddles the 500 will pull hills in 3rd and 4th where the 450 can barely pull 2nd gear.
Cost to build these bikes is all relative to how fancy you want it. U could build a 500 for 1500-9000. I know guys who build 500AF's and they sell them for 6-8000 and know guys who buy SH 500AFs for 12000. It just depends on what you want to make. No different than sleds. You can have a 13000 turbo Yamaha or a 30000 yamaha that will go the same places. Might not be as shiny lol.
Now the real factor on where the 4 stroke is better is the little red happy button (although 300 has that)! Kicking a big CR500 sucks balls ! Then you have power for goodies in stock trim which is a bonus (hmm 300 has that as well) !
Ha Ha MtnDoo see what you started LOL. Its all your fault !
The 300 when ported and head modded will not go through top ends any more than a stocker. I have friends with 300's with years of racing on this type of mod. The power increase is not that extreme, rather makes the engine come on sooner with a nice increase throughout the entire range, more efficient and allows for more consistent jetting. The porting one would do from say Slavens or Mike S would work fine in either situation i believe.
It is also more fuel efficient than the 450. I owned both in KTM trim and the 450 would be empty and my 300 would still have fuel left over in the single track.
As for comparing a 450 to a CR/KX500 the motor in the 2 stroke is more powerful period. Its 50cc bigger and will kill a 450. In the sand with taller gearing and 5 more paddles the 500 will pull hills in 3rd and 4th where the 450 can barely pull 2nd gear.
Cost to build these bikes is all relative to how fancy you want it. U could build a 500 for 1500-9000. I know guys who build 500AF's and they sell them for 6-8000 and know guys who buy SH 500AFs for 12000. It just depends on what you want to make. No different than sleds. You can have a 13000 turbo Yamaha or a 30000 yamaha that will go the same places. Might not be as shiny lol.
Now the real factor on where the 4 stroke is better is the little red happy button (although 300 has that)! Kicking a big CR500 sucks balls ! Then you have power for goodies in stock trim which is a bonus (hmm 300 has that as well) !
Ha Ha MtnDoo see what you started LOL. Its all your fault !
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mtn-doo
Well-known member
Ha! Ya, good stuff. Get's people thinking of options. Great point on building a good 500 for just a couple grand. Very true. That 300 with the little red button, some porting, head, CDI, and an SX or ST will be all the fun most folks could have. Don't forget the thousands of clean 250-2's out there in garages. I have ridden with some and they really rip. People who have one can be playing on the snow for about 7K ,....kit included! inexpensive fun little ripper.
Here's an example. A friend on a 2006 YZ250 turning an ST kit...... For comparison, the other bike is a 511 with a Long Track,
http://www.youtube.com/watch?v=WoUQ4BH5Hj0
This bike is running a stock PWK Carb. Then simply add a 38MM APT Smart Carb. No jetting or tuning. All altitudes spot on. Not like the "old jetting days", and no EFI tuning required. An inexpensive MX bike for a couple grand, a $375 Smart Carb, then go have a blast!
Ya, good stuff. Get's people thinking of options. Great point on building a good 500 for just a couple grand. Very true. That 300 with the little red button, some porting, head, CDI, and an SX or ST will be all the fun most folks could have. Don't forget the thousands of clean 250-2's out there in garages. I have ridden with some and they really rip. People who have one can be playing on the snow for about 7K ,....kit included! inexpensive fun little ripper.Here's an example. A friend on a 2006 YZ250 turning an ST kit...... For comparison, the other bike is a 511 with a Long Track,
http://www.youtube.com/watch?v=WoUQ4BH5Hj0
This bike is running a stock PWK Carb. Then simply add a 38MM APT Smart Carb. No jetting or tuning. All altitudes spot on. Not like the "old jetting days", and no EFI tuning required. An inexpensive MX bike for a couple grand, a $375 Smart Carb, then go have a blast!
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eskimojoe77
Well-known member
Personal testing
I'll be conducting my own tests this winter on my new bike CR500AF (stock porting etc), homebuilt snowkit, 38mm cast Smartcarb (when it finally shows up), Rekluse auto clutch. I've been riding my Ktm 525sx (fairly stock with Rekluse) the last 3 winters, 2yrs on a 2moto, last season on a homebuilt MH copy. I'll have them both going this winter so I'll get to do some side by side testing, nothing scientific, but seat of the pants style. I have high hopes for the Cr500, hopefully not disappointed.
I'll be conducting my own tests this winter on my new bike CR500AF (stock porting etc), homebuilt snowkit, 38mm cast Smartcarb (when it finally shows up), Rekluse auto clutch. I've been riding my Ktm 525sx (fairly stock with Rekluse) the last 3 winters, 2yrs on a 2moto, last season on a homebuilt MH copy. I'll have them both going this winter so I'll get to do some side by side testing, nothing scientific, but seat of the pants style. I have high hopes for the Cr500, hopefully not disappointed.
M
mtn-doo
Well-known member
Hey guys and gals,
Most folks have some knowledge of the American Performance Tech, Smart Carb. But for those curious or everyone else, their Facebook page is a great resource. Interviews, Dirt Rider mag tests, new releases etc. Anybody interested in 2-stroke or 4-stroke, no efi tuning, no jetting, from sea level to the clouds, literally, I feel this is a must have. Our current technology is breaking amazing ground. For technical discussions, call and ask for Corey.
https://www.facebook.com/PowerAPT?ref=profile
Most folks have some knowledge of the American Performance Tech, Smart Carb. But for those curious or everyone else, their Facebook page is a great resource. Interviews, Dirt Rider mag tests, new releases etc. Anybody interested in 2-stroke or 4-stroke, no efi tuning, no jetting, from sea level to the clouds, literally, I feel this is a must have. Our current technology is breaking amazing ground. For technical discussions, call and ask for Corey.
https://www.facebook.com/PowerAPT?ref=profile
M
mtn-doo
Well-known member
He is swamped! Great things though. We had a good visit about things, etc. The final triple jump, big air testing done. Your 38's are coming.
Very very well worth the wait. A new release is always bumpy. They are perfectionist's. I love that. You will own the most advanced fuel delivery system in the world. 
You know what makes me laugh is that its only a matter of time while watching someone's snow bike vids that you start to hear the rider hooting and giggling like a school girl. They are just so much fun so 2 stroke/ 4stroke get it done, just doesn't matter. That said I plan to throw a leg over SB's CR500 once he starts it for me LOL, there's probably a dedicated snow bike in my future. My 450 thumper is getting a rebuild this fall with a few extras, I could almost buy a used YZ250 2 smoke for the same money. Makes you think.
M5
M5
S
somepunk22
Member
He is swamped! Great things though. We had a good visit about things, etc. The final triple jump, big air testing done. Your 38's are coming.
I just hope they are done perfecting before the snow flies!
M
mtn-doo
Well-known member
Ya, that will be a fun little ripper. But I wouldn't go EFI. EFI is a "fixed" fuel map. No altitude or temp compensation. Then you must get a programmer to "re-map" the fuel map, to "re-jet" the EFI electrically. I would just slap on a 38 Smart Carb. No tuning or programming and 8 to 10 % more power.
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most modern EFI has temp and baro corrections KTM doesnt do much of anything, but the jap bikes all do they just arent very accurate below 32F
