Why isn't big-bore 2 strokes popular for SM? - Speedzilla Motorcycle Message Forums
 
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post #1 of 16 (permalink) Old 03-31-2007, 03:40 AM Thread Starter
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Why aren't big-bore 2 strokes popular for SM?

I was just curious about this from the experienced Supermoto guys. It seems the power and light weight of a newish big bore 2-stroke would make them popular for conversions to SM bikes. But I never seem to hear about a CR500 or KX500 being converted, it seems today it is almost 100% factory-built bikes like the KTM or Husqvarna, or guys take a CRF450 and modify it. Any reason why an open 2-stroke doesn't work?

I was thinking about buying a clean CR500 and converting it into a street-legal SM. In my state you can register them as customs, with all of the required lighting of course, and no emissions tests are required where I live. 60 hp and 240 pounds sounds entertaining to me.

About $2500 for the bike, and about that same amount in mods and new plastic, I would have a fun, simple, little scooter to play around on.




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post #2 of 16 (permalink) Old 03-31-2007, 04:39 PM
 
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that "simple little scooter" would have brutal power and no engine braking. though guys(men) do build them. i would like to ride one just to get an idea how the original superbikers did it. then i would give it right back.
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post #3 of 16 (permalink) Old 03-31-2007, 06:09 PM
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the four strokes have a longer, more linear powerband than 2 strokes, even the 500's. peak HP doesnt do you much good if it's hard to control and you have to shift 10 times more than on a 450.
that and the fact that they are not readily available, have dated chassis and go thru fuel twice as fast.

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post #4 of 16 (permalink) Old 03-31-2007, 11:35 PM
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There was a pair of dudes racing CR500s up at Road America (Superbikers2) a couple years ago - they were perpetually at the back of the pack.

Those big 2 strokes would spin the rear tire in a straight line, and they appear to be hard as hell to handle on corner entries.

I wouldn't waste my time riding one even for the nostalgia value.

But I totally encourage others to ride them in competition - I need someone I can beat on a regular basis.
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post #5 of 16 (permalink) Old 04-01-2007, 02:50 PM
 
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If anyone has a CR500AF set up for supermoto with all dirt parts available, I would trade my 05' YZ450 for it in a heartbeat. I have ridden two strokes all my life, and feeel very comfortable with the power delivery of the big two strokes.

My favorite woods weapon was always my old CR500. Tons of torque and if you just ride it up a gear, it works quite well.

I think my 450 eats more fuel than my CR ever did.

Don't even get me started on maintainance. I think the 450 costs more by far to maintain than the CR ever did. Change the oil every other ride, set the valves, new piston and rings every season, and the cranks wear out just like the two stroke ones do.

I bought my CR500 used and rode it for three years. In that three years, I never cracked a bolt on the motor. It still had monster compression when I made the mistake of selling it.

I know that there are more supermoto specific parts available for the new four strokes, and that the four strokes are easier to go fast on, but once you get the hang of a two stroke, they are just as much fun if not more fun.

Face it, most of us are never going to be competetive at the national level anyway, so why not ride what you like.

later

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post #6 of 16 (permalink) Old 04-02-2007, 06:30 PM
 
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hey zero, have you ridden one on a SM track? i have not. however, i hear you on the other aspects. i roadraced 2 strokes and called the others diesels as they were pigs. sure, they're better now. but they're WAY more expensive to maintain. i'm kicking myself for selling my YZ250 that i used to play ride, etc. now i'm just putting more hours on my 450. more hours = more money. having said that, i rode a friends crf250 and it was so much fun that i want one. it was completely stock and docile compared to my 450 that i can barely hold on to on a tight MX course.
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post #7 of 16 (permalink) Old 04-02-2007, 08:21 PM Thread Starter
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The maintenance costs of big-bore 2-stroke versus 4-stroke was just one of the reasons I asked the question. For $500 you could have a very fresh engine, $1000 for wheels and tires, $500 for electrics for the dual sport, and $500 for new plastic. So maybe $5k total for a bike with mods, but it would be fully freshened up and look like new.

That would mostly be the same for a CRF450, except rebuilding the engine would cost quite a bit more if cams and such are needed on a tired MX bike. So maybe $1000. Since they are newer they also sell for more than the CR500, $3500 would be my guess in equal condition. So the CRF would be heavier, have less power, and be $2k more roughly to build back into a SM bike.



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post #8 of 16 (permalink) Old 04-02-2007, 08:43 PM
 
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how much money do you add for the total animal factor? i have no idea. but i've raced two guys in the vet class that formely raced cr500s. but you can't win if you don't enter. so build that bad horsie. if you chose to, you could modify crf stuff to fit if it doesn't already(wheels). that way you could adapt or have a better resale value whenever you go to sell the goods.
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post #9 of 16 (permalink) Old 04-02-2007, 09:39 PM Thread Starter
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It wouldn't be for racing, just playing around on or the occasional commute. I'm thinking hard about selling the Ducks, with a family hopping on and going for a ride all day just doesn't happen anymore. I also worry about where I park and leave them, I fret about if something goes wrong with them, I get tired of paying $$$ for every part for the things. You don't get much simpler than an iron-barrel, non-powervalved, two stroke dirt bike.

There are lots of places to ride a dirt bike around where I live. There is also a local winter hare scrambles series that is pretty low-key, several guys I know race it. Some friends now have a big farm/woods about 20 minutes from us, and have several miles of trails already cut, he keeps bugging me to get a dirt bike again.

I actually had an idea of buying two CR500s, convert one to supermoto and use the takeoff parts as spares for the other one to play in the dirt. I had an RM250 throughout my teenage years until I switched to streetbikes when I was 20, but rode a buddies' YZ490 after that on occasions.

And then if in a year or two I decide I don't want one or both, I could sell them and get most of what I have in them back. Owning a 999 has been an experience in precipitous depreciation.




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post #10 of 16 (permalink) Old 04-03-2007, 03:02 AM
 
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Why do people ask questions they already know the answer to (and their subsequent retort, too)?

4T's are faster on the track and the bikes and parts are more readily available. In MOST states, they're easier to get on the road, too, if that's your aim.

Dude, you like 2T's and you've already rationalized its purchase (of two, in fact ) Go buy them! Just make sure you post pics!
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post #11 of 16 (permalink) Old 04-03-2007, 04:46 PM Thread Starter
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Quote:
Originally Posted by bmxr View Post
Why do people ask questions they already know the answer to (and their subsequent retort, too)?
Hey I got you to respond didn't I?

The original question could have been better worded to ask what the main pros/cons were of each engine type. Further posts by me were attempts to clarify my reasoning, and to illicit responses if someone had a different opinion based on their experience.

I found very little concerning two-stroke supermoto bikes searching the archives, perhaps a discussion of the merits of each could happen.




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post #12 of 16 (permalink) Old 04-03-2007, 06:46 PM
 
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Why are smoker lovers always such tools?
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post #13 of 16 (permalink) Old 04-03-2007, 07:41 PM Thread Starter
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Quote:
Originally Posted by OMEGA View Post
Why are smoker lovers always such tools?
So is an advantage of 4-strokes that the rider isn't automatically lumped in with the tools?




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post #14 of 16 (permalink) Old 04-10-2007, 04:30 PM Thread Starter
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Found a good buildup thread

http://cr500riders.com/cgi/yabb/YaBB.pl?num=1166940804




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post #15 of 16 (permalink) Old 04-14-2007, 08:19 PM
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I think I know the perfect 2T motard. That would be my 04 KTM 300EXC but with SM wheels and brakes and different final drive ratio.

If anyone has ever ridden a 300EXC they no it's not really a 2-stroke, it's a 3-stroke . They pull down low just like a 4T but still have a good top end hit like a 2T. I have added a Rekluse clutch, a G2 throttle cam, and an FMF Gnarly pipe that really brings the power into the low RPM. I rarely need (or want) to be up in the power band when riding this bike. It can pull stumps off idle as good as any 4-T of similar displacement. It would be really interesting to see what it would be like as a motard ...

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post #16 of 16 (permalink) Old 04-15-2007, 10:23 PM
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Quote:
Originally Posted by Highpower View Post
I think I know the perfect 2T motard. That would be my 04 KTM 300EXC but with SM wheels and brakes and different final drive ratio.

If anyone has ever ridden a 300EXC they no it's not really a 2-stroke, it's a 3-stroke . They pull down low just like a 4T but still have a good top end hit like a 2T. I have added a Rekluse clutch, a G2 throttle cam, and an FMF Gnarly pipe that really brings the power into the low RPM. I rarely need (or want) to be up in the power band when riding this bike. It can pull stumps off idle as good as any 4-T of similar displacement. It would be really interesting to see what it would be like as a motard ...
i've got a kx250 with an Eric Gorr 310 big bore in it. while i agree with you that they are a mix of a 250 2-stroke and a 450 4-stroke, i have ridden it in SM setup and will tell you that it is not the same as riding a 450. the power band length is much shorter, thus making it much "busier" to ride than a 450. and it still doesnt pull like a good 450.

big 2 stroke may be fun to ride, but 99% of all people will go faster on a 4 stroke. not to mention that unless you put a CR500 motor in a newer chassis, i have a hard time believing the chassis is going to be newly as good.

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