300 twostroke might be the magic number

CamP wrote:

I think if you really wanted parity with a 450, it would require a 350cc 2-stroke.

malachi177 wrote:

:blink: All this talk about them not reving out or having enough power etc is crazy...that IS what makes it a killer engine. It's more tractable...

All this talk about them not reving out or having enough power etc is crazy...that IS what makes it a killer engine. It's more tractable and they have a shit tonne of power/torque. Rip your arms off torque!! They are more then capable of staying with a 450. I haven't ridden a TM300, but I have ridden the KTM and it has a killer engine...and the rest of the bike is awesome too. The GasGas 300 racing (Nambotin) has an even stronger engine, but too bad it's an enduro only bike. I really hope they decide to join this European 300cc MX class because as I said that engine is gold!! I haven't rode the new Beta 300 but it looks good, and has had great reviews... but again it's an enduro bike.

mjskier wrote:

[b]Btw the power valve dolly spring is not really suppose to be adjusted. Yes it determines when the Pv starts to open but for max power...

Btw the power valve dolly spring is not really suppose to be adjusted. Yes it determines when the Pv starts to open but for max power there is an optimal setting. Anything more or less will be a drop in power. The PV timer is specifically set to open at a predetermined spot and the auxiliary springs just slow of speed it up from that point on. It's not meant to be a tuning device for the end user. Guys wind the thing out to flush and say it's so snappy now. Well it's snappy because you opened the PV too soon, lost bottom end power and now you get a huge surge in the middle so it feels like its stronger. Dyno graphs undeniably prove this.

Thanks CR. that's good info. I never adjusted mine but I have ridden with people who had and they were all raving on how strong their bikes was. Mine was working a lot better in the tight technical stuff. I was chalking that up to my superior riding skills, but maybe their bikes just sucked :-)

Last week in Utah:

bvm111 wrote:

So what's wrong with a 250 that was so good for so many decades.....Why are we all of a sudden messing with displacement again? Is it...

So what's wrong with a 250 that was so good for so many decades.....Why are we all of a sudden messing with displacement again? Is it because they are "too hard to ride" compared to a 450? Are you trying to make a 2 stroke run like a 4 stroke? I guess I just don't get it, if I'm out of shape and I can't run a 125 or 250 without barfing a lung and getting army pump like concrete I actually put forth the effort to get in better shape instead of developing a new racing class and motorcycle I can compete in!

Just sayin

mynewcr250 wrote:

the 300 just widens the powerband. you dont gain much peak hp, but you gain down low where it counts. its not like the 300 just...

the 300 just widens the powerband. you dont gain much peak hp, but you gain down low where it counts.

its not like the 300 just came out, its been around for quite a while too. theres a reason its so popular, it basically a 250 with more bottom end making it easier to ride.

believe it or not, some people would love a more 4 stroke like powerband on their 2 stroke. you get a strong tractable poweband, but with less parts and easier to service for the average joe.

why is better distributed power with less moving parts a negative? why is having more choices a bad thing? the point is it would be awesome to retain "true" 2 strokes like the 125/250 for guys that want the full "2 stroke experience" and give guys that want a more 4 strokish type of power a 300/350.

mynewcr250 wrote:

There's nothing wrong with the keihin it's just that the smart carb is self adjusting for ambient conditions and atomizes fuel much better. It's essentially a...

There's nothing wrong with the keihin it's just that the smart carb is self adjusting for ambient conditions and atomizes fuel much better. It's essentially a lectron style carb but updated so it doesn't have the "flaws".

Btw the power valve dolly spring is not really suppose to be adjusted. Yes it determines when the Pv starts to open but for max power there is an optimal setting. Anything more or less will be a drop in power. The PV timer is specifically set to open at a predetermined spot and the auxiliary springs just slow of speed it up from that point on. It's not meant to be a tuning device for the end user. Guys wind the thing out to flush and say it's so snappy now. Well it's snappy because you opened the PV too soon, lost bottom end power and now you get a huge surge in the middle so it feels like its stronger. Dyno graphs undeniably prove this.

this is from James Dean at JD jetting. you can see as the spring is turned outwards you get a drop in torque from 4500 to 7500 rpm. the blue line is optimal which is the red spring around 2 turns in (which is ~stock)



now you have the same runs but done by turning the screw IN, passed about 2 turns in. as you can see, you again lose power because the PV is held closed too long.



there IS an optimal setting and IMO you should be doing all PV tuning using the ignitions maps and aux springs only. to each their own.

Suns_PSD wrote:

I had to shift my 300 2 stroke dramatically more often than I do a 450F. I actually counted once and it was a huge difference...

I had to shift my 300 2 stroke dramatically more often than I do a 450F. I actually counted once and it was a huge difference. Even my 314cc needs a lot more gear work although I'm hoping the additional over-rev of a Smartcarb will cure that. Try to get over the largest jumps at Chicken Licks raceway in 3rd gear on a 2 stroke, just like you can do on any modern 4 stroke, and you'll see it doesn't work well. Okay now try and come out of a slow turn in 3rd gear on your 2 stroke with authority, that's tough to make work unless you use a lot of clutch which kills your traction and therefore lap times.

It's not that the 300 isn't fast, it's just that it has a very narrow area (compared to a 450F) where it is fast.

The 2 strokes we all ride are 'tuned' meaning ports, pipes, etc are optimized for the scavenging effect which produces optimum peak hp. But the consequence of this is that in other places the powerband is even less optimal.

When I was a kid I use to ride a friends blue 1982 Suzuki streetlegal 2 stroke endure bike. and that thing ran exactly like a low power 4 stroke. Super tractable, torque, very even smooth powerband, etc...

If the manufacturers didn't have to try to make 2 strokes compete with bikes of double the displacement, they could be very 4 stroke like.

The ultimate 250 class bike would be a modern 250SX DETUNED to have peak hp in the range of a modern 250F. It would be superior in every way because it could then have a very long and smooth powerband, plus the weight and cost benefits of a 2 stroke.

mjskier wrote:

So is the Lectron carb still the best bet if you ride at varying altitude? I can be anywhere from 5000 to 12-13000 feet on a...

So is the Lectron carb still the best bet if you ride at varying altitude?
I can be anywhere from 5000 to 12-13000 feet on a given day. The low end torque on my 300 (07) still pulls me out of trouble but I can tell it isn't running quite right as I go high(er)