Two Stroke Motocross
Two Stroke Motocross Forum => General Two Stroke Talk => Topic started by: chump6784 on October 27, 2010, 06:35:12 PM
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So i have been thinking lately, with 250 2T's running with the 250 4T's why couldnt the 2T's have their power mellowed out.
The main thing with motocross 2T's is that the power is very abrupt making traction an issue where as the 4T's produce very linear and tractable power.
So this got me thinking. lately in the enduro scene the 2T bikes have been coming out with adjustable power valve springs to mellow out the power and make more usable, more torquey power curves. Obviously this results in a loss of peak power but as 2T's already have a power and torque advantage by a substantial margin they could lose some of that if it ment a better power curve.
obviously this sort of defeats the purpose of a 2T as the snappy power delivery is one of the reasons why i and i suspect most of you bought a 2T but it would also make them a quicker bike on a track.
Now this is just what i have been thinking, it may have been tried before and failed so feel free to set me straight but i would be interested in hearing your thoughts on this as i really cant see it being a disadvantage
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Your not quiet right.
The adjustable power valve springs do not lower peak power at all.
All they do is control the speed at which the power valve opens.
If the power valve opens quickly the power will have a sudden surge (hit).
By slowing down the opening time it allows the motor to gain more revs and more power so when the power valve is fully open the "Hit" is less.
There are also Hydraulic adjustable powervalve adjusters available.
JRF & Porivoni ?. Not sure on the spelling.
Hope that answers your question.
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yeah it kind of does. my main question is why is no one doing it. it seems like the way to make 2 strokes faster is to make them easier to ride. make em faster and they will win. make em win and more people will buy and the two stroke is reborn
on another note. went into a yamaha dealership today and asked if they had any 2011 yz250's coming in as all they had on the floor were 4 strokes. the salesman then told me that they were getting more in as the ones they had just sold out. made me feel good that the 2 strokes went and the 4 strokes were sittin collecting dust
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it seems like the way to make 2 strokes faster is to make them easier to ride. make em faster and they will win. make em win and more people will buy and the two stroke is reborn
With respect, I'd have to take issue with that as I don't believe that's the problem. Modern 250 2-strokes ARE easy to ride, many people would be just as fast if not faster on them than the expensive, money absorbing time bomb they're presently droaning around on, and if there was more of them out there they WOULD be winning.
The problem is perception, there are lots of young fellas out there now riding and singing the praises of the 4-stroke and they don't even have a genuine notion what a 250 2-stroke is like in comparison. The only perception they have is that which has been implanted in their brain by the manufacturers via the press and dealers.
All you need to do is to get these poor unenlightened souls to actually TRY a 2-stroke but sadly that's becoming increasingly difficult to achieve due to various factors.
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Hey MMS, very true what you say. Alot of guys I ride with have never even touched a 250 two stroke. They figure they are too fast and too hard to ride. I know I am faster on a 250 two stroke when compared against a 250F, but I have had to really pull my finger out and start training properly and hitting the gym hard so that I can be as fast at the end of the moto. That is the biggest difference for me, it is much much easier to go fast on a 250F when you have already started to tire, or are completely worn out. With the rules changing at the amateur level here in Australia to come into line with the pro rules, allowing 250 two strokes in the lites class, I know a lot of guys talking about making the switch to a two stroke. It will be very interesting to see how many actually line up on the startline of the Sunny State series for the first round next year. I know I will be there !!
Chump, you can definitely achieve what you are talking about. For example, the powervalve spring option on the Kato's is good, and if you keep going, and add extra flywheel weight, along with an adjustable ignition, play around setting up the timing, and possibly change to a chamber more suited to low end power, and boom, you have a torque monster. Obviously going to give up upper RPM power, but you understand what I mean, and that the power on a 250 two stroke can be easily modified to suit each individual rider/application !!
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Hey MMS, very true what you say. Alot of guys I ride with have never even touched a 250 two stroke. They figure they are too fast and too hard to ride. I know I am faster on a 250 two stroke when compared against a 250F, but I have had to really pull my finger out and start training properly and hitting the gym hard so that I can be as fast at the end of the moto. That is the biggest difference for me, it is much much easier to go fast on a 250F when you have already started to tire, or are completely worn out. With the rules changing at the amateur level here in Australia to come into line with the pro rules, allowing 250 two strokes in the lites class, I know a lot of guys talking about making the switch to a two stroke. It will be very interesting to see how many actually line up on the startline of the Sunny State series for the first round next year. I know I will be there !!
Chump, you can definitely achieve what you are talking about. For example, the powervalve spring option on the Kato's is good, and if you keep going, and add extra flywheel weight, along with an adjustable ignition, play around setting up the timing, and possibly change to a chamber more suited to low end power, and boom, you have a torque monster. Obviously going to give up upper RPM power, but you understand what I mean, and that the power on a 250 two stroke can be easily modified to suit each individual rider/application !!
Hey Swapper, rule changes, what rule changes?
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Increasing crankshaft inertia IS the way forward ;)
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Hey MMS, very true what you say. Alot of guys I ride with have never even touched a 250 two stroke. They figure they are too fast and too hard to ride. I know I am faster on a 250 two stroke when compared against a 250F, but I have had to really pull my finger out and start training properly and hitting the gym hard so that I can be as fast at the end of the moto. That is the biggest difference for me, it is much much easier to go fast on a 250F when you have already started to tire, or are completely worn out. With the rules changing at the amateur level here in Australia to come into line with the pro rules, allowing 250 two strokes in the lites class, I know a lot of guys talking about making the switch to a two stroke. It will be very interesting to see how many actually line up on the startline of the Sunny State series for the first round next year. I know I will be there !!
Chump, you can definitely achieve what you are talking about. For example, the powervalve spring option on the Kato's is good, and if you keep going, and add extra flywheel weight, along with an adjustable ignition, play around setting up the timing, and possibly change to a chamber more suited to low end power, and boom, you have a torque monster. Obviously going to give up upper RPM power, but you understand what I mean, and that the power on a 250 two stroke can be easily modified to suit each individual rider/application !!
Hey Swapper, rule changes, what rule changes?
Yeah man, from all the information I have been able to gather, and I have been working at it for a long time, that will be the case. 250 two strokes legal in the lites class at all levels for next year !!!
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I believe that Swapper is talking about the Amateur program in Australia with the 250 vs. 250. Please confirm if I am correct.
Chump6784 - you bring up an excellent point. Although this has been tried in the past with the 500cc two-strokes. In the 1980's the manufacturers were attempting to get more and more power out of the bikes, but the pro racers were finding it more difficult to race the machines, so they began lowering the peak horsepower, making the bikes more tractable. This helped them to ride faster.
Another important factor is throttle control and gear selection. On the four-stroke you can be lazy on both and still do well in the amateur ranks. When you get lazy on the two-stroke, you end up breaking the rear wheel loose at times that can put you in trouble.
That "explosive" power that so many of you look forward to, is not necessarily the fastest way around the track. Ridden properly by a great racer, even a stock 250 two-stroke can be easy to ride.
Check out this video to see what I'm talking about.
MXPTV Rider Profile - Randall Everett (No Music) (http://www.youtube.com/watch?v=bF6ke8Iy8Lo#)
To answer your question, can it be done? Yes.
But then the question becomes will the advantages out weigh the dis-advantages?
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Heck, just get a flywheel weight.
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lol
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Rob Peter to Pay Paul. But I ask this to anyone who has ridden either. Do you really want 4 stroke feel? I had an XR600 lately and hated it so much that I traded it off in a short time. I just couldn't stand the no bark feel of a 4 stroke. It was boring, even though it had all kinds of power.
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If toning it down is your goal, why not try something like this. Instead of buying say the KTM SX motocrosser, buy the enduro 250, and set it up for MX riding. I personally, always want more power, but it would be interesting to see if one could turn quicker lap times on the enduro version of the KTM 250 in the SX frame and same gearing. I stated elsewhere that I believed KTM could make a 450, just like their 300 enduro, only bigger, and have a bike with about as much power as an old KX 500, but which is easy to ride like their own 300. I don't think that would be hard to do at all, but maybe 2T Institute can straighten me out here if I am mistaken. I wouldn't want that for a desert playbike though. For that, I want all the power I can get. Might help in MX though, who knows.
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Hey MMS, very true what you say. Alot of guys I ride with have never even touched a 250 two stroke. They figure they are too fast and too hard to ride. I know I am faster on a 250 two stroke when compared against a 250F, but I have had to really pull my finger out and start training properly and hitting the gym hard so that I can be as fast at the end of the moto. That is the biggest difference for me, it is much much easier to go fast on a 250F when you have already started to tire, or are completely worn out. With the rules changing at the amateur level here in Australia to come into line with the pro rules, allowing 250 two strokes in the lites class, I know a lot of guys talking about making the switch to a two stroke. It will be very interesting to see how many actually line up on the startline of the Sunny State series for the first round next year. I know I will be there !!
that was my point, the smooth power is easier to ride more consistantly. i am not looking to tone my bike down as i dont race but was just thinking that for racing application it could give the rider an advantage
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I believe that Swapper is talking about the Amateur program in Australia with the 250 vs. 250. Please confirm if I am correct.
Hey John, yes that is exactly correct. All of this year, the pro's have been allowed to compete on 250 two strokes against the 250F's, and for next year, any racer, at club level, state level, or again in the pro ranks, can compete on a 250 stroke in the lites class.
;D
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I believe that Swapper is talking about the Amateur program in Australia with the 250 vs. 250. Please confirm if I am correct.
Hey John, yes that is exactly correct. All of this year, the pro's have been allowed to compete on 250 two strokes against the 250F's, and for next year, any racer, at club level, state level, or again in the pro ranks, can compete on a 250 stroke in the lites class.
;D
Swapper,
Has this rule change officially been released from MQ, or is it just pit talk at this stage?
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Probably call it officially unofficial at the moment. I have received confirmation from plenty of guys in the know, but we will have to wait for the new rule book to be released for it to be confirmed.
Are you going racing next year EVO ??
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Increasing crankshaft inertia IS the way forward ;)
I'll agree with that. As much as I love my Husky, its engine inertia is virtually zero, and it makes the thing more tricky to launch, really easy to kill on a tight turn or on hard braking (though it compression starts like nothing) and it lets you feel every little eccentricity in the power curve. I rode dad's '77 Maico 250 just once, and although it didn't have the raw power of the Husky, it was incredibly smooth. It didn't have nearly the low-end of my bike (which is normal for a '77 of any description) but because the whole thing was so smooth, it felt like there was more. And of course, it follows the Maico tradition of big and beefy crankshafts that look like they belong on a Cummins Turbodiesel.
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Probably call it officially unofficial at the moment. I have received confirmation from plenty of guys in the know, but we will have to wait for the new rule book to be released for it to be confirmed.
Are you going racing next year EVO ??
Yep, I'll keep racing till I'm about 60 I recon...then I might take up vintage.
The second half of this year has been a bit of a write off, injuries and wet wheather have played havoc with the season.
Just got back from Sat morning practice at Stanmore the place was swarming with bikes, 3 groups of seniors by 10.00.
Coolum is 3 round behind, there's talk of a couple of double race days to catch up ???
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Hey I rode the Stan today. What number are you again. I was out there on my YZ. Track was good. Just a bit dusty. But yeah alot of guys, cos they knew the track had been prepped for race day, and then the race day had been cancelled due to no officials. Just sux have to wait so long to get a ride !!
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E50.
I enjoy going to Stanmore, although it's a bit of a struggle getting any rythm going after spending 6 months going around Coolum, transfering to hardpack from sand is tougher than I thought.
Armpump was killing me.
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you guys need to go to reedy creek if stanmore is that busy. was there 2 sundays ago and there was only 2 senior classes for about 2 sessions and then it went back to one class for the rest of the day. there were also the juniors and 50's but not real busy at all.
the track was terrible tho
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Reedy Creek is a joke on the weekends, the track is rough and slick and then they have morons doing community service watering the whoops and up ramps of the jumps. It is flat out dangerous and nothing ever changes. I used to try and help them out, but got sick of the track being so dangerous. The only night to ride that place is Tuesday nights after it has been prepped and watered.