Two Stroke Motocross
Two Stroke Motocross Forum => General Two Stroke Talk => Topic started by: chump6784 on August 18, 2011, 12:57:37 AM
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This is a comparison from last weekend riding.
It was never intended to be a comparison day but as things turned out I rode 3 different bikes and thought I would give a review of what I found.
The bikes:
2007 RM 250. This is my bike and is bone stock. The suspension is set up for me but that is it
2011 KX250f. This is my brothers bike. He bought it the week before, it was brand new and he got it cheap as the 2012??s are about to arrive. It too is bone stock
2006 YZ 250. This is my mates bike. It is set up for freestyle with cut down seat and high bars and all. Mods: PC pipe and muffler, Boyseen RAD valve, Race Tech suspension and some mild porting just to clean up the ports.
First session I took out my bike. The track was very hard packed, a little rough and they were watering it. It was like riding on glass. Still the RM rode well and it was looking like a good day.
Second session I got half way round the track on the first lap and next thing I lost drive. Looked down and saw my chain dragging. Turns out the clip that holds the front sprocket on came off and I lost the front sprocket. I found the sprocket but couldn??t find the clip and no bike shops anywhere had one in stock. I parked the RM up for the day.
Third session. As my brother hasn??t ridden in years and his fitness isn??t the best we decided that he would ride until he was stuffed and then I would finish out the session on his bike.
As I rolled towards the first corner I cracked the throttle and initially it felt similar to the RM with a fairly decent bottom end that started transitioning to the midrange but then it kind of flattened off. It was kind of like a 250 2 stroke bottom end that transitions into a 125 top end. There was just no surge and it just ran kind of flat.
Coming out of the first corner I opened the throttle where I usually would and there was kind of nothing. The power slowly built up and I realised I had to get onto this thing. Each corner I would get on the gas a little earlier until I was hitting the throttle well before I would even think about hitting it on the RM. Despite this I was only arriving at the next corner at about the same speed as the RM or even a little slower. The thing with the KXf was that if I got on the gas too early quickly chopping the throttle would bring everything back in order. There was no rear wheel sliding or front wheel lifting, just the feeling that I had got on the gas too early. It was very forgiving.
It also felt like the engine was pulling the bike towards the ground. Over the back straight ski jumps it didn??t lift off the lip like the RM. Also by backing off the throttle on the lip of a jump would make the bike stay a lot lower off the lip than the RM. The engine braking made it feel like I was dragging the back brake off the lip. It wasn??t bad tho, the bike stayed level and predictable in the air.
Through the whoops the bike just drove forward. The rear wheel didn??t kick sideways or spin, just grip. One thing is for sure, this bike could be very quick.
Everyone was looking at me when I got back to the pits to see my reaction. I had been trying to convince my brother that 2 strokes were the way to go but he just couldn??t see straight. As much as I hate to admit it when I pulled off my helmet I had a smile on my face, looked him in the face and said ??I know why you bought that thing, its pretty good.? That was a bit of a shock to everyone and they told me that while I was riding they were saying that even if I did like it I would never admit it. I even said that if I were to get another bike I would have to give a 250f some consideration.
I was gearing up for the fourth session when my mate with the yz said for me to take his bike, he was done for the day.
Cracked the throttle and this thing has some power off the bottom. A lot more power than the RM straight off the bottom and through the mid range but about the same on top. It felt as though the power band had been moved down the rev range a couple thousand revs. Even though it was set up for freestyle it was still a blast to ride. After about 2 corners I realised again why I bought a 2 stroke. I spent the rest of the session blasting around on the YZ. One thing I did noticed was the added bottom end and midrange made it harder to ride on the slick track even compared to the RM. Because the power was there straight up I had to make sure there was grip there when I got on the gas but when I got I right it was a blast. One thing I did find that in the slicker corners I would go in a gear higher than I should. This would allow me to roll on the gas a little earlier and then when I was ready a flick of the clutch and the engine was back on the boil. This kind of made the bike feel more 4 strokish and more rideable.
My saving grace of the day was when I got back to the pits, looked everyone in the face and said ??I know why I bought a 2 stroke.? The four stroke was as quick but just wasn??t as fun
This was never ment to be a comparison so no lap times were taken or anything and none of the bikes were adjusted in any way and lap times and speeds were all just seat of the pants feelings but it was enough to get a feel for the three bikes.
For 90% of the population the 250f would be the bike to race if winning was your only goal. Lap times felt about the same and being a slick hard pack track gave it an advantage. I could get on the gas earlier on the f so my corner exit speed was higher but the 2 stroke would run it down on the straights but not enough to make a big difference. The thing is you can make mistakes and it really doesn??t affect your lap times that badly, it??s a lot harder to get out of shape on the f than the 2 strokes. Loads of grip and the latest chassis and suspension components made the 2 strokes feel really old and the thing was easy to go fast on. It is nearly idiot proof. If the moto??s you are doing are only 5-7 laps or so there wouldn??t be much difference but over the course of a 30 minute moto you are going to be in better shape at the end on the f. Motocross isn??t a drag race, if it were the 2 stroke would have it in the bag. Motocross is about stringing a whole moto of laps together and for me that would be easiest on the f. Its bugger all difference but there is a difference
But in the hands of someone who really knows what they are doing or someone that wants to have fun and not have to worry about how long the engine will go before blowing up the 2 stroke is the way to go. If you can use the extra power and not make mistakes and really know your limits then I think you would be quicker on the 2 stroke. Its all about consistency.
Then there is the fun factor. If I thought I had a smile on my face after the 250f it was nothing after getting back off the 2 stroke again. Raw nasty horsepower is addictive and I will leave the smooth power of a 4 stroke for when I am too old to hang on to a 2 stroke.
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Raw nasty horsepower is addictive and I will leave the smooth power of a 4 stroke for when I am too old to hang on to a 2 stroke.
AMEN... :D This is why I ride a smoker... for the fun of arm ripping horsepower... yes it is verty addictive
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In a pinch safety wire can take the place of your counter shaft sprocket circlip. ;D
Nice article,thanks.
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I thought about but it was a brand new chain an sprocket and I didn't want to risk damaging something if the sprocket came flying off again or it to come off on the face of a jump or anything. To be honest it was kind of a blessing I couldn't ride a lot, had a mad chest infection and felt like throwing up between sessions from dehydration. Probably shouldn't have been riding at all. Didn't tell my bro before I took his bike out tho