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250f vs 450f reliability?

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all I have heard is 250f's being time bombs and well I just don't get it. On the other hand I have heard the 450's are really reliable. I'm 15  5'11 and around 170lbs. I am currently riding a 2005 yz 125 that I just don't have to much fun with because im afraid im gonna blow the engine because I do a lot of open field riding where im going a lot of 3/4 throttle and I just don't like it because it limits me to go slower than I want or else I feel as though im gonna blow it. On the other hand I don't do much racing on track because well that's just not my thing. I do hit jumps on my farm but that's it. I am wondering if ill be in the same situation if I get a 250f and not a 450? The main reason I want the 450 is because the speeds that I want to go in the open there would only have to be like half throttle compared to full throttle on a 250f. Also how much  maintenance do you REALLY need to do if all you do is keep the engine at a low rpm in a high gear and not a lot of shifting because in my experience I have never done anything to my yz 125 except change the oil once after about 50hrs and the reason is, I don't go around gunning the SH!# out of it and treat it better than you would be while racing. In other words would a 450f be good for me if im just gonna be hitting occasional jumps and hit the track once a year and my friends a couple times a year but mostly just going around my farm with not much maintenance besides changing the oil every so often? And if not what would be a good bike? And as you can see in prefer Honda and Yamaha. Thanks!

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The only way to know is to ride both. Personally I'd be more worried about not changing the oil in 50 hours than going full throttle on your 125

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You need to look at a couple things. The purpose the bike was designed for and the maintenance that allows it to live up to it's intended purpose. Your 125 was built for racing purposes. It was designed to run at full throttle and be reliable if regular maintenance schedules are followed. It's no different for any other bike. How you ride your bike is a factor but so is time, including sitting in the barn not being ridden. Changing your oil at 50hr intervals is asking for trouble, no matter what or how you drive. Whatever you get, drive it the way it was intended to be driven and maintain it the same way and you'll probably never have a problem.

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You only change the oil every 50 hours on a 125cc two stroke?  I rebuild the top end sooner then that on mine.  To each their own but oil is so inexpensive and easy to change I don't see why you would put it off that long.

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Any motocross 4 stroke will require valve checks/adjustments every 10-15 hours with casual riding, much more often if racing. Did you not change your top end in that 50 hours? I did my 125 top end every 35. I went from a 250f, to a 125. Mainly because I was spending more time on maintenance that I was on my 125. On the 125 it was a top end every 35 hours and a oil change every 5. However I just moved to a KTM 250sx and it would be better suited for your riding than a 125, and there are no valves to check and top ends last longer than on the 125s. But please, pay a bit more attention to your maintenance, an oil change is what? $5? And takes 10 minutes.

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Any motocross 4 stroke will require valve checks/adjustments every 10-15 hours with casual riding, much more often if racing.

 

This is fallacy. By the same token that Honda recommends a new piston every 15 hours on 250s and 450s, both operations aren't needed that often for casual riding.

 

I check my valves when I change my pistons, once a year. They tighten up a bit when they are new due to break-in and then not again until they are failing hundreds of hours later.

 

To answer the OP's question, 250s and 450s last the same amount of time if used in the same way. Meaning that you need to change out the piston on schedule to protect against failure. The valves typically last through a couple of piston changes before needing replacement. Replacing the titanium valves with stainless greatly increases longevity.

 

You'll hear that 450s tend to have fewer catastrophic failures because they aren't being revved as hard. It's my feeling that 450s are mostly adult-owned as well and get better maintenance.

 

But if you plan to maintain a 250F or 450F the way you have your 125 it won't last you long. They need more and better care than you have been giving your current bike, which is one of the reasons why kids and lazy adults like 2strokes.

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Ok I was exaggerating when I said 50hrs its more around 20 or so but its the point that do you really have to do a ton of maintenance if you really aren't pushing a bike to its limits?   

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The only way to know is to ride both. Personally I'd be more worried about not changing the oil in 50 hours than going full throttle on your 125

XD my uncles grizzley 660 has 250 hours and not a single oil change yet!

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I have a grizzly 700 and it runs BEAUTIFUL. however, responding to the topic of 450 vs 250. i feel that a 450 has much much longer gears and a 250 feels so short. the power on a 450 just gives you so much more potential 

Experience: 2010 Kx250f & 2012 Rmz-450

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A 250 will have around the same power as your 125 and theoretically more maintenance than the 450 because the smaller engine will wear itself out faster. (Smaller so it has to work harder)

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So in other words would the 450 have just as much maintenance as a 125 if your just using it for tooling around on the farm and a couple non professional track hits a year along with a couple professional tracks a year. Now don't get me wrong I treat my toys with extreme care and what I said about the oil was a over exaggeration I actually change it at normal times. What im trying to get at is am I gonna break the bank in order to own a 450 or am I gonna be able to treat it like a 125? I just cant get It through my head that you have to do all this crazy maintenance if your not going crazy on it.

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Any motocross 4 stroke will require valve checks/adjustments every 10-15 hours with casual riding, much more often if racing. Did you not change your top end in that 50 hours? I did my 125 top end every 35. I went from a 250f, to a 125. Mainly because I was spending more time on maintenance that I was on my 125. On the 125 it was a top end every 35 hours and a oil change every 5. However I just moved to a KTM 250sx and it would be better suited for your riding than a 125, and there are no valves to check and top ends last longer than on the 125s. But please, pay a bit more attention to your maintenance, an oil change is what? $5? And takes 10 minutes.

valve checks at 10-15 hours? Maybe on a junk Honda not on a Yamaha
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Checking the valve clearances is more of a preventative thing.  If you start seeing them creep out of spec you can fix it before you have any issues.

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do you really have to do a ton of maintenance if you really aren't pushing a bike to its limits?   

 

if you're too lazy to do maintainenance 1. Post your info on here so I can never buy a bike off you and 2. Avoid performance 4 strokes like the plague.

 

It doesn't matter how you ride them, they have to be meticulously maintained unless you want to spend $3000 every 6 months rebuilding it. A 450 is only in theory more reliable because of the way they get ridden. Most 250f's get their necks wrung and spend most of their lives at high rpm or on the rev limiter but you'd have to be a pro to ride a 450 like that. 

 

Stick with your 2 stroke. 

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if you're too lazy to do maintainenance 1. Post your info on here so I can never buy a bike off you and 2. Avoid performance 4 strokes like the plague.

It doesn't matter how you ride them, they have to be meticulously maintained unless you want to spend $3000 every 6 months rebuilding it. A 450 is only in theory more reliable because of the way they get ridden. Most 250f's get their necks wrung and spend most of their lives at high rpm or on the rev limiter but you'd have to be a pro to ride a 450 like that.

Stick with your 2 stroke.

You might wana check out the Yamaha forums everyone gets 200+ hours out of their motors before anything needs to get done

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You might wana check out the Yamaha forums everyone gets 200+ hours out of their motors before anything needs to get done

my grizzley 660 has 242 hours on it. It's my dads but i use it to mess around with and we've yet to change the oil! :D haha

:edit: ive put maybe 30 hours on my bike and change it about every 30 lol

Edited by YZF_MX_rider

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You might wana check out the Yamaha forums everyone gets 200+ hours out of their motors before anything needs to get done

 

Thanks for the info bud. Don't know what I woulda did without it.

 

Yeah, those guys maintain their stuff. I had a YZ250F, I too got about 150 hours before I had to open the motor up but I changed the oil every other ride, I adjusted my valves every 15 hours aprox and I changed the top ends frequently. 

 

4 Stroke race bikes require maintenance, if they are not properly looked after it's not about IF, it's a matter of WHEN they will grenade themselves and take everything with them. 

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my grizzley 660 has 242 hours on it. 

 

Not even close to comparable. 

 

4 stroke race bikes are a totally different thing and you can't compare the two. They may share similar designs but nothing about them is alike. But yeah, change the oil. It doesn't look cool to say you never changed it, it just makes you look stupid. 

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Not even close to comparable.

4 stroke race bikes are a totally different thing and you can't compare the two. They may share similar designs but nothing about them is alike. But yeah, change the oil. It doesn't look cool to say you never changed it, it just makes you look stupid.

i know I know and I know. I was just putting that out there! My dad forgets a lot. And I know the engines of a 230 and a 250f are completely different and for different styles. I was just putting that out there.

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