Four stroke mx bikes

[Snox90]

I'm curious as to what the life expectancy is on a four stroke motor. I'm interested in a 250 fuel injected bike. Brand new. Not sure if I should just stay on a 2t or make the switch.

[Snox90]

I also understand u gotta check valves. How often do they need adjusting? If I keep them in spec and regularly change oil and air filter will I get many years of riding?

[Bill_B]

I have a 2007 CRF 450R with 255 hrs on it, I'm a vet rider and pretty much ride mostly MX. Lot of guys sell a bike when it hits100 hrs. I've checked my valve clearance probly only 4 times over the 7 years I've had the bike and they are still within spec. I've only had 1 major thing go wrong, last year the counter shaft bearing broke witch was a full case split to fix it.

[hawaiidirtrider]

I'm curious as to what the life expectancy is on a four stroke motor. I'm interested in a 250 fuel injected bike. Brand new. Not sure if I should just stay on a 2t or make the switch.

What kind of 2 stroke are you riding now? ..and what 250 fuel injected 4 stroke are you interested in?..and what 2 stroke new 250 would be what you might get if you don't get the 250 fuel injected 4 stroke? .. also there are tons of 2 stroke vs 4 stroke threads to check out.. just put a search here on TT and click forums.. There's a bunch of information already there for you to look over... there's also carb vs efi threads too.... 

[pomoco]

There's no need to check the valves often if it is starting right up and running good. Most will tell you that once the valves need adjustment that they will soon need replacement. 135 hrs. on a Honda 150rb, nothing but routine maintenance, never checked the valves, 110 hrs. on my Honda 450r, just checked the valves because I felt guilty. They were fine. Changed my piston at 60 hours based on what I've read. It looked perfect. I switched to 4 stroke two or three years ago and have had great luck. I was always going into our smokers.

[Snox90]

Hawaii dirt rider I currently have a kx 125. 2004. I'm in the process of a top Nd bottom end rebuild. Whole thing is 315 dollars in parts. That's cheap. Ive had my eye on an rmz250 at the dealer. The 2015s are cheap now and I like the idea of fuel injection. I'm just worried about maintaining the thing. This might be a stretch but I'd only buy a 4t if I could get 5 or more years of use out of it before any major repairs. I'd obviously do routine maintenance like its a religion. I'd take every step necessary to prevent serious engine problems. I'm also looking into the Yamaha yz250. It's a 2t. I just like the fact that a full tank of gas on the rmz will most likely last twice as long as a two stroke. The pits I ride are huge and by the time I get to any good spots I gotta turn right around to go get gas.

[hawaiidirtrider]

Hawaii dirt rider I currently have a kx 125. 2004. I'm in the process of a top Nd bottom end rebuild. Whole thing is 315 dollars in parts. That's cheap. Ive had my eye on an rmz250 at the dealer. The 2015s are cheap now and I like the idea of fuel injection. I'm just worried about maintaining the thing. This might be a stretch but I'd only buy a 4t if I could get 5 or more years of use out of it before any major repairs. I'd obviously do routine maintenance like its a religion. I'd take every step necessary to prevent serious engine problems. I'm also looking into the Yamaha yz250. It's a 2t. I just like the fact that a full tank of gas on the rmz will most likely last twice as long as a two stroke. The pits I ride are huge and by the time I get to any good spots I gotta turn right around to go get gas.

I'd say read a bunch of threads from TT searches and see what you think. Make up your own mind. How much would it cost if the 2 bikes you mentioned would blow up or give trouble.. Those kinds of questions are part of your choice.

[Snox90]

Well the two stroke I can do myself. Entire motor for bout 300 bucks. If the four were to need work I couldn't do it myself. I kno a Complete overhaul would be over 2000 bucks at garage. I'm reading through the forums and am having a hard time finding anything I want to hear. My two stroke is good for about two or more years before it needs any major work. I always hear how the four strokes last longer but I can't find any proof. Keep in mind I ride 3 to 5 days a week for about 4 or so hours. If I got the day off might be riding 6 or more hours. In a nutshell: I want a four but I need to hear from people they are mechanically worth it in the long run. Most likely I'll stay on a 2 t but I really want to go four for the technology behind them.

[leafsrule16]

Unless you need the smooth power for some racing advantage on a track, stick with your 2 stroke. You're riding a lot of hours and they're not worth it. $ for $, a 2 stroke gets you a lot more riding. Plus you already have one so.

[Snox90]

Yeah. Regardless I'm getting a new bike. At this point it is going to be another two stroke. They are just way too cheap and easy to work on. I've been searching very hard to find evidence that a 4 t is as reliable but I just can't find the proof. Thx all for the input

[shrubitup]

Yeah. Regardless I'm getting a new bike. At this point it is going to be another two stroke. They are just way too cheap and easy to work on. I've been searching very hard to find evidence that a 4 t is as reliable but I just can't find the proof. Thx all for the input

Seems to me the four strokes can go abt double the life of smoker pistons so that's money saved up for the eventual head repair bill with new valves and seats cut once they zero out. If you are freak crazy religious about clean air filters (and make sure intake boot remain clean while removing dirty filter) and change motor oil often then a RMZ250 should go about 100-120 trail riding hours before needing a new piston and possibly a cam chain. MX change intervals will be less obviously. Once you get comfortable with the four stroke maintenance things such as cam chains, pistons, valve adjustments, etc will be easy but you're right you can't cut the seats for new valves yourself. That's why some just buy a new head when needed. 

 

You add in the price of pre-mix and compare that to quality motor oil for the four strokes and you're about the same price consumption wise. Either one if ridden many hours will cost money to keep rolling. 

[hawaiidirtrider]

Well the two stroke I can do myself. Entire motor for bout 300 bucks. If the four were to need work I couldn't do it myself. I kno a Complete overhaul would be over 2000 bucks at garage. I'm reading through the forums and am having a hard time finding anything I want to hear. My two stroke is good for about two or more years before it needs any major work. I always hear how the four strokes last longer but I can't find any proof. Keep in mind I ride 3 to 5 days a week for about 4 or so hours. If I got the day off might be riding 6 or more hours. In a nutshell: I want a four but I need to hear from people they are mechanically worth it in the long run. Most likely I'll stay on a 2 t but I really want to go four for the technology behind them.

So you know whats out there... get a 2 stroke 250 and a big tank. I rode a cr 250..it sucked gas more than I liked so I got a big tank and rode it for over a decade...bike was and is awesome..a friend is still riding it... a 250 2 stroke is a world different than your 125.. and you should transition well..

[hawaiidirtrider]

This kind of illustrates it for me.. but that's me.. everyone is different on what they like.