Long term reliability of modern four strokes

newmann
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6/15/2018 1:44pm
newmann wrote:
Although I haven't read this whole thread, I'm guessing a good bit of it is guys comparing 450's to 125's on top end rebuilds instead of...
Although I haven't read this whole thread, I'm guessing a good bit of it is guys comparing 450's to 125's on top end rebuilds instead of 500 2 strokes.Laughing

I'm impressed with the 05 CRF story. My 01 YZ250F and my son's 04 CRF250 are still here as reminders as to why you don't buy 250F's but those new KTM's and Husky's keep calling out to me! How is the reliability on those these days?
GrapeApe wrote:
You bought the first year model ever for the YZ250F, and was surprised it had problems? Then followed it up by buying the first year model...
You bought the first year model ever for the YZ250F, and was surprised it had problems? Then followed it up by buying the first year model ever for the CRF250, expecting, better? Believe it or not, they have made some advancements in reliability over the last 17 years.
Actually, the 2006 YZ250F was worse. So bad that they issued a recall for bad heads and valves. And according a lot of "experts" here, the KTM's are junk. And the new Yamaha frames break with amazing regularity. Someone even posted up a broken Honda frame the other day. How many people switched out their air forks to springs? The newer, better and more reliable they get, the more problems they seem to have.Wink
coastie44
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6/15/2018 7:47pm Edited Date/Time 6/15/2018 7:49pm
I wouldn’t trust a modern four stroke with over 300 hours on a motocross track. The modern bikes roughly 2009 and up have gotten lighter with smaller bolts, slimmer castings etc. They aren’t built for 300 hours of full on Moto. I think after about 150 hours, they should be retired for desert or trail/Enduro riding.

I have had 8 450’s (one was a 426) since 2001. I’ve put 120-130hrs on 4 of them, and 40-50 on the others. I’ve never had a single engine failure. In fact not a single unexpected failure of anything except flat tires. I’ve had every brand except Suzuki.
Flip109
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6/15/2018 8:23pm
It’s very cool these bikes are lasting so long. But on the other hand who the hell would trust a 100 Plus hour bike going around a track with jumps and stuff. Much less a 300 hour bike. People are cray cray lol
user760a
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Shelby, NC US
6/15/2018 9:23pm
do we all realize that 100 hours is not jack shit on any other type of machine? are we all just twisting it so hard, we are all such bad asses that at a point when any other type of machine would still be considered brand new (100 hours) we sheep think that its tired junk? ridiculous lol
1

The Shop

999
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6/15/2018 10:07pm
How could you afford to buy a new bike every 100 hours? That's insane. Fresh bike every year? And if it's not "trustworthy" after 100 hours what do you do, just throw it in trash?
MSM
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6/16/2018 5:48am
Is a modern 450 engine actually more reliable mechanically, or is it just the nature of how you ride them compared to a 250f?
MSM
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6/16/2018 6:08am
999 wrote:
How could you afford to buy a new bike every 100 hours? That's insane. Fresh bike every year? And if it's not "trustworthy" after 100 hours...
How could you afford to buy a new bike every 100 hours? That's insane. Fresh bike every year? And if it's not "trustworthy" after 100 hours what do you do, just throw it in trash?
I'm not wealthy buy any means but It's quite easy to get a fresh bike every year. The hardest part is getting the first one. I put down a big down payment, and make triple payments. Buy the end of the moto season, (far less than 100 hours) I can sell the bike for far more then I still owe, use the remaining cash for down-payment on the freshie as well as some savings if I choose. The key is never allowing yourself to owe more than your bike is worth. I'm also lucky enough to run a series that has pretty considerable contingencies, even for a C guy like me. I'll be switching manufacturers next season for this reason alone. Hard to ignore the fact that Honda pays 75$ for an overall win for vet C class, Every single round.

Woods Guys have it pretty rough thought, they can easily rack up +150 hours in one season. Also if you live in an area that at allows you to race 12 mouths out of the year it can be pretty difficult as well.
MX915
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6/16/2018 6:12am
MSM wrote:
Is a modern 450 engine actually more reliable mechanically, or is it just the nature of how you ride them compared to a 250f?
I would say it defintely has part to do with how you ride. A 450 is peaking at 8-9000 RPM where a 250F is 12-13000. Thats a lot more revolutions of every gear, crank, piston, clutch abuse, etc.

Fundamentally, the design is pretty much the same. Look at the YZF engines. If you put 250 and 450 side by side, most probably couldn't tell the difference other than physical size.
6/16/2018 6:12am Edited Date/Time 6/16/2018 8:08am
user760a wrote:
do we all realize that 100 hours is not jack shit on any other type of machine? are we all just twisting it so hard, we...
do we all realize that 100 hours is not jack shit on any other type of machine? are we all just twisting it so hard, we are all such bad asses that at a point when any other type of machine would still be considered brand new (100 hours) we sheep think that its tired junk? ridiculous lol
Is the other equipment you speak of also purpose built racing machines? I didn't think so. I would never keep a bike for 100 hours, but it'd be 5 years old at that point anyhow. To each their own, but when I ride, a bike failure at the wrong time could mean the end. As expensive as bikes have become, they are way cheaper than medical bills.
mingham97
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6/16/2018 6:48am
And yet there are many thinking the sport needs to go with smaller engines. Brilliant.
Ted722 wrote:
If you're defining the sport as Supercross, then yes.
There is no need to have engines with a short fuse if you want to slow down racing. Restrictors.
In university FSAE, they have intake restrictions. You must compete with a 20mm intake restriction. The competition supply a type of washer if I remember correctly.
Ted722
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6/16/2018 6:51am
It's my opinion 4-strokes have come a long way. I got on and off the bandwagon with one bike. Everyone had gone or was going Honda by the time '05 rolled around. There were a few stragglers here and there and those that went another direction. That was me. The '06 RM-Z450 just spoke to me. Good handling, mellow/torquey power delivery, good mid-range, but not too much power and certainly not much over-rev, but you don't typically need that too much as a Vet on a 450 anyway.

Immediately, became one with the bike. Confidence inspiring and probably one of the best 4-strokes for a 2-stroke lifer to transition to. I was winning races, was religious on my oil changes, valve and manual timing chain maintenance.

At just 30 hours, started hearing a knocking noise. Got it checked out by a trusted shop (ironically the same shop who helped with the recent 2016 frame breakage thread). Connecting rod / crank bearing was going. Didn't catch it early enough. Oil pumps, Crank, Cylinder and other stuff repaired replaced. Wrote the $1,400 dollar check to fix, but I was never quite the same after that. Never had that kind of failure and dollar rebuild on a 6 month old 2-stroke in the 20 years prior of racing.

Did I get a lemon? Possibly. But, I did hear of other guys having the same early hour issues on their '06's and similar experiences from the repair shop too.

Ended up selling the bike and picking up a left over '06 RM250 for $4200 OTD in March '08. Had good racing results on that too. Great bike, but you definitely have to work a bit harder against those traction torque machines of the 450 variety.

For me, if I was to get another 4-stroke, it'd probably be another RM-Z450. Just speaks my language. Handling that I prefer, power delivery I prefer, more power than I could ever use, and the price is right. Plus it looks bitchin! I've had the MX-R on my radar too, but keeping another $5K in my pocket is appealing too if I went with the Zook.

I hear you guys here with your 100 plus hour / no issues experience with your 450's and if I had that from the get go, there's no doubt in my mind I'd still be enjoying the amazing torque / traction of a 450 outdoors.
dirtmike86
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6/16/2018 6:54am
If I had to rebuild my bike at 10hrs max I would rather beat my gentleman’s sausage with a beer bottle filled with gasoline.
Gentlemen's sausage!!? Fuck iam crying LaughingLaughing
mingham97
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6/16/2018 7:01am Edited Date/Time 6/16/2018 7:03am
Flip109 wrote:
It’s very cool these bikes are lasting so long. But on the other hand who the hell would trust a 100 Plus hour bike going around...
It’s very cool these bikes are lasting so long. But on the other hand who the hell would trust a 100 Plus hour bike going around a track with jumps and stuff. Much less a 300 hour bike. People are cray cray lol
People who have a tight budget, and decide to maintain a bike/engine for $1500 every 100 hours/2 years or so. That's all it takes. And maybe bearings all round every year or so and keep riding
Flip109
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6/16/2018 7:53am
Flip109 wrote:
It’s very cool these bikes are lasting so long. But on the other hand who the hell would trust a 100 Plus hour bike going around...
It’s very cool these bikes are lasting so long. But on the other hand who the hell would trust a 100 Plus hour bike going around a track with jumps and stuff. Much less a 300 hour bike. People are cray cray lol
mingham97 wrote:
People who have a tight budget, and decide to maintain a bike/engine for $1500 every 100 hours/2 years or so. That's all it takes. And maybe...
People who have a tight budget, and decide to maintain a bike/engine for $1500 every 100 hours/2 years or so. That's all it takes. And maybe bearings all round every year or so and keep riding
I was referring to the people that never open them up. Shoulda rephrased that.
6/16/2018 8:10am
Don't forget to replace the cam chains. I do every 25 to 30 hours. Some say nope. Cheap insurance
mingham97
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6/16/2018 8:56am
Flip109 wrote:
It’s very cool these bikes are lasting so long. But on the other hand who the hell would trust a 100 Plus hour bike going around...
It’s very cool these bikes are lasting so long. But on the other hand who the hell would trust a 100 Plus hour bike going around a track with jumps and stuff. Much less a 300 hour bike. People are cray cray lol
mingham97 wrote:
People who have a tight budget, and decide to maintain a bike/engine for $1500 every 100 hours/2 years or so. That's all it takes. And maybe...
People who have a tight budget, and decide to maintain a bike/engine for $1500 every 100 hours/2 years or so. That's all it takes. And maybe bearings all round every year or so and keep riding
Flip109 wrote:
I was referring to the people that never open them up. Shoulda rephrased that.
Oh lol that's way different haha
mx900
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Decatur, IL US
Fantasy
796th
5/29/2019 11:53am
I have both two and four strokes all yellow. With that said I have a 08 rmz 450 with over a 100 hours that's never been apart and it runs great still no
worries taking it to the track or racing it. I do change the oil every three hours along with the filter and check and clean the air filter every ride.

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