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CR450 piston design
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Posted by: Buzz Bomb---------------------

I have heard from a number of people that this bike's piston is not going to last long at all. Honda recommends changing it after 17 hours of use. That's more frequent than most two strokes! The people I've heard from (others sites and a Honda dealer) all insist that the pison will rock back and forth in the bore since it is "skirtless." I've also heard of someone's 450F linkage bearings seizing after 2 hours of use! Honda quality isn't showing here.

Posted by: J.B.426---------------------

I'm certainly interested in seeing how the bike holds up over time. 17 hours sure is a short amount of time between piston changes for a 4 stroke, although the manufacturers usually do recommend more maintenance than most will need to follow. They are usually very conservative in that respect.

Here is quote from dirt bike magazine regarding the short skirted piston. "The piston has almost no skirt; even less than a YZ426F’s. Honda engineers say that it has no tendency to rock in the cylinder because the crank is offset 8mm to the rear of the bore’s centerline."

We'll see what happens as everyone gets the hours put on their bikes. I wouldn't bet on any major problems though. I don't know about the maintenance, maybe more will be in order for this bike.

Posted by: CanadianRidr---------------------

Quote:

Honda quality is not showing here

But you have to wait until these things actually start happening, the key in your post in, so and so says and this person said so before we judge we should probably wait and see what happens. Isolated incidents are usally made to sound worse than they are, but if something bad like this does happen Then shame on honda!

Posted by: DualSportr---------------------

What's the suggested replacement period for a YZF piston? 20 hours??

The CRF does have a skirt, the front and back of the piston appear to be about the same height as a YZF piston. Side skirting does absolutely nothing for piston life, so the lack of side-skirts on the CRF piston won't change reliability issues.

As stated about a billion times before on dirtrider.net, don't believe ANY so-called technical babblings of the magazines. Their statements regarding possible piston life issues on the YZF have proven false over the last 4 years. I belive the same will hold true of their worries on the CRF.

I guess the main thing to keep in mind is that the replacement regimen for the YZF and CRF are designed for the Pro MX'er. If you are planning on using this bike as a play machine, or ride at less than expert level, as they say, 'your results may differ'. We've seen many a YZF 400 that is just getting it's first rebuild now. All of them have well over 100 hours of use, and most are still in decent condition when disassembled.

Just ask yourself, how many non-racing CR250 or YZF 426 riders follow the parts replacement schedule for their bike? What, maybe 20%? Probably less than that. Reliability is excellent on these bikes, in spite of folks riding them into the ground and selling them 3 years later with nary a rebuild.

There will always be exceptions to this, but on average, reliability is beyond excellent for modern two and four strokes. We're really spoiled by the longevity provided by new designs, technology and metallurgy.

Posted by: huffa---------------------

Thats highly possible being that the bearings and steering stem come with little grease on them from the factory. This should be done or at least inspected before riding. Have a buddy that says his makes a noise when pulling in the clutch - how many out there have the same thing. How is coolant holding up? Anyone have it pushing out the overflow or is it acting normal? Lets get more details on suspension. whats a good set up for someone 185lbs on outdoor tracks thats a average rider? How many satisfied with the stock settings. For how many are sold seems like not a lot of feedback so far.

Posted by: Buzz Bomb---------------------

Quote:

Originally posted by DualSportr
Just ask yourself, how many non-racing CR250 or YZF 426 riders follow the parts replacement schedule for their bike? What, maybe 20%? Probably less than that. Reliability is excellent on these bikes, in spite of folks riding them into the ground and selling them 3 years later with nary a rebuild.

I agree with this statement. My CR250 has over 60 hours on it and its getting it's first top end rebuild. I'm only doing it cause the bike is apart and I won't have to do it again for a while. My friends CR250 has over 100 hours on the original top end, and he does virtually no maintenance. It still runs strong. Hopefully the CR450F will be the same because next year in 2003 I'm going for either another CR250 or the 450F.

Posted by: J.B.426---------------------

Well put DualSportr,
That's kind of what I was getting at. I couldn't remember what my 426 manual recommended for changing the piston, but I know it recommends changing it much more often than what mere mortals need to.

Posted by: marcusgunby---------------------

The only shedule thats reasonable is that for a 125-10 hours for a expert rider is about right on a piston.Ive read a 250f should have a top end job every 12hours-how many have head one i wonder-makes me glad i have a 2 stroke.These low maintenance 4 stokes we were told about sure need alot of looking after

Posted by: MotoGreg---------------------

I got my YZF in Feb '99. Since then I've ridden twice a week, mostly MX but also a lot of long (80-100 miles) dual-sport rides. I've never touched the piston and see no reason to. The bike still has incredible power, as much as it did on day one. It doesn't burn a drop of oil either. All I do is change the oil (Mobil 1) every 10 or so rides. I've checked the valves a couple times but they are always in spec. When the bike was two years old I figured I'd change the plug because I'd never changed it, when I pulled the old one out it hardely looked used, the center electrode wasn't worn down and it still had a nice sharp edge to it.

As far as I can tell, these things are practically maintenance free, the only part I've had fail was the seal for the water pump shaft.

Posted by: OZ_dirtrider---------------------

CRF piston wear....do you change tyres everytime you ride, the full potential life of a motorcross tyre is only a few races isn't it?

If you ride like Jeremy McGarth or Steffan Merriman, then you should be in the AMA or World Enduro Championship.

Totally agree with Dualsportr, magazines beat up bikes and their maintenance/part wear of the assumptions that we are all sponsored motocross/enduro pilots. Heck, the majority in this list probably only ever go to see these events and rarely compete at the highest form, even at club level, we don't push the bikes to the extreme that the top riders do.

In saying this, if you do race then you should maintain the bike more frequently then the average weekend rider - if you don't then you only have yourself to blame when the bike doesn't fireup.

Like everything mechanical in this world, general maintenance/inspections and it will last forever. Ride it, abuse it, ride it and abuse it somemore without bothering to do any maintenance - I'd say more money than brains.

J

01 TE400
00 WR360
92 KDX250

Posted by: MotoGreg---------------------

Quote:

every 10 or so rides? if you are doing mx you should change it every ride especally on a 4 stroke. your goin to blow it up

It's been going strong for almost three years, there is no sign of a problem, it runs as good as the day I bought it, I doubt it will "blow up". Last time I checked the valve adjustment I pulled the cams to look for any wear on the journals and it looked like new. Mobil 1 is synthetic, it doesn't break down as quickly as petroleum oils. Also, I don't use (slip) the clutch very much so I don't get all the clutch fiber contamination in the oil.

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CR450 piston design

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