WR450F Max hours on engine?

[Adamridesorange]

If you take a look at this thread, people are telling me completely different things about when to rebuild a WR...why is it you guys are getting so much..? https://www.thumpertalk.com/topic/1072867-when-to-replace-wr450f-piston-and-rings/

[Hans Schmid]

I would believe 300+hrs easily on a WR...

[Adamridesorange]

And does that go for modded and stock? In my mind I believe a stock WR only running the horsepower of a xr 400 would be just about as reliable as the XR, but once you open up the WR motor and let it breath allowing a lot more horepower, heat, and rpms, it wouldn't last quite as long..maybe 200hrs? What do u think?

[Hans Schmid]

And does that go for modded and stock? In my mind I believe a stock WR only running the horsepower of a xr 400 would be just about as reliable as the XR, but once you open up the WR motor and let it breath allowing a lot more horepower, heat, and rpms, it wouldn't last quite as long..maybe 200hrs? What do u think?

I would believe 300+hrs easily on a uncorked WR. I have a uncorked 500exc with over 300hrs on the stock motor and I consider the WR even more reliable...

I remember my dad mentioning he met a guy down in South America with a WR with something crazy like 50k miles on the stock motor...

[GuyGraham]

Mine now on 350hrs and i decided to change piston & rings and it had started to burn a little oil

IT looked pretty good inside and I think I will go>400hrs on the new piston

The bike is used for Xc/H&H races and had 6900 off road miles on it - see earlier post

[Adamridesorange]

alright cool...and 50k must of been all street? and still thats hard to believe.. but what makes a wr450 so much more reliable then all the other 450s, even a yzf450 for that matter, which needs a top end around 150 hrs in the same conditions...i mean the WR is still a high revving, mx style motor with a little slipper piston with barely any skirts which start to rock in the bore if ran past the service limit...thats why i was thinking that they are the the most reliable stock, because they arent putting out much power for a 450.. but whats the other secret to this motor...less compression then others? different piston design? doesnt rev as high? what is it?

[Adamridesorange]

and at 350 hours was your rings out of spec? and your piston? is yours stock or fully uncorked?

[grayracer513]

.. but whats the other secret to this motor...

 

 

A sound design executed in quality materials without compromise, stressed to nowhere near its limit.  Simple as that.

 

Taking an average of 48 MPH, 500 hours is only 24000 miles.  By comparison, my truck has over 4250 hours on it. 

[Adamridesorange]

  but i mean the design isnt any different than say a crf450 and if your using an aftermarket piston such as wiseco, its the same part...but the yamaha somehow lasts alot longer..? the old XRs had big slug type pistons that ran at low RPMs and lasted a long time, but the WRs and other high performance 4 strokes have little slipper pistons with very small skirts running at high rpms, and more compression..  

even tho you guys are running 300+ hours, when do the rings actually go out of spec, is it more like 250 hrs when they go out of spec? for example i ride a ktm 2 stroke which are known to last a long time..and at 200 hours the rings are usually just out of spec for the riding i do, but that doesnt mean i couldnt ride it alot longer with worn out rings, as alot of people do..i was reading one forum where somebody had 600 hours on the stock piston and rings in a ktm 300 2 stroke...

[SteveThe Snakes]

 I think you should be comparing the pistons to modern street bikes with slipper pistons that also rev to the moon and last. Also Yamaha uses a three ring piston. Honda uses a two ring even in the CRFx.

[Adamridesorange]

but also a street bike has 4 cylinders compared to 1 doing all the work...and is the after market pistons for WRs three ring?

[Hans Schmid]

Adam, I don't understand your argument.... Grayracer513 explained it with the answer being quality of materials and build....

[SteveThe Snakes]

but also a street bike has 4 cylinders compared to 1 doing all the work...and is the after market pistons for WRs three ring?

 

One piston three ,six don't think that's what wears them out. Aftermarket pistons come in two and three ring pick your choice. It's not piston problems that plague the CRFx and r it's the valves. Yamaha has an excellent valve train system and that's what usually wears out in a four stroke.

[SteveThe Snakes]

A sound design executed in quality materials without compromise, stressed to nowhere near its limit.  Simple as that.

 

Taking an average of 48 MPH, 500 hours is only 24000 miles.  By comparison, my truck has over 4250 hours on it. 

Your right I think a WR,YZ based motor can achieve a reliable 60 hp.

[Adamridesorange]

ok i see...but people still repace the piston and rings alot in the new modern, high revving 4 strokes...in the 250fs they replace them just as much as 125 2 strokes... what im trying to say it that honda and yamaha or any other brand all use high quality parts, but it seems that the yamaha piston lasts alot longer.. a buddy of mine has a crf250x and trail rides it, and maintains it very well...and he can barely get 60 hrs out of a set of piston and rings..

[GuyGraham]

and at 350 hours was your rings out of spec? and your piston? is yours stock or fully uncorked?

 

Fully uncorked

Didn't bother checking rings / bore as I had already decided to replace piston have a replated

[grayracer513]

Your right I think a WR,YZ based motor can achieve a reliable 60 hp.

The head is the limiting factor.  It's extremely difficult to get a real 60 RWHP out of the 5 valve setup because of complexities that develop related to the 3 valve intake port.  The area at which the three ports diverge from one is very, very critical, as is the two different shapes the center and side intake pockets have to have.  It has been done legitimately on 450cc gasoline engines by only a small handful of people. 

 

OTOH, snow sled types have turbo-charged the same basic engine to upward of 100 hp without them flying to bits constantly, and the 2014 model (4 valves) comes right from the factory breathing 58 HP already.  Compared to what the engine is capable of, the WR450 starts to look more and more like the small block 350 in my Silverado; way tougher than need be for its job.

[GuyGraham]

. but what makes a wr450 so much more reliable then all the other 450s, even a yzf450 for that matter

 

 

type of use?

An mx bike is ragged to an inch of its life, but even though I'm racing my WR, its not getting anywhere near the abuse it would get if it were being used for mx

[grayracer513]

... what im trying to say it that honda and yamaha or any other brand all use high quality parts, ..

Why do RM450's have more transmission trouble than the WR?   Why did Honda have such a long history of munching valves? 

 

 

Maybe they don't all build to the same level of quality? 

[GuyGraham]

You are deluding yourself if you think 'high' quality parts are used in production bikes - they are all built to a price

 

The Japanese are very good at designing / making the stuff so that it is just good enough to do the job, and hence the cost is kept to a minimum.

When they get it wrong, you get situations like CRF valves

 

Over engineered components is just wasted cost to them

Edited March 12, 2014 by GuyGraham