used 05 crf450 needs a good once over

[Muroc]

basically all i have to say is that if your done patronizing me and you would like to help me build this thing for longevity it would be appreciated.

I'm sure they'll be lining up to have you as a customer. :rotfl:

 

[Ol'89r]

Ol89r's shop would be an excellent choice.

Thanks, but no thanks.

 

[Rich Rohrich]

Thanks, but no thanks.

I've regretted posting that for a couple of days now. :bang:

Money is too expensive when gotten that way.

 

[Ol'89r]

. Something is wrong here when the same manufacturer produces two ohv engines and one has one tenth the service interval. Sounds like you need ss valves and stiffer springs to fix a valve float issue. On top of the fact that people have seen longer service intervals by running the valve lash tighter than hondas "recommended" specification. Sounds like Honda triple f$@*#d up crappy valves, crappy springs and a bad specification because they probably cheeped out on R&D.
.

Honda hardly "cheeped out on R&D". In fact, they held the first year/model over for a year to do more R&D. While Yamaha was selling their new 400F, Honda was busy doing R&D. Your logic on the difference between a multi-cylinder engine and a single cylinder engine doesn't make sense. Your math is even more confusing. :coocoo:

Honda gave us exactly what we asked for. A lightweight, powerful engine in a modern MX chassis that hooks-up to the ground. In order to do this they had to build what amounts to a single cylinder F-1 engine. The technology in this engine is amazing. Unfortunately, with technology, comes expense. Also, a more intense maintainance schedule. I also ride a CRF450 and it is without a doubt the best motorcycle I have ever owned. It does everything and it does it well.

If the CRF is more trouble than you want to deal with then, sell it and buy a two stroke or an older XR. Yamaha and KTM are still making and selling two strokes and there are many good used XR's available. No one is forcing you to ride a CRF.

If the CRF is properly maintained, it will give you many miles of dependable service. If you go to the expense and trouble of installing the Kibblewhite valves, (as was mentioned in the second post of this thread), you won't have to worry about sucking a valve and damaging your head and that will give you the longevity you are looking for.

Good luck. :cool:

 

[holeshot]

The main difference between a street bike and a dirt bike - is *drumroll* - the dirt bike is ridden in the dirt. This is the main reason that valves don't last as long. Plus, you want a really compact, lightweight head on your dirt bike (gotta be just like the pros, ya know) and you need Ti valves to squeeze that little extra horsepower, just so maybe you can sneak past your buddy in the Nervous class.


So, if you crash, it knocks your valves out of adjustment? :rotfl: :rotfl: :rotfl: Please...entertain us some more. Ol'89r can knock your valves out of adjustment just by looking at your bike hard. It's all his fault.

 

[Patman]

Man if valves got out of adjustment from dropping a bike I'm in BIG trouble! That might also explain why JBS has so much trouble after a crash, his valves are out of adjustment :laugh:

The way I see it you either need to stop taking advice from whatever other forum you are getting these little nuggests from or go ask them how to fix your problem and then live with the results of that advice. If you only had a clue of the resources you have commenting on this very thread. :|

 

[motometal]

While I don't agree with all of the numbers and logic thrown out here, I have had some thoughts along the same lines.

Example (these are rough numbers):
1000 cc sport bike
155 hp to the rear wheel (stock)
250 cc per cylinder
13,000 rpm redline
That's 38.75 rear wheel hp per 250 cc cylinder, not a lot unlike a 250F BUT...Many of these sport bike engines don't even require a valve adjustment at their 15,000-20,000 mile 1st checkup. And as mentioned, they do it with those low tech, heavy steel valves.

How much of a factor of reliability, or power is gained with four cylinders vs. one? Other than that, I can't see why the big difference sport bike engine vs. mx.

I understand dirt wears out vavles but are we really saying that a CRF with diligent filter service ridden in non-dusty conditions (negligible dirt/dust entering the engine) would last as long as the street bike engine? I highly doubt it. Some of the MX bike failures are cyclical fatigue, not wear.

 

[_JOE_]

I understand dirt wears out vavles but are we really saying that a CRF with diligent filter service ridden in non-dusty conditions (negligible dirt/dust entering the engine) would last as long as the street bike engine?

No, dirt bikes are ridden in a completely different manner and subjected to much different stresses than a street bike. In the dirt you go from off throttle to rev limiter while throwing a roost constantly. The tire hooks and slips constantly. On the street there is a consistant load under consistant throttle. Not to mention the dirt getting in the motor, which can happen even if the air filter is well maintained......









And I think I peed a little when I read the bit about accident induced valve train damage! :)

 

[motometal]

good points there. I suppose considering most sport bikes are ridden at steady throttle/highway miles a good portion of the time, I would think this would be at about 1/2 the rpm of redline, or less. The average engine speed of an MX bike might be higher.

Are the valve seats affected by load? I would think this would be more like cyclical fatigue

 

[Papakeith]

I think another consideration is that the engine in a MX bike isn't intended to last forever. It's a race engine. It is the lightest it can be made without grenading (hopefully). Sure they could make it an XR engine that would last forever, but I imagine that there would be a considerable weight penalty that racers wouldn't want.

 

[IndyMX]

Sure they could make it an XR engine that would last forever, but I imagine that there would be a considerable weight penalty that racers wouldn't want.

Which is why you never see an XR on the track I suppose...

 

[dirt bike dave]

How much of a factor of reliability, or power is gained with four cylinders vs. one? Other than that, I can't see why the big difference sport bike engine vs. mx.

The extra displacement will let you run a much more radical cam in a 1000cc 4 than you could in a 250cc single. So the big bike can put out superior hp/liter numbers.

The 250cc race single will be under full throttle much more of its life than the 250cc cylinders in the liter sport bike, so the little MX bike is more stressed more of the time.

The emphasis on light overall bike weight and getting the best hp possible out of a small single is why the MX bikes are so much more maintenance intense. IMO, the bikes simply would not sell if they weighed 5 pounds more and made 3 hp less, even if they never needed a valve adjustment.

 

[helio lucas]

plus, a 4 cylinder exhaust can be more efficient than a single exhaust per cylinder even more with exhaust valve (like yamaha exup), the same on inlet side. not to mention friction losses and some other things that are just too ***** to compare.

the valve out of adjustment thing has an explanation: the guy bent his frame and since the head is fastened to the frame it bents as well. simple, then just adjust the valves and you ready to go.

, then you probably should stick to two-strokes.

If the CRF is more trouble than you want to deal with then, sell it and buy a two stroke

i know this is the thumper forum but no need to speak in a depreciatory way of smokers like that. i still like them :fft:

and ol'89r, never look again to my bike please. despite my bike is a two stroke without exhaust valve you may well throw my ports out of spec. and no... don´t even think on my bike!!!
but you may think in gomer hard and throw his exhaust valve out of adjustment :uh:

mxcrazed, the fact that you have bought a 250 km/h bike that has crashed at least two times tells a lot of what you look for in your bikes. you may need a quad. :ride:

 

[IndyMX]

mxcrazed, the fact that you have bought a 250 km/h bike that has crashed at least two times tells a lot of what you look for in your bikes. you may need a quad. :ride:

Effing Priceless!!! ;)

 

[_JOE_]

mxcrazed, the fact that you have bought a 250 km/h bike that has crashed at least two times tells a lot of what you look for in your bikes. you may need a quad. :ride:

:rotfl:

 

[whenfoxforks-ruled]

"Can you take this motorcycle back that I bought yesterday Mr. Motorcycle dealer, I do not know how you stand all that wind in your face?" Aye Ca-rumba! I did lose the beating the dead horse gif, sorry. And of all the odd things people do, has anyone ever actually set up a CBR600 for MX? No way it would last 15 minutes imo, with a A-class teenage racer, but fools with tools are everywhere! Vintage Bob

 

[_JOE_]

I've seen videos of sportbikes in the woods, no mx tracks though......

 

[Patman]

I've seen a BMW street bike on a MX track... with Gomer riding it.

 

[whenfoxforks-ruled]

I have seen the Dakar bikes and such. But a road race bike? What does a new engine go for? Gomer in a tutu on a BMW?

 

[_JOE_]

Gomer in a tutu on a BMW.......with a cape?

 

[Papakeith]

I've seen Doug Henry do a lap at Southwick on a street bike

 

[Ol'89r]

and ol'89r, never look again to my bike please. despite my bike is a two stroke without exhaust valve you may well throw my ports out of spec. and no... don´t even think on my bike!!!:

Hey Helio.

I just telepathically lowered your transfer ports 2mm's. :nener:

Naw, really, I can't do that. Although my wife timed a set of cams for a guy over the phone once. :nod:

In defense of the original poster, (if he is still here) ;) I guess you could knock your valves out of adjustment if you crashed your bike and the throttle got pinned wide open. That is about the only thing I can think of that would affect the valve adjustment.

In regard to making your bike dependable, the 15 hour replacement on the piston and most of the other maintainance schedules given in the manual are 'Worst Case Scenario.' Or, in other words, if you are a pro rider and you keep your bike pinned against the revlimiter the whole way around the track, then you should adhere to the strict maintainance schedules spelled out in the manual. But of course, if you are a pro rider, you probably have someone that maintains your bike for you and all you have to do is worry about is showing up at the track on time.

BUT, if you are the average rider that playrides or races in amateur events, you will have to determine your own maintainance schedule. Your piston will last much longer than a pro riders piston will. Your valves will not have to be adjusted as often and if you install the SS valves, your valves will probably last until you sell the bike. Other things can be done like adding a coolant recovery system that will make the bike more trail worthy along with a RevLoc clutch.

One of the best additions to your bike would be a Hour Meter. These are inexpensive and will tell you how many actual hours the bike has been ridden. By paying close attention to your hour meter and the wear on certain parts in your engine, you can determine your own maintainance schedule. This requires tearing down your bike periodically to inspect and measure the wear. After you do this a few times, you will be able to determine how often these parts will need replacement. You need to keep a notebook and write down everything you do to your bike and at what hour on the hour meter.

IMO, these new four strokes are getting a bad rap because there are too many people buying them that really don't belong on them. Very few riders can ride them (450's) to their full potential and many don't seem to want to take the time to maintain them. So, as a result, we keep hearing how Honda, Yamaha, Suzuki, Kawasaki, KTM, (pick one) sucks for building them for us. :bang:

 

[Ol'89r]

Gomer in a tutu on a BMW.......with a cape?

I've seen Gomer in a tutu on a Suzuki at Elsinore. :yikes: He forgot his cape though. ;)

 

[2strokerfun]

I've seen videos of sportbikes in the woods, no mx tracks though......

There was a pretty good video couple years ago with some really good MX rider on an XR650 smoking someone on a 450(I think it was a 450) MX bike. Loved the brake light coming on before every corner!! Can't see vids on work computer anymore (being held down by The Man here), so I can't find it to post the link.

 

[_JOE_]

I saw that! I think someone posted on here.