crf 450 making knocking nosie

[steveotimmy]

Was out rideing and I started hear a knocking nosie over the sound of the motor. What could that be and what should I be checking. Please help

 

[whenfoxforks-ruled]

What year is it, and what has been done that you know of, maintenance wise? Information about your bike is kind of important. Vintage Bob

 

[steveotimmy]

Its a 07. I've only have put 14 hours of ride time on and two oil changes. Don't know what was done before I got it.

 

[plynn41]

Knocking noises are not good. It could be a main or rod bearing going bad. I'd have an experienced mechanic look (and listen) at it if I were you. It would be far less expensive if you had to bite the bullet right now and replace the bottom end, than it would be if the rod/crank failed while you were riding it. And a good mechanic can tell you if it's nothing to worry about.

 

[Patman]

Your CRF is not like the XR's of old so it's going to require more love than one. My guess is if you bought it used that it is WELL past needing a top & bottom end. Until you have it figured out consider it a time bomb.

 

[originaldirt]

There is an "epidemic" of rod failures in 450's of all brands. Many riders who bought used never saw the factories generally recommend running 97 octane gas. Well you can't buy 97 pump gas so running 92oct or lower you will get "micro" detonation, that is maybe 1 almost undetectable detonation in 4500 to 45,000 rpms. "Micro" detonation rarely leaves a visible mark on the piston unless the whole motor grenades. If you look at the wrist pin with the naked eye it also looks like no damage, but with at least a 10x magnification you can see some discoloration from the rod bronzing de-laminating on the wrist pin.

You cannot fix or hide the problem messing with the F.I. program or the E.M box program. You pretty much are just delaying or accelerating the problem.


At the recent motor builders (cars, bikes, boats, etc.) conference in Ohio the main topic was detonation and how it is the most common cause of motor problems in all applications (especially in hopped-up J-model F.I. cars).

When that happens one of the roller bearings on the big end at t.d.c., you are going to get a damaged roller. That leads quickly to a damaged roller cage and then more damaged rollers. Bingo the crank is toast. This can happen in a new bike with less than 20 hrs. of use.

Be safe, run at least 100 octane fuel/gas. Yes you have to pay to play! Honda's and most other J-model fuel injected bikes seem to be more susceptible to this problem. 250's also need at least 97 octane!

I have one pro-rider friend who blew three '10 RMZ450 cranks in 7 weeks, before he found that his Dad was trying to save money by mixing VP U4.4 with 92 pump gas. Well, U4.4 is roughly 97 octane, but mixed with 92 it was a time bomb arrangement.

You are not alone. The harder you run the bike or the harder the previous owner ran it the less time you'll get on your crank.

OriginalDirt

 

[whenfoxforks-ruled]

When these 97 octane race bikes trickle down to the trail riders $$$$!

 

[Rich Rohrich]

There is an "epidemic" of rod failures in 450's of all brands.

If you look at it on a percentage basis, rod failures are the least common issue seen on the current crop of 450s. Most of the rod failures I have seen on 250F and 450F engines over the last 8 years (and I've investigated quite a few) have been a direct result of a rider mechanically driving the rpm past the rev limiter on a regular basis with downshifts. This constant overworking of the rod manifests itself as a plastic deformation of the rod which eventually leads to a fracture. You will usually see this failure about 2 inches below the small end bearing. Generally the rod fails when a rider closes the throttle after a period of sustained high rpm running. The change in cylinder filling and the resultant change in cylinder pressure available at TDC to help slow down the piston, increases the rod stress and seems to contribute to the final failure.

The real issue is riders ignore the service intervals and treat these engines like XRs. These new engines are proper race engines and the parts have shorter service intervals as a result. Ignore them at your peril.

Many riders who bought used never saw the factories generally recommend running 97 octane gas. Well you can't buy 97 pump gas so running 92oct or lower you will get "micro" detonation,

The recommendation from the Japanese OEMs is based on an RON number not a pump octane number. US based pump premium satisfies the OEM requirements for all of the current Japanese 4 stroke MX bikes.

You cannot fix or hide the problem messing with the F.I. program or the E.M box program. You pretty much are just delaying or accelerating the problem.

Assuming you are actually experiencing detonation on a late model 4t MX, which is pretty unlikely on a stock Japanese 4t engine under most conditions, you can always TUNE around it. You won't necessarily have an optimized power combination with that level of tune but it is most certainly a work around that is effective. High ambient temperatures with sustained high loads (hot days running in sand or mud for example) are the only times that "most" 4t riders would ever be in situation that they would "need" higher octane fuel than they can get at the pump.

At the recent motor builders (cars, bikes, boats, etc.) conference in Ohio the main topic was detonation and how it is the most common cause of motor problems in all applications (especially in hopped-up J-model F.I. cars).

OriginalDirt

Detonation has always been the upper limit demark for performance, there is nothing new about that.

While my preference has always been to run good fuel in my engines to avoid the vagaries of pump fuel it's in no way a requirement with current four-stroke engine designs from Japan.

The idea that current Japanese 4t MX bikes with stock equipment are rolling timebombs if you run them on pump fuel is ludicrous and just plain wrong.

 

[originaldirt]

WOW, Rich! I'm glad that you think are right!!!! LOL!

However that does not make my comments definitively wrong. You see what you see, and I see what I see. We both analyze the situation, gather information and from experience we then make conclusions from that basis.

I appreciate your comments and input, however your judgment of my conclusions and input as biased on your own experiences, as well are mine.

Thanks for the comments,

OriginalDirt

 

[Patman]

WOW, Rich! I'm glad that you think are right!!!! LOL!

However that does not make my comments definitively wrong. You see what you see, and I see what I see. We both analyze the situation, gather information and from experience we then make conclusions from that basis.

I appreciate your comments and input, however your judgment of my conclusions and input as biased on your own experiences, as well are mine.

Thanks for the comments,

OriginalDirt

Until your "experiences" have a bit more than your opinion and words backing them up it still falls under the Definitively Wrong heading. Please feel free to share with the class as we are always interested in having more FACT thrown our way. We'll understand if you choose to run off with your tail between your legs Rich seems to have that effect on people that can't back up their opinion (this is once again FACT with years of proof on DRN :laugh: )

 

[ellandoh]

maybe theyre both right??

the rod failure could be an epidemic depending on the definition of epidemic even if looked at from a percentage basis if the more common issues are a worser epidemic :)

allthistalkofepidemicismakingmesickandtired :whoa:

 

[whenfoxforks-ruled]

Thank you Rich.

 

[pesky nz]

I think that by rod failure you are talking of different kinds of failure. A snapped rod is what I think rich is talking about and his descriptions are true to that situation. The detonation relating to big end roller failure has been blamed on everything under the sun from under reving and tar seal riding without a cushdrive to octane and voodoo. My personal experience with 3 WR yams per year and 6000 miles on each for the last 4 years is octane above 91 has caused no ill effects. The riding is high milage easy going down to push and drag in the mud or redline on beachs and backroads. 1 rebuild due to lost sump plug (not my work) and no dissatisfied buyer of the bikes after our use. Most bikes were sold within our client base. If the bike in question has a pitted big end it will be due to cheap or dirty oil or lots of riding by a previos owner. Get it cheked before the piston starts beeting into the head or the rod snaps. On another note a similarly bad sound will occur if the primary drive nut comes loose on the end of the crank so I would have the sides stripped and inspected first.

 

[Rich Rohrich]

WOW, Rich! I'm glad that you think are right!!!! LOL!

However that does not make my comments definitively wrong.

Sadly that is not the case. You made explicit claims about running pump fuel and damaging an engine as a direct result due to invisible, inaudible detonation that have zero technical merit.

Maybe I should clarify my point a bit.

The "micro" detonation theory you posted is one I've heard bandied about by any number of people calling themselves "tuners" trying to explain things they don't seem to have a firm understanding of. Forensic analysis of failed parts is more difficult than most people want to believe.

I don't know if what you posted is an original thought on your part or is something you are repeating from another source, it's the same degree of definitively wrong as you put it.. Either way, these people who embrace this concept so dearly tend to have nothing more than "trust me" as the basis of their proof.

No one with any sense will argue the fact that unchecked detonation in an engine will destroy crank bearings in short order. That's been a solid proven fact since the 1920's when Harry Ricardo first explained detonation to the world.

The idea that some invisible "micro" detonation caused by running pump premium is destroying Japanese crank bearings while leaving rings lands and piston crowns unscathed is a nice cute "theory" but doesn't hold up to an sort of critical examination.

It's clear to me when I read stuff like this, that the "appetite for bogus revelation" that H. L. Mencken wrote about seems to be as voracious as ever in the performance community.

I have no foolish expectation that anyone will take my word on this, so I'll suggest anyone with any interest do a SEARCH through the peer reviewed spark ignition engine research from the SAE, the JSAE, or the ASME and you'll find the "micro detonation" concept noticeably absent.

That's NOT a coincidence.

Peer reviewed research publications don't believe in the Easter Bunny, Santa Claus, or invisible detonation gremlins anymore than I do.

If anyone finds anything "real" to prove me wrong on this I would be grateful for the edification when you pass it along.

More to the point. The Japanese motorcycle OEMs are NOT building 4t MX engines that require anything more than US pump premium to run safely without knock or detonation. Unless there has been a recent change when I wasn't looking, the standard fuel recommendation from the Japanese OEMs is 95 RON octane. US pump premium which is rated at the pump as (RON+MON / 2), more than satisfies the OEM requirement.

There is no question that there are tuning advantages that can be gained from running fuel better suited to engines that can turn 12,000 + rpm, but high octane race fuel is not a requirement for reliable operation. With whatever respect is due your experience, to imply otherwise is just misinformation.

Wrong is still wrong, experience be damned. ;)

 

[originaldirt]

OK, I give up, 40 years of dirt bike motor building is trumped by an opinion respected by "almost" the "entire" dirtrider.net community.

Rich is certainly the Guru and I respect his position, it just does not invalidate my post. ...and BTW I was specifically offering input about roller bearing failure, not total rod failure

I defer to the king of the domain!

Thanks Rich for stating your informative positions so authoritatively.

OriginalDirt

 

[Patman]

Was it years of opinion stated with authority or was it fact based information stated with confidence that makes him an authority? There are lots of people with lots of years of experience and opinion under their belt but few that go to the trouble that Rich does with fact checking and investigation. I guess one way to look at it is would you rather stand in court with representation that knew all the facts and had all the backup material as well as a long history of wins or would you prefer to have somebody there that would say "I've been doing this a long time so trust me."?

 

[whenfoxforks-ruled]

Oh no, I know what I know, because I know? No?

 

[ellandoh]

is this japanese micro detonation crank bearing thing related in any way to the sun burst stuck accelerator pedal thing??


i am inclined to believe these japanese are micro pulling my leg :whoa:

 

[Ol'89r]

There is an "epidemic" of rod failures in 450's of all brands.
At the recent motor builders (cars, bikes, boats, etc.) conference in Ohio the main topic was detonation and how it is the most common cause of motor problems in all applications (especially in hopped-up J-model F.I. cars). OriginalDirt

OriginalDirt.

Not taking sides here but, in my experience of working on modern thumpers on almost a daily basis, I haven't really seen an "epidemic" of big end bearing failures. What I have seen is an epidemic of riders that will not do basic maintainance. Most big end failures seem to be caused by the lack of a sufficient amount of oil or dirty oil. These things are not your grandpa's XR's and they don't like being treated like one. This has also been backed up by friends of mine at American Honda. One of those friends was at my shop yesterday and we were discussing this very topic.

If there is any "epidemic" it is with the valve train. There again, caused by a lack of maintainance on the part of the owner. Failure to check valve adjustment or replace valves in a timely fashion or running a dirty air filter. These are usually the cause of these so called epidemics.

I feel the modern day thumpers are getting a bad rap simply because people won't do the proper maintainance and then when their bikes spit their cookies, they blame the brand.

Carry on. :cool:

 

[steveotimmy]

I took my bike to the shop and said there was nothing wrong and it sound like a 09kx 450 that he just did a top end on. But still here the nosie .

 

[Patman]

Find a new shop. If you can hear a knocking sound over the engine noise that was not there previously there is something that needs checked out. If it's a sketchy shop they might send you back out hoping you will come back with a bunch of little fragments which means more shop hours and parts which = $$$

If you really have no idea how much time is on the top / bottom of the engine this might be a good time to pop the engine out and send it off to a known quality engine builder. My suggestion Eric Gorr. :cool: :cool:

 

[pesky nz]

to stevotimmy I hope you have your bike running and the noises have been repaired
I had a quick search on intimitent detonation and was given verbal advice from a Mobil petrol distributor in New Zealand and pacific islands that it does happen and closer to home for most of you you can find reference to micro or intermittent detonation on the Lucas Oil advertising. It makes sense to me that not every engines revolution is the same as the one before and the one after so an occational wayward bang would show no marking on the piston top as many more than one is needed to raise the piston temperature enough to leave a mark. What it can do is raise the pressure between the bearing race and ball or roller enough to break the oil film and allow metal to metal contact and begin early wear.

 

[Rich Rohrich]

closer to home for most of you you can find reference to micro or intermittent detonation on the Lucas Oil advertising.

Advertising is written by people who wouldn't know a Wiebe function from a water balloon, so quoting them as a source of info is akin to parroting back the nonsense printed in Motocross Action

Peer reviewed research is worth reading and taking as fact, marketing drivel that appears in advertising is best left to the mouth breathers who consider it "technical information".

Someone infinitely smarter than me said it best:


"It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong."

- Richard P. Feynman