crf intake valve wear HELP!!!

[zx12r]

I too thought that was it early on. So I did some tests using thin plastic bag to see just how much air flow was actually going through these vent tubes. This is a methode that watches a bag colapse under vacuum. It is a way of detecting very very small vacuum flow. It turned out there is almost no measurable flow of air through the vent tubes. There is some of course but it is super low. From this I believe it is not likley that the valve wear is due to dust flowing into the vent tubes.

As well think carfully about the above post. There was a huge amount of dirt in the carb slide area before I sealed thta carb cap and now that its sealed there is no dirt in there. NONE. YET the valve on left side continues to wear. This was a huge amount of dirt everywhere inside that carb slide area. If that amount didnt have any efeect on valve wear then its hard to see how a much smaller amaount would be it.

Just thinking out loud here. could this be a heat problem. the intake valves are cooled somewhat by the incoming air/fuel charge and lubrication , if the right is receiving 70% of the charge, 70% of the cooling effect, the left is going to wear faster. also have you tried to richen up the jetting, to lower combustion temps. maybe lubrication to the left side is low. when warming the bike up, do you lean it up against something, always on the same side, maybe causing low oil to the left side. like i said just thinking out loud here. good luck with your mystery.

[D-K]

The intake valves are pretty hard to cool with oil and water. The hottest parts (valves) are pretty far away from the water ducts, and have just small surfaces to transfer heat.

Maybe just overall lower temperature can help?

I would like a Twin Air oil cooler, but it´s a bit pricy.

[lowmass]

Well I too am thinking heat at this point. I dont think its me doing somthing like a warm up with it leaned to one side or anything of that nature. I start the bike , wait about 20 seconds , put in gear and motor slowly for a couple minets untill warm, and then blast off. I never let the bike just sit and idle for a long time. Even at starts at races I dont start bike till 2 min warning and then I dont rev it like all the guys who think there still on 2 strokes ?.

I do suspect heat though. I like the basic idea " maybe just a little cooler temp would help" . That might be an easy fix.

The point was made that its hard to get cooling water around valves. I bet it is. As I look at the complexity of the heads structure I suspect its quite difficult to design the water passages and flow rates around these ports, valves, etc. etc...

This is part of the reasion I suspect heat may be the issue. Perhaps on the 450s the left intake port runs hotter than the right and visa versa on the 250Fs simply due to water passage design.

HOWEVER there are people reporting no problems at all too. This leads me to suspect that there may not be a design issue so much as a quality control issue. Such as perhaps some casting flash or web of aluminum from the casting process that is not getting completly cleared out in head manufacture. This perhaps causing a partal blockage of coolant flow in the problem area.

BTW , yea that twin air cooler is pricy!! Ya know all I really need is the oil filter adapter plate. I can make my own cooler and get my own hoses. I wonder if I can drill and tap my stock oil filter cover plate??? Hmmmmmm...

Edited November 23, 2010 by lowmass

[CamP]

HOWEVER there are people reporting no problems at all too.

I'm one of those people and I attribute it to never overheating any of my bikes. I always ride/race on well prepped race tracks so I rarely have any mud blocking the rads and I always have plenty of airflow through them because speeds are up.

It seems like most of the guys that have valve issues are off road riders that do a lot of muddy slow speed stuff, which tends to overheat bikes.

[lowmass]

ALL repeat ALL the guys I know, including myself, are NOT off road riders. We are all MX guys. And I rarly if ever ride in the kind of mud where the rads are clogged. I wont even ride my practice track when its that wet so as not to distroy the track.

This problem may be heat related but in this case its definatly not from riding slow or clogged rads.

[CamP]

ALL repeat ALL the guys I know, including myself, are NOT off road riders. We are all MX guys. And I rarly if ever ride in the kind of mud where the rads are clogged. I wont even ride my practice track when its that wet so as not to distroy the track.

This problem may be heat related but in this case its definatly not from riding slow or clogged rads.

That's why I said "most" of the guys that have valve problems are off-road. This has been reiterated to me by one of the most respected engine builders in Texas. A guy that's been in business since 1976.

Anyway, I live in what is arguably one of the hottest motocross areas in the nation. There are over 25 tracks within 1.5 hours of my house. I'm at the track three days a week and literally know 100's of riders and racers, the majority of whom ride CRF's. Valve issues amongst them are relatively rare.

[lowmass]

Interesting. Well the heat issue does seem to have merit. I dont understand why so many in my area have the problem racing MX though. Just the other day we had to reshim a friends crf 250. Its a 2005 but the motor was a fresh rebuild about mid seasion. He is a novice and hardly puts a load on the thing but no trail riding.

You have me thinking though. Most of us having issues are on 3or 4 yr old bikes. I wonder about our radiators. We dont ride a lot of mud BUT old radiators tend to have a lot of bent fins. I will check this tonight.

[tpars121]

I just traded a 05 CRF250R and in three years I only had to replace the valves once. I knew buying the bike that they had a habit of eating valves so as a precaution I always used a good coolant like Engine Ice and always ran my jetting on the rich side. It is my understanding two things cool the intake valves, one is when it contacts the head it will dissipate heat and the other is fuel.

[MELK-MAN]

The intake valves are pretty hard to cool with oil and water. The hottest parts (valves) are pretty far away from the water ducts, and have just small surfaces to transfer heat.

Maybe just overall lower temperature can help?

I would like a Twin Air oil cooler, but it´s a bit pricy.

im my humble opinion, the potential for damage caused to a motor after one of the lines got yanked in the woods or perhaps a crash, would not be enought to offset the ever so slight oil cooling this item could possibly do.. just my opinion. And oil temp i suspect is not the issue with the valves anyway.

[zx12r]

another angle, cams are ramped so the valves close as slowly, softly as possible. Honda OEM cam?

[Shawn_Mc]

another angle, cams are ramped so the valves close as slowly, softly as possible. Honda OEM cam?

the 02's had the hottest cam, they also were the worst on valves. In 03, the cam got milder and the valves got more dependable to a point. There are a couple after market cams that are much easier on the valve train and make considerably more power.

The RHC 187 comes to mind.

This idea is also why some guys close up the lash to .004 on the intakes from .006", to keep it on the closing ramp as long as possible.

Ive got well over 120 running hours on my intakes with zero movement. Ive never over heated the bike, but i have run it out of coolant a couple times during a moto because of a bad WP seal. Still no issues tho.

You guys can sweat this issue all you want, its not going to change anything though.

[NorCalRider]

Every CRF I've owned ended up needing a valve job. It's just the nature of the beast. Crappy intake springs with an aggressive cam profile. Just get the seats recut or a new head, stainless valves and springs and be done with it. You'll. Never have to adjust you valves again.

I can't believe this is still being discussed, 8 years of threads about valves. LOL

[D-K]

im my humble opinion, the potential for damage caused to a motor after one of the lines got yanked in the woods or perhaps a crash, would not be enought to offset the ever so slight oil cooling this item could possibly do.. just my opinion. And oil temp i suspect is not the issue with the valves anyway.

The oil temp affects the water temperature in a big way.

And both oil and water cools the head and valves.

I really don´t believe marketing numbers, but here is their claimed reduction of engine heat after certain minutes of running:

http://www.btosports.com/p/TAOILCOOLERS?query=http%3A%2F%2Fgear.btosports.com%2Fsearch%2Findex%3Fquery%3Doil%2Bcooler

Of course, more parts equals more stuff that can fail.

How come for example other brands can make the valves last longer? Must be a combination of things, since Honda wasn´t born yesterday, but cooling, cam angles, spring rates and coating quality must be the factors to look at.

[lowmass]

Some data to think about...

1-In my area only the hondas are eating valves at this rate

2- On the 450s its the left side , on the 250s its the right side.

3- Arguments like dirty air or fuel or bad oil etc etc are not valid in light of the consistancy with left , right side valves.

4- my bike has 3 hard seasions of MX on it and I NEVER had to replace or even shim eather of the exhaist valves . NEVER. Think about that for a moment. That says a lot. Yet I cannot get more than about 1.5 months of rideing without replacing intake valves.

5- Most of the issues I speak of above are MX guys ( in my area anyway)

6- most of the bikes I speak of are a few yrs old but kept up well.

7- If you dont like talking about this issue find somthing else to do.

Ok so continuing with the Heat theorys.....

Everything and I mean everything on my motor that has anything at all to do with the valves has been replaced and expertly set up. In a couple short months at end of this seasion the left side intake has once again gone from .006 to .002 " clearance. Same wear rate as always and only left valve.

Goin on the data that engine builders are seeing more of this from offroad guys than MX I am leaning twards heat. I was talking with the engineers where I work and they tell me that the coating on the Ti valve may be crtical of heat. They suspect it is very good up to a point and then it looses it.

On the above thoughts I whent home last night and took a look at my radiators. To my suprise they are quite beat up. No big dents or anything like that BUT there is possably a significant surface area on both where the thinn fins between the cors are bent at a 90 deg angle to air flow. A conservative estimate is about 25% of total rad area is blocked.

I live in an area where the soil is full of small rocks. They get through the lovers easly.

So the question is, how on the edge are these motors as far as heat and cooling capacity goes?? Is this reduction in radiator flow area enough to rase the average oper temp to point of reducing life span of valves??

I see a TON of aftermarket radiators on Ebay. CXracing, Fluidine, Black, etc and a number of others with no name but they all look the same build and they are all about the same price, about 1/2 oem!!! They are all suposedly about 30 % more flow than stock. Whatever that means exactly they dont say. Does it mean 30% bigger tubes ? 30% more surface area??

Anyway this thred is a step by step investigation into why some are experiencing acelerated valve wear. It will be a slow and painfull process as I will do one thing at a time and then give it even more time to be sure whats happening. Im sure there have been many threds on this issue. I suspect though that none of them have put in the time nessasary to do a "one thing at a time" approch. It simply too time consuming. However that is likley the only sure way to answer this question.

Heat is the focus for now. Radiators are the next step I supose. Any info on these aftermarket radiators will be appreciated.

[CamP]

I don't think oversize radiators are your solution. I live in Texas where it stays over 90 all summer. I've never run anything but OEM rads and never had a boil over, but my rad cores are perfect, I constantly keep my speeds up and never allow the bike to idle after it's warmed up.

Something else is very wrong if you can't get more than 1.5 months out of a set of intakes. I would suggest that you find a new machinist, install steel valves and forget about it.

[MELK-MAN]

i don't think it is a heat issue either.. My 04 head ? ate LOTS of intake valves even after having seats cut. Never one side, BOTH. With clockwork-like regularity. Over 800 hrs on the 04 head i think we used 6 sets of intakes or so and countless adjustments (ex never an issue, changed once just cause). I have posted about this numerous times in other threads. Changed to KW ss valves AND spring kit?? STILL ate valves just at a slower rate. Moved on to an 08 head.. ZERO VALVE issue after over 100 hrs of riding. zero. nothing. nada. Will see in another hundred hours, but i am convinced it is the better seat material in the 06+ heads that helped with this. I made no other changes, still on my original stock rads (thanks to devol guards and wc supports, bent them a few times), no fancy water pump, nothing.. Same type of riding, same hours or so per week, same conditions here in dusty FL, same cam, even resused the old KW spring kit from my 04 head. Im not the authority on this, but it is a pretty long test on the same machine.. 04 head, issues. 08 head.. no issues. ALL other things equal, the definition of a test ?

[lowmass]

Yea I wasnt thinking oversized rads as the fix but simply new rads as mine have a fair amount of fins bent blocking air flow. The oem rads are big bucks. There are HD oversized rads for less than half oem price.

I only race in the summer. Here in central NY most summer races are close to or above 90 deg too.

As far as the heat and Ti valve coating thing goes. The engineers tell me that if the coatings have a heat limit they only have to reach that limit once for a breff amount of time. They question the coatings connection with the Ti. They say it may loose the mechanical bond. Its all downhill from there.

As far as the "new machinist" goes. I have not just replaced intake valves, I have completly replaced the entire head and yet the same problem is happening. Left intake valve wear. The right intake wears at a much slower rate.

BTW interesting to note here that untill I replaced the entire head I just replaced intake valves w/o getting seats cut. Many would call that a no no but the seats looked perfect. Well sure enough even with new head thus new seats, the valve wear rate is still the same. In fact it may even be worse now. The idea that it may be getting worse is somewhat supported by the theory that the damaged rads are at least part of the prob. As the rads get more time and thus more rack damage the average operating temp is getting higher.

I have heard guys that have this issue say that the SS valves wore better BUT still wore relativly fast. Especially when you consider there are plenty of people with Ti valves and little or no wear!!

BTW MELK- MAN my bike is a 2007 crf450. It is suposed to have the same head as the 2008. And I have been through two of them, both same issue.

[lowmass]

Ron Hamp11-05-2004, 08:57 AM

"I beleive hondas valve problem is there coating process .I have gotten replacement valves that have a entirerly different apeirence in the color of the coating .also it looks to be somthing like aluminum nitrate , which would be soft compared to casidium like procircut uses and i think probally yamaha also uses .casidium is exspensive to have applyed and raises the cost of the valve this would also explain why a yamaha valve cost more than the hondas .i have been testing a vapor deposition coating like these, only it has a higher operating temp so i have been able to run it on the ex valves also in my race engines .so far the results have been good."

The above is an intereting bit from another thread...

https://www.thumpertalk.com/forum/archive/index.php/t-183575.html

Edited November 24, 2010 by lowmass

[MELK-MAN]

yes, the 07-08 are basically the same as i understand too. Don't know what to tell you.

[tjg53]

If it is a heat prob. yamaha should have the same prob. but they don`t seen too. Lots of blue bike in the woods too. I`m a woods rider , and ride with guys on yamaha`s that are on 426`s , and 450`s 5 , and 8 year old bikes that have never had a valve even move.