RFS valvetrain discussion (continued)

Originally posted by EricGorr
The thread I started regarding the KTM valve train issues has raised some controversy and peoples’ blood pressure. People have suggested that I’m incompetent at basic tasks like looking up correct part numbers. Here is some background information on what led up to the thread

My suggestion that KTM has some problems with wear on valve train parts is backed up with observations and actual service on KTMs and Japanese four-stroke engines. Just this week, two of my friends who own 2000 KTM520SX models disassembled their engines as part of their annual maintenance. Both bikes have severely worn intake valves and guides, one bike has about 40hrs. and the other has over 100hrs. of run time. Jim’s bike was the biggest surprise for me, because I rode it on the ice recently and it didn’t display the typical symptoms associated with “cupped” intake valves. The bike started fine, didn’t tick or fart at idle, and the power was what I expected. I’m guessing that if I can be so easily fooled by a bike, there are a lot of you guys that wouldn’t have a clue that their bikes are headed for a major engine failure.
These two bikes that I described are minor in comparison to some of the engine failures that I’ve seen when worn valve train parts are allowed to go too long without service.

The whole point of my original thread was to make you guys aware that you need to do some maintenance on four-stroke engines. With more moving parts than two-stroke engines its ludicrous to think that four-stroke engines are as maintenance free as the popular press has pronounced them to be.

As far as tips on replacement parts are concerned, I recommend Kibblewhite valves, springs, and retainers. The telephone number of Kibblewhite in Pacifica California is (650) 359-4704 and the part numbers for the intake valves are 96-96007 exhaust valves 96-96004 and the springs/retainers kit is 96-000 Find a qualified technician to check the condition of the valve seats before installing new valves. A good valve job will go a long way towards protecting the new valve train parts.

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%&#(^>S here. I'm done too. But I did write down the numbers for the Kibblewhite stuff. :eek: Maybe for future reference? :thumb:

Eric, I agree with the above quote completely. I'm still not convinced you got the correct parts. Not nec your fault. KTM has had plenty of time to correct any mis-info you may have gotten. I'm not interested in placing "blame", just want accurate info.

%&#(^>S over & out. :moon: :p

Anyone know if the SX’s black box has the rev limiter threshold set higher than the EXC/MXC box? Didn’t KTM recently update the 03 525SX CDI with a lower rev limit?

I think the followers of this thread were only looking for some specific's... ie; details on what Eric had experienced that promted his original post. Some of those details were announced in Eric's most recent post. 

Lets also keep in mind the many variables that come to play in the form of stress to the valve train.

Improper jetting - can increase combustion temps, inturn can cause 'cupping' and errosion of valves/seats, guides, seals, ect. The added heat can eventually effect the temperment of springs, rockers, cam, ect.

Improper valve clearances - Can literally have all the same effects as above, with the addition of increased valve stem and rocker impact if clearances is greater than .005. 

Cam Chain Wear - Can effect valve timing, not really an issue yet with the RFS, but I have seen this become detrimental to some older XR's. 

Over revs - Most people are aware of the fact; four stroke are less tolerant to sustained high rpms. (in comparison to a 2 stroke) This is not really mechanically related, but it is when the given rider may have previously ridden 2 strokes.

Fuel Quality - Low octane/additives

Air filter & Oil changes - We all know this one.

My opinion in summary,.... I dont think the failure rate is anything to be alarmed about, or for that matter, the RFS is no more prone to failure than any other 4 stroke!

 

 

Sounds like some parts person at KTM seriously messed up-dont suppose we will be flaming them-noo wouldnt do that.

I can accept that someone in the parts department gave us wrong information about the availability and updated part numbers of valve springs, serves me right for trusting a manufacturer. That doesn't explain the intake valve wear (cupping) that I'm seeing on engines I service. This morning I disassembled two 400MXCs, one with 650 miles on the odo. Both have cupped intake valves and worn seats.

I think this discussion should turn towards identifying what causes cupped valves with regards to cam lobe shape, seat and valve materials, and spring design. Last summer I heard of a KTM dealer in the Reno area who routinely replaces the seats, guides, valves, and springs on KTM 400 and 520s. If there is anyone out there who knows the dealer and the reason why he does this, and what brand of parts he uses I would appreciate it.

When talking to Mike Perry of Kibblewhite at the PRI show, he talked briefly about the compatibility of valve and seat materials to prevent wear on the Honda CRF. Mike, if you read this post please enlighten us!

Perhaps the problem is in the cam? Maybe there is a better choice of OEM or aftermarket cam that is easier on the valve train?

An interesting note, the new software from Professor Gordon Blair and Hans Herman has a feature for diagnosing valve train problems are related to spring design, cam lobe profile, and valve mass. Maybe that software can help us narrow down the problem.

Since this engine is a knock-off of Husaberg and they used to have a lot of rocker-arm problems, are the valves, seats, cams, etc all that different? Did they have valve/seat wear issues? Thought the KTM was de-tuned a little?

Maybe we need to run a leaded (race) fuel to protect the valves/seats?
Fuel is cheaper than valves and seats plus labor!!!
What specific changes did they make to the Husaberg design?

Eric, these questions aren't directed at you specificly. I do thank you for continuing to particpate in this discussion. I know you have better things to do. The people that have direct experience with Husaberg's problems of the past may have some answers. :thumb:

I'm thinking fuel quality & no-lead vs leaded, plus jetting/temp effects on material compatibility (valve/seats). I still believe the spring issue comes back to RPM related harmonic's more than anything. Guess that points to cam profile, HUH? Jeez, dude! It's my day off! I don't wanna think! :laugh:

I hope THIS guy doesnt see this post...... :)

http://dirtrider.net/forums3/showthread.php?s=&threadid=72515

I've posted twice in the last hour trying to get Mr Blair's input in the Adv fourm. Of course they were deleted.

I'm done with this board. Later guy's. Good Luck. :)

Eric - I know the shop in Reno and THE bike they referred to. I referred the owner of the '01 400MXC to you to get 'your' 450 kit. He loves the bike btw. He had NEVER adjusted the valves on the bike since he owned it. He also is no marshmallow when it come to dirtbike riding. He had almost 2dozen races on that motor, and probably 3000+ miles.
Nothing against the owner, because he is a friend and client of mine, but his maintenance schedule could use some refining (not just on his dirtbike either).
Knowing the shop WELL that you spoke to, one valve train failure may equal the term 'many'.

Eric - I trust you and your judgement 100%. The motorcyle performance handbook sits on my coffee table and is used as reference regularly. I have nothing to add regarding the springs, due to my ignorance on the topic.

Thump - Mike Rosso is for real. I have spoken to him myself, great guy. I too wish he spent time on the 'hot' KTM boards to add his expertise. Probably one of the, if not 'the' most knowledgable KTM representative in the U.S. Thump, why the concern regarding a bike that I have never known you to own?

Thanks for the info Strick,

I thought you might have an angle on the Reno connection.

Its interesting that a local shop suggested leaded race fuel in RFS motors since they first hit the beach here. KTM Lew might have something there. I'll see ya on the other boards, Lew. ;)

Originally posted by Strick
Thump, why the concern regarding a bike that I have never known you to own?

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Ivan said it best but I also wanted to add that I sat here reading this thinking to myself... if I owned one and heard of this possible problem I would be trying to find out more about it to see if I needed to panic or not. But what I was seeing was a bunch of people defending their pride by calling into question Eric's professional knowledge and integrity rather than trying to finding out for themselves the truth. I started to get a bit pissed to be honest then I thought I might as well do what I can to find out the what's what otherwise I am just like all the rest of the people griping wanting to be spoon-fed.

I didn't mean to poop in ya'lls house, and trust me it is a bit frightning getting into a discussion like this when 1) You are technically challenged like me and 2) the only thing you know about KTM is that they are orange. Hope I was more of a help than a hinderance.

Thanks Thump, I was just curious.

I hope you can rest assured Eric's integrity is intact.

Thump-

I think you just came up with the info that everyone was looking for!!! Thank you.

MP

About intake valve cupping-

KTM Lew may have seen this on heavy duty Ford trucks. If he's old enough... 361-391 style gas V-8 engines that get so hot they use sodium filled exhaust valves- but not the best quality intake valves. When those engines would overheat the intake valve material was soft enough that it would allow the heads to tulip, or cup. Just as if a blacksmith was heating it up and pounding it into a new shape. (nothing wrong with V-8 experience Lew!)

Most of the time in the M/C industry what we see is valve face recession, but there can be cupping also.

GENERALLY SPEAKING, if I see face recession I look at spring pressure/ valve train mass and rpm first. Valve bouncing on the seat stuff. In a case like the CRF 450 materials compatability comes into play. We will also look at rockwell values if a steel valve is having problems. Of course cam profile is a concern, but it is not the first thing considered. You start with the simple stuff and go down the line.

Now, if I saw the entire head of an intake valve cupping, I would first look for abnormal combustion temps, for which there can be many causes. Then I would look at materials.

When you start to examine failures you find that while you may come across something obvious, you need to play out the string to see if you find anything else that may be a contributing factor, to see if you can address that potential problem also.

Now- I have a spring in my hand 598 360 28144- conical design-supposedly for the new 250. Is that the right number?

A note about conical springs- they are a good way to circumvent specific harmonic problems, have good lateral stability, allow for small retainers, (light weight) good rocker clearance, and work very well when the design and materials are executed correctly. They are not new. The conical or "behive" design has been around for a long time. Chevy uses them on the late model 350 LS1engine, Lew's modular 4.6 Fords use them, and Oldsmobile used them in the 60's and 70's on some of their production stuff.

In some instances they may offer an OEM the best design option for a specific application, and could in that case be considered a "step up" from a previous design.
Mike

Ok....Eric, I have the utmost respect for you and your willingness to "seek the truth". If your post had read "Attention 4-Stroke Rider's" and gone on to explain what you were seeing on various 4-strokes I would have had NO problem. This is my first KTM and first 4-stroke. If the YZF's had some sort of auto-decompressor from the get-go I would have been on a Yamaha from the first 250F. I like my KTM but it's just a damn motorcycle! My biggest problem with the original post was that you just dropped a bomb and left. No details on how to fix the problem that seemed reasonable to me. Somebody screwed-up! Now lets figure-out how to fix this thing!!! :yeehaw:

Eric: When I final get my 400. Like alway's as with all my other bikes. the head will be shipped off to Beaver Dam!

Beaver Dam ????, I thought he was in a Van down by the river, oh well,

All I know from this whole thread is that there may (or may not) be a problem with the valve springs on my bike and no matter how this thread was started or how it ends, Mr. Gorr has made me aware of it and for that I thank you, when the time comes ( soon ) I will do some premptive maintains

Thanks Eric, you may have just saved me a few hundred bucks :thumb: