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.
Last autumn, one of my customers had a top end failure with a 2000 400SX. I went to my local dealer Barr’s KTM in Madison and ordered replacement parts. After 32 years in the motorcycle industry I know how to read a parts card. The suggestion that I was mistakenly reading a 2003 card rather than a 2000 is impossible because the dealer didn’t as yet have the 2003 parts cards in stock. I ordered all the valve train parts including a head. After three months on back-order, the parts started trickling in. Steve Barr’s son races a 400SX and their mechanics are keen performance technicians. When replacement parts are different in design than older parts we share information, discussing how the improvements will work with existing parts. We pride ourselves on being consciences technicians. When we received the conical springs we immediately questioned KTM, explaining that we ordered parts for a 2000 model not a 2003. A person in the parts department at KTM in Ohio told us “the conical springs are the updated part number, you get these when you order the old number”. We examined the cylinder head dimensions and immediately noticed that the spring seat diameter on the head was smaller than the diameter of the bottom spring seat for the spring. Barr’s was in the process of updating their own race bike and we figured that we’d have to bore the spring seat larger to accommodate the new conical spring. We both machined our heads accordingly. My biggest concern is that if the average guy orders these parts and fits them to their old head without doing the machining, the springs will be under greater preload and a failure will occur. I was also concerned that KTM didn’t put any written communication in the box for the spring warning about the need to re-machine the old heads. In fact that’s really what the heart of this whole problem is, a lack of communication on KTM’s part with regards to parts updates and service issues. Their newsletter features blibs about their sales outings but nothing about service updates, recalls, tech tips. Do they have any representatives browsing technical forums like the ones on DRN? I’ve never seen anyone in an official capacity from KTM out here or on Thumpertalk.
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. The two individuals are +45 vet experts, Fritz Heubner and Jim Webber. Both of these guys are accomplished mechanics and conservative riders who understand how to maintain a four-stroke. Fritz is a former factory mechanic working for Yamaha and Bultaco in the 1970s. His job is to restore and maintain a stable of vintage racecars for Bill Jacob, a wealthy auto dealer in the Chicago area. Jim is renowned for his Maico restorations and works in the motorcycle industry for Bell Industries. 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.
PS don’t expect to see me answering questions in this thread anymore because I’ve said my piece and that’s all that needs to be said. I’ve got the seasonal glut of performance work to deal with in my shop right now and that demands all of my attention. If the usual suspects want to take potshots at me again calling me incompetent and an imposter then so be it. I’m just going to ignore those %&#(^>s because it takes two to argue.