Titanium vs Stainless Steel

Why is everyone saying bad things about titanium valves?

by Paul Clipper

There are a lot of four-stroke dirt bikes with titanium valves. The Honda CRF, the Yamaha WR and the Husky four strokes come immediately to mind (KTM four-strokes use stainless steel valves). Every time a new bike came out with titanium valves, we heard all kinds of stories of doom and gloom. Cut away all the fat and the message is usually: They’re all blowing up!

In every case that we’ve investigated, the “They’re all blowing up!” declaration was about as true as Chicken Little’s warning about the sky coming down on us. Our panic-stricken society is a result of the bad aspects of the information age. One person in New Mexico has a four-stroke 250 turn into a hand grenade and by the time the story gets to the east coast we hear that the factory is recalling all of them and that model is no longer for sale.

It just doesn’t happen. Look around, and there are plenty WRs, CRFs and TEs chugging along in complete defiance of the story that They’re all blowing up!

So what’s the truth of the matter? Okay, here it is, in a nutshell: titanium is softer than steel. It works really well as an intake valve until there are problems; but, if there are problems, titanium can fail in a spectacular way. The valves close up, the metal stretches and/or breaks, the engine goes boom.

So why do manufacturers use titanium? Because it is light. The lighter the valves, the less spring pressure you need to keep them shut, the less force you need to get them to move, and consequently the faster you can make them open and close. So you can get more power out of an engine with titanium valves, and you can get the engine to rev higher.

As long as you keep the oil fresh and full, the engine fairly cool and your valves adjusted properly you won’t have any problem with titanium valves, and they’ll last you at least two or three seasons, possibly more.

Now if you don’t pay any attention to maintenance you’re going to run head-first into the Evil Legend of titanium valves, and you’re going to have expensive trouble. What do we mean? Okay, all valves need to be checked and adjusted for clearance, and titanium more so than steel. It’s easy to check the valve clearance on any of the new bikes, but it’s a hassle if you’re in need of a correction because then you have to mess around with shims and buckets and all that stuff in the cylinder head. For most of us, that means a trip to the dealer and some fairly expensive valve-adjustment work. Who wants to bother? But if you don’t, you’ll wind up with an engine that is hard to start or won’t start at all at some point. If you’re lucky. Force it to start and keep riding it, and getting it to run again afterwards will be a very expensive proposition.

The other big deal with titanium is oil. The way titanium valves get their strength is through the use of a surface treatment, like a coating similar to anodizing. Keep it running in lots of fresh, clean oil and it’s happy. But, if you let the oil get low, old or dirty, the surface coating on the valves will get scuffed off or compromised in some way, and at that point the valves lose their integrity and all manner of destruction will follow. Usually the valves will deform and become tulip-shaped, stretching out to the point that they won’t open any more and the engine will not run.

So you can see, if you get this new bike in the hands of a person who thinks he’s got a stone-axe reliable, stainless steel valved Honda XR or something similar, and never needs to do any maintenance, well, the rumor mill is going to get all cranked up once his bike explodes. You usually hear, “It wasn’t my fault, they’re all blowing up!”

On a new four-stroke, you have to keep your oil topped off (they all “burn” oil) and changed regularly, and you have to keep the valves adjusted properly. There is no way around all this work.

Or is there?

What if you had the titanium valves replaced with high-quality aftermarket stainless steel valves? Would that give you a broader margin of safety? Or would it even make your new high-strung thumper as reliable as an old Honda XR?

We wanted to find out for ourselves. We ran a Honda CRF250X for a whole season, in some of the sloppiest, muddiest trail rides we could find. The end of the year saw about a thousand miles on the bike, and in the mean time we kept after the oil and watched the valve adjustment. The valves tightened up over the season just a little bit, but nothing to cause alarm. While we were wintering-over, we tore the engine apart and had everything inspected and all the parts looked perfect. So much for They’re all blowing up.

But, what if we changed over to stainless steel valves? Would we then buy into XR-style maintenance-free longevity? We figured on finding out.

Litz Racing was suggested to us by C.H. Wheat at IMS. C.H. is an engineer who spent his days working on top-secret projects for the U.S. military before he “retired” to go full time with IMS Products back in the 1980s. C.H. has always been a scientist when it comes to engine performance, and IMS builds some of the most reliable racing engines known to man, and they are highly regarded on the west coast—well, and on this coast by people who use them. C.H. told us that Steve Litz makes the best racing valves—stainless steel valves—of anyone in the country, and coming from C.H. we had no reason to doubt he was sending us on the right path. So we sent the head to Litz Racing and told them to do us up right.

In these engines, titanium is only used for the intake valves. That’s because the exhaust valves are smaller, and consequently lighter. The intake valves are much bigger, so it’s an advantage to make them out of the lightest metal you can find, to keep their weight down. What Litz Racing does is replace the intake valves with their special stainless valves, and also grind out the stock valve seats and replace them with a copper beryllium seat. Replacing the seats is a critical part of the job. Litz claims that changing to the softer seat material is the key to longevity, since the new seat cushions better than the stock steel seats. Litz also says that with the new seats you can run the stock titanium valves, if you like, and still get a benefit from the softer seats that will result in longer valve life and better sealing.

But, we wanted the long-life potential and greater durability of stainless steel, so we opted for the stainless valves and the copper-beryllium seats. We tore the engine down and sent the entire head off to Litz, and waited about a month for its return (we were in no hurry). Having the seats replaced was the lion’s share of the work, with a cost of about $300, and a new set of valves was another $100. New valve springs were also installed, and Steve Litz said that considering the low cost of them, valve springs should be replaced every time any head work is done. When the head came back we rebuilt the engine and filled it with full-synthetic Spectro engine oil, and started riding it again.

Incidentally, Litz also suggests over-filling the CRF250 with oil, just to be on the safe side. He adds 100cc of oil over the factory recommendation for both sides (transmission and top end). We also have been having excellent results using a full-synthetic 15W-50 motor oil in the top end and a 90W motorcycle gear lube in the transmission. You have two completely separate oil systems, why not use the oils designed for the task in each case?

What has the long-term effect been on our engine? Well, as long as we were taking care of it, we’re pretty sure the stock engine wouldn’t have “blown up” like the rumors said. But with the Litz valves installed we’ve checked and noticed only a slight change in valve clearance over the past season. And besides that, we haven’t detected any negative effect on performance at all. Possibly you could tell a difference on a dyno run, but dynos don’t ride bikes, as the saying goes. If you can’t feel a difference in performance, to us that means nothing bad has happened.

So the up-side is that presumably this engine, with the new Litz valves and seats installed, won’t be as sensitive to oil, heat or abuse problems as the stock titanium valve train would be. However, we intend to keep up with oil changes and maintenance as usual, and maybe we can look forward to much more time before necessary valve clearance adjustments, and ultimately longer life from the entire top end.

Would we recommend all this work? Yes, if you want the peace of mind that comes from having an engine that is stone reliable. We would definitely recommend it if you need to rebuild the top end because the bike is getting a little tired—but please note that the prices we quoted for the valves and seat work are for an engine that is in good shape. If you wreck your engine somehow, we can guarantee you that the cost of rebuilding the top end will go well over a thousand dollars. And you don’t need obvious shrapnel to have a wrecked engine, all you need is a bike that won’t start. Take care of it, and do the maintenance and/or modifications before things get that bad.

Yes, if you are a high-strung motocross racer with a high-strung need for maximum RPM and power, maybe you would find a benefit from a lighter titanium valve. But for the average trail rider or enduro rider looking for longevity—as well as performance—we’d say the Litz valve and seat job is the way to go.

Where to find out more: Litz Racing, 469 Centenary Road, Blountville, TN 37617. Telephone: 423-323-0489. Website: www.litzracing.com.