I am in the process of rebuilding my 01 YZ250F. A friend of mine is doing the head work for me. He has reground the faces of the stock ti exhaust valves and is putting in ss intake valves. To save some money he bought stainless valve blanks and is machining them to fit. We have already bought new stock Yamaha valve springs. However, I have serious doubts about the stock springs ability to support the stainless valve weight. Do I need to spring the ss valves with stiffer springs. Any advice would be greatly appreciated. I DON'T want to trash my new motor!
valve spring rates
- Thread starter NathanA
- Start date
NathanA said:
Once you grind the hard face coating off of the OEM titanium valves you are left with an unprotected titanium valve face running against a hard steel seat insert. You'll be very lucky if they last more than a couple of hours of hard running. You can't grind or lap the OEM titanium valves without ruining them.
NathanA said:
You absolutely need a higher seat an open pressure to control a steel valve. Kibblewhite springs kits are the best choice for this application. www.blackdiamondvalves.com
- Thread starter
- #3
valve surface treatment
Thanks for the info, Rich. I will definately put in stiffer springs. My next question is about the surface treatment of the ti valves. Is the titanium simply anodized to form a layer of ti oxide as done with aluminum, or is there some other process? Also, how long does the surface treatment actually last under running conditions. If i'm not mistaken, Al hard anodizing produces AlO2 to a depth of aproximately 0.0005 to 0.0015". If this is the case for the valve surface treatment, wouldn't it be worn thru in short order anyway? In Eric's valve train article he mentioned that the stock valves had cast heads inertia welded to the stems. Is the treatment of the cast ti diferent from that of machined billet ti? I know there are a lot of questions here, but valid information seems to be in short order. Unfortunately, there seems to be a wealth of misinformation. Some of the things I've been told at the track are so wrong its scary. Again, thanks for sharing your knowledge with us!
Thanks for the info, Rich. I will definately put in stiffer springs. My next question is about the surface treatment of the ti valves. Is the titanium simply anodized to form a layer of ti oxide as done with aluminum, or is there some other process? Also, how long does the surface treatment actually last under running conditions. If i'm not mistaken, Al hard anodizing produces AlO2 to a depth of aproximately 0.0005 to 0.0015". If this is the case for the valve surface treatment, wouldn't it be worn thru in short order anyway? In Eric's valve train article he mentioned that the stock valves had cast heads inertia welded to the stems. Is the treatment of the cast ti diferent from that of machined billet ti? I know there are a lot of questions here, but valid information seems to be in short order. Unfortunately, there seems to be a wealth of misinformation. Some of the things I've been told at the track are so wrong its scary. Again, thanks for sharing your knowledge with us!
