what is the adjustment interval on stainless vs ti valves, im sure the life span of the kibblewhites is much longer? what about valve guide replacement with new valves? I have spoken to 2 reputable shops, 1 says always replace guides with valves, the other says, not necessary man, who to believe? also since i have your attention briefly, is it wise to replace exhaust valves when do intakes while Im "in there" Thanks so much!!!!
stainless or ti
- Thread starter phazerrd
- Start date
CRF250s tend to wear out exhaust valve guides fairly quickly but rarely have much wear on the intake guides if the oil is changed regularly.
Most CRF250s that are run on pump gas will erode the face of the exhaust valves due to the deposits that are left behind and they need to be replaced once this happens. Engines run on good unleaded race fuel tend not to have this problem.
Titanium valves work well if you are willing to change valve springs a couple of times a year. If you don't want to go through that hassle then Kibblewhite stainless steel valves with their spring kit is the best solution.
Most CRF250s that are run on pump gas will erode the face of the exhaust valves due to the deposits that are left behind and they need to be replaced once this happens. Engines run on good unleaded race fuel tend not to have this problem.
Titanium valves work well if you are willing to change valve springs a couple of times a year. If you don't want to go through that hassle then Kibblewhite stainless steel valves with their spring kit is the best solution.
motometal said:
The OEM springs cost very little to make so I'm sure you can imagine the quality of the steel the springs are made from. Mix high rpm, with low quality steel, and throw in abrupt cam dynamics and you have good reasons to change the springs each time you change the rings. ;)
OEM springs lose pressure almost immediately, and they get progressively worse over time. Even with the light valves, the pressure loss allows the valves to float and causes seat bounce problems on closing. It's a big part of why OEM titanium valves get hammered to death so quickly. A soft titanium valve bouncing off of a hard cast iron valve seat has a short life span.
The good quality springs made from ultra-clean steel can go for hundreds of hours and only lose a couple of pounds of presure, even with a heavier valve. The problem with clean steel springs is they don't come cheap so people try and convince themselves they can get by without them. :coocoo:
I wonder if the titanium nitride coating actually fractures off due to impact/bouncing off the seat?
Regarding the springs, steel cleanliness is important up to a point, depending on the failure mode and type of inclusions in the "dirty" steel referenced. That being said, I wouldn't be surprised if steel chemistry and heat treat methods are the real deciding factor here. Austempering has a lot of potential for variance, just like any other process.
Regarding the springs, steel cleanliness is important up to a point, depending on the failure mode and type of inclusions in the "dirty" steel referenced. That being said, I wouldn't be surprised if steel chemistry and heat treat methods are the real deciding factor here. Austempering has a lot of potential for variance, just like any other process.
I'm being told that cryogenics may actually help the oem springs...but I can't see spending that money when the heavier set-ups are available.
Been awhile since you guys talked cold treat....
Been awhile since you guys talked cold treat....
Im by far no expert on this. But.....to me time is worth just as much as anything else. And to tear your machine down and do some work to the valve system....just to have to tear into it again fairly soon......to "me" thats expensive, "time out of the saddle".
So i say while you are in there, do everything you can do.......and do it the best you can afford to do so. You have a top notch machine, treat it that way!!!!
At least that how i justified buying a $125 rear sprocket, ahahahah.
So i say while you are in there, do everything you can do.......and do it the best you can afford to do so. You have a top notch machine, treat it that way!!!!
At least that how i justified buying a $125 rear sprocket, ahahahah.
