Wrf426 dropped valve! Ahhhhhhhhh

Hi, my mates wrf426 has dropped an inlet valve, it appears to have snapped 2 mm under the collets. How can I tell if they are stainless or titanium.? I've not messed with many 4 strokes but loads of 2 smokers.

Should I replace just the 1 valve as I have a limited budget. Piston seems ok, has a slight mark but no cracks.

Think we intend to replace 1 valve, all valve seals and replace camchain. Should do the job I hope.

Regards. Stan.

It probably dropped the middle intake, right? I would seriously consider putting all new Intake's in at the very least! I personally would put all 5 new valves in and be done with it, as I'm sure you don't want to have it happen again, right?

Hi, it was the left Intake valve which snapped, I've had all the valves out now and they look ok, If it was mine if replace all 5 too but unfortunately it's not mine and my m8 has limited funds. The bike doesn't get riden hard. I just hope it don't blow another valve after all this! Cos it's me that will have to tear it down again. Any idea how I can tell if these valves are stainless or titanium??

Regards. Stan

Stainless steel has a shiney silver look to it while titanium has a darker almost blue rainbowy colour effect

or use a magnet...steel will attract while titanium will not

from what ive been told (:

Most stainless steel is not magnetic. Titanium valves are much lighter weight and generally a dull gray finish.

I suspect your mate is going to end up regretting his earlier decision to just replace one valve.

I have managed to twist his arm and persuade him to replace all 5 valves with new springs, valve stem seals, cam chain and piston rings. This should put the bike right at a fairly low cost considering ill do the work for free. Do I need to use cut nd grind paste for the new valves to seat correct? The seats looke fine with no sign of pitting. Or will they be fine?? Obviously re-shimming is going to be a pain without a full shim kit, so prob send to the shop for that bit..

Regards. Stan

Don't lap the valves!!! They are titanium, and you will remove the hard protective coating! Just install as is. And perhaps you'll get lucky with the shimming. Hey, you never know!!

If you're on a budget, go with the OEM stainles steel valves from a 2000 WRF/YZF ratherthan the Ti valves from the 01/02. Whole bunches cheaper and whole bunches more durable...just be sure you order the right springs to go along (same year...SS valves, being heavier, require stouter springs to control the motion). Then, take the money you save and have the seats cut by a reputable shop with a Serdi valve cutter. If you don't cut the seats, the new valves will vwerey quickly wear in to match the wear patterns of the old valves, significantly reducing their life. If you go with the SS valves, even with cutting the seats, you will be cheaper than going with OEM Ti valves, and you will have a much more durable ride.

Hi guys,

Many thanks for the info given, we are defo goin to put SS valves in, all 5 are getting replaced. And I've just told him to order uprated springs to go with them. As for cutting the valve seats, I don't think this will be done, due to cost and nowhere local does this kind of work. The seats look ok under close inspection with no visible pitting, scoring or burn marks. They look like new to be fair. I understand they will wear quickly, but hey let's see wot happens.. Ill update when the works complete. Getting fed up with the 4 banger now, too many moving parts and bloody expensive to re-build. Glad my kwak 250f is sweet as a nut!!

Regards. Stan

You are crazy if you dont get the seats cut. And their will be someone relatively close by that can do it for you. You just need to do some research, England is a pretty small place.

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