Valve Length

[brownfella]

Does anyone happen to know what the length of DRZ valves are supposed to be? Intake and exhaust valves same length? Is there a spec for stretch? I will have my motor apart in the coming weeks and would like to check my valves. My manual has all the specs for the valves and seats, but no valve length spec.

Thanks,

Chris

[mdlifcrisis]

I dont have a direct answer for you. I wouldnt be concerned with stretch. Im fairly certain its not even an issue. Valve face wear is what you should concern yourself with. It IS an issue. Valve recession is pretty common and cause for an occasional re-shim as the valves sink deeper into the head.

Search the forum and consider replacing the valves if your motor has some mileage.

[brownfella]

Thanks mdlifcrisis. Yes, I am aware of the possibility of seat wear, and will check that as well.

Anybody know the stock valve length? Perhaps someone has a new valve sitting around they could measure.

Chris

[Tinwings]

Thanks mdlifcrisis. Yes, I am aware of the possibility of seat wear, and will check that as well.

Anybody know the stock valve length? Perhaps someone has a new valve sitting around they could measure.

Chris

I don't think you are going to get any useful measurements this way. There's know way to know what tolerances the valves were manufactured to. There could easily be .08mm variation in length, or even more between batches. And there's no way to know if there has been a change in specs between the '05 valves in your bike, and a new '09 valve. I've got two new Ferrea exhaust valves here in front of me, presumably from the same batch. Their over all lengths differ by more than .04mm

[Erik Marquez]

SUZUKI DRZ 400

Exhaust Nominal over all length 81.75 mm

Intake nominal overall length 82.65 mm

The info means little for any serviceability check.. But there ya go.

If you have a measurement of the specific valve you looking at before install and then after, you could measure stretch.. But measuring a mass produced valve not produced to an exact length, but to some nominal production spec... You’re not going to get any useful data from checking a used valve.

[lynk]

Bronco, maybe the guy just wants to play with his new valve spring compressor tool.

[brownfella]

Bronco, maybe the guy just wants to play with his new valve spring compressor tool.

Well actually you correct!

Anyway, thanks for all your insights and info everyone. I had no idea the production tolerances would be so "loose" when it comes to valve length.

Anybody want a set of used - possibly slightly stretched - valves??

Chris:ride:

[Wayward Son]

they arent stretched.

[joneill4]

What is the fix when your valves start sinking?

[Erik Marquez]

Well actually you correct!

Anyway, thanks for all your insights and info everyone. I had no idea the production tolerances would be so "loose" when it comes to valve length.

Anybody want a set of used - possibly slightly stretched - valves??

Chris:ride:

What is the fix when your valves start sinking?

Once the valve face wears, you replace it, have the seats cut, and new valves, seals, locks installed...

[brownfella]

they arent stretched.

I have read multiple threads here concerning these valves and their tendency to return to their original state (two pieces). I had assumed that this was caused by stress, and also assumed that the valves would stretch slightly before separating.

Are these catastrophic failures simply the result of mechanical interference?

Chris