cracked & leaking K & L tubeless valve stems

I've recently had an unusual problem with K & L tubeless valve stems.
About a year ago, I had a local Honda dealer in Las Vegas, NV replace 2 tires on the wheels from my 1996 Honda ST1100. I brought in the loose wheels and 2 new Bridgestone tires to the shop. They installed the new tires on the wheels and replaced the valve stems with short, straight, rubber tubeless valve stems (K & L part #32-8210).
About 10 months later I noticed that the valve stem on the rear wheel had cracked & was slowly leaking air. I then removed the rear wheel from the bike & had the Honda dealer replace the cracked & leaking valve stem. 2 months later, I noticed that the valve stem on the front wheel had also cracked & was slowly leaking air. I then had to remove the front wheel & have the Honda dealer replace the cracked & leaking valve stem.
The repair shop & parts department both tell me this is a very unusual problem.
Anyone here ever had any similar problems with cracked & leaking K&L tubeless valve stems? Thanks!
Pic follows:

Valve stems have a pretty rough life and get subjected to a lot of force while underway. Failures are unusual, but they do happen. Having both fail the same way might mean you got a pair of bad ones from the same batch or, more likely, they were improperly installed. Can you describe where they failed?

If you've got the tires off, you might want to switch to solid, angled valve stems that never have to be replaced. Most of us who've gone angled have installed the Ariete valve stems for many miles without problems. The Arietes run about $25 per pair and pay for themselves after a few tire changes. K&L sells what look like the same thing, right down to the stamping on the side, as part number 32-2978. (K&L may be the original manufacturer.)

--Mark

I suspect both stems were improperly installed.

As a forensic question what methodology of installation would result in them cracking almost a year later. That is how do you install a stem improperly to lead to cracking and leaking. Maybe bent at an extreme angle when pulled into place?

The bad batch thing seems like a real possibility since there were two not quite simultaneous failures. Or maybe a small stock stored improperly or old stock.

I'm not familiar with K&L brand and also never had a valve stem failure nor have I installed one. At least it was leaking and didn't separate while at speed.

ST Gui said:

As a forensic question what methodology of installation would result in them cracking almost a year later. That is how do you install a stem improperly to lead to cracking and leaking. Maybe bent at an extreme angle when pulled into place?

Click to expand...

I could see pulling the stem by the rubber with a pair of pliers causing problems. People that work on bikes for a living have a remarkable way of coming up with new ways to screw it up...

I'm not familiar with K&L brand...

Click to expand...

K&L is a manufacturer and wholesaler of motorcycle supplies. They supply parts to some of the manufacturers, and I wouldn't be at all surprised to learn that some of the minor parts on our bikes came from there.

--Mark

Oldbikefixr said:

I suspect both stems were improperly installed.

Click to expand...

That's also what I thought as a distinct possibility. Maybe that's why the Honda dealer was so willing to replace them for no charge, even after 10 months (for the rear wheel), then after 12 months (for the front wheel).

I just expected better training for Honda certified motorcycle service "technicians."
Call me old fashioned. I am a 1959 model year.

Agree with the recommendation to fit permanent metal stems and then forget about this problem. When I was a kid working in a gas station one of the guys would smear bearing grease on the stems to make them easier to pull into place. Turns out the grease was attacking the rubber and we had customers coming back with split stems. Boss said to use "Rubber Lube" instead, the same stuff used to mount the tires. Seemed a no brainer for most of us to do that as the brush and reservoir for the stuff was right there on the mounting machine, but this one guy had a "better" idea....

Yep, only metal stems on any of my bikes. Never had an issue with them.

I see issues with rubber stems in bikes that have poor access for pressure checking and air filling. Folks bend the stems to do that and the flexing causes the cracking/tearing. Dry rot is the biggest issue we run across.

sleazy rider said:

I see issues with rubber stems in bikes that have poor access for pressure checking and air filling. Folks bend the stems to do that and the flexing causes the cracking/tearing.

Click to expand...

Fortunately that's not a problem for the ST. I recently bought a 90º valve stem extender for that very reason. Use it to fill the tires then put it back in the glove box. This will have to do until the next tire change when I can have my metal stems installed.