Two Wheel Tales

The Phatt Files

The Sphincter Valve

A few people such as Rsnow have written about having trouble with the adjustment of their sphincter valve. To help he and others I shall explain a bit about how these useful devices may be looked after.

As far as RSnow’s personal observation that his valve seems to come on more frequently in spring than in summer, this is normal. Remember it is the widening of the eyes that trigger its operation. As you ride through the year and skill improves the need for widening of the eyes diminishes.

So first a brief history:
Back in the early years when they were manually operated they were kept clean as a matter of common sense. But even back in the dark times when machinery was hardly thought of as a thing for the common man a yearly spring cleaning was considered sufficient.
Usually the coming of strawberry season and similar fruits coming into season was the signal to do the yearly cleaning, something our ancestors have know from way back.
You can find reference to the spring maintenance procedure in Walton Weatherby's classic book or Bentan Bumptit's neo novel on traveling in the early years of cars.

There are not too many among us here any more who actually saw such machines as the Scott Squirrels at speed, but early reports indicate that the sphincter valve was about the only brakes these things had. Some of those among us will remember that very early versions such as those found on forties through sixties machines with single leading shoe brakes actually had two settings: stage one was when the eyes widened; stage two was activated with the severe clenching of the teeth. A few creative individuals managed to overdrive the limiting "blow out valve" and created a third stage which was activated by the grabbing the bars with gorilla strength grip and pushing away for all they were worth. This modification did not really work all that well.

As modern brakes and tires evolved in the 70's and the switch to disks became more common, there was less need for the second stage and a simpler valve was developed, which required less maintenance and eventually they were made fully automatic.
Unfortunately there was a time when the mounting and activation methods were less than successful.

It took a while before the universal mounting of today was agreed upon by all makers.
The legendary H2 Kawasaki triple two strokes had a unique idea of mounting the activator in the front fork leg, so that upon extreme compression it would activate. Unfortunately since it spent a lot of time on the back wheel this did not work as well as hoped.
Also when the front end came down the valve would often kick in rather suddenly
causing either a lack of control, a pitching of the rider over the bars or both!

Norton had a very nice twin cylinder 750 that was noted for its handling, thus they felt that a use once and throw away sphincter valve would be sufficient. This was OK until they installed the now much sought after Combat motor, with the extra horsepower and no improvement in braking. The valve tended to go off more often in the new Commando Norton and thus the phrase Going Commando was born.

So while modern bikes actually do not need valve maintenance, other than an annual spring cleaning, there are still a few individuals like to do a complete inspection as well as maintenance. These individuals tend to be those who like their bike to be considered solid and with sense of history behind them. The kind of thing that has a style that has not really changed much since the forties

They still like to tinker with their bikes.
They insist on keeping them spotless.
They do not ride them in the rain.
They are sometimes seen cleaning their chain with a tooth brush and put a cover over them at night and for reasons unknown many do an annual inspection of their bikes sphincter valve.

These people are often referred to by others as having their head up their a$$
Now as with any product there are always those who jump on the brand name band wagon.
Sometimes they purchase used equipment that has not been maintained well. Other times they purchase brand new equipment that is often too tight or too loose from uneven manufacturing tolerances. As with any new owner they are often confused as to why everyone does not ride the same bike as them. Sometimes in their desire to "Join the club" as it were, they get overly excited about tinkering with their new toy and perform the sphincter valve maintenance poorly or with improper tools and lubricants.

These people are often referred to as having their head stuck up their a$$
So if your valve does not seem to be working it is probably working fine.
If your bike has been built since about 1988 you have the fully automatic model and you do not need to do anything.
You are welcome
Johnnie Phatt

Johnnie Phatt is a Regular Contributor To CMG

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