2001 ST1100 overheating

Moisture in the clutch fluid, boiling to vapour, creating air bubbles?

could be??

I am planning on replacing the fluid of course, but wonder if it might be something else?? any other ideas?

energy conserving (not wet clutch compatible) motor oil?

Bush said:

Moisture in the clutch fluid, boiling to vapour, creating air bubbles?

Click to expand...

+1 If it works well when cool, my bet's on moisture in the fluid.

How would moisture get in there? i keep it in the garage, i DO live in a rain forest tho...

I guess what I am asking is what method does the moisture get in it? what do i look for to correct?

Your garage has the same humidity as the rest of your environment.

Brake fluid is hygroscopic: it loves water and will absorb it from the humidity in the air.

If you live in a humid area you need to really stay on top of changing the brake and clutch fluid due to the absorption.

HTH,
Mark

Edit:
If you don't live in a humid area you have to stay on top of changing the brake and clutch fluid too... because brake fluid is hygroscopic...
And this means never using brake/clutch fluid from a previously used container as it *will* have absorbed water!

Yea, what Mark said. Change it, at least, every two years, maybe every year under damp conditions.

OK, makes sense.. but should it be normal for a bike sitting at idle once warmed up will over heat the clutch fluid? or only if there is moisture in the fluid?

superdiver said:

OK, makes sense.. but should it be normal for a bike sitting at idle once warmed up will over heat the clutch fluid? or only if there is moisture in the fluid?

Click to expand...

The boiling point of brake/clutch fluid is much, much higher than water. The dry boiling point of DOT4 fluid is 230?C compared to 100?C for water. Note that the DOT4 boiling point drops to 155?C with only 3.7% water by volume, so just a little moisture can cause a problem. This is why most recommend using a new, unopened can of brake fluid when changing.

Good info... I will be sure to change the fluid with a fresh new DOT4 container... Is all DOT 4 the same basically? or are there things to avoid?

I think it's all the same within name brands.

Also, I would say that if this is the cause of your clutch problem, it's an extreme case IMO. I've heard of brakes/clutch getting spongy when hot but not completely failing, except when racing. I would assume that your fluid is very dark. New fluid is pretty clear.

I saw a table of the different Dot 4 brake fluid stats once, I have no idea where on the net I was when I saw it...

The bottom line was all of them met the specification.