G12 Loss Of Power

snatchpiece · Post by **snatchpiece** » Thu Jul 12, 2007 12:32 pm

quote:
Wish I had hearing that good! Probably just fumes from the 'shook up' fuel. If you can blow through the hole in the cap when it is fitted it should be ok.

My hearing is nothing special, the sound was quite loud which makes me think the vent could be restricted thus amplifying the sound!

GSAX1 · Post by **GSAX1** » Thu Jul 12, 2007 1:18 pm

Snatchpiece, I had problems with my tank cap some while ago. Here's what I did to clean it (old posting):

quote:
I recently "dismantled" my petrol tank cap by mistake when I pressurized it with compressed air through the went hole on the top. I tried air pressure to clear the stoppage in the (inside) vent hole, but instead the spring loaded part bent where the two indentantions are and the contents shot out! Thus I could find out how it is built up. The pin in the centre has no other function than providing anchorage for a chain. Loosening or taking out this pin will have no effect on removal of the inner assembly.

Try instead to jam one side down under one of the indentations and pry it upwards with a small screwdriver over the indentation on the other side. Don't worry if it bends slightly, you will be able to straighten it out afterwards.

When you take it apart you will notice a lot of rust and rubbish inside. Clean it out and clear any ventholes.

It sounds difficult but now that I know the technique I am able to dismantle the oil and tank caps (they are similar) without much difficulty.

Good luck.

Michael

Biscuit · Post by **Biscuit** » Thu Jul 12, 2007 1:38 pm

I'm only a simple soul, but surely the fact that you heard a 'whiffle'
(thats the technical term for the escape of fuel vapour) then it would seem that the vent is clear, unless of course any gunge is acting as a non-return valve.

GSAX1 · Post by **GSAX1** » Thu Jul 12, 2007 2:13 pm

One way to try out the tank cap theory is to loosen/open the cap when bike stops or is about to stop. If it starts going again the cap vent is clogged.

Biscuit · Post by **Biscuit** » Thu Jul 12, 2007 4:37 pm

In spite of a possible knuckle rap from Eamonn, I must say what magnificent scenery Michael.

snatchpiece · Post by **snatchpiece** » Thu Jul 12, 2007 4:46 pm

quote:
I'm only a simple soul, but surely the fact that you heard a 'whiffle'
(thats the technical term for the escape of fuel vapour) then it would seem that the vent is clear, unless of course any gunge is acting as a non-return valve.

Alan,

I was working on the theory that if the vent was partially blocked and therefore not allowing sufficient air in, then the 'whiffle' would be louder...a bit like when you squeeze the neck of a balloon when deflating it to make a rather loud raspberry!........if you see what I mean.

paul knapp · Post by **paul knapp** » Thu Jul 12, 2007 5:16 pm

If you think that the tank vent is at fault, remove the fuel line off the carburettor and turn the fuel tap on. The flow will surely indicate if there is a venting problem.

...

Biscuit · Post by **Biscuit** » Thu Jul 12, 2007 5:19 pm

The whiffle volume is proportional to the volume of fuel left in the tank (VW=TV-FV). Michael's is the fail-safe solution, ride the bike 'till the symptoms occur, then whip the cap off. There's a formula for 'whip', involving rotation speed/distance travelled.

snatchpiece · Post by **snatchpiece** » Fri Jul 13, 2007 9:04 am

quote:
There's a formula for 'whip', involving rotation speed/distance travelled.

If I ride until the problem occurs the machine will be hot, do I therefore need to take into account the coefficient of expansion when applying the above formula?

Merlin · Post by **Merlin** » Fri Jul 13, 2007 10:39 am

Just add in the piffle factor