Condensation on Carb...

[slow-lane-Matt]

Is this normal.

After years of running well the bus has started back firing when taking foot off gas and coasting in gear to slow down.

Doing research it seems an air leak is most likely culprit....

I have checked tappets and points - they were OK.

Before I attack the carb (never done before) wondered if this condensation could be a clue...

The base of the carb is cool to the touch, but nowhere near freezing - so I assume the exhaust/heating is working

Any one got any ideas, bus starts and runs beautifully - so reluctant to pull the carb if not really necessary and make things worse...

Photo taken after a 10 minute gentle drive

 

[Trikky2]

Most likely culprit is the exhaust. Check carefully for small holes, check the flanges and gaskets.

 

[thejinx]

I have this. Why would the exhaust cause it. How do you fix it

 

[slow-lane-Matt]

I'll check the exhaust, but is it anything to worry about - I can live with it, unless it's advance warning of something worse to come....

 

[Trikky2]

I have this. Why would the exhaust cause it. How do you fix it

Find the leak and fix it :lol:

Another common cause of backfiring is having the idle mixture set too lean.

 

[thejinx]

Doh!! So condensation on the carb is caused by heat in the engine bay caused by leak in the exhaust.

 

[Trikky2]

Doh!! So condensation on the carb is caused by heat in the engine bay caused by leak in the exhaust.

No.

Backfiring is caused by leaks in the exhaust or too lean mixture.

Condensation has nothing to do with either.

 

[monkeyvanwestybike]

I think condensation on bottom of carb
is common on single carbs
I get it on mine sometimes on a run in the early hours
It's more frost like
I suppose it varies with a higher dew point
I think that's what the hot spots
Are for on inlet manifold to help prevent this

 

[BRAD]

Matt is your carb and inlet ice cold?

Mine has just developed this.

 

[slow-lane-Matt]

No - but they are cool to the touch. The constant vaporising of the fuel does have cooling effect, (like aerosol).

The smaller tubes on the manifold are meant to divert exhaust heat to under the carb to keep it warm and prevent icing, and these do get blocked
with soot. Maybe your's is blocked and mine on the way to getting blocked....

I think you should be able to feel the heat on these tubes with your hand - so if they are cold at the lower end, and rest of exhaust system hot, probably safe to assume no hot exhaust fumes are getting through to provide the heat - and manifold needs replacing (get a second opinion!)

 

[BRAD]

Yes mate I thought it was blocked, wrong time of year to be sitting in the driveway taking the alternator out for the 4th time this year.
I suppose I will get round to it eventually but I cleared a heat riser out on a beetle years ago, I remember it being a pain in the arse and taking forever, wire with a drill, burning with a torch it takes ages! :shock:
I wonder if an acid dip would be a short cut

 

[slow-lane-Matt]

...I struggled to clear one I bought on Ebay. I got refund when proved it was blocked but still spent hours trying to
unblock it - various chemicals/petrol, very stiff wire in drill etc etc . Nothing worked for me.

In the end pretty much gave up, but last ditch attempt was to chuck on very hot bonfire. The alloy that joins the two
pipes together melted away, leaving two bent pipes - so that was the end of that...!

 

[Matt84]

Yep,

I remember having this prob on my beetle - it's called carb icing, you've got it spot on, the manifold should heat the carb but it gets blocked with carbon over the years, someone said caustic soda can clear it but never tried - nasty stuff that.

Best bet is new manifold I guess!!

Matt

 

[gas1man]

Patience ....Caustic soda and water, every evening after work for a week, then 2 days with a piece of clutch cable
with one end ragged and the other in my battery drill. A leather ish glove and eventually it all came out.
The glove is for protection of the hand guiding the cable so it does not kink or bend before going right in.
Never on a high speed , the glove can catch or the ragged end catches and it kinks so fast you can't catch it
meaning another piece of cable. Good luck.

J & P

 

[hobbo]

Hi I have a wrap around heater blanket which goes round the base of the carb and is electrically connected to the live on the coil. I have no idea where it came from, but it seems to work have never suffered from carb icing even in the coldest of weather. Mike