Popping sound

[john1]

Hi Folks

I noticed a popping sound when comming down hills in gear the other week.
Now I cant' get any speed and running rubbish!

Starts fine revs are a wee bit rough tho. Flat spot when reving.

I have checked Vac pipes and they look fine, servo pipe looks ok also.
Im thinking air leak poss at inlet manifold, am I on the right path here or is there something more I could be looking at.
Thanks for your help in advance,

2L air cooled 1982

john

[BOXY]

Check the nuts holding the carbs to the studs on the manifolds haven't come loose. Also have a good look around the carbs in case one of the fuel solenoids has come loose or a blank has rattled out. Did you check to see if the rubber elbow & rubber tee at either end of the servo balance pipe haven't split?

[kevtherev]

what "looks" OK might be leaky.
for the price I would replace

take a look at the choke pull down unit. failure of that will allow air into the carb.
Pull the pipe off the carb and suck
the ability to constantly suck means it's buggered and is sucking air into the carb

[john1]

Thanks for replys folks.

rubber elbow & rubber tee at either end of the servo balance pipe, is that the pipe that runs from carb to carb?

I will check nuts tomorrow.

fuel solenoids has come loose, would this be the idle solenoid im looking at?


take a look at the choke pull down unit. failure of that will allow air into the carb.
Pull the pipe off the carb and suck
the ability to constantly suck means it's buggered and is sucking air into the carb

Im not sure where this pipe is, left or right carb? Around the choke set up i take it?

Thanks again for the help,

john

[kevtherev]

Sorry john my mistake you don't have a choke pull down with an air cooled engine

[BOXY]

rubber elbow & rubber tee at either end of the servo balance pipe, is that the pipe that runs from carb to carb?

It's a metal pipe that runs across the bulkhead and is connected to the manifold under the right carb by a rubber elbow, and under the left carb it is connected by the tee to the servo-pipe & the manifold. If this pipe is leaking and weakening the mixture, normally the van mis-fires and won't idle.

The "popping" could be a symptom of a weak mixture or could be an over-advanced ignition timing.

Starts fine revs are a wee bit rough tho. Flat spot when reving.

This might not be caused by a weak mixture because of an air leak, it could be fuel starvation or timing. Check the fuel filter under the van, if it hasn't been changed for a while it's probably worth blowing £1.50 on a new one.

[john1]

Kev/Boxy

Thanks for your help, it will idle fine and rev not bad with choke on.
Its when its off its rough and lumpy, thats why i thought it must be air intake.

Fuel filter was changes 300miles ago, new lectky pump and regulator.
I haven't touched the dizzy so timming should be the same but i will give it a check.

Boxy what is (blank has rattled out)? Im not sure about that mate.

Thanks again guys

John

[BOXY]

what is (blank has rattled out)? Im not sure about that mate

A while ago I noticed that the side of my right hand carb looked like something had run down the side and cleaned off the layer of dirty! The clean trail lead to a threaded hole, and a closer search turned up a small threaded blank on top of the tinware. I can't say I noticed any running problems but the fact the blank was still in the engine bay means it probably wasn't AWOL for long. It was certainly letting petrol out, so was probably letting air in.

The twin Solex's have got a lot of "bits" attached, it worth having a good look around every so often to make sure no fuel is getting out where it shouldn't be.

[jason k]

99 times out of 100 its the inlet manifold gasket.

try spraying some wd40 round the inlet when the motors running.

if the note changes then its the gasket

[john1]

99 times out of 100 its the inlet manifold gasket.

try spraying some wd40 round the inlet when the motors running.

if the note changes then its the gasket

Thanks Jason, I tried this yesterday and if anything the wd40 seemed to blow away from the joint!!
no change in note tho!
I expected the wd40 to suck in and disappear but to blow away! Exhaust manafold blow?????? just a thot.

Thank you for input mate Im just about ready to blow myself!

john

[kevtherev]

Oh dear...

[john1]

Oh dear...

Yes oh dear!

any ideas Kev?

[kevtherev]

I think you may need a compression test.. that "blow back" is not good

[john1]

I think you may need a compression test.. that "blow back" is not good

Oh dear dear!

I will get back to you if the rope snaps!

john

[kevtherev]

Are you sure it bows the WD away?