Club 80-90 Forums

Took the van out today and noticed a popping sound when going downhills when in gear (engine braking), it was worse when i was in second gear on a very steep hill. I could also hear it when I wasnt using the throttle on the flat.

I have recently had the carbs done by gasure and it has been running lovely up until today. It still goes OK and pulls up hills as well as it did after the carb refurb and a lot better than it did before the refurb.

Could this be the timing? Its almost as if the fuel that I put in it toay could have caused it.

Or is it "pinking"? and if it is what is causing it?

I have recently lost my tail pipe but havent noticed anything until today

Any ideas

sorry 2ltr 1982 air cooled

A little more information

I think the idle is a little to low as it takes a little time to get warm.

Ive had this, when i serviced my carb. Cut off valve was leaking. Exess fuel in exhaust was ignighting due to the heat.

It was just a case of tightening the cut off valve, (if yours is the same as pct 34) then to check it blow through the inlet pipe with the cut off depressed and no air should pass through.

Sounds like an air leak to me

or an imbalance on the throttle stop

pmulcahy wrote:It was just a case of tightening the cut off valve, (if yours is the same as pct 34) then to check it blow through the inlet pipe with the cut off depressed and no air should pass through.

thanks

Where is the cutoff valve?

Cheers

Ok, on my carb (i only have one) its what the fuel pipe connects to on the carb (from the pump), theres another pipe on the carb going to the fuel tank (return pipe). Basically its in the top half of my carb which can be removed by the screws on the top, this reveals the cut off valve and float float chamber (fuel cut off: gravity operated pin for when you turn upside down). Push the pin in and blow down the pipe going into the carb, there should be no air passing through, if it does fuel will pass into the carb constantly, overflowing the float chamer changing everything...warm starting..fuel econ....power. This was coupled in my case with air leaking into the exhaust which enabled the ignition of fuel. Im no expert this was just my case..Dont rule out timing etc

Need to add to this one..when i had driven around and got the engine was hot, stop the engine and take a look into the top of the carbs. I had smoke (vapourzed fuel) coming out like a small chimney .

pmulcahy wrote:Ok, on my carb (i only have one) its what the fuel pipe connects to on the carb (from the pump), theres another pipe on the carb going to the fuel tank (return pipe). Basically its in the top half of my carb which can be removed by the screws on the top, this reveals the cut off valve and float float chamber (fuel cut off: gravity operated pin for when you turn upside down). Push the pin in and blow down the pipe going into the carb, there should be no air passing through, if it does fuel will pass into the carb constantly, overflowing the float chamer changing everything...warm starting..fuel econ....power. This was coupled in my case with air leaking into the exhaust which enabled the ignition of fuel. Im no expert this was just my case..Dont rule out timing etc

OK mines a twin carb but ill have a look at that tomororrow. I have just been out to my van and I dont think it is an air leek as I have just had new t-peice balance bar rubber things put on and all the other pipes are very secure

Cheers

PS I also susspect that there is air leaking in to my exhust as it does appear to be blowing a little

paul

I think you just answered you question there! It's the exhaust leak. It allows air to get in when you are on engine braking and ignites the unburnt fuel coming through with the exhaust heat. Without this leak there would be no oxygen in the exhaust system and no rather loud popping!
I had this on mine for a while and it eventually blew the silencer apart... Not good!

Hi Paul

If you don't mind, I'm gonna join in on this thread as I have recently been suffering similar problems, ie:

- Erratic Idle (starts high like chokes sticking then after a few good revs it drops too low so the engine rocks side to side and wants to stall)
- Backfiring/popping in exhaust on engine braking (although not an awful lot)
- Erratic acceleration, often a bit spluttery, not always a smooth pull away.
- On a couple of occasions there has been a small amount of overrun when turning the engine off, ie: switch ignition off but engine still runs for a second rather than going straight off.

Sometimes though my problem seems to go away mid drive - the idle speed seems to level out and therefore the engine does not rock side to side, plus the acceleration problem smooths out... then the problem comes back.... hhmm.

So reading these replies it seems i need to look for an air leak/intake and check the return pipe on the carbs, which is ok. But when looking for air leaks/intakes - am I looking at the connections of the exhaust/manifold etc or holes in the silencer, or both? Or elsewhere?

Some tips would be great please

I have recently had a new clutch fitted, could this be connected in any way? Does any part of the exhaust system need removing to replace the clutch kit? Could the mechanic have accidentally made it possible for air to enter or escape the system?

Good luck Paul, I'll be looking forward to your feedback on your van.....

Ta
Dave

Got to come back to this one

I have had a look around the exhaust and cant see anything that might be leaking. Mind you one of my heat exchanger casings is completly missing and the other one is rotton where the exhaust system goes through it and reaches the silencer, so there is no seal. But I think that is why the heating doesnt work. Am I right in assuming that the exhaust comes out of the cilenderheads, down to the heat exchanger and then on to the silencer?

Both heat risers have come adrift as well, but this again is only to do with the heat. So my exhaust system is in a right mess but all the actual exhaust parts seem connected properly. But again its really rather loud. Could this be due to not having a tail pipe? or is it possible that the silencer is knackered inside and needs replacing.

Can anyone point me to a schematic diagram of the exhaust system so I can get a better understading of how it all works.

Cheers again

I'm getting the same symptoms, pinking, lack of power.
1982 1.9 Aircooled
Replaced exhaust a few months back.
I have a single weber twinport carb, checked advance and retard pipes for leaks. Checked advance was working by sucking and blowing into the advance pipe.
Tried timing at different deg BTDC, not sure what the optimum is but 12BTDC seems about right.(it starts and moves!)
I'm lost as to where to look next.

Did you manage to get to the bottom of your problem?

I will be taking the engine out over winter to rebuild, but would like to get a few more weekends out of it before then so any advice would be welcome


Thanks in advance

Mine pops like a bitch but my exhaust is like a rusty sieve. One day I will afford that stainless...

cygnak wrote:I'm getting the same symptoms, pinking, lack of power.
1982 1.9 Aircooled
Replaced exhaust a few months back.
I have a single weber twinport carb, checked advance and retard pipes for leaks. Checked advance was working by sucking and blowing into the advance pipe.
Tried timing at different deg BTDC, not sure what the optimum is but 12BTDC seems about right.(it starts and moves!)
I'm lost as to where to look next.

Did you manage to get to the bottom of your problem?

I will be taking the engine out over winter to rebuild, but would like to get a few more weekends out of it before then so any advice would be welcome


Thanks in advance

If it's pinking then the timing is too far advanced and could cause overheating leading to more pinking! Drop it back a bit, should improve pinking problem and lack of power hopefully.

albertramsbottom wrote:Got to come back to this one

I have had a look around the exhaust and cant see anything that might be leaking. Mind you one of my heat exchanger casings is completly missing and the other one is rotton where the exhaust system goes through it and reaches the silencer, so there is no seal. But I think that is why the heating doesnt work. Am I right in assuming that the exhaust comes out of the cilenderheads, down to the heat exchanger and then on to the silencer?

Both heat risers have come adrift as well, but this again is only to do with the heat. So my exhaust system is in a right mess but all the actual exhaust parts seem connected properly. But again its really rather loud. Could this be due to not having a tail pipe? or is it possible that the silencer is knackered inside and needs replacing.

Can anyone point me to a schematic diagram of the exhaust system so I can get a better understading of how it all works.

Cheers again

You need to check for exhaust leaks with the engine running btw.