Farting Series 3

While the S2 is in bits and being slowly rewelded thanks to the wise words of other forum members I need some help with a S3 problem that's being going on for a few months......She's a 1972 SWB and she drives absolutely fine, plenty of power etc but when going downhill in gear with my foot off the gas the exhaust starts popping and farting until I put my foot back on the gas a bit. I've checked plug gaps, fuel mixture, tried to see if there's a leak in the manifold, even tried a bottle of the dubious liquid decoke juice! If I can't figure it soon I'll have to do the unthinkable and send her to the garage! Any ideas.......Cheers Lard

erm its a petrol with a carb yes?

its normal for a petrol to pop on over run the engine still draws in fuel on over run but cant burn it so it chucks it into the exhaust so every so often it will ignite this little bit of fuel and pop it does it

Yeah, my '82 series 3 does that, more of a crackling/popping noise, maybe it's supposed to as it's carb fed. You here bikes do after they gun it then come off the juice.

Is this a zenith carb thing? i have a Solex (the better carb.....in my opinion) and it don't do that sir!!!

my webber carbs will do it too, as g spot said above its from still drawing fuel on over run , with out being fully burned and combusts in the exhaust ! they recon different air filters will stop / help it , changing the air flow/ intake pressure. i doubt it tho

If the ignition timing is set up properly it shouldn't do it.

Yes it's petrol and it's had a weber fitted at some time before I got it. I'm sure it's popping more than it's used to. These days it's every time it goes downhill. It's only been doing short hops for the last 6 months so maybe I've got some carbon build up. Might just need a bit of a thrash (as far as that's possible in this!). Thanks for the suggestions.

Hi,

Mine did that. Fitted Ducelier dizzy, made it worse. Fitted Hillman Imp D25 dizzy, cured it ......but engine sounded harsh - different advance curve?

This makes me suspect that dizzy is losing electrical continuity when at full vacuum advance. D45 dizzy?

Try pulling the vacuum advance pipe off, see if that makes any difference. Don't forget to put it back.

602

602 - tried a new condenser? worked on mine, i thought it was to do with the advance, just a 5quid condenser stopping from running proppa at higher revs.

Good ideas. I'll try them both (starting with the condenser). Credit where it's due though I think the wife has solved the problem - 'if that's the noise that's bothering you just shut the bloody window!'. Fair enough!

ours has just started doing this after having a new dizzy fitted and having weber carb adjusted timing was done with light and lots of fiddling lol and it's spot on but now when it's stood idling it sounds like me dad after a bottle of pop have found a crack in the manifold tho so got a new one on order so hoping that helps as it didn't do it before the adjustments, just was a bitch to start lol

it will be drawing in too much air and running lean.causing it to run ****ty.

I had a goldwing bike that did that, changed the inlet fanimold air bleed valve, changed the plugs, changed the plug leads, changed the head gaskets and then felt like headbutting the wall when changing the condensor fixed it, it was an old fart in the pub that told me that when the problem first started.

got a whole new dizzy complete so shouldn't be any probs there, altho it is a sh1tpart one plugs were done last month and those have been rechecked and regapped just to make sure, all this has come about because she was running on after the ignition was turned off, seems we have cured one problem and started another lol, about normal with landys i guess

bit like my wife you do 1 job she finds another

Are the plugs the correct ones?, the engine running on is a sign that something in the cylinders is warm causing it to 'diesel', sometimes caused by too 'hot' a plug, also this is symptomatic of unleaded petrol in a leaded engine.

yep plugs are correct, it is an old recon leaded engine but it had a Broquet fuel catalyst fitted in 2000 and has only done 80,000 odd miles since, catalyst is supposed to have life of at least 250,000 miles so shouldn't be causing us problems.

brnocz said:

bit like my wife you do 1 job she finds another

Click to expand...

how rude lol