Can anybody out there offer any advice as to why my Lambretta is going through spark plugs roughly every thirty to forty miles. I'm not sure what she was like before, but since a full engine rebuild, i'm only getting around that mileage per plug. The engine runs sweet for thirty or so miles then total cut-out, change the plug at the roadside, and off she goes again, fine for another 30 miles or so, then same again. I'm not riding her for thirty miles in one go, these are all roughly five to ten mile journeys at a time. I am running her on 4% oil mixture at the moment whilst running her in, intending to drop to 2% after a couple of hundred miles. Is engine running too hot perhaps with 4% oil, therefore burning plug out ? If so, should I change to a cooler running plug, from a B7ES NGK to a B5ES NGK ?, or adjust my air/fuel mixture to run cooler ?
Any advice would be most welcome,
Condenser working OK? A tricky coil can bleed charge to the electrode through the charge cycle and make it act like a glow plug, an intermittent positive short onto the coil feed line could do that as well and might be worth just checking your stator just in case a rivet hasn't fallen out inside and playing silly buggers on the coils in there, actually saw something like that when a LML rivet had fallen out inside and because it was magnetised it was causing the hall sensor to go crazy lol
Thanks for the response Ian, I'm more mechanically minded than electrical, so any advice I can get is appreciated. I do have two spare coils, one working, one not working, i can't remember which one is which but it won't be too much hassle to fit them and test them out. I hadn't thought of the condensor, is there any way that I can test the condensor, or do I just buy a new one and fit it to see ? I guess the best thing for me to do is look at the coil and condensor first before looking at the stator side of things as both are cheap to try in my case. The only slight problem I have is that even after fitting new coil or condensor, I'm not gong to know if the problem has rectified for thirty miles or so. Hey-ho, that's part of the pleasure of owning a Lammy, I suppose. I'll keep you updated Ian, thanks !
Don't think you can check a condensor function other than replacing with a known good unit :( They're not very expensive and at least you know its done.
Its really annoying when you get such an odd fault like this m8, I had an old Vespa that had frayed its sheating out of the stator area and the wires underneath had cracked with age and would periodically blow all the lights out, put new loom in, bulb holders, checked the stator but that tiny fray in the outer drove me nuts lol
You're right, this issue is driving me insane, she runs superbly with a new plug, but only for thirty miles or so. Even when the plug decides to die, there's no coughing or spluttering, just total cut out. Change the plug, then she's tip-top again. It's been 12 months of this, and I can't seem to get to the bottom of it. Still, i'm never going to get to the bottom of it without trying different things, I just hope it doesn't cost me a fortune in plugs in the meantime. Thanks again for the pointers, I don't think I'll change the condensor and coil at the same time cos if it sorts the problem out, I won't know which of the two was responsible, for future reference. Which would you advise that I change first ?
Condensor is the cheap one to replace, might be worth seeing if your coil is getting hot or its just knacked out if its an old oil filled one.
Been doing some searching for plug premature death and so many different causes, wrong heat range of plug for driving conditions, jet issues, stator issues, condensor and points, mixing some synthetics and mineral 2T oils, air leak aargh no wonder its driving you nuts lol
Apologies for the delay in responding Ian, i've been away for a week and haven't been on line. The coil isn't getting hot at all, so it might be worth me changing the condensor first as it's minimal cost. From there on, not sure what to try next at this stage but i've tried using a B9ES plug instead of a B7ES and was worse, the plug only lasted around three miles. So far as jet issues go, i've got a standard 100cc with standard jets. I've never mixed synthetic with mineral oil at all, so after changing the condensor it may be worth me pondering over stator, points or air leak issues. AAAAARGH !!!! IT GETS WORSE !!! Bloody Lambrettas !!!