Well I'll drop the needle half a clip and replace the float valve with the correct (300) one and see what that does.
And I'll re-check the manifolds too.
Do the jets look ok?
I'll check what the timing is also
Plug chop and plug colour help please - happy ending
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Shipleystevep
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Adam_Winstone
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The current Mugellos run high comp heads and will quickly hole a piston if run too advanced.
There are lots and lots of people out there that have pistons sitting on their garage shelves from running over advanced ignition timing on high comp motors. Perhaps people will be good enough to post photos to provide all the proof you require. I can't post such photos for you as I wouldn't dream of running a high comp kit at 19 degrees!
If you want to understand how high comp influences ignition timing requirements then just look at factory Vespa P-Range ignition recommendations: Original P125 = 21 dbtdc, whereas the tuned high comp T5 125 = 16 dbtdc... and that's when you could get decent colder burning fuel!
As for why today?... because today's fuel is NOTHING like the decent fuel that you could buy when the original figures were determined. Today we have fuel that burns hotter because of ethanol content and 'run clean' additives/detergents to help clean fuel injection 4-strokes, making 2-strokes run hot and need less ignition advance to stay cool.
"... who banded that figure around" = Cambridge Lambretta, the main UK importer and supplier of the kit, hence the link. Why would you listen to anyone else in favour of the kit's supplier?! These are their latest set-up instructions, superseding all older instructions, so taking into account their wealth of first-hand experience of this kit and any changes that may result from the change in fuel.
"trust me"... certainly don't trust me... trust the instructions given by the importer!
Adam
There are lots and lots of people out there that have pistons sitting on their garage shelves from running over advanced ignition timing on high comp motors. Perhaps people will be good enough to post photos to provide all the proof you require. I can't post such photos for you as I wouldn't dream of running a high comp kit at 19 degrees!
If you want to understand how high comp influences ignition timing requirements then just look at factory Vespa P-Range ignition recommendations: Original P125 = 21 dbtdc, whereas the tuned high comp T5 125 = 16 dbtdc... and that's when you could get decent colder burning fuel!
As for why today?... because today's fuel is NOTHING like the decent fuel that you could buy when the original figures were determined. Today we have fuel that burns hotter because of ethanol content and 'run clean' additives/detergents to help clean fuel injection 4-strokes, making 2-strokes run hot and need less ignition advance to stay cool.
"... who banded that figure around" = Cambridge Lambretta, the main UK importer and supplier of the kit, hence the link. Why would you listen to anyone else in favour of the kit's supplier?! These are their latest set-up instructions, superseding all older instructions, so taking into account their wealth of first-hand experience of this kit and any changes that may result from the change in fuel.
"trust me"... certainly don't trust me... trust the instructions given by the importer!
Adam
Yup a good answer. But it doesn't alter the fact that, that plug is showing classic lean burn symptoms. Arsing about with the timing ain't going to fix it. Jetting is the issue. That's my advice/opinion take it or leave it.
Chris in Margate wrote:I strongly disagree. 15 degrees BTDC is far too far retarded and I don't know who bandied that figure around. There is no evidence to suggest that 15 is better than 19; no evidence whatsoever.
19 degrees is fine, might dtop to 18, trust me; that's 4 degrees retarded from where we used to be with Innocenti recommendations when the fuel was purer.
You don't have a timing issue. You have a burn issue with either dangerously weak mixture and/or an air leak somewhere. Check exhaust nuts.
no evidence?
Do you understand what retarding ignitions does and why it should be done on a 2 stroke, especially a 2stroke that has an expansion and therefor a powerband, I take it you don't know why an expansion gives the powerband and why that is directly related to retarding the ignition?
I agree that plug colour is due to lean running and not ignition though as he said he hasn't opened it up, so I doubt its revved high enough for ignition position to come into play.
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Evesy
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If you've only gone up to 3/4 throttle you probably haven't even touched the main jet yet. Pilot and atomiser sounds fine but I recon the needle needs changing. I wouldn't ride it with a plug that colour unless you fancy pushing it home.
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Chris in Margate
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Over 40 years building, tuning, running, repairing Lambretta engines and thank you but YES I do know how a 2 stroke motor works and am fully conversant with the tuned pulses of an expansion chamber so please don't try to teach me how to suck eggs. You build yours your way and I'll build mine my way.
That spark plug is nothing to do with timing !
I didn't come on here for an argument; I presented my opinion through years of learning albeit "strongly".
Cambridge Lambretta whilst a trusted dealer with whom I have dealt many times are not the only tuners in the world and not the font of all information. Some of these figures and facts have not been arrived at by any technical investigation backed up by forensic evidence; they are merely numbers quoted very safely to ensure their kits don't blow up.
Most of the holed pistons will have been the result of overheating caused by pre-ignition brought about by weak mixtues.
I didn't google any 2 stroke theory; I am talking from experience.
C'est la vie; we can't all agree but it's no reason to fall out !
That spark plug is nothing to do with timing !
I didn't come on here for an argument; I presented my opinion through years of learning albeit "strongly".
Cambridge Lambretta whilst a trusted dealer with whom I have dealt many times are not the only tuners in the world and not the font of all information. Some of these figures and facts have not been arrived at by any technical investigation backed up by forensic evidence; they are merely numbers quoted very safely to ensure their kits don't blow up.
Most of the holed pistons will have been the result of overheating caused by pre-ignition brought about by weak mixtues.
I didn't google any 2 stroke theory; I am talking from experience.
C'est la vie; we can't all agree but it's no reason to fall out !
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Shipleystevep
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Hi all, I really appreciate the responses....
If I haven't got on the main jet yet do you think that 55 pilot AV 266 slide 40 needle X7 are in the ballpark and would moving the needle make a big difference? If I've got too small a float valve (which I do at 200) would that cause a problem with fuel starvation?
I'll check the manifolds too.
Thanks
If I haven't got on the main jet yet do you think that 55 pilot AV 266 slide 40 needle X7 are in the ballpark and would moving the needle make a big difference? If I've got too small a float valve (which I do at 200) would that cause a problem with fuel starvation?
I'll check the manifolds too.
Thanks
Shipleystevep wrote:Hi all, I really appreciate the responses....
If I haven't got on the main jet yet do you think that 55 pilot AV 266 slide 40 needle X7 are in the ballpark and would moving the needle make a big difference? If I've got too small a float valve (which I do at 200) would that cause a problem with fuel starvation?
I'll check the manifolds too.
Thanks
From "experience", float valve will make it run lean for sure.
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Adam_Winstone
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^... agreed but the fuel starvation from a small float needle valve shouldn't restrict flow to the point that the rate is causing this sort of weakness at lower throttle positions and fuel demands. I'd expect float valve restrictions to be highlighted when holding it for long periods of high fuel demand (using it faster than the 200 valve can supply), probably 3/4 and full throttle only, whereas that plug looks crazy hot at all throttle positions so far.
I wonder if something else is having an issue here.
For the record, I quoted Cambridge's Mugello settings as IMO it shows the direction that the timing should be going, however, if you look again, I've suggested no more that 17 dbtdc and stated that earlier versions are more forgiving when run with reasonable compression ratios. I would not be looking to set the timing to 15 but I would be happy setting it to 17... very happy. Obviously, timing requirement goes hand in hand with exhaust duration (corrected compression ratio) so we're unable to give any informed opinion of timing requirements without knowing more about head and barrel.
Good discussion though and food for thought
Adam
I wonder if something else is having an issue here.
For the record, I quoted Cambridge's Mugello settings as IMO it shows the direction that the timing should be going, however, if you look again, I've suggested no more that 17 dbtdc and stated that earlier versions are more forgiving when run with reasonable compression ratios. I would not be looking to set the timing to 15 but I would be happy setting it to 17... very happy. Obviously, timing requirement goes hand in hand with exhaust duration (corrected compression ratio) so we're unable to give any informed opinion of timing requirements without knowing more about head and barrel.
Good discussion though and food for thought
Adam