Timing confusion, PX electric start models

[partanen]

I have PX200 2003. Timing was set half way between "IT" and "A". I'm pretty sure it's factory setting. How accurate it is, who knows. Do they set these properly at the factory?

Then I set it to "A", as been advised all over internet for PX200. Today I read Haynes manual, and it says that ignition timing for for PX125/150/200 electric start models should be set 18 degrees BTDC at 2500 - 3000 rpm.

We all know Haynes, but then I found this: beedspeed.com/html-pages/IgnitionTiming.htm To me it says 18 degrees for PX200 modern, and 23 degrees for older P200.

Now I wonder what is the big difference between 150 and 200cc engine. So big that they need different ignition timing? Or why different setting for older 200?

I use 98 octane fuel because our 95 octane fuel includes up to 10% of ethanol. (98 includes up to 5% ethanol which I don't like at all.) I haven't noticed any pinking so far.

Then how accurate are timing marks? This might be the only way to be sure:

I just wanted to ask what you think? Thanks in advance.

[henri]

the early 200 where set to the "a" mark ,later electric starts its the "it" for 125-200's as far as ive ever known.the 23deg for older p200 is because they needed the advance for the petrol at the time.most people set to 21deg an then retard a deg or 2 til pinking is no longer heard on 2/3rds throttle under load (ie up a hill).the 18deg is in the supplement for later models in haynes manual ,early 125-150's it states as 21deg if memory serves .
as to factory marks ,if you put a degree disc up to them there almost a whole degree in width or more ,an wether there set right in factory depends on guy doing the job (before/after lunch,friday afternoon,an monday if his team lost on saturday,)an wether he can be bothered to do it right.there only a guide for "static timing" so engine can start an be set proper, a piston stop/tdc gauge,degree disc,strobe light(1 with own power source)an a blob of paint/tippex is the tools to do the job right .
you only have to do a full job once on any engine if the marks are made permanent i.e. scratch/centerpunch.an strobing is the only way to be sure where ya timing is set,an also can be altered for state of tuning or local petrol type.where are you ,as my understanding of ethanol in england is your more likely to find it in the super unleaded than ordinary (95octane)an also theres no difference between supermarket an named brand stuff.they have to use so much re-newable fuel(ethanol)by law an so long as its under 10%dont have to label the pump,so mix it in in variable ratio's depending on availability/cost, an damm the old vehicle consumer when he fills up on a ethanol/additive rich day .
i set my px150 an mates 200e an other 125e to 19 degrees an hav no problems on 95 octane fuel .H

[kru251]

As an aside, the higher quantity of ethanol in fuel can make floats in carburetors expand too. More of a Lammie problem as they can jam on the internals carb walls.
You're though using a red tipped float needle too?

[partanen]

I'm in Finland. In here they have to label how much ethanol is included in petrol. We have 95E10 and 98E5. Latter number tells maximum ethanol amount included. I guess ethanol and 2 stroke oil cannot work together very well.

I have timing lamp, but I guess I have to purchase degree disk someday soon.

[henri]

not just lammie's ,have swapped floats an fuel lines on my older car to ethanol resistant stuff ,an ethanol eats fiberglass,so dune buggy/70's bsa/triumphs an 70's trial bikes all need to swap or use sealant too. havent seen a ethanol resistant vespa float yet,but most needles supplied today are red tips 1's,wether there resistant or the red is put on the tip by bloke earning 15ruppees a day to do it is down to the quality/price of supplyier.
if youve had your tank sealed a long time ago ,its worth re-sealing with ethanol resistant sealer as some older sealants dont resist it.tapox is reported to still be ok for metal tanks an there's another sealant for fiberglass tanks or 1's that have non-welded repairs (chemmy metal/jb weld) .H

[partanen]

I have new float needle in, I think tip was red. I may have to take carb out again anyway as fixing bolts were loose. New gaskets and some thread lock might work.

[partanen]

The reason I brought octane to this discussion is that if it has influence to ingnition timing.

[sbwnik]

The main reason that the later ones use 18 degrees is that they use a lower compression head compared to the earlier Rally 200 type head. Nothing to do with ethanol, that's a bonus result.

It's also why I'm buying all the early 200 heads that I can find

[partanen]

Beedspeed says: 18 degrees PX Electric Modern setting for Unleaded.

Makes me think if I can use more advanced ignition with 98 octane petrol. Any benefits, propably not. Piaggio allows 95 octane, but that I don't want to use because it contains more ethanol.

[partanen]

I was trying to make video, but still picture looks better:



Timing marks at the stator where at "A" as I told earlier. But with running engine marks were between "A" and "IT". I tweaked stator marks between "A" and "IT", and now "running engine marks" seems to be at "IT".

So ignition was spot on from the factory. I'm not saying they made it on purpose. I believe they didn't have time time to check it. These days. I dare not to think what's coming.

[henri]

to be really accurate you need to remove the flywheel cover an make marks on the cases ,as cover can settle in slightly different places when removed/replaced. h

[partanen]

I might do that some day. For now I think it's close so I can sleep at night.

[joey]

I was under the impression that P2s still run 23btdc as standard and the lower comp head was introduced to reduce the chance of pinking?

[vespasco]

May 4, 2014 18:44:59 GMT joey said:

I was under the impression that P2s still run 23btdc as standard and the lower comp head was introduced to reduce the chance of pinking?

23* Blimey. Im glad im not the only one!
I believe that a lower compression head will also help with reducing emissions/suits restricted exhausts/electric start?/poor quality fuel.

Hey Nik! I'm sure i have a spare 200 head. How do i tell if its an early one?

[sbwnik]

Later ones have four little tabs underneath, and there was a time when these were marked 'US', but it seems the most recent ones no longer have this. The earlier ones are just plain apart from the ignition bowl. I think there is about four or five ml difference in size too, but I could be wrong, never measured either.

I'll get some photos next time I'm in the garage.

[vespasco]

Excellent. If ive still got it then it will be the older one if you want it Nik?!
I'll have a rummage!

Id be interested to know the cc difference between the 2 heads if you do ever get the chance. Handy to know for re profiling purposes.

[partanen]

Here is one from year 2003 model:

[vespasco]

Hey! It looks like you are measuring the volume of the head? Thats exactly what id like to know!!
Or are you checking the spark plug hole does not leak

[partanen]

I wanted to know if this crack was leaking, luckily it didn't.

[henri]

it might not leak cold/oil but under pressure an heat it could be different ,not a head i'd try an tune but 1 i might dremel back a bit to see if i could get rid off crack an use again.most cracks like this are from casting flaws an can be used if careful,the only way apart from pressure testing is to use crack test fluid,its magnetic an ya fill the orifice an put horseshoe magnets over the suspected crack area outside .the fluid is extremely thin an bright orange so if drawn through crack will show up,an can withstand being heated to mimic running conditions .
but for tuning purposes you could re-profile that head but why bother when other heads are cheapish an the crack might run too deep to be profiled out.
h

[partanen]

Some sanding and the cylinder head looked a lot better. It's in use at the moment.

Now I wonder should I purchase early Piaggio head, or mmw head.

[sbwnik]

OK, I think a heads up and possibly a warning is needed here.

I'm off over to Doncaster Hunters rally in the morning, so thought I'd give the scooter a once over before I went. Pulled the plug to clean it, and there were a couple of small flecks of metal attached. Panic time... Took the head off, and the piston has got slightly dimpled. Nothing major, but showing a few signs of pre-detonation.
Now this is a P2 with timing retarded to 18 degrees, this isn't a racing bike, it's almost standard bar the exhaust and head. I've stuck the later type head back on, and will be checking carefully for further damage when i get home on Sunday, it being a 50 mile round trip.

Ethanol may cause more ignition problems than I realised.

[henri]

which type of petrol do you use ,normal or super,an named garage or supermarket. there's loads of debate in classic car an bike circles about ethanol.all very confusing an no consensus forming yet,doesnt help that the suppliers mix an match,so say shell might have more ethanol in super but texaco stick it in the normal unleaded,an then next week swap around,an supermarkets just buy the cheapest the supplier offers with/without ethanol.
there's been more talk on lambretta forums about ethanol/holed pistons ,but as most of em run kitted or "original"30-40 year old pistons ,just blaming the fuel dont fly with me .ive holed pistons in past,leaded days ,wrong spark plug/timing out by 2-3 degrees the wrong way/an just thrashing full bore for too long.not saying youve done the above nic,cept maybe the last ,an from ya post the engine sounds set right ,with a later lower comp head you should get away with no more probs,when ya get a chance are ya swapping the piston out ,just in case .as a jet of molten ali-plasma shot into the cases can be expensive.running in a new piston/rings will be annoying in rally season tho,maybe a fingers crossed an do it in winter moment,i know i'd be tempted. H

[vespasco]

As far as i can tell, the main/only difference between the heads (old P and the mmw 0.0mm) would be the squish gap.
Do you want to experiment? Then go with the mmw.
Do you want something you know should work? Then go with the stock.
Compression is the same, if not 1cc less, in the mmw.


Nik! Am i reading that right? Youre using 18* with the older head? Do you mean 18* with the late type head?! Where on the head is the piston pitted? Is the spark plug melted/broken/or? Likely its detonation. Not pre ignition.
Ethanol has more oxygen in it, making it leaner! By how much i could not say.

Esso super no ethanol, shell won't say. Bp not in Ultimate and not in texaco super.

All the 'normal ' 95 unleaded is required to use minimum 5% ethanol. Renewable energy agreement thingy.

But .....! this was in feb 2011. Im not sure whos changing what now as they have been phasing in more ethanol , 10% in some cases to unleaded and adding smaller amounts to super inleaded.

Taking that into account , a llower compresion will help with pinking , as will timing +/-, which you would need to find a sweet spot with the mmw.

Ive always used shell v power on my kitted engine. But may change that v soon as i did have to adjust my carb very slightly the other day for the first for a v long time and then got paranoid it was trying to pink?!

[henri]

vespaco is right in saying ethanol has oxygen in it ,on a atomic layer ,1 molecule of oxygen to the hydrogen/carbon ,where as petrol is just hydrogen an carbon.but as its a part of the fuel an not free it doesnt "lean" the mix up .its 1 of the reasons that ethanol burns "hotter" than petrol giving the same effect as a lean mix .but if you up-jet or richen the mixture your just adding more fuel/ethanol making the "lean" effect worse .so long as you can get mix right an timing good wether your engines can run on ethanoled fuels comes down to the grade of ali ya piston is made off.piaggio originals are a low-heat expansion aircraft grade stuff an should be ok. cheap indian replacements-god knows but probably not,an kitted ones you'll have to ask the makers,an ha-ha to purist bretta owners who insist on original italian pistons as i think innoccetti made em from war surplus ali pans melted down an re-cast ,even back in the day they were of dodgy composition an quality.tho most of the talk on there forums is more about fuel lines/floats problems .
if you check the bulen fuel systems (SU carbs)website there's some good info on ethanol an its affects on carbs ,but it doesnt go into combustion stuff as carbs is all they do.does anybody speak portugese as brazil has been running cars/bikes/scoots on pure ethanol for 20 years or so ,so i guess thats were we should ask the questions .H

[partanen]

I don't know a lot about molecules. I've understood that ethanol does lean the mixture. That's why a car consumes more if ethanol blended fuel is used. As fuel injected car can (and it needs to) enrich mixture when ethanol is used to reach stoichiometric air-fuel ratio.

Back to carburetted engines. Better put bigger jet is fuel contains ethanol.

The oxygen content of ethanol is 35%. The oxygen content of fuel determines the stoichiometric air/fuel ratio, which is 9 kg air/kg fuel for ethanol, whereas it is 14.6 kg/kg for gasoline.

Quoted from here: www.iea-amf.org/content/fuel_information/fuel_info_home/ethanol/e10/ethanol_properties

You may also want to read this: www.ext.colostate.edu/pubs/farmmgt/05010.html

Or this: www.e85mustangs.com/tuning.html