Alternative cylinder heads for PX200

[partanen]

I was almost forgotten this thought already. Then "sbwnik" said magical words "early 200 heads".

So can I use early higher compression head on my modern PX200 with electric start? If not, why? One thing came to my mind. More compression and starter cannot turn the engine anymore? Starter struggle already with original head, sometimes.

Then I've been thinking about MMW head for original cylinder:

www.sip-scootershop.com/en/products/cylinder+head+mmw+px200+for_13013930

Anyone tried MMW? Does it work?

Or is 10,5:1 compression ratio too much for stock crank shaft for example?

Thanks again.

[sbwnik]

It's not noticably higher, I can't remember the exact figures, but it's only quite a small amount. The 10.5:1 isn't a mile away from the 9.8 of the original.

Anyway, you have boots and a kickstart, don't you?

[partanen]

I do. I have to start to practice the right technique to kick start.

[henri]

anybody who scoots in finland has definetly got the balls to kickstart a scoot high compression or not ,much respect.have only met 1 finnish biker who claimed to ride all year round ,his mates backed him up but said they thought him mad.he kept a scoot for town an rode his bike further.
how many months of good scootering weather do ya get over there a year,i get told i'm nuts by some in england as i ride scoots/bikes through are winter ,well mild compared to yours.
kickstarting is easy to master ,on centerstand kick 1-2 times ignition off to prime it with fuel tap on,then ignition on ,choke out where its needed,kick an twitch throttle at same time an bingo it should start ,if in good trim in 1-2 kicks.if not running after 3-4 start thinking its not right an try no choke as quite often they will start without.if you keep kicking or have left fuel tap on when standing it might be flooded,then its fuel/ignition off,open throttle wide an kick a few times to clear it.
its a knack thats easy to learn but every scoot has its own quirks ,when learnt they start easy in standard tune.
1 thing tho,keep the kickstart rubber in good nick ,they dont get called "shin-scrapers" for nothing.an kicking down on a wet/shiny/oily 1 without a rubber can give you scars you can boast about in the pub .H

[partanen]

Usually we have only 6-7 months scootering time in year. At least how I see it.

[sbwnik]

I know a couple of lads in Norway who ride all year. One has a ski that mounts to the front hub, and an ice speedway type tyre he built himself... Nutter. I'll have to look and see if I still have the photos.

I'd not use the above method to start the scooter, anything like that will eventually splay the stand and/or bend the floorboards.

I use the 'climb on, off the stand, lean it over a few degrees, kick twice, put the choke on and it should fire in the next two kicks' method.

Each to their own though!

[sbwnik]

Henri... Try a Lammy without a rubber - they have a bloody blade for a kickstart. I've got a scar that's twenty years old from one!

[henri]

i leave mine on stand at moment as choke knob tube is buggered so ive got a wire with a nut on end coming out my airbox for a choke ,have to take my panel off to hold it on with 1 hand ,leaning over with other on throttle when kicking.its a bit dodgy when off stand sometimes,but your right you should kick em when on wheels really.it really depends on wether i left it on center or side stand the night before being a lazy bugger.
lammys 1's are absolute killers ,an you try an buy a rubber that will fit 1 tight an not fall off.after 3 goes with "reputable" scooter shops ,an getting either 2 big or too rock hard to fit,took grinder to the edge an slimmed down the foot pad an with hot-water an swearing got a clear px kick rubber to fit .looks good,still hurts my mate when he forgets the clothes peg for the choke an try's to hold choke an kick at same time.sometimes its hard to get a view out pub window when he trys as the crowd gets 2-3 deep. H

[partanen]

Maybe dumb question, but what gives or cause the scars?

[sbwnik]

The Lambretta kickstart is shaped a bit like an aircraft wing, and the back end thins almost to an edge. Tune the engine and the compression can cause your foot to slip off, and you'll almost invariably catch your calf/shin on the pedal as it comes back up. That's if you don't catch your leg on it turning the scooter round or something.
As Henri says, the rubbers are cr*p, if you can get them on then they split very quickly, or they slide off the first time you take it for a spin! I ran a stage six SX225 for a couple of years, I'm lucky only one of the scars has lasted this long. (Although I have another from a screwdriver in the other calf, but that's another story)

[vespasco]

May 3, 2014 12:39:03 GMT partanen said:

I was almost forgotten this thought already. Then "sbwnik" said magical words "early 200 heads".

So can I use early higher compression head on my modern PX200 with electric start? If not, why? One thing came to my mind. More compression and starter cannot turn the engine anymore? Starter struggle already with original head, sometimes.

Then I've been thinking about MMW head for original cylinder:

www.sip-scootershop.com/en/products/cylinder+head+mmw+px200+for_13013930

Anyone tried MMW? Does it work?

Or is 10,5:1 compression ratio too much for stock crank shaft for example?

Thanks again.

I had one of the MMW heads as above.
With regards to compression, I measured the volume at 28cc. (But these are hand finished so may vary slightly).
A stock head i had measured higher compression at 27cc!

I 'd be very interested to hear how the MMW head with (almost) the same compression but smaller squish band performs on a stock engine.

*i may still have the (unused) head somewhere if you're interested?!

[partanen]

I am interested. But I'm in Finland so postage may be issue.

Someone (american) said It's like chasing dragons if I buy cylinder head which increase compression ratio. He could not say the reason though.

MMW offers cylinder heads for original cylinder with O-ring as well:

www.sip-scootershop.com/en/products/cylinder+head+mmw+px200+for_13013935

[henri]

vespaco the stock crank can easily handle 10.5 bhp its the clutch that struggles , partenen ,the yank might of said that as there is no "out the box" magic head .its more about using the head youve got to suit tune you want . measuring stroke/volume an squish band,an then going from there .either skimming head for higher compression but less volume,or with re-profiling getting squish right.
too little squish =thicker base gasket , unless you do this sort of thing to new/old heads ,billet excepted, no head will magically suit your engine.an billets still need squish checking.
you can get a jump on the process by finding a head from earlier/different model ,early Pseries being a favourite ,but will still have to do the above to get best out of the combination.
to check squish,head off,tape a twist of softest solder across piston crown so it nearly touches barrel at 1 end,head back on torqued down,rotate engine once,head off an measure thickness of solder at barrel end.adjust accordingly. racers use to use thinner base gaskets or just sealant for a smaller squish but they only last 1-2 races if lucky. H

[vespasco]

Right. Ive had a look for those heads i had, HAD being the appropriate word. I must have sold them last year!? Sorry Nik, Partanen.

If all you really want to try is upping your compression to gain a bit more power, then the easiest thing to do in your case is simply... wait for it......skim the head! The old classic way!
Or borrow an older head. Henri.

On a stock engine there's plenty of room to achieve a smaller and 'within-the-voodoo-limits' squish by skimming the head and it would raise your compression. As would the old p200 head?!
My stock deck height (on mine) is 1.8mm!!! So the MMW 0.0mm head would surely be suited. As the compression is more or less (less)! the same. In theory anyway!
My head spinning calculations came out at 1mm off a 200 head would loose you about 3.5cc, raising compression. To??

But be careful, simply increasing the compression can lead to all sorts of potential problems.

As Henri says, there's no head out of the box solution.

I'd still like to see what effect a smaller squish height but same compression head would have on a stock 200.

This is all the assumption that the later heads are indeed lower compression. If anyone knows the actuall volume of the late stock head i'd like to know. Just for kicks. It could prove a a few theories!?

However, If all you want is a little extra power there are better and more well known ways to do it. (Air filter holes, Sip road etc etc)

[partanen]

I have sip road and air filter with holes already. I think next step is the cylinder head as I like the way stock engine behaves. I would not like to buy the Malossi cylinder yet.

[henri]

i use to tune ,mostly 2stroke bikes (rd's,motorcrossers an karts),have cured myself of the cost/pain/disapointment/heartache an yes,joy of it now.tho seeing a cute little smallframe on bank holiday did make me itch/dream again.an first step is blueprinting your engine,basiclly checking its right/standard an then changing 1 thing at a time an seeing the result .if youve drilled n sip road exhaust thats the engine breathing better ,checking your squish is the start of getting the max bang for your bucks.my px150 i run as standard ,or as i call it optimised.drilled filter/free'er exhaust/pre-mix/an blueprint head -barrel matched to casings,an slightly worked inlet track n gaskets.can pop wheelie n spin wheel on dry tarmac in first an pop wheelie in 2nd ,pulls 45mph on half throttle so expect 50-55 cruising when run-in with 60 possible in bursts .not amazing figures but it starts 1st-2nd kick everytime from cold or hot,has never heat seized an in traffic will pull top from 15mph .makes for a nice scoot to ride .
better than a high compression/thin power band tuned monster that only starts on the third tuesday of the month if ya lucky,an when running snaps ya neck n pulls the shoulders when there's clear enough road to hit power band .an yes is mentaly good fun when right ,but the lows soon outweigh the highs,well for me anyway.
to get a slightly faster scoot thats more tractable an usable on the road you have to start looking at the gearing,both box an primary ,so you move the power band where you want it,sort off.its a whole other can off worms .
as an aside ,nic mentioned a finn with a ski on front for snow .if you go to vespasmallframe forum ,pictures, smallframe gallery thread,page 2 ,there's some pictures of i think german guys racing scoots on what looks like a snowed over car park,an 1 of them has a ski fixed to a front rim on his scoot ,mad bugger.better than the picture of a lambretta powered snow plough i saw once. H

[sbwnik]

I've not got the heads together for comparison yet, but USA ones are marked.... USA.

I got it the wrong way round BTW, it's the Euro ones that have the lugs, not the other way round, and from a chat yesterday, it seems there may only be a small batch of quite late UK P200s with the US head on - possibly from Serie Speciale onwards. The best guess on the subject was, with the SS being a little bit of a parts bin special, they were the last of the ones manufactured for the US market - ones they couldn't/never managed to sell.

[henri]

ive often thought that about the "ss" being a parts-bin /clearance type of deal,that piaggio couldnt import/sell before USA emissions laws shut the market down .they seem to come in quite a variant spec.like the old dealer specials back in the 60's .an piaggio do use a parts bin philosophy a lot,thats how there the longest living scoot manufacture.some times its good for spares that there common between models,other times it annoys me as model changes seem to be done to cheapen/easier the making of em on mass.leading to crap like printed ribbon wire head looms,quick to assemble but impossible to repair an such like , sorry rant over , glad ya cleared up the lug thing as i was getting confused which was which, cheers H

[sbwnik]

Common knowledge/acceptance that the SS was a clearout job

[partanen]

I now have MMW cylinder head with o-ring for stock PX200: www.sip-scootershop.com/en/products/cylinder+head+mmw+px200+for_13013935



No problems with starter, it turns the engine just like it should. So I use kickstarter only when someone is watching.
 


Better performance? Not much, if at all. I have not tried top speed yet, because I'm still trying to find correct carb settings and jets.



I think it worked better when I had stock cylinder head with 23 ignition advance. With MMW I use 18 ignition advance.

[henri]

you could advanced the timing to 19-19.5 an get away without pre-detonation/pinking ,but i wouldnt go much further as if got wrong it will hole your piston ,but the difference in power i doubt would be worth the risk ,an you might find your starter being kicked out of turning the engine more frequently ,or scoot kicking back when kickstarted , get some shin pads an when jetting is sorted you will have a better idea of the difference , henri

[partanen]

pre-detonation/pinking, how easy it is to hear if it do so?



I've heard pinking too many times when I had Ford Sierra with turbo charger.  But I haven't hear how 2 stroke sounds if it's pinking. Is it the same kind of sound?

[vespasco]

Its no suprise there is no significant power improvement.
This head has a larger volume than a stock head (but only 1cc) = less compression.

Detonation is often describe as ' a bag of nails/marbles' being shaken violently. 'Metallic popcorn' is how i remember it.
I used to hear it. I was setting up a Pinasco 225. Without the right head/timing it would detonate.

I suggest you re set your timing to suit , as per Henri, to approx 18/19/20 btdc. But experiment until you feel its just right.

[sbwnik]

Handful of ballbearings in the cylinder head = pinking.

[swm]

May 4, 2014 19:39:51 GMT sbwnik said:

Henri... Try a Lammy without a rubber - they have a bloody blade for a kickstart. I've got a scar that's twenty years old from one!

Just added another to my collection tonight !         

                                                                                                                 

                                                                                       

                                                              

[partanen]

Jun 10, 2014 20:19:45 GMT vespasco said:

Its no suprise there is no significant power improvement.
This head has a larger volume than a stock head (but only 1cc) = less compression.

Vespa PX owner's manual says compression ratio is 8,8:1. So I though that 10,5:1 would be a bit more noticeable than it is. I had ignition at 18 with stock head, then I put MMW head. Engine sound is a bit different, but I didn't feel other differences.

[rab]

Kick start scars ye goto love em but boy do the feckers hurt haha

[pxguru]

Jun 13, 2014 9:31:12 GMT partanen said:

Vespa PX owner's manual says compression ratio is 8,8:1. So I though that 10,5:1 would be a bit more noticeable than it is. I had ignition at 18 with stock head, then I put MMW head. Engine sound is a bit different, but I didn't feel other differences.

As I see it, increasing the compression increases the bottom end torque. Reducing the timing reduces the bottom end torque. If its still the same it looks like the experiment worked
Put the timing back to 23 degrees and up jet a little and it will go better than now. If the plug is chocolate brown at high rpm and it pinks a bit, reduce it one degree at a time until the pinking stops. If it pinks and the plug looks lean or grey, first try to up jet more to try to stop the pinking, before reducing the timing.

[partanen]

That's my plan. I have one problem. What ever tweaks I do, I cannot test it at the same day. It's not allowed drink and drive. Or even ride.  

[vespasco]

Jun 13, 2014 9:31:12 GMT partanen said:

Jun 10, 2014 20:19:45 GMT vespasco said:

Its no suprise there is no significant power improvement.
This head has a larger volume than a stock head (but only 1cc) = less compression.

Vespa PX owner's manual says compression ratio is 8,8:1. So I though that 10,5:1 would be a bit more noticeable than it is. I had ignition at 18 with stock head, then I put MMW head. Engine sound is a bit different, but I didn't feel other differences.

I dont know how these compression ratios figures came about but i know for a fact (because ive physically measured them) that the mmw head above has a larger volume than the stock head i compared it to. 
Like i said before, if all you want to do is raise compression then skim some of the original head and reset ignition timing to suit. It should also work out a lot cheaper to do this.
 By fitting this mmw head you will not raise your compression at all. Despite what these figures say.  (You will actually lower it)! 
all you are really doing is changing your squish height and slightly altering the combustion chamber design. Not raising your compression.