stroking a px200e

[shaunpx]

Does fitting a 60mm crank make much difference to performance on a standard px200e?

[vespasco]

Possibly yes. Youd need to do a bit of porting work. Even if its just raising the barrel (and head) to suit.
Theres room to do it thats for sure.
I considered doing it myself at one point.
Theres other things better to do than adding a stroker...
Exhaust, carb, gearing

[henri]

as your normally changing the barrel/head aswell yes , but just stroking a stock barrel does change the characteristics of the engine noticeable ,H

[vespasco]

Ah yeh! I forgot the obvious! Try a kit!!

[pxguru]

Without any other change just fitting a 60mm crank in a P200 and no packer goes well. I've done it before. Will need to upjet about 5

[shaunpx]

Cheers px guru... does that mean you didn't use a head gasket either???... also was that in recent times with unleaded fuel?

[henri]

if youve any doubts about your head gasket , a smear of permatex ultra-copper sealant can settle ya mind , keep it of the studs an its a light smear ,theres others from loctite an other manufactures but thats the 1 i use .
an most retard there timing a few degrees to cope with modern fuel , 18-19 degrees btdc , tho sum go as low as 16 , H

[shaunpx]

Thanks For the info Henri I already run my px at 16° btdc... my concern is would that set up run ok without raising either the barrel or head without a packer plate or head gasket due to the higher compression and hotter nature of modern fuel

[vespasco]

After digging through my old notes for something else, guess what i found....!
I did indeed look into stroking a stock 200, mainly as i saw the deck height and squish on the stock being unfeasibly large.....and heres what i found with long stroke, no base gasket...
I would double check these figures if you anted to use them!!!

0.4mm deck height
164° exhaust duration
126° transfers
208cc
9.9:1 compression ratio with stock head.
Stock head 27cc, no gasket, less 5cc piston displacement(needs double checking), plus 1.4cc squish
Exhaust height @ 38.7mm
Transfer height @ 47.1mm

Hope that can be of use.

Keeping the compression down will help with any overheating issues you have.
As will retarding timing but see youve already done that....is that astock kotor you have running at 16° ??

Does that look anything like the figures you had Guru ji?

[shaunpx]

Cheers Vespaco...my motors near as damn standard apart from having 9mm removed from the opening edge of the inlet port a 25mm carb and sip rd2 exhaust...I reset the ignition timing to 16°btdc when I used to have a tuned up standard top end on it which ran to hot

[henri]

is that a positive or neg deck height ,i'm guessin as theres no -sign its positive deck, did ya measure the squish in mm as youve 1.4cc up there ,typo maybe , that would give you a 1mm squish if so ,an explain 9.9/1 comp, tempting me to think a double base gasket could lower the comp an get a slightly safer squish ,say 1.2 to 1.4 , all a guess if it was cc ya meant ,interesting figures tho , H

[vespasco]

I should point our that these figures were made a few years ago and i didnt know as much then as i do now! How ever much/little that is!
Yes, + deck, measures at 0.4mm, which i worked out to be 1.4cc.
Theres plenty of clearance on the head to get a nice squish gap
BUT looking at my figures above......
I do recall p200 stock compression is 9.8:1 !? Not sure if thats true or not nowadays.
I worked out (years back, so could be wrong!) with stroker its only 9.9:1!??
Somethings not quite right somewhere!?
So my figures could be wrong somewhere....likely the piston displacement as that wasnt noted. The bells ringing in my head are saying 8cc for stock displacement??? That would then give over 11:1 CR, as a guide.
Im ready to be put right on any of that.

Either way, a stroker fits without a lot of work but ....
may need a little work on the head to get the compression down to a usable, non pinking, ratio.

(With stock crank, deck height would then be 1.9mm)

Its all similar to a pinasco really, similar deck,transfers and squish/compression.

[pxguru]

Dosent overheat with high compression, just goes better. Any problems are all due to jetting.

60mm crank and nothing else. No head gasket or base packer. Even the timing is ok at 23 degrees. Its the easiest tune you can do to a stock P200

[vespasco]

I see what your saying guru ji. That ultimately its about having enough fuel in the combustion chamber to suit amongst other things, the compression (whether its high or low compression).

Id imagine if it ended up less than around 10:1 CR then, with todays ethanol induced, non leaded fuel, it would be ok. Of course its possible to go higher, im just a little cautious!!
A relatively lower compression (amongst other things) helps combat overheating, especially when using a low grade fuel.
Im sure with todays fuel, if you had a motor tuned to the ragged edge with high compression, using premium fuel and then ran it on the high ethanol 'economy' grade fuel you would notice the difference. (I think ive gone in a circle here)..... So the jetting would need to be richer...!

[shaunpx]

Cheers fellas!

[partanen]

What are changes for engine then? More power at higher revs, or more torque at low revs? Or both?

This is getting interesting now.

[pxguru]

When I did one it had more power and revved higher. Torque about the same on standard exhaust. Was noticably faster

[henri]

the comp ratio wouldnt be to high for pinking , but a too thin squish =higher pressure spots an too thick a squish =higher fuel load in squish band , both can exagerate a engines tendency to pink ,specially with modern fuel ,as guru suggests this can be ironed out with careful jetting ,but i'd always retard the timing aswell , 23btdc is a bit close to the ragged edge for me ,personally , tho the more advanced you dare the better the response from engine , upto a point , H

[pxguru]

One of the most common reasons for pinking is that the head doesn't fit the barrel. As you say a narrow squish carries less mixture and is less likely to pink but if the head squish overhangs the edge of the barrel it holds an extra ring of fuel right at the edge. This can add to the problem.
If the head is correctly profiled to the piston the squish can be as tight as you dare for mechanical contact. On my own scooters I often use less than 1mm, without any issue.
Pinking can usually be fixed by properly jetting across all throttle positions. Ignition timing often gets the blame but is rarely the real reason

[shaunpx]

What speed was the speedo showing compared with the standard set up G???

[vespasco]

I think stroking would certainly be better than some of mods ive seen done to a stock barrel.
One of which is machining mayhem.... Skim cylinder with negative deck head that sits inside cylinder (hotspot alert)! .... Thats far too much machining work to make it worthwhile in my opinion.

[henri]

i'd agree on a stock barrel, an use to think it a waste of time on others , til i met a man who's nicname is "johnny snatchsniffer" or johnny SS for short. he takes polini barrels n machines em to be close to worb5 spec ,takes a stock 5bhp smallie upto 20+bhp, with other mods 25+ is obtainable .
which has me thinkin maybe i've been missing a trick, will have to measure up n think , an maybe make a offer on 1 of ya cylinder heads if there part of the clear-out , H

[vespasco]

I will be looking to clear out a lot of my stuff thats been kicking around too long.
I almost fitted your polini pipe today H! For curiosity s sake. dont worry h, i wont want to keep it however good it may be. Just wanna see how it compares to a sip road on a pinasco. I wheeled the vespa to my workshop (outside my front door) to swap pipes and it started to snow!

[henri]

same here , snow then rain , perfect excuse to nurse my hangover inside ,an kick myself for the tap idiocy , nearly swore off beer i felt that guilty ,luckily saw the "light" cracked a hobgoblin an now feel better ,well ,consider my idiocy is livable with an no reason to get the tanto n slit me guts out ,seppuku/jap style.
the head thats peaked my interest if memorys serving is 1 you had n didnt fit as it had a really high comp ratio/profile , mallosi maybe , i'm investigating a long stroker with the barrel raised by packer maybe +possibly machining , hunting a sweet spot for valve timings like johnny ss has found on the polini evo , as the gains he's got really justify the machining cost . for example kit n machining cost bout 600-700 , but equivalent bhp quattrinni or falc = 2000+ ,
more work less cash outlay is my sort of gig ,H

[pxguru]

While it just had the 60mm crank in it was just a few mph quicker top end. The most noticable though was it rode better and didnt slow down so much up hill. Main jet was 128, no barrel packers and timing 23 degrees.

[shaunpx]

Cheers G!

[partanen]

One thing concerns me a bit. With long stroke crank piston rings needs to go 1.5mm further at top end and bottom end in barrel. So wouldn't it be good to hone the cylinder at least, if not re-bore before stroking?

And is there a crank you could recommend to stroke stock cylinder? It would be good if rotary valve timing is close to original I guess.

My engine is splitted at the moment because I needed to replace cruciform after 2500km, because I had problems with clutch. So it would be so easy to change crankshaft now. I cannot feel any step in barrel made by piston rings, but I can see colour change.

[henri]

i always hone if pistons out the barrel ,but usually am replacing rings aswell , H

[shaunpx]

I agree with Henri it may be a good idea to hone the barrel while the engines apart as the bore may require deglazing but it wouldn't have anything to do with the extra 1.5mm on the stroke that's why I asked about whether the barrel or head would require raising... which apparently it doesn't... with regard to a long stroke crank with standard inlet timings Tameni make them

[pxguru]

If there's a step at the top of your bore then, sure you need a rebore (thin ring Grand Sport piston is much better).
www.sip-scootershop.com/en/products/piston+grandsport+200cc+_12091000

If just a colour change at the top of the bore then a hone is enough. Or go full cowboy with some 600 grit