Modern Vespa

Hello everyone

My bike is 94my PX200.
I've done engine rebuilt with o-tuning. Enlarged Port and polish , spaco 26/26si with autolube mainjet 120. 68mm piston. Flowed 57 stroke chrankshaft and cylinder head is skimmed 2 mm. Squish gap is 2mm or 2.30mm , İgnation time is standart 23 degree. Gianelli expansion chamfer type exhaust. My problem is bogging at low revs. First start and idle perfect but after 5 minutes riding problem starting My bike run high rpm (3/4 throttle and full throttle ) very well but when I want to stop for traffic lights engine bogging and stop in 5 seconds. And the other hand too much and splatter burnt black gunk oil is coming out the end of exhaust stub and exhaust clamp. I need your suggestions.

Where should I start ignation , air or oil suck , jetting ?

What does your plug look like?

"Kickstart is slightly hard but working. " Do you mean that there's a lot of resistance to rotating when you kick it or do you mean that it is difficult to start up the motor but it spins as it should?

Turn the stator clockwise to retard the timing to 18. Check with a strobe. Should be a screamer after that.. May have to dremmel the slots a bit to get the required rotation.
good luck

kickstart hard than standart but first kick or second kick start normally.

I will do today if l solved l write here. I hope this problem only ignition timing.

Last night I wathed youtube video

İt's about gearbox oil suck can cause blowback..

İs blowback cause bogging until stop at low revs ?

And the other hand my bikes idle and high revs perfect first start perfect.

Low and middle rpm goes bogging until stop.

This is very confused.

You should really start with retarding the timing to 18degrees as bluecati said!

I would check if your choke closes all the way. remove the airbox lid and try to see.

Then if you still have a problem you can start changing jets to find the best setup.

It would be helpful if you check all the jets and report here.

Or take pictures of all the numbers on all the jets.

Jets BE3 air 160 - pilot 55/160 main 120

I cant remove flywheel for timing because I dont have removal tool.. tomorrow l will go vespa specialist..

Spark plug totaly black and little oily..

A 120 main sounds way too small to me. I would think that will all your mods, you'd need closer to a 128 or 130. I would also think that bringing your timing back to 18 degrees would be way too much for a semi-stock top end. Usually 18 degrees are recommended for just the performance cylinders. I probably wouldn't keep it at 23 degrees with the modern fuels though. I'd say try adjusting it to around 21-22 degrees. I would think that 18 degrees would make it even more boggy at the low end.

I'd start out by cleaning your carb and jets out really well (it's the cheapest and fastest thing to do). Maybe you have a partial blockage in there? If it's not that, I'd almost think that sounds like a possible air leak.

Maybe you are right but fuel is fresh and modern 97 octane.. beed speed say 18 degree is ok for modern fuels. I want to tryin less then 23 degree.

My carb is new. I am controlled but not l am not cleaning.

All engine parts new gaskets seals all new.

Monday I am go to PX different specialist for engine re-rebuild. I am take a picture and post here.

l think this is air leak you are probably right.

My bike[/img]

Before machined rotary pad...

This is laser weld , not tig weld..

Tig weld is dangerous for aluminum because too hot. Hot can cause bending on aluminum.

2 mm skimmed and polished head...

Port and polished engine case..
I am port polish and match carb, carb case and air inlet but l forget take a picture.

These are old pics. I will upload new pics on monday from specialist.

Today when engine work in short time my speedo show 65 km/h in 2. Gear. Is this good or normal l dont know ?

Have a nice riding...

With the o tune was the carb box open to match the carb? Was the inlet open to match the carb box? A 26/26 carb is not really needed for your set up and can take a while to tune. Definitely not plug and play. I would imagine this was done but just going down known issues with 26/26 carbs.

https://modernvespa.com/forum/topic87680.2

I want to learn my ability and skill.
These mods only trying and learn.
I am 28 years old. I love PX and this bike is not my first PX.
I want to malossi 221 mhr on last summer and I will go to the professionel specialist. Generally I am tune my cars. Thank you for your suggestions.

Oh, I missed that it was a 26/26. I don't know which main jet for that carb. I bought one new years ago, tried to get it tuned in, then realized it wasn't going to happen. It's sitting in my shelf gathering dust along with the other failed performance adding bits that failed to deliver.

My real reason of choose 26/26 for autolube system. Because l am drive daily in summer. And I dont want to extra effort every refueling.

Yes it dont any different 24/24 but pinosco si 30/30 is utopia...

Anything bigger than the SI24 is a waste of money. A dialed in 24 is equal to a PHBH30. The 26 is just a rebored 24 and impossible to dial in. The 28/30 from Pinasco are just a joke. Go back to the 24 and it will probably work better if your problem is not related to seals. I have a longstroked O-Tuned PX and the 24 works great. I tried a 26 I also had on the self and it was crap...

Looks good ezel the welding is interesting do you have a photo after machining?

My friend really I dont have any pictures after machining because when we want start to machining we cant put in cnc because is too big , so we put in classic big old lathe machine , adjust to true clerances and true radius is painfull and stressfull , we cant use any technology for machining. Maybe work on 3 hours.. 1 micron skim and try 1 , micron skim and try. I forget take a picture. I was very stressed l am really sorry..

rotary pad repaired very wll dont blowback
bogging problem is short choke cable
shork choke cable cause a little bit open choke hook
when I removed choke cable from carb engine works well in all rpm range.
thank you for everyone...

Great, Ezel. I love it when people post back with the solution.

this is real comedy for me. one short choke line turn to nightmare.

short line dont allow to sit properly choke arm (in to the carb )

too hard find and guess. Every detail very important

Hello SaFiS , can you share your jetting please? It is a 150 or 200 ?

good job ezel, respect 8)
Cheers to turkey!

did u also set cyl and intake timings?
see my channel for info
Also just published an urgently needed falsr air guide

start using gsf dyno to see the differences
Of all tuning steps


si24, 25 or 26 doesnt matter
All the same performance yes
The pinasco si28 is a waste of money.

Btw. cause i read MHR somewhere
Dont. Use sport, as the mhr has too high cylinder timings esp transfer ports are too high which causes lack of power in low rev

In general a not needed cyl the mhr
Rotary: sport 210
Reed: m232/244

The difference of mhr to the quattrini is huge
So not needed at all the mhr

I am follow your youtube chanel and already l am member your chanel.

Now l have totaly different setup.
Completely O-tuning
Fake ports opened and porting
Crankcase milling porting
68mm milled piston
Skimmed high comp cylinder head
2.5 mm bottom cylinder barrel gasket.
Cylinder skimmed 3 mm on top
Cut chrankshaft
Port timings same as the malossi mhr
I keep rotary valve
Pwk 30 carb
Sip road xl
Now I hit 110 km/h in 3.gear
All parts original
Only add aftermarket carb.
Bike run very well. Px 200 lusso

Skimmed cylinder

Skimmed cylinder
You can see thin metal

Cylinder barrel bottom gasket made aluminum

Too much milling make a hole.
Repaired aluminum welding

This is old picture.
Now ports are extra wide

i see alreday FMP influenced 8)

whats the exhaust port size and shape?


si24 or 30mm carb doesnt matter
same power on rotary valve
i would

oh, same timings as mhr, thats brave
ideal are 176/118 like as sport 210 with longstroke & head gasket





try get a different exhaust, the sip road XL is 10y old
and outdated, it a throttle nowadays, as the sip road 2 boxes


polinibox and megadella slx8 are state of the art box exhausts in 2020
sr1, sr2, srXL design is from around 2010 = 10y old = outdated
(xl 2014-2015)

see my #FMPboxtest comparisons

polinibox vs srXL:
https://www.facebook.com/freakmoped/photos/a.2389236811184447/3173078322800288/?type=3&theater

sr3 vs srXL:
https://www.facebook.com/freakmoped/photos/a.2389236811184447/2815513885223402/?type=3&theater

forget that an optic FAT manifold & body is needed, its not
see how the slx8 swallows the XL

https://www.facebook.com/freakmoped/photos/a.2389236811184447/3173091009465686/?type=3&theater

slx8, sr1, srXL, sr3:
https://scontent-vie1-1.xx.fbcdn.net/v/t1.0-9/118421840_3138619589579495_7259519308729696921_o.jpg?_nc_cat=100&_nc_sid=cdbe9c&_nc_ohc=yLHfs4jmWWYAX9yG8nu&_nc_ht=scontent-vie1-1.xx&oh=7a719ce11e6335fb78b0e00e9209a157&oe=5F7A96DD

polinibox vs sr3
https://www.facebook.com/freakmoped/photos/a.2389236811184447/2578308798943913

dont like the sr3 so much, only bit better in high rev (that you dont reach anymore in 3rd gear) but loss in low rev
its too similiar to the polinibox, which they tried to copy & improve
its also hanging too low sadly...