Modern Vespa

Hello.
Previously on this forum I have asked about the strange symptoms I've had with my 2012 PX125E scooter. I found the problem but before I start I want to say a huge thank you to the helpful members of this forum. I hope this post will contribute to the vast amount of useful information and help someone else

I asked a short time ago for advice about the strange things my scooter was doing. Originally it would run great one day and crap the next and I couldn't be sure if it was my imagination.

The scooter was somewhat de-restricted with a Zeus CDI, drilled air filter and sip Rd 2 exhaust. When the engine ran backwards, someone on here suggested the Timing was way out.

Upon close inspection I found the head was warped so I fitted a DR177 top end and changed the CDI back to the original one. but I was still unhappy with the ignition and wondered if the fault was the pickup on the stator plate.so I decided to swap the flywheel, Stator plate and CDI unit with the one on my P200E project.

The flywheel rocked as if the taper was different. So I removed the stator again and tried the original flywheel torqued to it's correct setting.
This is when I discovered the shaft was moving. The flywheel side bearing is faulty. I mentioned this to a forum member who helped me recently with my Carburettor jetting. His advice and offer to help me set up the new engine has prompted me to go for it.

Today I stripped the engine ready to come out and sit on the bench ready for major surgery. I shall log things as I go but would appreciate advice as I'm a Vespa engine virgin. (It's funny, I've stripped and rebuilt Lambretta, Honda, Triumph Tiger and Harley Davidson engines but never a vespa).

I stripped it partly and measured the Inlet timing which is an amazing 71 Deg BTDC. 39Deg ATDC. 140 Deg total. Norris Kerr recommends 185 Deg for a road tune with 70Deg ATDC max.
The engine is going to be rebuilt with a 60mm Mazzucchelli Crank and Pinasco Magny Cors Top end. The instructions show a crap diagram of a port in mm. So my first question must be. What Inlet timing is best for this kit? I have a 24 Si carb on the shelf.

Paging Dr Jack 221!!


I'm not much on inlet timing but Jack will sort you out.
When you say the crank was moving, how much is it moving? To be honest I don't know how much a new bearing allows movement, if any. The bearings used on the flywheel side are a little bit lightweight but should last for years in a stock motor. I've had a couple that allow quite a bit of movement but still don't leak at the seal. I try to replace it every time it's apart.

Looks like this one is right up my street. I see at least 20bhp here.

Ok. First job. Buy a new calculator. 71 + 39 = 110 degrees total duration. I thought this was a bit bigger for a stock 125 inlet. The things Mr Kerr said in the 1980s are no less relevant today but have developed a little. The more ATDC duration the more top end orientated the ride is. 70 degrees ATDC is still a good number for a fast road build. The total duration should be at least over 180 minimum but nearer 200 is better.

Engines are engines. Don't be fooled by the simplicity. One mistake with anything and they get painfull. Get the whole engine stripped and inspected and see what you need to order.

As I found when opening up the inlet on my 2012 PX150, the late cases have a lovely long rotary pad, so you can remove a lot of material towards the back (for BTDC), to help get into Jack's 180-200 range. Your choice of crank will also help. I've used a Worb5 Mazz which gave me 70 degrees ATDC, yet the Jasil in my other engine was a more conservative 55-60 degrees ATDC for the inlet close. This was without any Dremel work on the front

Have you bought the Magny Cours yet? I ended up ruining one by trying to keep the electric start. I shaved some material, but it left the side transfer wall too thin and it blew!

Hello Ginch
I tried to upload a short film but I took it with an IPad will try when I'm at work. For now the films are on facebook under Derek Forbes.

Hello Jack.
Yes my computing skills are as crap as my maths. I've ordered a Muzzucchelli 60 mm crank. I'll take loads of pictures when the cases are split tomorrow.

Hello swa45
When I bought the scooter and we'd shook hands on the deal, the chap produced a box of tuning goodies. The Pinasco kit was with it. I didn't want to split the cases just to gouge out the transfers. I thought I'd sell it and fit a DR instead. The starter and toothed ring are long gone.

I do hope you ordered a race/sport crank. There are a few variants.

Fingers crossed you ordered this one
https://www.sip-scootershop.com/en/products/long+stroke+crankshaft+mazzu_46005000

Hello Jack I ordered this one.
Fortunately it looks the same apart for a K2D Crankpin.
I dont like ordering stuff from ebay but the seller is someone I regularly purchase from. Why the crank's on ebay and not his web page?
Wasp-performance.co.uk

https://www.ebay.co.uk/itm/Mazzucchelli-K2D-60mm-Long-Stroke-Racing-Crankshaft-Vespa-PX125-and-PX150/302969977684?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

I think this should be on the project list of the Forum. Admin please?

It's the webs that are case hardened on the K2D, rather than the pin I believe.
The timing on the one you bought is the same as the one Jack has recommended.

I really hope so Mate. I weighed out £150 for it.

Hello.
The engine's in bits and so far the movement is in the flywheel side bearing. The crank web inlet side has blueing on the edge opposite the crankpin. Suspect rubbing. The sealing pad has light scoring. I don't know what's acceptable. The crankshaft is in the fitters shop to check runout.

I was going to look at installing the Pinasco kit. Then talking to someone here about the DR. I'm without transport at the moment. I may just replace bearings and seals for the time being.

The advice I've been given so far has made me realise it's a science and not a case of grind a bit off here and there. My first concern is how thin the crankcases around the transfer ports are.. The inlet port however is horrible. It's 8.6 mm across at the back and 9.9 mm across the cylinder end. There's also a step each side of the carb box hole.

Surely I can improve this by making the slot 10 mm parallel and blend the carb and box to the cases. I haven't given up. I need to take my time and do it properly..

When I work out how to put pictures here I will.
Regards Del.

I ordered the non-finely-balanced version of that crank for my Sprint build. Should pair nicely with a Polini 177, though.

This will also be my first meaningful foray into intake timings. I've always cheated and gone straight to the reed in builds past.

I'm going to stick with an si24/24 and autolube this time around, though.

Hello Jack.
I'm going to take a chance and fit the Pinasco magny cors kit, 60 mm mazz crank and a Sip vape ignition kit which I was saving for later.

I shall just tidy up the inlet port and lengthen it a bit. Now the transfer ports (this will make the engineers scream) I'm just going to open them out to match the barrel with a 45 degree chamfer. I expect the 1.5 mm base packer will help.

Regards Del.

Del, sounds like a good plan. Be ever so careful with those crankcase ports if you're not using a bit of chemical metal on the other side. I matched a Magny Cours gasket to a 2012 PX150 case, and like you I went in shallow to avoid breaking through. I had taken the precaution of filling with chemical metal and I did expose a little of it, despite my conservative porting.

The later cases are nowhere near as 'portable' as the old style. A good friend runs the MC 190 and EFL gearbox in his 125 t.s and it's a lovely ride.

I also filled in behind the transfers with JB Weld before cutting, but on old cases didn't get that deep - I didn't know new casings were less forgiving.
Del, with a few quick measurements, if nothing else, you could know what thickness base packer to use. I understand you want to get it bolted up and running as your only transport, but I can't imagine skipping this quick job and taking a chance.
Having said that; you're in good hands here, and all the best with the build...

Just be careful not to go through. Anything to reduce the step will help.

Have a quick measure of your cylinder and we will know what a 1.5mm packer will do.

Exhaust port to the top of the barrel
Main transfer to the top of the barrel

Is your MC the one with 3 exhaust ports or just one big one?

Hello.
The cases are webbed and very thin. I quickly measured the cases at 4mm thick in places. I thought that JB weld suffers from modern petrol additives which is why I overlooked that Idea, I hope I'm wrong. I may as well order a head and base gasket set for a Parmakit cylinder giving me a choice of thicknesses to choose from.
I'm working over the next few days. I shall measure the ports and let you know. I just assumed 1.5 mm to compensate for the extra stroke.
Cheers Del.

Hello.
Situation not too good today. I got the original crank back but no info if it's useable. The Transvestite welder gouged the shaft whilst removing the bearing race anyway.

The barrel has a single exhaust port. I tried measuring the ED and TD but couldn't get the vernier calliper down the bore. I tried putting the piston in the bore, shining a light through and raising the piston to just close off the light and then measure the crown to top with a depth gauge. It worked splendidly until I put it into practice. I couldn't get consistent results. The difference being 0.9mm so I'll have to find another method. Anyone have a better way please?
Cheers Del.

I usually press something up against the roof of each port, such as a feeler gauge, then use the depth gauge on the verniers to measure the distance from top of port to top of bore. I'm just about to measure my shiny new MHR 210 cylinder, so I'll post some photos.

I cut the short parts off the caliper - the bit that you normally use to measure internally. Now you should be able to get it in there.

Hello Ginch.
Thanks for that. I thought about doing that but it's my only one and I don't want to damage them if I can help it

Hello SWA.
I tried that first but found it was too inaccurate. But you've given me an idea.
I will make an L shape bit of metal or hard plastic that won't score the barrel and hold that against the port edge. I could grind down an Allen key.

I should have thought about the bleeding obvious before posting.
Cheers Del.

Yes, an allen key would work well. I just used a picture hook to measure my 210 cylinder. I had to bend the hook beyond 90 degrees to account for the angled ports.

I use this for all sorts of measuring and marking; the 90° end is perfect for your job:

https://www.ebay.co.uk/itm/Silverline-MT60-200mm-Engineers-Scriber-Straight-90-Scoring-Metal-Plastic/392103099169?epid=1937303184&hash=item5b4b2a7b21:g:zV4AAOSwXLVbdAf1:rk:4:pf:0

To counter any possible measuring inaccuracy, I take the average of several measures, which might vary by a few /10ths of a mm.

Hello.
Well had the gearbox out and checked over. Shaft a little gouged where the cruciform presses against it. Inlet port top matched to carb box and bottom made the sides parallel and lengthened the opening end of the port 5.5mm (measuring across the chord).

Heated bearing inner for the flywheel side and pressed it on. Then I noticed the pretty brown and purple rainbow colour. Bearing was heated to 280 deg. SKF recommend 125 Deg above shaft temperature absolute max.
Next time I'll heat it in a pan of cooking oil. Throw in some spuds too.

So now it's Christmas Eve, my brand new crankshaft has a useless bearing fitted and the shops are shut for a week.

Today I had enough time to fit the crank and measure the inlet timing.

With the Mazz long stroke crank it's 178 deg. Then it went pear shaped. I measured the inlet sealing pad/crank web clearance. On to close side its 0.06 mm but the open side it's 0.16 mm.

Mr Freakmoped says +0.1 mm is bad. So what now? Buy a set of Indias finest LML cases or see if I can get the pad repaired or lastly build the engine as is and thrash it into the ground.

Not a happy bunny today.

Did you grind the sides of the inlet, or just the front and back? Extended front will give you a later close, extended back gives you an earlier open. The cut of your crank will add some duration as well. The sides are tricky, and I tend to leave well alone on a 125/150. If your rotary pad has been widened so that the seal is compromised, it's time for a reed valve conversion or new cases.

Or maybe a 200 crank with the wider sealing surface... that would require other work to the case however.

I can't quite work out where you measured the 0.06 and 0.16? You have a photo? The number given by Freakmoped is 0.05.
A mate had a large clearance at the rotary valve in a set of cases. It started and ran but could not make enough power to actually ride.

Pictures would help. I hope you measured with the casings closed.

I doubt your casings are bad enough to need replacing.

Hello.
This is what I did. Sorry for lack of photos at the moment. I'm going to have a word with the child from IT when I get back to work Monday.

I fitted the main bearings but left out the seals for now. Bolted the crankcase halves together just with the 4 studs in the flywheel housing. Fitted a degree disk and measured the duration the inlet's open for.

It's 178 degrees. I only removed material from the back edge of the inlet slot as the crank has already got a cut back web. I was aiming for 180 deg so I'm happy with that. Then I checked the clearance between the crank web and sealing pad using the method Mr Freakmoped demonstrates on youtube. "HOW TO CHECK ur vespa ROTARY VALVE / ANTI blowback / FMPguides".

You simply slide a feeler gauge across the top of the crank web edge towards the back and again towards the front. (I checked the feeler gauge thickness using a vernier calliper).
The tolerance given in the FMP guide is between 0.05mm and 0.1mm.
Cheers Del.

Hello. It's me again. I've been riding the 125 for a while now and I have time between rallies to have a quick play. I want to outrun angry lorry drivers. I spent all day last week pissing them off on the Motorways from Somerset to Home. I was riding between 59 and 65 MPH. (Strange how they knew where I was going though, they kept shouting "Kent" at me).

This is what I have. 2012 PX125E. Drilled air filter, Sip vape variable ignition kit. Sip Road 2 exhaust. (PM24 expansion chamber and sip road XL To hand). Standard gearing. Ignition timing 19 degrees.

On the Bench I have a DR177. The sealing face to edge of squish is 2mm step. Inside covered in teenage pimples. Dr Dremel is going to polish it and grind face to give 1mm step. The piston sits 0.96mm below top of barrel with 0.2mm base gasket. I'll measure the volume and squish properly later.

I measured the ports by paper/pencil rubbing and used vernier calliper to get best estimate and used the Lambretta timing program to get the following results.

Exhaust port width = 38.5 mm which is 61%
ED= 167.3 TD= 119.2. Blowdown= 24.3.

I'm looking at efficiency and holding 65MPH from it rather than top speed.
Cheers Del.

Are you doing those port durations with a 60mm crank?

As Sime66 will tell you the DR needs quite a lot of Dremel work. FMP did a video too, might be worth a watch. It will be more reliable with a GS piston. The one supplied with the kit is not really suited to the power. To get the most out of it the cylinder will need to be shortened.

Take some measurements of all the ports using a cheap vernier gauge with the end cut off and we can get started.

Hello Jack.
It's a standard crank in there at the moment (You remembered).
Thank you.

they kept shouting "Kent"...

Are you just bolting this on without splitting the engine? Last time you talked about this you were going to get a 60mm crank.

Hello Jack.
I do have a 60mm crank and the Pinasco Magny Cors kit. I had to get my scooter on the road quickly so I put it back together in standard form.

I have the DR kit sitting on the bench I just want to use it for a while and sell it on later when I fit the other kit properly (built up cases round the transfer port area etc). I guess your going to say "Long stroke crank and base packer". I would like to keep the job as simple as possible just for now. Skim head, possible turn the top of the barrel and dremel the ports.

I have just ruined a set of vernier callipers by grinding off the internal jaws. I'm going to go measure all the ports now.

I will line up the beers when we eventually meet. Cheers Del

Hello Jack.
The measurements are as follows

Top of barrel sealing face to top of fin 1.5mm.

Exhaust port centre =36.6
The four Side transfer ports = 46.6 to 46.9

Rear transfer port is three narrow slots.
middle =49.1
Either side = 48.6 and 48.1

I hope this makes sense. I don't know how to send photos yet.

Can you post a picture of the DR cylinder inside? Just want to be sure which you have.

As you're just bolting this DR on it needs to be easy. Just cylinder, timing and re-jet and done.

Ok will do. I hope these are sufficient.

another one for luck