Ignition timing to engine mega tune up
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PX125E
Joined: 06 Oct 2018
Posts: 44
Location: Gravesend, Kent, UK innit
Fri Nov 30, 2018 9:44 am quote
Hello.
Previously on this forum I have asked about the strange symptoms Iíve 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 couldnít 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 itís 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.
Member
PX125E
Joined: 06 Oct 2018
Posts: 44
Location: Gravesend, Kent, UK innit
Fri Nov 30, 2018 9:56 am quote
Day 1
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 Iím a Vespa engine virgin. (Itís funny, Iíve 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.
Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6500
Location: Victoria, Australia
Fri Nov 30, 2018 3:00 pm quote
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.
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PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 924
Location: London UK
Sat Dec 01, 2018 12:32 am quote
Re: Day 1
worrywort wrote:
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.
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.
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One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
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Location: UK (South East)
Sat Dec 01, 2018 2:49 am quote
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!
Member
PX125E
Joined: 06 Oct 2018
Posts: 44
Location: Gravesend, Kent, UK innit
Sat Dec 01, 2018 4:13 am quote
Notes
Hello Ginch
I tried to upload a short film but I took it with an IPad will try when Iím at work. For now the films are on facebook under Derek Forbes.

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

Hello swa45
When I bought the scooter and weíd shook hands on the deal, the chap produced a box of tuning goodies. The Pinasco kit was with it. I didnít want to split the cases just to gouge out the transfers. I thought Iíd sell it and fit a DR instead. The starter and toothed ring are long gone.
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PX221 Malossi, O tuned PX200 and some motorbikes
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Location: London UK
Sat Dec 01, 2018 11:43 pm quote
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
Member
PX125E
Joined: 06 Oct 2018
Posts: 44
Location: Gravesend, Kent, UK innit
Sun Dec 02, 2018 10:33 am quote
Crank
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 crankís 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
Member
PX125E
Joined: 06 Oct 2018
Posts: 44
Location: Gravesend, Kent, UK innit
Sun Dec 02, 2018 11:01 am quote
I think this should be on the project list of the Forum. Admin please?
Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6500
Location: Victoria, Australia
Sun Dec 02, 2018 10:29 pm quote
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.
Member
PX125E
Joined: 06 Oct 2018
Posts: 44
Location: Gravesend, Kent, UK innit
Mon Dec 03, 2018 2:50 am quote
Ginch wrote:
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.
Member
PX125E
Joined: 06 Oct 2018
Posts: 44
Location: Gravesend, Kent, UK innit
Tue Dec 11, 2018 2:09 pm quote
Day 2
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.
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05 Stella, '62 VBB, 76 Sprint V
Joined: 16 Jun 2011
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Location: Chicago. Well, Evanston, but that's almost Chicago
Tue Dec 11, 2018 3:12 pm quote
Jack221 wrote:
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
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.
Member
PX125E
Joined: 06 Oct 2018
Posts: 44
Location: Gravesend, Kent, UK innit
Wed Dec 12, 2018 3:12 am quote
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.
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One or two fun scoots....nothing too precious
Joined: 17 Jul 2013
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Wed Dec 12, 2018 5:15 am quote
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.
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1984 PX(177)EFL
Joined: 14 Apr 2017
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Location: Cornwall UK
Wed Dec 12, 2018 7:24 am quote
I also filled in behind the transfers with JB Weld before cutting, but on old cases didn't get that deep Ė 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...
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PX221 Malossi, O tuned PX200 and some motorbikes
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Location: London UK
Wed Dec 12, 2018 9:30 am quote
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?
Member
PX125E
Joined: 06 Oct 2018
Posts: 44
Location: Gravesend, Kent, UK innit
Wed Dec 12, 2018 11:13 am quote
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 Iím 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.
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