LCGB Forums

Having given Italy a miss this year I've been muttering with clubmates about doing Euro Spain next year and talking about possibly rebuilding the engine of a Jet 200 that came into my possession recently, however, it would be my intention to 225 it and sort out some of the issues that some of the original Spanish components that they (at least some of the variants) were fitted with. As well as allowing it to breathe a little better, the standard small toolbox variant struggling to supply enough airflow for the standard Jet motor configuration, I will have to sort out a freer flowing exhaust to allow the motor to rev on more freely (BTW this bike came with a spare factory SIIII exhaust with cut tailpipe, as per the original still fitted) as the standard exhaust has a sealed entry pipe in the neck of the exhaust (similar restriction to the 'mushroom baffle' type that many blame poor Jet performance on) however, these exhausts have a sealed entry pipe with just a few (4 or 6) 8mm'ish holes going through into the exhaust box body. Just as I'd read about in a number of older period texts, that exhaust design completely strangles anything that wants to rev a little or pass any larger capacity volume of exhaust gas. I've ridden this bike in standard trim and it feels amazingly relaxed and just hums along but only hums up to what is realistically high 50s and then allows no more, just as described in period texts.

Anyway, back to the point, the issue that concerns me most is the crank/flywheel/electrics configuration. Sure, I've read countless quotes of high mileage Jets and talk of assembly errors or weak components being responsible for any failures, however, I've also read countless reports of crank tapers shearing, and have 3 examples of clubmates shearing Spanish cranks with Motoplat electronic flywheels, 1 Spanish friend shearing her taper on her Jet200 Motoplat points example, a mate repeatedly shearing tapers on his standard Innocenti TV200 and 1 example of an SX200 shearing its taper. Added to this you find the issue of flywheel/taper shearing being acknowledged in the Official Home Workshop Manual, and countless other instances being rolled out when this issue gets raised, time and time again, on forums. So, in light of this I'm considering my options for keeping this motor 'in character' yet addressing the weak link. Currently my mind is working along the option lines of:

1. Risk it and carry a spare crank, flywheel and stator. I'd even keep it as the original configuration.

2. Look into flywheel options as a lighter flywheel massively reduces the chance of it shearing the taper of the crank. I was comfortable enough to build up a spare Milan engine in 1997 which, following big end failure on a high mileage engine, was put into service and this used an LI/SX type crank with lightened 4-pole flywheel and fan... not missing a beat and then continuing to run very reliably in a different frame for a number of years.

In changing flywheel I could even consider swapping to electronic with one of the Indian produced AF flywheels, however, I've first hand experience of 2 of those having magnet covers come loose and trash the stator, which would rather negate the idea of improving reliability!

3. Rebuild on the stronger foundation that is a GP crank and then use whatever flywheel I like, opting for points or electronic. Potentially, I could swap coils from Spanish stator base plate and put them onto a suitable Italian or Indian laminate thickness, condenser would need to suit though.

4. Go GP crank and look to replace the Motoplat centre boss with a GP item but I do not currently even know if the bosses are interchangeable / rivets in the same positions (anyone tried this?). If this could be done then I could even keep the original Motoplat stator.

5. Stop messing about and swap out the Spanish crank and electrics for something more reliable and maintenance free (GP crank and decent electronic ignition)!

Hmmmm, how far to go before keeping it standard'ish becomes not standard'ish enough?

TBH I don't even know if I will do Spain yet and/or whether this bike would be ridden... but there's nothing like planning early

As ever, your thoughts/feedback is welcomed, ta.

Adam

off the top of my head options.. depends on how 'standard' you want to retain it

although I think the taper shearing issue particularly affected the very heavy later 'lynx' motoplat electronic systems, the ones with a moulded red stator. there must be thousands of LI/TV/SX's with small tapers running ok as standard and mild tune versions..

lighten Spanish flywheel in a lathe
swap bosses (taking into account rivet positions as mentioned)
use a non electronic flywheel and an external 'scootronics' pickup..
Go GP and put the original bits an a box in case you want to return it to standard in the future..

Personally, I went GP crank, electronic kit and simplified loom for reliability.
However, I retained the Serveta switches and rear ignition switch meaning it kept it's character and feel.

Hi adam,
i think i would go down the gp crank route, its a design proven to be stronger, as to which flywheel and stator thats a harder choice, i noticed the other day that anthony tams is selling a new separate coil and cdi unit to compliment the stators he sells, im thinking about going down this route with my rotax 290,

holty

I fully comprehend your dilemma Adam.

The fact that you intend to raise torque with a larger capacity probably means that you are bound to check out the bottom end.

Despite my outspoken opinions on the smaller crankshaft taper issues, I would think that a GP crank is the sensible option. That said, whether a standard stroke of 58 mm is then the natural choice depends on what bargains might be available...

I’m not sure that the Motoplat flywheel will readily convert to a GP flywheel bush. Surely we would have heard of such instances by now & wouldn’t such strong advocates of Spanish electronics as Dave Webster have done such an alteration?

As for flywheel mass, having ridden full weight & lighter flywheel equipped motors, the latter type offers so many benefits, I figure that it’s an automatic choice.

When it comes to exhaust choice, you’d be wise to await DT’s full test of all the Clubman type exhausts before committing, unless you convert what you have, which is not such a momentous task.

Interestingly enough, you haven’t said whether you intend to upgrade the carburettor, only the air supply to it.

I appreciate we are talking about Spanish Lambrettas here but.....

Almost every change Innocenti made to their scooters in the sixties was about reducing production costs. Just about the only alteration that they did which increased costs was the introduction of a DL crank. They would only have done this if that there was a need to address a significant shortfall that was likely to affect the brand if ignored. Therefore, I would go DL crank, and as the rest is hidden under the flywheel cowl, I'd find a suitable quality flywheel beneath with an Anthony Tambs stator. Only you will need worry about whether it is original in this area.

Good luck

Hi all,

Thanks for the responses to date, which are helping me to bounce the idea, pros and cons, in my own mind.

I tend to agree that a GP crank probably is the way to go but I'd be equally as happy using the smaller taper crank if the flywheel was suitably light enough and I have a couple of new/nearly new small taper cranks sitting on the shelf as I do all I can to avoid them. This is a shame and as Webbo stated in his tuning manual, there really is no reason to avoid them if you don't have too heavy a flywheel... supported by my own experience.

To respond to a few of the points raised...

Lofty - "I think the taper shearing issue particularly affected the very heavy later 'lynx' motoplat electronic systems, the ones with a moulded red stator. there must be thousands of LI/TV/SX's with small tapers running ok as standard and mild tune versions.", yes, I've known a number of standard Jet 200s (including factory assembled and to factory tolerance) shear the taper off when using this setup, however, I've also known standard TV200s and 1 SX200 to shear the standard taper when running original Ducati flywheels and the acknowledgement of failures in the Home Workshop manual suggests that this was an issue that had already revealed itself to Innocenti, otherwise they would never allow such a quote to go into print. Also, this failure seemed to increase in frequency when the larger capacity 200 came into play, suggesting that the engine braking of the larger capacity (trying to stop the engine turning, whilst the heavy flywheel keeps wanting to spin... and sometimes does ) may well be the straw that broke the camel's back. If this is the case, an increase to 225 will only compound the issue and increase my chances of such an engine failing.

Northern Jordan - Yes, you're 100% right that this seems to be the sensible way to go, however, I do love to tinker and it would be so nice to tailor an assembly that allowed me to use one of the as new cranks sitting on the shelf.

Holty - If I go GP crank then I already have a number of options for flywheel and I have enough faith in my ability to sort a stator that I wouldn't necessarily look to change to something different. Anthony does seem to be selling some very nice kit though.

WT1 - I've considered 60mm crank options and am still open to the idea. I have configured various motors around 60, 62 and even 65mm stroke cranks and do like what they have to offer, however, again I am coming back to the issue of 'how standard' to keep it?

Yes, your point about boss swaps is what my mind is playing on and I imagine that I'd have read about it if it was easy, however, I guess that most would not look to swap unless it could give the added bonus of converting to electronic. As the Motoplat electronic flywheel uses a very different boss / construction this might be why we've not heard about others swapping bosses just for the sake of going points boss (Spanish LI) to points (Italian GP). I best dig out some flywheels and have a look.

I've modified a number of mushroom baffle type to non... as per performance manual drift and mallet technique and that does make a really impressive change to performance but this odd Spanish sealed tube with holes may not be quite as easy to modify. I'll certainly give this a go though as I'd not want to fit one of these in standard trim to anything more than a standard LI125! I am keeping an eye on that very interesting feature though, regardless of whether I'll apply it to this motor.

Carburettor... currently thinking of a reamed 21.5mm or a 24mm reamed carb, both of which I've run before with decent results. I understand that there is now a Jet toolbox type hose made specifically for 22mm carbs, which would allow me to use my reamed 24mm. I did play with the idea of a 25mm PHBL (not ruled out yet) but I'd like to keep a standard shape item if it works well enough. FYI - I recently had this 24mm on a different 225+ cc motor (very mild tune and clubman) but I was aware of it gasping for more, changing up to a 30mm in that case. With subtle changes to the Jet toolbox type filter system I hope that I can end up with flow enough to supply the 21.5mm or 24mm (the 21.5mm might not seem like much of an increase but it made a real difference to the revs that an old motor of mine could reach when compared to the 20mm that had previously been on it).

Knowledge - Again, you're quite right in all you suggest and I know that the straight forward swap to a GP crank and decent (reliable) electronic ignition is the sensible route to go down.... it just seems too sensible and too easy . It also does take me away from the Spanish flavour that I'd like to retain. Frustratingly, this bike had not been run for around 10 years, however, I cleaned the tank and carb, put some fresh fuel in it and it started up very easily. I did check for a spark first and even at low kick-start turnover revs it had a really healthy blue spark. If it wasn't for my first hand inspection of too many failed LI/SX tapers then I'd not give it a second thought... points and all!

Hey, thanks to you all for your feedback and input, which is helping me to consider my options. It be interesting to see if the boss swap is straight forward... I'll let you know.

Cheers all.

Adam

Great thread so far with the contributions from all reinforcing the fact that the LCGB Forum is very much like a Carlsberg sound bite.

I forgot to add that I have modified the internal Motoplat variety of rotors to take a GP flywheel boss in the dim, distant past & despite the warnings that the things would fall to bits or the magnetic internals would escape & infect the World, they didn’t.

However, I found the easiest solution was to bore the rotor with a taper to match the GP crank leaving the existing extraction thread in place & filing a keyway by hand to suit. The fact that the softer alloy of the exposed bore was expected to do the same job as an original steel type flywheel boss didn't seem to be a problem as might have been anticipated.

The same procedure may well work for your flywheel. In fact, logic suggests that it should as the magnetic elements are almost certainly more outboard than the internal rotor type.

^... more food for thought, thanks.

I had planned to keep my Lince 200e as standard as possible, including the Motoplat points ignition but the cooked crank forced me to reconsider and it only made sense to go GP on the crank leading me to Scootronics ignition, Wassell and AF mid weight flywheel.

Following on from that and failing to comprehend the mass of green and yellow wire, some of which appeared to be earths and some which appeared to be lives, I've binned the loom too and fitted an Italian type loom. This required rewiring the CEV switch on the left to act like a GP/SX style and fitting a DC ignition keyswitch. The Lince also has no sidelight or junction box in the headset so I'm connecting it all up with the neat little WAGO connectors.

So much for keeping it standard...