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contrary to what some people believe, building a Lambretta engine is far more than just taking things out of boxes and bolting them on...

for example :
A new Mugello 198 kit, 26mm PHBH and Ancillotti box pipe to fit to a series I.

This kit literally wasn't a bolt on. It wouldn't fit on any casing unless the studs were removed. So it was sent back to camlam to sort out.
Also in the mix was a 60/110 GT crank, a nice component I think, but more to throw the port timings out... packers will be needed.
With the crank in and piston fitted I checked where the cylinder was going to sit; of course the piston was sticking out of the top...
On paper with the extra stroke and longer rod one would think that a 4mm packer would be needed, but that would have really messed with the port timings. The series I casing may be a little shorter on the cylinder mouth, but if this kit had been fitted without any checking to an engine with a 58/107 crank I don’t think it would have run ever so well…
I ended up just fitting a 1.0mm base packer, this got the exhaust & transfer openings ok, then I had to trim the inlet skirt of the piston to get the inlet timing up to where I wanted it.
So that was all good, but of course the piston was sticking out of the top of the bore now….

So had a spacer cut, fitted this and then had to machine this down to 3.7mm to get the squish right…

The tangs on the side were to hold it in the mill for the inevitable machining. I cut them off before final fit.
It all seemed to work out just fine, first run on the dyno was just over 13bhp, got it to 16.4, but that was a little on the edge, so richened it up and ended up with 13.8bhp, and an almost matching torque curve too…
So a fair amount of work for that figure, but not too bad for the parts involved...
and does demonstrate what can be involved when straying from a standard setup

That’s a good insight & realistic view of what ‘upgrading’ involves.

Fortunately, you have access to the knowledge & resources to make everything work, but the days of “bolt on power” as quoted by Royspeed have long gone...

You could have done with the longer Mugello cylinders (that existed in some form once upon a time) so that you still had some nikasil bore for the piston to run in within the combustion area, as well as being a means of centralising & insetting the head.

That is an observation, not any criticism BTW.

My belief & experience(!) makes me avoid any type of head packing as they are always the first place to fail.

It would be interesting to know what port timings came about as the result.

Warkton Tornado No.1 wrote:You could have done with the longer Mugello cylinders

didn't know there had ever been any of those... That spacer is a potential weak spot, but it is made from the right grade of alloy, will be getting the bike back in to check after a few miles...

Warkton Tornado No.1 wrote:It would be interesting to know what port timings came about as the result.

I will check my notes and post, but I based them around those my version 2 Mugello 186

Post by byron » Wed Jan 25, 2017 7:07 pm

Warkton Tornado No.1 wrote:
You could have done with the longer Mugello cylinders
didn't know there had ever been any of those... That spacer is a potential weak spot, but it is made from the right grade of alloy, will be getting the bike back in to check after a few miles...

There were in the large block range, but the availability may not have been the same for all potential tuners, although I'm not casting aspersions on that...

I suppose that if ever you need a replate (God forbid!) would be the time to make the spacer a permanent addition by welding it on prior to the job.

As it happens, I have such a small block cylinder & head that is 'borderline' in need of a replate as it came into my possession following a blow-up, if any enterprising readers were thinking of going down that route... I even have a (non Lambretta) Ø66 mm single ring piston with 18 mm gudgeon pin that can be used with collars, much like the Suzuki RM (Ø67 mm) piston...

I acquired it via a heady mix of late night browsing on eBay & alcohol not realizing it was a small block kit It's funny how you tend to 'buy' rather than 'sell' whilst intoxicated.

I even have a (non Lambretta) Ø66 mm single ring piston with 18 mm gudgeon pin that can be used with collars, much like the Suzuki RM (Ø67 mm) piston...

Warkton Tornado No.1 wrote:..so that you still had some nikasil bore for the piston to run in within the combustion area

and, with that in mind, I did deliberately make it so the rings don't go beyond the original cylinder.

"You could have done with the longer Mugello cylinders", my current build is another one of the V1 225 Mugellos, which are 103mm long, compared to the standard 101mm. These were slated for having low port durations and not putting out much power but they lend themselves nicely to long stroking, my current build having a 62mm stroke crank with 116 rod and the later Meteor Mugello piston to suit the rod (30mm compression height). After machining a head to suit (no head or base gasket results in 1.45mm squish) and dowelling it, I've ended up with a 238cc motor that has roughly the same port timings as a SIL factory IV but better rod to stroke ratio, alloy cylinder and compression suitable for touring. This is the beauty, IMO, of these longer V1 Mugellos... some of the mid production Mugellos are also longer, as described by WT1, but the port durations start more advanced and can become a bit extreme if stroked.

NB: The above motor is not intended to put out high BHP, rather it is intended to be a sedate tourer... a take on the original TV200 if you like, just a 238cc version of it. My 262 (72 x 64/65) is another version of a long V1 and that is not 'FAST' but it is a pleasure to ride.

Adam

Warkton Tornado No.1 wrote:It would be interesting to know what port timings came about as the result.

exhaust ~ 174°
transfer ~ 118°
inlet ~ 165°

^... sounds very useable.

Adam_Winstone wrote:^... sounds very useable.

thanks, yeah, I think that it will be; can chip along ok, but should also be pleasant enough to ride around town easily...

Post by byron » Thu Jan 26, 2017 2:56 pm

exhaust ~ 174°
transfer ~ 118°
inlet ~ 165°

Those port timings show the benefit of selecting a fairly conservative kit, particularly the transfers.

By contrast, 'taming' of the Rapido by 'stroking' them to 60 plus stroke still only gets the transfers down into the high 120°'s (if you're lucky, after cleaning the top edges up) in my limited experience.

You've certainly got plenty of blow-down...