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Tuning options for 125/150/175cc engines using the Imola kit

IMOLA UPDATE JAN 2003

It has come to our attention that the inlet port / reed valve arrangement has sometimes caused problems.
The recessed reed valve got too close to the piston and the reeds could hit using the original paper gasket.
Later kits were supplied with a rubber gasket that lifted the reed block away from the piston.
The new set up doesnít have a recessed machined inlet port so the reed valve locates with in it.
The reed valve now sits on the port as per a TS1, which opens up the boost port.
A gasket now goes either side of the block.

The old ally inlet manifold has been changed to a rubber type, this looks nice but our experience tells us this type of manifold usually splits on reed valve engines.
We have found this with genuine Kawasaki and Yamaha items on the old Lambretta reed valves and Vespa reed valves.
Time will tell if they are reliable.

NEW CYLINDER

The good news is the exhaust port has been thickened up and a true tune can be done to the exhaust port with out breaking through to thin air, which is what happens to a TS1.
The exhaust port width has been increased to 48mm which is very wide indeed, the port shape isnít very good still and with some tuning to clean it up makes the port even wider, close to ring dropping.

More good news for power freaks.
The casting of the cylinder has been beefed up around the transfer area and below the reed valve.
This gives so much more potential for more tuning if you have the casing welded and ported.
Still we would consider converting to a TS1 spec for increased power, saying that, WHEN the updated Monza 200 Ė 240 cylinders come through they will be our preferred Ally cylinder for fast big bore conversions.
They will be copies of some of the fastest Lambretta cylinders ever made.
But it will mean we donít have to grind, weld and retune TS1 cylinders itís already done for us and will be cheaper.

The bad news is the inlet port is still a horrible shape and requires one side to be tuned quite a lot to open the inlet feed on the piston.
If this tuning mod is done then assembly of the kit needs to be done with the inlet manifold and reed block off as the piston ring can pop out if you are not careful.

More good news, the last kit we did had a lower transfer timing this will make the kits more driveable and powerfull lower down the rev range.

Update October 2002
We have noticed that there is an updated version of the 64mm Imola barrel now available, these seem to have been considerably improved since the last batch and have a lot of scope for tuning.
Have a look at the new thumbnails at the bottom of this page to see the differences.

The Imola cylinder is basically, to look at, a direct copy of the TS1 200 cylinder but uses a smaller piston of 64mm with some other small changes.
It uses the same style of port designs as the TS1 i.e.; reed valved inlet port, 4 transfer ports instead of two, a round exhaust port and new exhaust flange.

TRANSFERS

The transfer feeds have been reduced in size so they fit and seal on the 150-style engine casing (Apparently the very first cylinders used TS1 200 transfer feeds and were too big for 150 casings so they had to be reduced in size!).
Inside the cylinder the transfer ports resemble the TS1.
The Imola uses larger transfer ports compared to 125, 150, 175 cast cylinders.
They are reduced in size by a bridge to support the rings but still has a larger transfer area.
The ports are all at a different level some higher than the others giving staggered port timings from one side of the cylinder to the other.
At bottom dead center the lower edge of the transfer ports are 2mm higher than the piston!
This now means the transfer timings are too big!
Basically it's the main design fault of the cylinder, they are approximately 136 degrees, at least 10 degrees too large!
This has the effect of flooding the engine and kills the power output.
136 degrees suits a racing engine capable of revving to around 14,000 rpm, then in contrast it has a relatively small exhaust port of 175 degrees more suited to touring engines revving to around 8,000 rpm.
This combination of ports seems to work when set up in conjunction with a 28mm carb and a restrictive Clubman exhaust.
I would say that the exhaust is the controlling factor allowing the engine to work with in reason.
Fit an expansion and you will find that the scooter then doesnít work!
I have in the past done a handful of cylinders in this way and none of them ever worked correctly.
Customers have informed us that the Imola cylinders do 70 mph set up correctly and that seems their limit this is due to the transfer port timings, any more and you have been very lucky!
Smaller transfer timings would allow more revs and power.
Another way to help the cylinder but in this instance wouldnít work is to increase the exhaust port to near on 200 degrees as used by high revving motor bikes.
But as Lambrettas have big heavy bodywork and only 4 gears this does not work (unless it was a track bike).

INLET PORT

The inlet port of the Imola looks similar to the TS1 but is now much smaller, it uses a smaller reed valve than a TS1 and both reed blocks cannot be swapped without major modifications.
Above the inlet port is the boost port similar to a TS1.
The inlet port has more of a rounded shape compared to the TS1ís square shape.

EXHAUST PORT

The exhaust as mentioned has a smaller exhaust port height giving 175 degrees compared to the TS1ís 185 degrees, also the diameter of it's outlet is slightly smaller!
These smaller port timings are ideal for a 190cc engine used for touring and suits a Lambrettas weight and size.
To go much over this would loose the bottom end power that the Imola seems to have.

REED BLOCK

The Imola uses a different reed valve which is smaller than the TS1.
This valve has similar petal sizes to our Yamaha item but the screw holes are different and makes using after market reed petals difficult.
This means the only reeds available are the standard ones, which are carbon fibre.
The reed block uses small reed stops compared to other TS1 styled reed blocks.
This if you push the valves open fully go further than the piston but in practice this never happens to a running engine showing that the reeds never open that far!
The inlet feed of the reed valve is much smaller - if using the MBD inlet manifold the fingers would need trimming to fit in.
If using the TS1 inlet manifold this modification isnít required and fits straight on to the Imola cylinder.

INLET MANIFOLD


The Imola inlet manifold is now a hybrid copy of a TS1 and an MB Developments manifold.
Externally the manifold looks like a standard TS1 type but has been modified to use a smaller carb, the manufacturer recommends a 28 or 30mm PHBH carb.
But this opens up the possibilities to use a carb as small as 20mm using a stepped down rubber mount.
By swapping the Imola manifold with a TS1 item you could use carbs up to 39mm if needed.
The Imolaís reed block doesnít seal with a flange as with the TS1 cylinder, the flange has been cut down so it seats into a recess with in the cylinder.
This means the standard inlet manifold is 3mm further away from the frame making life a little easier.
Because the flange is now smaller the inside area has been reduced to suit the smaller carbs, in doing this two alloy fingers now go inside the reed valve as a copy of our own inlet manifold.
The MBD inlet only uses one finger but the larger size of carb manifold could not allow for us to use two.
This idea is very good and should promote low down pulling power!
It is possible to fit either the TS1 or MBD Yamaha reed block into the Imola cylinder, but a lot of grinding is needed for this to happen.
The advantage would be to use the better quality Yamaha item with Boyesen reeds.

PISTON

The early pistons were made by GOL and were not strengthened and used to break!
The later piston with IMOLA and MP1625 cast into them have been strengthened around the round holes on the inlet side.
Unfortunately the pistons have been made with the age-old design of sharp corners below the gudgeon pin, this is the weak point of the piston and failures occur when the skirt falls off!
The piston rings are 1mm thick and are very high up towards the piston crown, these rings are the same as rings used by Wiseco!
The piston is designed to use piston shims to guide the con rod on standard crankshafts or if using a race crank you would need to use a Yamaha DT175 small end bearing.
MB Developments consider the piston to be the weak point, we believe that it will fail and customers have already told us this.
The SRP piston was designed to fit into the Imola and TS1 styled cylinders as well as all cast cylinders.
The only modification would be to cut a hole in the inlet side to give 360 degrees inlet timing.
The SRP piston was the first real designed race piston for Lambrettas but would have worked in standard or race cylinders making an ideal replacement for the Imola piston.
Unfortunately, the SR pistons are not suitable for use in Imola cylinders due to a problem with the taper.

CYLINDER HEAD

The Imola kit doesnít come with its own cylinder head, your head needs machining to suit.
Beware we have seen some very badly machined cylinder heads made for the Imola kit.

SET UP

To set up the Imola cylinder you would need to fit a standard 150 cylinder base gasket, this needs cutting to suit the larger than standard transfer feeds.
Ideally your casings need tuning to match them to the kit.
Most cylinders, depending on the casing height, would not need a cylinder head gasket this should give a squish clearance of approximately 1mm - perfect!

The Imola kit could be considered the top of the range kit for the 125 / 150 / 175 stud patterned engine, if modified and put together correctly.

PROS: Alloy cylinder good heat dissipation. Has the potential to be tuned for much higher horsepower compared to cast cylinders.
CONS: Very expensive! (Consider buying a 200 casing and converting to a 200 / 225 TS1) Long term the piston will fail its is not that good.
Requires a larger carb fitted on the offside of the scooter (a Battery tray may need removing) a new or modified exhaust is required.
Although the manufacturer recommends standard Li / Sx crankshafts and ignitions MB Developments recommend converting to GP race crankshafts and electronic ignitions.

MB Developments have already improved the Imola cylinder kit

  1. The cylinder could be fitted with an iron liner then a variety of pistons could be used.
  2. The cylinder can be modified to use a bullet proof Yamaha 65mm piston kit, then re ceramic plated. This can be done in two ways either machined to use the standard length con rod (107mm) or swap the con rod to Yamaha (110mm) which requires no machining.
  3. MBD recommends machining 2mm from the cylinder base, this lowers the transfer timings to a good working timing. The Imola piston has a very high top piston ring so the top ring comes out of the cylinder, use a base gasket to prevent this, then machine a recess into the cylinder head to give a correct squish clearance. Then centralise the head with dowels

MB DEVELOPMENTS RECOMMEND THIS IMOLA CYLINDER PACKAGE

MB DEVELOPMENTS RECOMMEND THIS IMOLA TUNED CYLINDER PACKAGE

This is really pushing the kit to it's limits and would not be recommended for road use, unless you considered using a different piston and ceramic plating the bore to suit the new piston.

MB DEVELOPMENTS RECOMMEND THE TOTAL IMOLA 190 KIT

th_dsc00037.jpg - 11155 Bytes On the left is a TS1 200 piston. On the right is an Imola 190 piston.
Note the Imola has been improved around the inlet port windows. The TS1 200 piston hasn't changed in 10 years. They are both prone to breaking in this area.
th_dsc00038.jpg - 9536 Bytes Left is the TS1 200 piston which uses rectangular windows, on the right is the Imola which uses a more rounded off shape. There is no difference in terms of strength or performance.
NOTE: Both pistons, below the gudgeon pin, follow the round curve of the gudgeon pin hole into a sharp triangular shape.
It is here that these pistons usually start to crack.
Have a look in the scooter horrors section to see what happens when these pistons crack.
WHY remake a piston and leave in the original design fault from 50 years ago???
The SRP pistons are the perfect replacement for both pistons.
th_dsc00039.jpg - 11155 Bytes Left is the standard TS1 200 inlet port. Right is the smaller Imola inlet port.
The Imola kit uses a different locating method for the reed valve.
The valves look similar but they are not interchangeable.
It is possible to modify the Imola to take the more reliable Yamaha item that MB Developments use in TS1 engines.
th_dsc00040.jpg - 11544 Bytes Left is the TS1 200 standard exhaust port, right is the Standard Imola 190 exhaust port.
The TS1 uses larger port timings - approximately 185 degrees which gives higher horsepower and revs higher up in the rev range.
The Imola uses an exhaust port of approximately 176 degrees which is much smaller and would be gives less revs, less horsepower and would be ideally suited to a touring spec.
The TS1 cylinder is much more nicely made than the Imola. The top edge of the Imola exhaust port is not square to the piston and slopes to one side.
th_dsc00041.jpg - 11921 Bytes Left is the TS1 200, right is the Imola 190 showing the difference in the transfer size.
The Imola is basically a 125/150/175 copy of a TS1 but with a few subtle differences.
The first Imola barrels apparently had TS1 sized transfer feeds on the gasket face, these didn't seal on 125/150/175 casings (obvious really).
They have now been nicely reduced in size.
125/150/175 and 200 casings both need matching to their respective barrels for the transfers to flow properly.
th_dsc00042.jpg - 12162 Bytes Left is TS1 200, right is Imola 190.
The TS1 uses a larger outlet diameter for the exhaust port compared to the Imola.
Despite the smaller ports on the Imola they can be tuned to TS1 spec for more power, only using the SRP piston though!
The Imola seems totally cocked up in terms of transfer port timing - 136 degrees compared to 130 on a TS1.
MB Developments machine TS1 and Imola base faces to lower the transfer timing below 130 degrees.
This gives more power lower down the rev range making the scooter more rideable, especially around town.
th_dsc00096.jpg - 12162 Bytes The MBD modified Imola 190 cylinder kit.
Note that the cylinder head is recessed, this is not normal on Lambretta conversions.
The reason we did it on the Imola barrel is that it has massively oversized transfers.
To reduce the transfer timing we shorten the base of the cylinder.
This causes the piston to stick out of the top of the cylinder at top dead centre, hence the recess.
We used dowels to locate the head centrally. This conversion doesn't use a head gasket.
th_dsc00097.jpg - 12162 Bytes The tuned, polished and flowed Imola inlet port.
Not too large!!, it isn't necessary.
A Yamaha YZ250 has a similar inlet port!
th_dsc00098.jpg - 12162 Bytes The Imola has a slightly smaller exhaust exhaust port compared to the TS1.
The height is smaller as it uses a lower port timing which promotes lower down power - ideal for plodding around town and touring.
The outlet diameter is smaller. This kit has had a Stage 1 Road tune and the port has been opened out to suit a modern expansion system.
Because the cylinder has had the base machined to lower the transfers it also lowered the exhaust port.
We had to raise this exhaust port to suit the stage of tune!
th_dsc00099.jpg - 12162 Bytes The tuned Imola inlet port has a slightly different shape to that of the TS1.
The Imola is more of a rounded shape whereas the TS1 ends up a more square shape.
th_dsc00100.jpg - 12162 Bytes Two views of the Imola inlet manifold.
We actually like this manifold, it opens up a whole new area of tuning for the TS1 styled cylinders.
Basically the manifold is a copy of the original TS1 manifold.
The outside is the same but the carb spigot has been reduced so it has the same diameter inside.
This runs into two finger shapes which is a copy of our style inlet manifold.
The people that made the Imola have gone a little further and uses two fingers instead of our one.
We would have liked to have used two but the larger internal diameter would not allow it when used with 32-38mm carbs.
th_dsc00101.jpg - 12162 Bytes This manifold can be used with a sleeved down carb rubber allowing 20,22,24 and 25mm dellorto carburettors to be used.
We offer two rubber mounts to suit 26, 28 and 30mm Dellortos and also the 28mm flatslide dellortos.
You could also use a 24 or 27mm Mikuni flatslide carb.
This manifold can be used straight on a TS1 200/225 but the standard reed block needs modifying!
It can be used with on a TS1 200 with a Yamaha reedblock without a reed packer but not on a 225 as the manifold would hit the frame.
It would be possible to cut away the manifold or modify the frame to suit.
t_dsc00955.jpg - 12162 Bytes Update Oct 2002

On the left is the early type Imola 190 cylinder, on the right is the new version.
Note the new thicker base.

t_dsc00956.jpg - 12162 Bytes Now that the castings have been beefed up, the transfers can be enlarged and tuned more.
The engine casing would require welding up around the transfers for this to happen.
It gives us a lot of scope to tune Imola cylinders more than we have done before.
t_dsc00957.jpg - 12162 Bytes The new version Imola barrel now incorporates an extra section of casting in line with the inlet port.
This would allow you to put in another port connecting the inlet port to the crankcase.
This is not a new idea by any means, we have been doing it to TS1 barrels for over 15 years.
It would entail a fair amount of welding to your casings to work.
t_dsc00958.jpg - 12162 Bytes Compare this old style barrel to the one above to see where is has been strengthened to allow for the extra boost port.
t_dsc00959.jpg - 12162 Bytes This is the old type Imola cylinder view from the side.
The casting around the transfers is the same as a TS1.
t_dsc00960.jpg - 12162 Bytes The New Imola has now been beefed up and upgraded around the transfer ports leaving scope to do large motorcycle style transfers.
Normally this would entail cutting the fins off, welding up around the transfers to strengthen them and tidying up the weld but the donkey work is already done here.
t_dsc00961.jpg - 12162 Bytes The area around the exhaust port has also been improved.
This gives scope to tune and do a decent sized exhaust port without breaking through to thin air as you would on the early Imola barrel or all TS1 barrels.
t_dsc00962.jpg - 12162 Bytes This is the old type Imola exhaust flange casting, showing the potential for breaking through when tuning.
t_dsc00963.jpg - 12162 Bytes This is the third incarnation of the Imola piston that we have seen (New on right, old on left).
The new pistons come with lubricating holes in the piston which line up with the four cylinder stud holes.
It has been known for all types of Lambretta cylinder to seize here.
TS1 cylinders often seize here if not set up correctly.
The primary reason for the seizures which line up with the stud holes is overtightening of the cylinder studs, this bows out the cylinder walls into the bore when hot, causing the characteristic seize marks.
We don't know if these holes will stop it happening but they are a step in the right direction.

Please E-mail us with any questions or comments.