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210cc Gilera runner engine

So far, the emphasis on tuning Gilera runners has been what we at MB Developments call "tickle tuning" - a carb kit for couple of horsepower , a head for a couple of horsepower, play with the rollers for a few more mph etc.
But no-one (apart from Malossi with the 172 kit) has looked at it from the old fashioned point of view - more CC's = more power.
It was with this in mind that we have taken on this one-off commision for a 210cc runner engine.
It will be going to an Austrian dealer who is going to put it in an Italjet dragster and try to break a world record.
We are just sorting out the casings, crank and barrel for him, we will leave him to play on his dyno to set the rest up!
It looks like the 210cc is the upper limit for a Runner engine as we have have to use an eccentric crank pin and rotax con-rod to gain some of the extra cc's and this in turn means a lot of machining work to the casings, which would make it a prohibitively expensive road conversion.
We plan to offer a conversion using the standard crank (Well, the standard Malossi race crank!) which will be more economical.
This would be 198cc so you'd effectively have Gilera 200!

This page will build up into the story of what we do to the engine, so you will be able to see exactly what is involved.

Special note:- This project is a unique special project. We will NOT be doing another one like it. Please do not ask us if we will do one for you because the answer will be no.
Ce projet est un projet spécial unique. Nous ne ferons pas encore comme lui. Veuillez ne pas nous demander si nous ferons un pour vous parce que la réponse sera non.
Dieses Projekt ist ein einzigartiges spezielles Projekt. Wir werden NICHT ein anderes wie es tun. Bitte fragen Sie uns, ob nicht wir ein für Sie tun, weil die Antwort nein ist.
Questo progetto è un progetto speciale unico. Gli non faremo altro. Prego ci non chieda se vi faremo uno per perché la risposta sarà no.

On with the show!!

(As ever clicking on the picture lets you see a bigger version of that picture.)

One half of the bare casings before we do anything to them.
You can see how tiny the hole for the reed block is - something we will be working on!

A view down inside the standard 180 barrel we are using as the basis for this top end.
This will be fitted with an iron liner to suit the 70mm piston we are using.

What looks like a great big transfer port at the bottom of the picture is actually where the coolant goes into the barrel from the casings. What a shame.

A picture just to illustrate the ports in the barrel.
As you can see the barrel has had a seize but using a liner means that the seize marks don't matter - in fact they could be great big gouges and it wouldn't matter - the beauty of using a steel liner.

A con-rod from an Ape three wheeler finds itself modified and waiting to be fitted to the webs of the Malossi crank.
This rod uses a larger big end diameter, it is 5mm longer between centres and uses an 18mm small end.
All this had to be taken into account with the dimensions of the new piston.

The next three pictures illustrate the eccentric crank pin we are using (we actually had it specially made as a one off for this job).

An eccentric pin is used to change the stroke of the crank without actually having to machine the webs.
It is the crankshaft stroke rather than the conrod length that alters the C.C.'s.

There are no worries about the crank pins spinning when the eccentric pins are being used because the crank pins are oversized to be a tighter fit.

The finished article!
Eccentric crank pin changes 52mm stroke to 54mm. Vespa ape con rod modified and assembled correctly. No loctite needed, the crank lined up perfectly with no run out. Rare in Vespas and Lambrettas, but looks like the Malossi full circle crank was very well made.

The finished crank ready to fit into the casings, we will need to make a special puller to draw the crank into the bearings, rather than bashing it in with a hammer and putting the crank out of line.

View of the Gilera 180 cylinder bored out to allow the new 70mm race piston to fit in.
The step was done so we could fit the crank, piston and cylinder on to the dummy engine so the port timings, packing plates and liner preparation can all take place.

The differences between the piston sizes for the one off 210 engine.
On the left a standard 180 gilera piston - 65.5mm, on the right a Husqvarna 70mm piston.

On the left the standard piston, on the right the new 70mm race piston

View of the Gilera 125 crankcase mouth before we get our hands on it!
The 125 and 180 casings are basically the same. The main difference is that the 125 crankcase mouth is much smaller that on a 180. This is because the bore is larger on the 180 and it needs a bigger spigot to locate into the casings.
The Malossi 172 kit fits directly into the 125 casings but also goes into the 180s. It uses the same small spigot as the the 125 cylinder. Fitting a 172 kit to a 180 engine would work but it would mean the crankcase compression is a little lower.

View of the standard Gilera casing showing how small the inlet port is.

Photo showing the Gilera cylinder being bored out for the 2nd time.
The first time it was bored to the diameter of the piston to set up the tuning basics. The 2nd time it was bored out to 76mm to take the iron liner required to fit the piston.
We were going to use an alloy liner and have it ceramic plated but there is not enough meat in the cylinder to do this and for it still to be reliable.
So we have chosen to use an iron liner for strength, also increasing the cylinder height (which we needed to do to get round the problem of sealing the cylinder head - normally there is an o ring but the groove was too near the bore).
The piston used is from a nicasil cylinder so there are no oversizes available. Iron liners are fine if you have pistons with oversizes but in this case we haven't so will we have to get the iron liner ceramic plated to stop it wearing.
NOTE: The amount of alloy in the tray under the boring bar. We had this amount the first time around.

To draw the rebuilt crank into the bearings in the casings safely we had to make a pulling sleeve. The other option was to use a hammer!
NO! DON'T DO IT!!
It was so tight there would have been tears!

Standard casings with our Malossi crank fitted with the new 70mm piston, assembled so we could set up the cylinder porting and find out what else required doing to seal the cylinder and head.

We were supplied with new 125 casings, a genuine 180 cylinder and Malossu crank and head.
The cylinder would not fit down the studs without a 10lb hammer!
So we had to drill out the cylinder stud holes 10mm from 8.5mm. This way the cylinder fitted on but was still very tight.
Once we got the cylinder going down the studs we found the casings required some grinding to allow the piston down!!
When we tried the head we found that the stud holes were misaligned to the bore.
This all indicates that the stud holes on the casing were machined in a different pattern to the barrel and head!
This was the first major problem we had to sort out before our work could start.

This picture shows the small inlet port of the Gilera's engine.
With the crank and conrod conversion there is not much scope to fit a larger reed block that you would expect to use with the size of the engine.
The fact that some Gileras have already hit 28bhp shows that massive reed blocks like on a motocross cylinder aren't necessary.

Two views of the Gilera cylinder bored out ready for the iron liner/sleeve to be made.
Boring it out to 77mm took away a lot of alloy making the tuning much easier.

The boost port feeds have been enlarged to suit the new piston we are using and the transfer feeds have been increased to give a small bu sealable gasket face.
This was done because the larger piston and liner will decrease what were already small transfer feeds.
We have chosen not to alloy weld the transfer area as we are using a big thumping piston that will do the pumping job, rather than relying on the transfer feeds.
It has already been proven that smaller transfer feeds can produce 28bhp - we are aiming for just over 30bhp. We don't want to go too mad as it appears the drive set-up restricts the power you can use because it isn't up to handling massive power.

Please E-mail us with any questions or comments.

	One half of the bare casings before we do anything to them. You can see how tiny the hole for the reed block is - something we will be working on!
	A view down inside the standard 180 barrel we are using as the basis for this top end. This will be fitted with an iron liner to suit the 70mm piston we are using.
	What looks like a great big transfer port at the bottom of the picture is actually where the coolant goes into the barrel from the casings. What a shame.
	A picture just to illustrate the ports in the barrel. As you can see the barrel has had a seize but using a liner means that the seize marks don't matter - in fact they could be great big gouges and it wouldn't matter - the beauty of using a steel liner.
	A con-rod from an Ape three wheeler finds itself modified and waiting to be fitted to the webs of the Malossi crank. This rod uses a larger big end diameter, it is 5mm longer between centres and uses an 18mm small end. All this had to be taken into account with the dimensions of the new piston.
	The next three pictures illustrate the eccentric crank pin we are using (we actually had it specially made as a one off for this job).
	An eccentric pin is used to change the stroke of the crank without actually having to machine the webs. It is the crankshaft stroke rather than the conrod length that alters the C.C.'s.
	There are no worries about the crank pins spinning when the eccentric pins are being used because the crank pins are oversized to be a tighter fit.
	The finished article! Eccentric crank pin changes 52mm stroke to 54mm. Vespa ape con rod modified and assembled correctly. No loctite needed, the crank lined up perfectly with no run out. Rare in Vespas and Lambrettas, but looks like the Malossi full circle crank was very well made.
	The finished crank ready to fit into the casings, we will need to make a special puller to draw the crank into the bearings, rather than bashing it in with a hammer and putting the crank out of line.
	View of the Gilera 180 cylinder bored out to allow the new 70mm race piston to fit in. The step was done so we could fit the crank, piston and cylinder on to the dummy engine so the port timings, packing plates and liner preparation can all take place.
	The differences between the piston sizes for the one off 210 engine. On the left a standard 180 gilera piston - 65.5mm, on the right a Husqvarna 70mm piston.
	On the left the standard piston, on the right the new 70mm race piston
	View of the Gilera 125 crankcase mouth before we get our hands on it! The 125 and 180 casings are basically the same. The main difference is that the 125 crankcase mouth is much smaller that on a 180. This is because the bore is larger on the 180 and it needs a bigger spigot to locate into the casings. The Malossi 172 kit fits directly into the 125 casings but also goes into the 180s. It uses the same small spigot as the the 125 cylinder. Fitting a 172 kit to a 180 engine would work but it would mean the crankcase compression is a little lower.
	View of the standard Gilera casing showing how small the inlet port is.
	Photo showing the Gilera cylinder being bored out for the 2nd time. The first time it was bored to the diameter of the piston to set up the tuning basics. The 2nd time it was bored out to 76mm to take the iron liner required to fit the piston. We were going to use an alloy liner and have it ceramic plated but there is not enough meat in the cylinder to do this and for it still to be reliable. So we have chosen to use an iron liner for strength, also increasing the cylinder height (which we needed to do to get round the problem of sealing the cylinder head - normally there is an o ring but the groove was too near the bore). The piston used is from a nicasil cylinder so there are no oversizes available. Iron liners are fine if you have pistons with oversizes but in this case we haven't so will we have to get the iron liner ceramic plated to stop it wearing. NOTE: The amount of alloy in the tray under the boring bar. We had this amount the first time around.
	To draw the rebuilt crank into the bearings in the casings safely we had to make a pulling sleeve. The other option was to use a hammer! NO! DON'T DO IT!! It was so tight there would have been tears!
	Standard casings with our Malossi crank fitted with the new 70mm piston, assembled so we could set up the cylinder porting and find out what else required doing to seal the cylinder and head.
	We were supplied with new 125 casings, a genuine 180 cylinder and Malossu crank and head. The cylinder would not fit down the studs without a 10lb hammer! So we had to drill out the cylinder stud holes 10mm from 8.5mm. This way the cylinder fitted on but was still very tight. Once we got the cylinder going down the studs we found the casings required some grinding to allow the piston down!! When we tried the head we found that the stud holes were misaligned to the bore. This all indicates that the stud holes on the casing were machined in a different pattern to the barrel and head! This was the first major problem we had to sort out before our work could start.
	This picture shows the small inlet port of the Gilera's engine. With the crank and conrod conversion there is not much scope to fit a larger reed block that you would expect to use with the size of the engine. The fact that some Gileras have already hit 28bhp shows that massive reed blocks like on a motocross cylinder aren't necessary.
	Two views of the Gilera cylinder bored out ready for the iron liner/sleeve to be made. Boring it out to 77mm took away a lot of alloy making the tuning much easier.
	The boost port feeds have been enlarged to suit the new piston we are using and the transfer feeds have been increased to give a small bu sealable gasket face. This was done because the larger piston and liner will decrease what were already small transfer feeds. We have chosen not to alloy weld the transfer area as we are using a big thumping piston that will do the pumping job, rather than relying on the transfer feeds. It has already been proven that smaller transfer feeds can produce 28bhp - we are aiming for just over 30bhp. We don't want to go too mad as it appears the drive set-up restricts the power you can use because it isn't up to handling massive power.