How to Fit Large Lambretta Engine Mounts Correctly
If you're rebuilding a Lambretta engine or restoring a chassis, the engine mounts are an area that's easy to overlook. They're a relatively simple component, but fitting them incorrectly can lead to excessive vibration, poor engine alignment and premature damage to the rubber.
In this guide, we'll look at the correct way to fit large-style Lambretta engine mounts, including the importance of using the correct frame cones, getting the orientation of the mounts right and, perhaps most importantly, not over-tightening the engine mount spindle nuts.
At Scooter Vista, we stock the Scootopia large Lambretta engine mounts, along with the matching large-style engine mount cones and other components needed to complete the installation correctly.
What Do Lambretta Engine Mounts Do?
The engine mounts, also known as silent blocks, sit between the Lambretta engine casing and the engine mounting spindle. Their job is to isolate engine vibration from the frame while allowing the engine to pivot as part of the rear suspension system.
The rubber within the mount is designed to provide controlled movement and absorb vibration. This is why the condition and correct installation of the mounts are important, particularly on Lambrettas running upgraded engines where vibration and power can be considerably greater than on a standard engine.
The large-style mounts were introduced as Lambretta developed, with the longer/larger design being associated with the more powerful later models. The large-style mount is now also a popular upgrade for earlier LI, SX and TV engines where the appropriate components are fitted.
Which Lambrettas Were Originally Fitted With Large Engine Mounts?
The large-style engine mounts were originally fitted to a number of later Lambretta models.
According to Scootopia's fitment information, factory applications include:
Series 3
- LI150 Special
- LI125 Special
- SX150
- SX200
- TV175
- TV200
DL / GP
- DL/GP 125
- DL/GP 150
- DL/GP 200
The larger mount can also be used on other LI, SX, TV and DL/GP Lambrettas as an upgrade, provided the correct large-style engine mount cones and long engine bar/spindle are used.
Interestingly, Innocenti changed the engine mount cone design to accommodate the larger style mount on TV models in July 1962.
This is why it's important not simply to look at the engine mount itself when carrying out a conversion. The frame cones and engine spindle need to be correct for the large-style mount.
Small vs Large Lambretta Engine Mounts
There are different styles of Lambretta engine mounts, and the smaller style should not simply be mixed with the components designed for the larger mount.
The large-style mount has a greater depth of rubber within the silent block and is designed to work with the corresponding large-style frame cones and longer engine spindle.
If you're converting a scooter from the smaller style mount to the larger type, you should consider the complete system rather than just changing the rubber mounts.
You will generally need:
- Large-style engine mounts
- Large-style frame cones
- Long engine mounting spindle/bar
- Appropriate washers and nuts
Using the correct components together gives the mount the correct seating and allows everything to work as intended.
Fitting the Large Lambretta Engine Mounts
Before starting, make sure the engine casing and mounting area are clean. Any corrosion, dirt or debris around the engine mount bores can make fitting difficult and can prevent the mount from seating correctly.
If the new mount is particularly tight in the casing, don't simply reach for a hammer and force it into position.
Check the condition and dimensions of the casing and mount first. Scootopia recommends checking the fit by hand before installation. If necessary, a slight chamfer on the leading edge of the mount can help with installation.
A clean and correctly prepared casing will make the job considerably easier.
1. Check the Orientation of the Mounts
The Scootopia large engine mounts are marked left and right, with arrows indicating the correct orientation.
These markings are there for a reason.
When the mounts are fitted into the engine casing, the arrows should point towards the 12 o'clock position.
Take your time here. It's very easy to install a silent block without paying attention to its orientation, only to discover later that it has been fitted incorrectly.
2. Fit the Correct Frame Cones
This is one of the most important parts of the installation.
The frame cones sit inside the ends of the Lambretta frame's engine mounting tube and locate against the engine mounts.
There are different styles of Lambretta engine mount cones. Although the small and large-style cones can look very similar, the outside edge angle is different.
If you're fitting large-style engine mounts, use the large-style frame cones.
Scootopia specifically recommends changing the cones when converting to the large-style engine mounts rather than simply reusing the smaller-style cones.
The cones should be correctly seated in the frame tube before attempting to install the engine.
The split in the cone should be positioned at approximately the 12 o'clock position, and the cones should sit correctly and evenly in the frame tube.
3. Line Up the Engine
With the cones correctly installed, position the engine between the frame mounting points.
The engine mount holes should line up with the frame tube and cones.
The engine spindle should be able to pass through without excessive force.
If you're having to hammer the engine spindle through the frame, stop and check the alignment.
A spindle that refuses to pass through normally indicates that something isn't correctly lined up.
Don't use force to compensate for poor alignment.
4. Install the Engine Mount Spindle
Once everything is correctly aligned, slide the long engine mounting spindle through the frame and engine mounts.
Fit the appropriate washers and nuts to each side.
At this stage, don't immediately tighten one side fully.
Start by tightening the nuts by hand and make sure everything remains central and correctly aligned.
It's a good idea to tighten the two sides progressively so that the assembly remains even.
Don't Over-Tighten the Engine Mount Spindle Nuts
This is an important point that is often overlooked.
The engine mount spindle nuts should not simply be tightened as hard as possible.
The rubber inside the silent block needs to work correctly to absorb vibration and allow the engine to move through its suspension travel.
Over-tightening the spindle nuts can put excessive compression on the rubber and can potentially damage or distort the engine mount.
Rather than assuming that tighter is better, tighten the spindle nuts correctly and evenly, using the appropriate specification for the components and application.
The objective is to securely clamp the assembly without crushing or damaging the rubber.
If the mount has been over-tightened, the rubber can become distorted and its ability to perform its intended job can be compromised.
Don't Grease the Engine Spindle
It's also worth remembering that the engine spindle isn't intended to rotate inside the frame cones during normal operation.
The engine's movement is accommodated by the rubber within the silent blocks.
For that reason, avoid treating the engine spindle like a conventional pivot that needs to rotate freely inside the frame cones.
The cones and spindle should be clean and correctly fitted so that the rubber engine mounts can do their job.
Check Everything Before the Engine Goes Back Into Service
Before finishing the job, check:
- The correct large-style mounts have been installed.
- The left and right mounts are correctly positioned.
- The arrows on the Scootopia mounts point towards 12 o'clock.
- The correct large-style frame cones are fitted.
- The cones are properly seated in the frame tube.
- The correct long engine spindle/bar is being used.
- The engine is correctly aligned in the frame.
- The spindle passes through without excessive force.
- The nuts are tightened evenly.
- The spindle nuts have not been over-tightened.
- The rubber in the mounts isn't visibly distorted or damaged.
It's much easier to correct a problem while the engine is on the bench than after the scooter has been completely assembled.
Why Choose Scootopia Large Lambretta Engine Mounts?
At Scooter Vista, we stock the Scootopia large Lambretta engine mount set for customers carrying out engine rebuilds, restorations and upgrades.
The Scootopia mounts are designed specifically for the later-style Lambretta installation and feature increased rubber depth compared with the smaller-style mounts. They are also marked left and right, with arrows showing the correct installation position.
Scootopia has also improved the fit of the mount within the engine casing, giving a slightly tighter fit and addressing vibration issues associated with some previous mounts.
If you're replacing your existing mounts, it's worth considering the complete installation rather than simply replacing the rubber.
We also stock the large-style engine mount cones and long engine mount spindle, allowing you to make sure the components are matched correctly.
Conclusion
Lambretta engine mounts might look like a straightforward component, but getting the installation right makes a big difference.
The key points are simple:
Use the correct mounts. Use the correct large-style frame cones. Make sure the mounts are correctly orientated. Align the engine properly. And don't over-tighten the spindle nuts.
Taking a little extra time during installation can help protect the rubber mounts, reduce unwanted vibration and ensure the engine is correctly supported within the Lambretta frame.
If you're rebuilding a Series 3 Special, SX, TV, DL or GP, or upgrading an earlier LI/SX/TV model to large-style mounts, check out the Scootopia large Lambretta engine mounts and matching components available from Scooter Vista.
