LCGB Forums

Hi Chaps

I'm finally rebuilding/assembling a 150 engine. As a relatively newby to the shaft driven motors of this age and following on from my earlier post on compression ratio's, some of the answers I got gave me some food for thought,

1. Some of you have fitted a stroked crank, what crank have you used? TV 175 S2/3?
2. Some of you have ported the heads/barrel, how much did you do and was the outcome worth it? (Iron barrel)
3. Some have fitted a Bantam D1 head, was it worth it?

As before, these are not rocket ships, its part of their charm, but I'm based in Gloucestershire and it would be nice to be able to climb some of the hills around the Cotswolds without some yummy mummy trying to mow me down in their 4x4.

I currently have a TV conrod to fit and have access to a press, but with fat fingers and my eyesight I kind of like to send it too somebody in the know to fit and true, the usual outlets don't want to touch them, who do you use?

I accidentally fit a 1 mm stroked, modified Li crank. I say accidentally because I ordered a modified Li crank and Howard Chambers mistakenly sent me the wrong one off his bench! Works great though. Normally the piston sits low in the cylinder and you have to machine a mill off in order to get it higher. I modified a 125DL head to suit as it had a squish band. Just had to mark and drill out the different stud pattern. I then chucked it on the lathe for fine tuning. I have the Tino S alloy cylinder, a custom expansion chamber (for low revs -- very, very long) and a period 24mm carb off a Harley dirt bike. I ended up with an engine that is a bit more powerful off the line than a stock Li150 and will make stock 175s and 200s work to keep up on the flats.

The issues?

- Gearbox, gearbox, gearbox: There is no alternative to the stock 3 spd and the gap between 2nd and 3rd is huge. You need an engine with a broad torque band and even then speeds build slowly after switching into 3rd.

- More power (are you sure?): There is a good reason Innocenti switched to chain drive. Adding power adds stress to a not particularly strong design. On my very first ride I snapped a rear axle. I keep a spare rear axle and drive shaft on hand but, knock on wood, have had no further breakages.

- Vibration: a stock D/LD doesn't vibrate much at all. It also doesn't rev much at all. It is very smooth and pleasant in the 40 to 50 kph (25 to 30 mph) range. At top speed in mine the handlebars vibrate like you would not believe. White knuckles are not longer just a figure of speech! Could I change the balance factor? Sure! But then I just move the vibration period somewhere else even more annoying.

- Brakes (Yes Virginia, Ds did actually come with brakes): Mine tops out between 90 and 100 kph (55 to 60 mph). If you need to slow down rapidly at that speed, forget it. Almost literally, nothing happens when you apply the brakes. I also occasionally tow a Pav trailer. Then the brakes disappear even at low speeds! I have been toying with fitting a front brake off a later Li but then...

I hope you are getting the picture. Can you modify a D/LD? Sure. But, why? Yes it's a slow scoot but it's an absolute delight to drive stock: smooth and vibration free. Trying to make it fast quickly raises many serious issues that are not easily overcome; and, significantly change the character of the D if you try to do so. Sure perform some minor mods to the engine to make it somewhat less anemic but ride something else if you want to go fast.