Scooterotica

Had a friends Lambretta in the garage after he thought he’d seized it.
Scooter is a Li Series 3 fitted with a brand new genuine SIL GP200 engine bought a couple of years ago from a reputable British scootershop as a batch of 6.
Engine was ran with a Clubman exhaust and Dell'orto 25mm carbu with Remote Ram Air filter.
Engine had been run in by a responsible Scooterist with +20 years of scootering under his belt and no history for roadracing, unresponsible riding or engine failures.
Scooter was mainly run on local roads with the occasional ‘high’-speed dozen of kilometers between a couple of highway exits. Never been overrev’s or sustained long stretches of full throttle riding.
Several weeks ago broke down on the motorway with what felt like a seize.
Last weekend finally had time to open the engine up to check out the cost of fixing it…
Very clearly the Big end bearing failed fantastically and took out the conrod, twisting and snapping it clean off halfway. The small end tore the gudgeon pin clear from the piston taking the lower half of it’s seat in the piston along with it. Mid you, the circlips are both still seated in the top half of their piston grooves…
Intertingly the piston and barrel show no signs what so ever of weak running or poor lubrication and the barrel even survived without so much as a mark in the bore and can be reused!

personally if the engine was untouched from SIL the first thing I would have done was swap the crank as these are known for being poor quality. if not swapping the crank then get it split and rebuilt with better bearings. if this has already been done previous to your mate running the motor then the only lucky thing was the big end didn't punch a hole through back of casing when it let go.
hope its soon up and running again.

i think its quite common knowledge that in indian bearings are of poor/ variable quality, most who buy these engines replace bearings and seals as a matter of course. indian big end bearings do have the same reputation,indian cranks are very good, maybe not the strongest rod, but fitted with high quality bearings will last a long time if not abused too much, if a quality rod is used as well, an indian crank can be a good bit of kit. i would say your friend has been lucky that the barrel is undamaged and the casing is undamaged, stick a new crank in there with bearings and seals plus his new piston and he should be good to go, i would probably check out the rest of the engine while i was as it, not ideal on a new engine but he might get a good deal on a crank and bearing kit, i think glasgow lambretta had some offers on mec cranks, which are good value on a budget build

Holy. . Cheers for the tip about Glasgow!

Thinking outside the box........it may have been part of the piston breaking that jammed the crank, causing it to seize...

mick1 wrote:Thinking outside the box........it may have been part of the piston breaking that jammed the crank, causing it to seize...

you could be right mick, the last photo seems to show some blueing around the big end area which made me think big end was the cause, it could just be some heat treatment to the webs, realy need the crank out to be sure and have a photo of it, either way new crank and piston needed, plus mains and seals gaskets etc, could have been worse.

ive seen the big end weld itself on 2 indian cranks , bearings were just bits if wire, I kid you not they blued and heated themselves together, but I must stress neither were bought from an sil dealer , i have an sil 200 that i bought from scooter restorations and in 5 yrs its been very reliable, not all indian engines are sil..

Wow! I know this batch of six engines and the other five are still running fine as far as I know. Looks like this was the "bad" one. At least the casing escaped damage which is amazing in itself. Throw a nice strong crank in there and put it down to experience!

Damn lucky not to have wrecked the casing there, by the look of it.

The crank on mine lasted under 1000 miles I swapped it for the previous owner
The engine was also new from reserectioion scooters
Also wouldn't go over 50 mph the squish was over 3mm also had a Pepsi can shim in gearbox