Blue Cat Motorcycle

Viva Midwest

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Sometimes stock is best

Posted on 05 Apr 2011 in On The Lift | 0 comments

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There’s something elegantly wonderful about a highly tuned, big bore racing engine. Take this 1962 Lambretta LI-125. This bike was not only restored when Joe and Rochelle bought it, it was highly kitted. The 125cc italian thumper had been kitted and tuned up to 190cc of high-strung fury. This turned an already quick little Lammy into a silver bullet. I’ve been on several rides with Joe and this bike could easily tear away from me on my modern, 200cc liquid-cooled, 4-valve Vespa. It sounded the business too. It was all fun and games until the motor blew up in the middle of the big Saturday ride at the Rattle My Bones scooter rally. That wouldn’t have been a big deal if Joe hadn’t been leading that 300+ scooter ride at the time. That’s another story, though. Getting this Lammy healthy again would be no short journey, but in a way, it would be a journey home for the bike.

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The original plan for this LI-125 was to simply fix it — to rebuild the 190cc version of the engine. That meant first diagnosing exactly what had failed in the motor, then figuring out just what kit had been installed (’cause it wasn’t ours), then trying to find the replacement parts needed to get it growling again. Jeff tore into the motor to finally uncover the true cause of failure. It was more autopsy than rebuild. What he found was troubling. Most performance tuning comes with a reliability trade off. Unfortunately this motor had been tuned so aggressively that it was making far too much power for the engine’s internal components. The flywheel had literally split down the shaft collar and the failure had also blown a huge chunk out of the solid steel crankshaft.

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With cause of death determined, that left two paths this project could take. The first, and original path would be to rebuild the motor back to screaming hot. We had a replacement piston, a new flywheel and replacement crankshaft. We’d be able to reuse the bored out top end, but looking at the parts, Jeff could see the future. Sure, we could put this motor back together and get the Lambretta back to its ridiculous, over-bored glory, but it’d just be a time bomb. It’d fail again, probably in a similarly spectacular way. Tuning that aggressive was simply asking too much of such a small motor. That’s fine for the racetrack, but not ideal if you want a scooter you can actually just ride around town reliably.

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The alternate, now seemingly more sensible path, would be to take the engine back to stock. Stock top end, stock piston, new crank and stock exhaust. Getting parts for these old italian ponies isn’t exactly easy, but with a bit of rooting around online and half a dozen phone calls later, we finally had everything we needed. The engine went back together with new guts and it was time to reassemble the LI. Finally this old Lammy that had sat disembodied all winter could have its tail end put back in. We painted the exhaust and all that remained were a handful of bolts and washers.

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Finally the moment of truth came. With everything buttoned up, it was time to kick start the renewed motor for the first time. It was still pretty cold out when Jeff took the Lammy on its proving run. It ran strong and the LI-125 was still plenty quick with a fresh, stock setup. However, as often happens with winter and late winter fixes, the motor needed just a touch of choke to stay happy. We’ll have to wait for slightly warmer weather before we can certify the carb adjustment. Detail tweaks aside, we’re just pleased to see this gorgeous little classic scooter back on the road, and here’s hoping we don’t see it back on the lift for a long, long time.