stuck Minarelli engine

I was given an old Testi with a Minarelli V1 engine. Sadly the engine is stuck. Some dis assembly reveals the big end of the connecting rod is married to the crankshaft. It will not rotate on the crank.

It's a shame really as this machine appears to have only 282 miles on the clock. The oil is draining now so I'll see if there's any water or other rubbish in there. The crank throws have some bright orange surface rust. I wonder if the con rod bearing is rusted to the crank...

Any thoughts or advice? I am on the fence about parting this bike out. Which would be sad I think as there's a lot of cool parts on this machine. The giant chrome bullet headlight and speedo combo for instance is sexy. With a good engine I could have this machine back in fighting shape in no time.

Re: stuck Minarelli engine

Update. It spins! I unstuck it. Took the engine out of the frame, removed the head and cylinder. Placed engine on workbench forward end facing up. Soaked the crank and con rod bearings with PB Blaster. Was able to move the con rod back and forth a tiny bit. Then more. Then quite a lot. More Blaster and some of my precious supply of Silikroil. And whammo. Now it rotates freely, round and round.

What kind of engine oil are these Minarelli supposed to run? I'd like to flush the insides with an oil change or two. Then put it all back together and see what's what.

Re: stuck Minarelli engine

Check for up/down play in that lower rod bearing. No use to put it back together if it has much play.

Re: stuck Minarelli engine

"What kind of engine oil are these Minarelli supposed to run?"

Whatever flavor of 2-stroke oil you choose to mix in your gas.

Re: stuck Minarelli engine

I think he means tranny oil. Use 20 or 30 weight non-detergent oil

Re: stuck Minarelli engine

Oil goes in the tranny side only. The crankshaft and conrod do not run in an oil bath. It sounded like he was talking about flushing the crankcase because he had a rusted stuck conrod that he broke loose.

Re: stuck Minarelli engine

Oh!

Re: stuck Minarelli engine

I might be wrong, I just don't want him thinking it runs in oil for lubrication like a four stroke.

Re: stuck Minarelli engine

Hopefully he'll read here again.

Re: stuck Minarelli engine

Hey everyone thanks for chiming in. Yes I understand how 2-strokes are lubricated. In the late 1970s I rode an Aermacchi 125 Rapido. See attached. That was my introduction to @2-stroke technology and the related quirks. It was my very first motorbike too. Since then I've probably owned 40 or more. You know that crazy little Italian bike had Harley-Davidson badges on the tank. But it truly was an Italian 2-stroke weirdo. Shift lever was on the right side!

Don is correct. I meant to say transmission oil, as the stuff I drained out could be 39 years old for all I know.

I've messed with many more 4-stroke motorcycle engines than 2-stroke moped mills. I checked the con rod very carefully and can measure zero play. It feels nice and snug which I'd hope to see with possibly under 300 miles of service.

2-stroke oil? I have but one love. Klotz Techniplate. Amazing stuff with a signature smell. Some people love it so much that Klotz now makes Klotz-scented candles!

Thanks for input!

Aermacchi-1972-SX125-Rapido.jpg

Re: stuck Minarelli engine

Quote Jeff: ` I checked the con rod very carefully and can measure zero play. It feels nice and snug which I'd hope to see with possibly under 300 miles of service.'

Man you are riding a winning streak there. Happy for you!

Re: stuck Minarelli engine

Good to hear! Man, we've seen some strange stuff on here. Anyway, glad to hear there's no end play. Minarellis are tough, bulletproof engines. I have two. Yours should last a long time, if the needle bearings aren't pitted from being stuck. Sounds like you maybe lucked out. The transmission takes 30 wt motor oil. Make sure it's non detergent. Read up on the Minarelli link in the wiki.

Re: stuck Minarelli engine

♣Slew Foot♣ /

I think it requires just a tiny bit of Axle play at least most mopeds do because if there is any kind of imbalance in the crank it will let it slide

Re: stuck Minarelli engine

Thanks for the help everybody! I am excited to work on this Testi/Minarelli. But I've got an Urban Express to finish first. It's getting close. It'll have new tires, tubes, cables, battery, carb overhaul, tank flush, and on and on and on. Should be great fun.

I know every moped maker has their own way of doing things. So far after working on a Kreidler, two Hondas, and a Moby, I think I like the Italian arrangement best so far.

Re: stuck Minarelli engine

Frank Bailey (MOPITT) /

I revived a crusty Sachs 504. The crank and big end bearing appeared perfect. Ran it for one summer but found later the big end was quite loose. I'd take that gamble again and think you should too but be prepared for a do-over. You know, kind of like everything on a moped...

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