Pressing Crankpin

Progressed to the point on my seized/rusted Hero MAL engine to where I need to remove the crankpin to replace large end rod bearing. I've had several tons of pressure on my work press with no movement at all. Afraid to put any more on it cuz I don't want to break the crank. New/used ones unavailable. I had it soaking in vinegar to dissolve the rust for about a week. There is movement of the rod on the crankpin now. Should I heat the area while under tension on the press ? Or what say the experts that have done this without breaking anything. It does not appear to be a tapered pin. This has been a challenging project so far.

Re: Pressing Crankpin

Blaine- The artist formerly known as Plumber Crack "(OFMC)" /

I’m assuming you’re supporting the crank like in the picture to press one side at a time. Do you have a new pin to verify if it does not have taper? If it was that rusted, i’d imagine the original pin is trashed.

Heat is always my absolute last option when messing with anything to avoid affecting temper and hardness.

Striking the crank wheel with a large flat punch (bar stock) and hammer right where the pin intersects the wheel (red dot) while it is under pressure may do the trick.


Re: Pressing Crankpin

todd amundson /

WTF is a Hero MAL engine? Single speed? Two speed or more? Hero Puch from India?

Is this on a moped?

Re: Pressing Crankpin

I'll try the press again with proper support and whacking it like Blaine suggests. To answer Todd's question it's a real moped, single speed, non-variated, made in India when it was called Hero Majestic, Panther model. Late 1990s. MAL Engine looks like a Peugeot 102 but not much interchanges. I think it was before Hero Puch version.

Re: Pressing Crankpin

Without proper supports the pin may become wedged out of alignment, and it may now take a bit of force to remove. BE CAREFUL. Watch for slips and rebounds of anything under pressure.

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