Author Topic: Mending small crankshafts  (Read 563 times)

0 Members and 1 Guest are viewing this topic.

Offline martin1957

  • Forum member
  • Port Hacker
  • Posts: 1329
  • Age: 65
  • Location: Gillingham, Kent
Mending small crankshafts
« on: September 17, 2022, 04:05:29 PM »
I had a small 2T tiller and filled it with straight petrol by mistake. Ran it at full throttle continuously and after 15 minutes it stopped dead. Seized. Its a 26cc vertically split engine. Piston port, Ball bearing mains, caged roller big and small ends.
After a bit of fiddling I worked out it was the bottom end. Pulled it apart and it was the big end caged roller broken up. Everything else was fine.
Using a big pin punch, club hammer, and big vice I drifted the end pin out. I read the numbers off it and got another for £2 on ebay.
I dropped it onto the old end pin that was only discoloured, not damaged.
I hammered the two halves back together, until they were the original distance apart.
To true it up I kept putting it in the crankcases and trying to spin it. Some taps to turn the crank webs a bit and more trial and error until it span freely when both the vertical crankcases were put together.
It took a bit of hammering but it now works perfectly.
Some nay sayers will say you need special equipment etc, but with nothing to lose I tried this and it works fine.
Retired Electronic Test Engineer (Avionics), Age 64, Owned P50, PC50, SS50z, YAS1, YDS7, RD350B till 1978, then in 2009 a  KH400 A4 - now sold. Have a fully restored YAS1, an AT3, and now a Suzuki T125 Stinger.  A show winner.

Offline robrd

  • Club Member
  • Back Lane Scratcher
  • Posts: 342
Re: Mending small crankshafts
« Reply #1 on: September 17, 2022, 05:14:59 PM »
Have you seen some of the crank rebuilds on you tube done in back street sheds, their tools include hammers only, lump and sledge, but, They seem to run OK!

Offline twostrokelooney

  • Club Member
  • Port Hacker
  • Posts: 1321
  • Age: 63
  • Location: Shrewsbury, England
Re: Mending small crankshafts
« Reply #2 on: September 17, 2022, 06:32:46 PM »
I had a small 2T tiller and filled it with straight petrol by mistake. Ran it at full throttle continuously and after 15 minutes it stopped dead. Seized. Its a 26cc vertically split engine. Piston port, Ball bearing mains, caged roller big and small ends.
After a bit of fiddling I worked out it was the bottom end. Pulled it apart and it was the big end caged roller broken up. Everything else was fine.
Using a big pin punch, club hammer, and big vice I drifted the end pin out. I read the numbers off it and got another for £2 on ebay.
I dropped it onto the old end pin that was only discoloured, not damaged.
I hammered the two halves back together, until they were the original distance apart.
To true it up I kept putting it in the crankcases and trying to spin it. Some taps to turn the crank webs a bit and more trial and error until it span freely when both the vertical crankcases were put together.
It took a bit of hammering but it now works perfectly.
Some nay sayers will say you need special equipment etc, but with nothing to lose I tried this and it works fine.

Top story, I like your approach.... 8)
Never Mind The Four Stroke.
Club Member 170.
RD350 (1973)
RD250E
TZR250 2MA YPVS
Z1000J3

Online pidjones

  • Club Member
  • Port Hacker
  • Posts: 654
  • Age: 70
  • Location: East TN
Re: Mending small crankshafts
« Reply #3 on: September 17, 2022, 07:28:46 PM »
AND, I bet you'll not make that mistake again.
"Love 'em all... Let GOD sort 'em out!"