Originally Posted by
davidej
if you don't have to remove the gudgeon pin before getting the big-end off, why would OS put two holes of the right size and in exactly the right position to allow you to do so?
To put any end to this disagreement, I will ring up Ripmax in the morning and get their advice.
If it’s like other engines past or present that have these access holes then yes you must remove the pin and separate the piston and rod for removal. Be cautious of advice from experts who may suggest forcing the rod from the crank pin. You may do enough damage to make the motor unsalvageable. Never a need to force anything in my opinion.
Look at the part of the pin that came out. It should be hollow. Is the hole in the front of the motor big enough to allow the pin to slip inside? If so the pin should be removable from either side. The pin will be hard but if you can find something small enough that you can get it to bind inside the pin you may be able to turn it while gently pushing or pulling it out through either access hole. If you feel the need to heat it try putting it on a piece of steel plate in the BBQ no more than 250 degrees. A welding glove makes handling it afterword comfortable.
Hint it is important to keep the holes in the crankcase lined up with the piston when assembling and disassembling the engine. If you use the liner (just slip it over the piston far enough to keep the piston centered in the crankcase leaving the pin bore clear) it will hold the holes in alignment making the removal and replacement of the wrist pin easier.
Keep your eye out for two teflon/nylon caps that go in the ends of the wrist pin. If you have not removed this from the part of the pin left in the motor it may be hindering you from pushing the pin out. Sometimes a heavy straight pin forced into it can aid in removal or push it out from the far side through the hole in the pin. As a last resort I have used a small drill and tap to get it out.
If you try and force the rod off the crank pin and damage/bend it you will be replacing it anyhow so as has been suggested better to cut the rod and try and save the piston.
To me it sounds like you will be replacing bearings, possibly piston/pin/rod assembly so you might want to investigate the cost of replacing these parts compared to a new engine.
And no you would not be the first to repair an engine where the parts almost cost the price of new. I think many of us have done the same at one time or another.
Good luck with it which ever way you decide to go
Dennis