How do I remove gudgeon pin? It won't move.

[nudedaytona]

(I've started a new thread on this. The bike is a 1996 aprilia rs250)

It looks like the piston in the right cylinder is broken. I've removed the cylinder and you can clearly see that on side underneath the head there is a whole chunk missing.

I've had huge problems removing this piston though. I removed one circlip, no problems. But I could not remove the circlip on the other side because the gap in the circlip is right where the hole is to put your screwdriver in, meaning I could not push it out using a screwdriver.

This shouldn't matter because I thought I'd just push out the gudgeon pin through the side where I have removed a circlip. But it won't budge. I've tried using a screwdriver and hammering with a mallet on the screwdriver handle, and that moved it a little bit, but not any more. Plus I'm worried that I might move the piston out of alignment if I keep at it like that.

I've tried using a clamp but that doesn't work either. Can anyone tell me the best way to remove the gudgeon pin. Is there a tool that would make it easier?

(There's no danger of bits dropping into crankcase because the piston is hanging downwards out of the engine).

[Subike]

this will be interesting to see what is posted
I take it the conrod is still attached to the crank
heating the piston around the wrist pin bosses will expand the alloy to allow for the wrist pin to be withdrawn.
Using a screwdriver to remove the retaining clips is not wise, but I guess cost is a factor here,
I am not aware of the type of wrist pin, floating - semi floating.
A press is needed if semi floating
Others will have more info than me
Dont try and force it out using a hammer, a bend conrod will be the result, not noticed till you assemble the engine, thenwonder why it dies sooner than you expect from ring failure. ! .005 thou bent conrod is not needed.

[Ixion]

Heat the piston up. GENTLY (NB , gently) play a gas torch on the crown. Lacking that, use a hot air gun, your wife's hair dryer (DON'T LET HER CATCH YOU! DAMHIK) , or even just a one bar heater . You want it too hot to comfortably touch, no hotter. (Actullay, probably doesn't really matter in this case since the piston is stuffed anyway, but good practice is always good practice)

You should be able to move the circlip around in its groove by pushing it radially with a screwdriver blade. But, as you note, it's not really necessary because you can push the pin out from the free side . BTW be sure you are pushing on the gudgeon pin, not the still-in-place circlip

[Ixion]

this will be interesting to see what is posted
I take it the conrod is still attached to the crank
heating the piston around the wrist pin bosses will expand the alloy to allow for the wrist pin to be withdrawn.
Using a screwdriver to remove the retaining clips is not wise, but I guess cost is a factor here,
I am not aware of the type of wrist pin, floating - semi floating.
A press is needed if semi floating
Others will have more info than me
Dont try and force it out using a hammer, a bend conrod will be the result, not noticed till you assemble the engine, thenwonder why it dies sooner than you expect from ring failure. ! .005 thou bent conrod is not needed.

Unfortunately, it'll be wire circlips, no real option but a screwdriver (you can file a wee notch in the end to prevent nasty slippages)

It'll be a needle roller little end, the pin is just held in the bosses. The piston bosses may have distorted as a result of whatever (presumably detonation) took the piston out. Those pins can be jolly tight.

If heating the piston doesn't allow you to push the pin out using the palm of your hand (support the other side of the piston with your other hand), then make a little extractor using a bit of tube and a long bolt.I find tube spanners very useful for the requisite bit of tube. And coach bolts come in long lengths and cost cents.

[moT]

Use the following tools....Hack saw, grinder, hammer, crowbar

[zxcvbnm]

Your rod is probably bent if have been hitting it Here's a picture of the puller Ixion's mentioned.

[nudedaytona]

Thanks for all the advice. Fingers crossed I haven't bent the conrod. It still looks pretty straight to me, moves up and down without any obvious sideways movement.

I'll heat it up and try again, using Ixion's contraption.

[Ixion]

Takes more than one might think to bend a two stroke conrod. Certainly can be done, but you have to hit pretty hard. Thing is if the pin is tight even hard hitting may not move it.

If you do want to hammer a gudgeon pin out, grasp the hammer immediately under the head (or, use what I do, a hammer head with no handle). And rata-tat-tat it out, series of short sharps taps, not hard wallops. Keep your free hand behind the piston, let the pin slide out between your fingers (which also makes it easy to catch if the last bit comes out fast! Before it goes down into the crankcase!)

[kevfromcoro]

Normally a bit of heat is enough to get it out..Alloy expands pretty quick.
I have done it by dunking the piston in boiling water.but have to take the rod off the crank to do that.
Wouldnt go near the thing with a hamer.
As stated .005 thou is sod all.if bent.

[westie]

If the piston is broken I'd go with toms advice and smash it

[MaxB]

Heat and patience is what needed. IMO.

The other thing is that did you get a chance to look at any causes of failure? Any bits, scorch marks etc? Last thing you want is to slap it back together and to fail straight away.

At least the motor is RGV based so you can still get parts, if required.

[munterk6]

Have you thought about where the missing alloy from the piston has gone?
Ya better split the cases and thoroughly clean out the crankcase, not worth NOT doing it, ya know how shit happens eh.
Also, you will need to establish the actual cause of piston failure/breakage.
Most likely detonation caused by lean mixture/poor fuel(low octane)

[nudedaytona]

Some alloy has rubbed off on to the cylinder. How do I get it off? I think that would account for most of it. I'd say it's a about a thumb full of alloy, no more than two thumb fulls at the most that has broken off from the piston.

Apart from the alloy on the inside of the cylinder it looks pretty clean. No scorch marks on the cylinder or inside the crankcase. The base gasket is looking a bit shitty so I'll get a new one of those, and a new head gasket too I suppose.

I appreciate your input about taking the crankcase apart but it just seems a bit of overkill. I've had a look inside - it looked pretty clean, just a few rust speckles - not bad for a 12yr old engine IMO. And the conrod moves around, the crank turns, no problems there. I guess I could rub around in there with a white cloth and see what it picks up. Or maybe use a magnetised screwdriver - Does that pick up alloy? If there was something in there wouldn't I have heard it when I turned the crank? So far I haven't heard anything.

As to what caused it? Seems to me to be the old in pieces air filter as the most likely cause. Everyone on this website seems to have their own opinion as to what caused it, so I'm going to go for the obvious and simple one. Nothing wrong with the fuel - I've emptied the tank and put the fuel in my cage it didn't cause any problems there. It was 98 octane too. I'm picking up a new air filter on the weekend. And I'll clean out the carbeurettors as well.

[nudedaytona]

Thanks to Ixion who suggested bolt pulley system for removing the gudgeon pin. It worked like a charm! At first I tried dipping piston in container of just boiled water, (remember it's hanging down) and having another few taps at it, but that didn't work.

Then I had the idea of using the exhaust mounting bolt - it was just the right size and length to go inside gudgeon pin. I combined that with a cylinder head nut, and some sockets, and pulled the gudgeon pin right out. I had to keep adding sockets, and then some wrenches so I could get more clearance, but eventually got there. So thanks

After removing piston, I spent about 10 min eyeballing conrod and turning crank. It looked straight to me, but I gave it a few whacks back the other way just to be sure. It still looked straight, and it lines up with an etching at the bottom of the crankcase, so hopefully that's a case of no harm no foul there.

[zxcvbnm]

There's an acid that eats the aluminum off without harming the barrels plating, can't remember what it is but I can find out.

Your crank might be poked from the melted aluminum from the piston going through the big end/main bearings if it was ridden for long like that.

Does it look like this.