YZFR125 - stuck Pinton Pin

[jtheobald]

Hi,

Son's bike seized as ran out of oil . Piston disintegrated. Removed cylinder etc and piston, but the pin is stuck. I understand best way to remove is to heat the conrod - my question is will this destroy the conrod and it will need to be replaced before fitting a new piston?

All advice must appreciated

[Riejufixing]

[Teflon-Mike]

Is thegudgeon pin stuck in the little end or in the piston ?
Have the gudgeon pin circlips been removed?
If genuinely siezed... what else has been damaged through oil starvation?
If conrod stuck on gudgeon to piston, is the conrid a split plain shell bearing at the bottom?
Does crank need regrind or rebuild, and new bearings, big ends and mains?
What state the bore? Piston? Piston Rings?
What about the two camshafts running in the head, usually first things to suffer when enginev starved of oil?
getting piston off conrod could, in the grand sceme be rather irrelevent, if most of the rest of the engine needs replacing anyway......
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[jtheobald]

YZFR125. Thanks for responding. Yes, I do mean gudgeon pin. I have tried to pull it out but it's very much stuck. I agree and worred that metal fragments are in the engine casing so I'm thinking ig having engine rebuild.

[MarJay]

[jtheobald]

Thanks for responding. Piston shot and left the gudgeon pin. Rings broken and piston warped and damaged, I think there is nothing other than an engine rebuild to fix. I agree pin may be the least of my problems

[jtheobald]

Thought about this and I agree but there no guarantee I am not buying a dud

[P.]

[Riejufixing]

[MCN]

I hope son is responsible for teas, clean-up and coughing up some of the cash?

He has to learn the hard way.
But the lesson learned that way is seldom forgotten.
____________________
Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[stinkwheel]

It'll be easier removed on the bench. Then you can just rest the side of the piston against a suitable tube and drift the pin out into it.

If it's seized in the small end, you're probably looking at a crank replacement/rebuild anyway because as far as I can see, it's a plain small end. Although the big-end is a roller bearing which will be more tolerant of oil starvation than a floating bush.

Any vertical play on the conrod? If there is, you're looking at a minimum of a crank rebuild and the viability of the motor is highly questionable because if those bearings have gone, what else has? There are more crashed R 1/8ths out there than there are blown up ones, this generates a surplus of engines.
bits of piston in every part of the motor.

EDIT: If I read one of your above posts correctly and it's ripped the gudgeon pin out of the bottom of the piston, I'd be amazed if it hasn't also bent the conrod. The pin probably wont move because it's bent too. The forces involved with this type of failure happening are astonishing and the metal becomes pretty plastic. Your episton went from moving at an appreciable fraction of the speed of sound to a full stop in a couple of mm. That's a lot of energy to dissipate as (mostly) heat. I've seen a conrod bent a full 360 degrees. It may even have bent the crankpin.

There will certainly be assorted alloy and hardened steel fragments strewn about in the crankcase, if the piston's been ripped in half, it's a deffo full strip. I've rebuilt enough engines after that to know the bits get literally everywhere. In the three or four revolutions the motor manages to do post self-destruct, it will have picked up alloy fragments and tried to pump them round the oilways and valvegear too.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[P.]

[Riejufixing]

[P.]

Ah yeah, the MT and WR use it now, Rieju was carved, so ball ache.

[jtheobald]

Hi, all really good advice. The gudgeon pin is well and truly stuck and could be bend. The conrod looks ok slightly moved side to side but not put and down.

Due to the fact that I would have to change the logbook, mileage would be wrong and to not raise suspicion I think I will have it rebuild.

Thanks all, you have been immense.

BTW, Son now in US so no tea etc!

[stinkwheel]

Fair enough.

It's easy to change the engine number though. You just get a letter from a garage on headed paper stating the registration and frame number and confirming it now has engine number XXX fitted then send it off with the completed logbook. Doesn't even cost anything. I did one earlier this year.

A receipt for the replacement engine with the number on will also suffice instead of a letter.

In terms of the mileage, the only time you'd be risking problems is if you SELL it with an incorrect/misrepresented mileage. That said, the mileage goes with the chassis, not the engine. If you fitted a brand new engine, you couldn't set it to zero so your mileage will still be be correct. My current bike is on its 4th speedo. When you look at the MOT history, the recorded mileage fluctuates up and down wildly.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[jtheobald]

Thanks for advice. If somebody looked up the history for the bike, would it state it's had a new engine? Does t

[ThatDippyTwat]

[stinkwheel]

[jtheobald]

Good points, well-made thanks and amusing. I am in no rush and can have rebuilt for approx. £400 so will do that. Thanks for replies.