Conrod/big-end bearing replacement when replacing piston?

LanaTheGreat · Scooby Slapper Joined: 04 Nov 2006 Karma :

The bike shop says my wife's DT175 piston must be replaced for an oversized one, due to piston slap. Also they mentioned that when the piston gets replaced it is wise to replace the connecting rod and big-end bearings as well. My concern is the amount of money it will cost, as it means that the crankshaft must be separated (with a 30 ton press), new crank pin, bearings, con rod etc.

Is it really necessary to replace all of that, or will it suffice to have only the piston, rings, gudgeon pin and rebore?

MaybeGuy · Super Spammer Joined: 12 Mar 2007 Karma :

shit they speak... they're trying to get more money.
change the small end bearing for about £3 for the part.

if you show them this thread they'll say something like ''well its better to be safe'' or something.

get it done when it needs to be done. big end bearings are pretty gradual, and pretty obvious.

also, a new crankshaft is probably more cost effective when it decides to go.
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!! Mr. Green

Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

hmmmnz · Super Spammer Joined: 22 Aug 2006 Karma :

to get the crankand pin out you need to slit the cases, then use a press to remove the pin,
so yep,

but you dont normally need to do that every time you replace a piston,

grab the top of the conrod and move it side to side,
it should only slide but not move too much pivioting from the crank pin,

also rotate the crank and see if you can feel any grinding on the bearing through the conrod,
if you can feel any at all, then you will have to replace the conrod,bearing and crank pin,

good luck Thumbs Up

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Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

As above, unless the previous piston / rings have made a real mess.

All the best

Keith
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LanaTheGreat · Scooby Slapper Joined: 04 Nov 2006 Karma :

I will follow your advice, especially as it is a cheaper choice to make. Thanks for all your replies.

Ariel Badger · Super Spammer Joined: 02 Dec 2006 Karma :

Bang goes the robbing knuts xmas bonus. I would not let them do the work that needs doing after trying to pull a stunt like that, rather I would find an honest trader.
If big end bearings are free from wear they do not need replacing, end of.
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