top end, bottom end, and rebuilds.

hopoffbaby · Spanner Monkey Joined: 16 Mar 2002 Karma :

this may sound like a dumb question, but cuz i skipped the 2 stroke stage of biking i have been hearing a lot about top and bottom end rebuilds on 2 strokes and stuff. i was just wondering whats the difference between the top end and bottom end and what a rebuild actually involves Embarassed

TGE125NSR · Banned Joined: 07 Jul 2003 Karma :

Top end on a 2 stroke just means the barrel, piston, head, gudgeon pin and small end bearing.

Bottom end i think is crankshaft, bearings,conrod.

I think someone will clarify the bottom end but i know what the top end consists of!

Smile

BIG_BENDER · Banned Joined: 27 Jul 2003 Karma :

I will clarify you're one UGLY BASTARD! Shocked

hopoffbaby · Spanner Monkey Joined: 16 Mar 2002 Karma :

TGE125NSR · Banned Joined: 07 Jul 2003 Karma :

Yea i bet when you popped out of your mothers manhole the doctor slapped your mother!

Oh and i'm tracing your IP and my mate is going to do the job of wiping your hard disk!

don't check your emails to often!

Haha Loser

Very Happy

Ste · Not Work Safe Joined: 01 Sep 2002 Karma :

irdawood · Banned Joined: 19 Apr 2003 Karma :

zaknafien · Joined: 25 Mar 2002 Karma :

Scotty · Scooter Boi Joined: 31 Jul 2002 Karma :

Back to the original question.

Top end rebuilds on 2 stroke machines are fairily common. (depending on the state of tune, or how it's been ridden)
There also not the most difficult job to do.
There needed once the lining of the bore is starting to show wear. Or the piston is a bit nackered.

Although most if not all 2 stroke bores use a nicsol plating means they can not be bored out like most other machines can be and they using oversized pistons / rings to make up the difference.

So either replating will be used, or a complete top end will be need to be brought.

Bottom end's shouldn't need replacing very much at all. although the standard life of them compared to a 4 stroke is about 2/3rds

But i imagine that would consist of bearings, big end bearing, conrod, shells, main bearings, crank tru'ing and it goes on...blah blah.
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Regards
Scott

hopoffbaby · Spanner Monkey Joined: 16 Mar 2002 Karma :

are rebuilds expensive then?

Scotty · Scooter Boi Joined: 31 Jul 2002 Karma :

Tops end's can range from about £60 - £150 depending on what bike, how many cylinders and what parts you actually use (pattern , OE, Aftermarket)
____________________
Regards
Scott

cagiva gezzer · World Chat Champion Joined: 17 Mar 2003 Karma :

TOP END - Piston, Ring(s), wrist pin, small end, cylinder and power valve.

As said, how often they are needed depends on the bike and how its used. An RS needs one every 10,000 or 16,000km. The idea is to strip it down and check everything and replace it before it fails. It also alows you to remove the carbon build up.

Rings wear thin where they traverse ports, small ends wear out, wrist pins wear out and pistons become lose and can crack.

The cost depends on the cost of the parts and labour.

Bores should last for the life of two or three pistons.

BOTTOM END - con rod, big end bearing, thrust washers, main bearings, crank seals.

Most people dont specify strip down intervals and its best to check it when the top end is done. A worn bottom end will make alot of noise. The bearings wear and the seals start to leak. Leaking seals are given away by the bike drinking gearbox oil and poor running.

Bottom ends cost more to re build because the crank has to be split and the engine has to be split.

for rough prices -
https://www.stanstephens.com/ (125cc bikes)

Its a fact of life with two strokes, vast amounts of power for their size, but vast amounts of TLC and short lives.
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"because one stroke isnt enough and four strokes waste two"