Big end bearing wear

[GE]

I've just bought a new 2000 (x-reg) engine for my (go on laugh!) mito. My last engine f***** up good style! Big end bearing went and as a result the piston was damaged- big job (knackered engine) I bought the new engine (x-reg) which was siezed (probably ragged from new) but had only covered about 1000 miles. I checked out the siezure and it wasn't that bad. The barel needs to be re-chromed by Abtech (are they any good?) and a new piston, rings and gasket will be fitted (for free!!) I was just wondering if any one reckons the big end bearing or crank will have been affected as a result of the siezure, bearing in mind the con-rod is straight and in good condition (should be the engines practically bloody new!) Should the siezure (due to heat) have caused the piston to stop (jam!) immediately and cause damage to the big end bearing? Could anyone also tell me what are the main causes for big end bearing wear. Thanks.... I luv the new NSR- just can't bloody afford one!!!

[Kickstart]

Hi

A big end on a 2 stroke going is highly unlikely to wreck the piston, likewise the other way round. I have seized more 2 stroke pistons than I can remember (20+ I think), and of those I have never had to replace the big end at the same time.

However, if the bike (fairly new at X reg) has been thrashed badly and abused, and so killed the piston, it is quite possible that the same abuse could have damaged the main bearings and the big end bearing.

2 strokes use roller or ball bearing cranks. Conrods will virtually never bend on any engine unless seriously abused. By that I mean revved way beyond the red line (ie, thrashing it hard and then knocking it down a few gears) or drawn water in. I managed the second in a car doing about 4500rpm (came round a corner, saw puddle, decided it hadnt been raining that hard so couldnt be that deep, so put my foot down, but the water was 30cm deep at the shallow bit in the middle of the road). This shortened the con rod by only about 0.5mm.

By the way, if you want a laugh the pics of my wrecked car engine are here:-

https://www.alfa-pages.co.uk/?go_to=oops

To be honest it sounds to me that you are half expecting to do just as much work to your new engine as was required to fix up the old one.

All the best

Keith

[GE]

Cheers Keith that has put my mind at rest for now. I think i'll get the big end looked at anyway, just to check before I get the mechanic I know to fit the engine in my bike. I was just worried that the sudden seizure of the piston could have damaged the big end. They said they would replace the little end bearing for free (if it is needed) I don't think that the big end bearing should be worn at all due to the low milage. Have you by any chance heard of Abtech who will be re-chroming the cylinder?
I think my old engine has died the death really- 22000km, damage to big end, crank and piston..... I think a 'donor' engine would be required to sort that at a reasonable price. The only snag now is that I loose my seventh gear!! Does anyone have any good opinions about the new Mito engine. Will it produce more or less power than my original engine?? Are there any other Mito owners here by any chance?

[Kickstart]

Hi

The little end bearing is cheap, a doddle to replace so they may as well do it.

Never heard of Abtech. There are only a few of places in the UK who do cyclinder replating, everyone else just sends it to one of them. The is a place in Wolvo (www.prox.co.uk), and one down in Bath (Lancourt Engineering), along with one in Wales. Dont know of any others.

The rod comes as part of a kit containing the rod, the big end bearing and the big end pin. I doubt any part of the crank is damaged that isnt included in that kit. At a guess to fix your old engine up you are looking at £150 for the barrel replating with a new piston, £30 for the gaskets and about £80 for a conrod kit, then some labour to get the work done. If you take the engine out yourself then you can probably get that done for maybe £100 max. All in around £350

Cagiva used to be quite cheap for barrel and piston kits (still twice the price of replating), but no idea now.

I have heard that the later 6 speed Cagiva engines are less powerful and more difficult to get serious power out of than the older 7 speed ones. All the hassle of trying to get them through noise and emisions tests.

All the best

Keith

[Peje]

Mito Mad Cunt--If its siezed big style then the bearings are bound to be fuked!!!

Mine had a light seizure and the wee-end bearing is fuked!!! It rattles like mad!!

Peje- Buy a 2nd NSR much more reliable!!!