siezed big end?!!

[Justin350]

right. i've really broken it this time. can any one give me any pointers?

The piston is not siezed in the barrel but does not move freely up and down. also the bike will not kick over. there was a growing rattley 'noise' from the engine just before this occured (after 700 miles) i'm guessing it's something to do with the big end bearing or some kind of lower engine bits, can any one confim this? it may save mo some time with the gear box which i have been assured is the problem by one older (and alledgedly wiser) than my self. i don't understand how that would work so any help would be appreciated.

many thanks, Justin F wood

[Rob Harknett]

Take off the primary drive chain, if the engine turns you know its not that. So you then suspect the gearbox.Maybe you will even find the primary chainhas come off and jammed things up.

[SideValve]

You're going to have to strip it untill you find the problem because it could be just about anything from the clutch to the mains, big end, oil pump (pretty unlikely), rings etc.
Personally I'd take the primary chain off because thats relatively simple and try turning it with a spanner - that isolates whether its engine or drive chain. Then, presuming its engine, remove the head and barrel (again not trivky jobs) which will prove whether its top end or bottom end.

edit - oops, drive TRAINEdited by - SideValve on 19 Aug 2011 3:35:22 PM

[SPRIDDLER]

There's the possibility that the alternator rotor has seized in the stator (been there).
Yep, it's a primary cover removal job.

[Janet]

In my limited experience of motorcycles, 'rattley' tends to be top end or chains. Big ends or bottom end problems tend to produce deep rumbles or gentle knocking first, building up in time ( and I don't mean after a couple of minutes ) to severe knocking. If you know your machine you should notice that before it gets to the point of a sudden stop.

Of course, I know nowt, but I'd poke about through the filler hole in your chaincase as see if you can feel anything amiss before taking anything apart. Lumps of metal lying in the bottom would not be a good sign although, depending on what else is damaged, they could be better than something like a broken crank.Edited by - Janet on 16 Aug 2011 12:40:34 PM

[bigwol]

I had the dynamo drive sprocket come adrift on my 16ms the other week, resulting in chains tangling and breaking. Lots of rattling there and with the primary wrapped round the gearbox drive sprocket it jammed up the gear box giving the impression of a seized engine when tried to turn over on the kick start. Was put together (by dealer following dynamo work before i bought it) without woodruff key or locking ring it seems. never mind, bits are here now so shouldnt take long to get it sorted! Take a look through the chaincase inspection cap and see if the chains are where they should be Justin

[Justin350]

right, done that. . . it doesn't look too good though. i have taken the caver off and removed said chain. it's certainly on the engine side. next step i removed the barrel (engine still in the bike) and the piston does not lift with it. its certainly some thing in the bottom of the engine and theres only one way to find out i suppose !

[bigwol]

Oh dear, sounds like a crank rebuild. Good luck with that Justin.

[Justin350]

oh well, i'm learning i did 650 miles on it and was last on the road in 1976 so it's to be expected i think.

i9 think it was preferable to an NVQ in motor mechanics

[SPRIDDLER]

That's rotten luck Justin.
You're a bit out of range of a local section I believe but you'll not be short of help from here if you need it.
If/when you do any more dismantling take photos if you can. You'll appreciate it later