tighten your belts

[mad muller]

hello all, putting the sport engine back together again! its a hobby of mine, I will cut to the chase have been plagued by engine probs in particular tiny bits of alloy in the oil difficult to tell were it comes from but not magnetic and all looks in order on stripdown, heres the question if the timing belt was to tight could this be putting to much strain on the crank plain bearing and causeing it to ware putting bits in the oil. when I bought the bike it had an original morini stamped b belt I replaced with nlm megadyne belt b type but is very tight to fit and to remove , recently bought gates powergrip from local bearing suppliers but the fit is to slack an easy sliding fit and would not like to ride round on that, any thoughts on this , I know the belt issue is an old chestnut, but need to sort this engine before I fire it up, maybe someone has had similar issues . thanks muller.

[George 350]

Hi Paul,

Whilst an incredibly tight belt will overload the main bearings, I would be surprised if you were able to assemble a belt on a Morini in the first place to get it tight enough to do that - I've only ever seen it on engines with mechanical belt tensioners. You would also see severe witness marks on the bearing and possibly debris building up in the oil feed slot in the crank, rather than nothing seemingly amiss.
When you had the engine apart, did you clear out the sludge traps in the crank? If so, were they full of 'alloy bits' (more like aluminium paste) beforehand? If not, it could be some of this 'sludge' washing out, especially if it hasn't been run for a while.
Otherwise, I would expect to see evidence elsewhere around the engine of parts rubbing where they shouldn't.
How long had the oil been in the engine when you noticed the 'aluminium'?
Sorry for the questions, but without some more info, its hard to say if anything is amiss.
If it were me, (and I knew the crank were clean), I'd be tempted to put some fresh oil in and run it and see if more metallic particles appeared.

George.

[mad muller]

thanks for reply George, propably not the belt , more like the pyscho who reground the crank for me as its tiny bits of what look like silver solder very small though and they do reappear when you drop the oil and find them in the mesh strainer it does get lesser the more you change the oil , have some barrels and pistons to go on as he knackred the first rebore, did use plastigauge to check big end clearance and it looked ok, clutching at straws really have cleaned out the sludge traps and oil pump there were bits in there as well, maybe it will stop when I run the engine in, on the other barrels and pistons ,danger is though if bits get dragged up in oil it could damage the bores as I said all looks ok to the naked eye when engines apart all bearings have been replaced its a real Scooby doo job, only time will tell any thoughts most welcome . muller.