Hi all, 98 748bp. Quick question.. What signs would you notice if your big end bearings have gone? Cheers in advance! JP
Mine started making a sound like a supercharger wurring from 4k rpm and vibrations through the bars/pegs.... not to mention all the metal particles when I dropped the oil to check.
Is it the big end or the main bearing? If the main bearing goes there is a real danger that the side casing will crack from vibration if it is the nearside, which is the more common side to go . Big end will possibly make a heavy rumbling, vibrate and may even seize if it's really bad. I have had both go at the same time! but the main bearing did the most damage. Drain the oil to see if there are any particles in it.
Take the clutch plates out then fire the engine up. If if's got any rumbles taps clonks or slaps it's time to get the spanners out. It's just an engine, being Italian doesn't make mechanical noise acceptable. As much as we all joke about it.
My mains and big ends have home. It cracked my alt cover and I had spikey shards as above, but also creamy sludge on sump plug. Also had vibes. Also had oil pressure light come on. At least it lasted a track day at Donny before it cracked!!
Sounds like it was pretty bad but typical of when mains and big ends go. The annoying part is having to buy a new alternator case into the bargain, I have had three go over the years like this. It gets pretty expensive.
The backing material for the bearings will be steel, that is almost certainly what is on the magnet, that plus crank debris. The layers on the bearing will usually be lead closest to the crank then tin, copper and steel.
Thanks for all the replies- mine sounds like a WW2 machine gun at tick over (mostly from the vertical cylinder)- guessing that's bad? Anyone got a ball park parts cost for replacing the main bearings - super keen to sort it myself but weighing up the parts cost against either getting a 2nd hand engine (anyone got one?) or just breaking the thing...
Yeah. I've got a 996 with the bid and mains gone. It didn't sound bad when I des covered it had cracked the alt cover. I have a new cover for it, but it still needs bearings. It has Nichols nuts, no clutch, bit I can supply you with a loom and oil cooler if you fancy a conversion. Be quick though. The throttle bodies are on eBay as we speak, so give me a pm if your interested.
