I have just completed a full restoration of a V50II and love the bike I decided to go for a long run prior to changing all oils and filter as I had done 280miles trouble fee so I covered 245miles and the bike ran great unfortunately changing down a gear a very loud screeching sound occurred I immediately stopped and the noise disappeared however I needed to find out what was wrong so removed the gearbox thinking faulty thrust bearing this appears good so stripped down the gearbox and no obvious faults although the oil was dirty which was surprising as the gearbox had been stripped and cleaned maybe the roller bearings were corroded but they felt fine although I can feel some play now
Has anyone any Ideas what could cause that noise engine runs great
I always let Nigel at NBS sort my gearboxes out, he knows them inside out
never had a problem since
I am not a trained motorcycle engineer, so leave well alone (I would only break something important !!)
might be worth sending him the box to sort out
That reminds me a horrible noise my V65 gearbox(so - needle bearings, not ball ones!) started to make at top gear once I went a step too far and treated very tired ex-Police unit with Agip top-shelf gear oil(as stated in manual…). The oil proved to be just too thin for a worn box, and after I realised what could be the reason, I poured the old oil back in, and heard the noise no more! So, as you’re not scared with gearbox seen from inside, possibly be even more brave, put it back together and try 80W90?
thank you 
Thanks The dream is to complete the whole restoration myself but I may have to get a specialist for the gearbox
the trouble is, its easy to spend time chasing up dark alleys in locating weird faults, whereas some one who has years of experience, will replace parts or uprate them as a matter of course, I know this from my particular trade, I had a big gearbox problem with my Breva, and a few other problems, caused by a motorcycle mechanic who I think has a drug problem, he seemed to have wrecked motorcycles everywhere !!
Nigel collected all the bits and rebuilt the machine to perfection, it was only 2 years old when it was damaged
20 years later I still own it and it runs perfectly ,
you can box it up and post it to him, or take it up in your car, but ring first, its a hard place to find
The whole point of buying the v50 was to restore to riding condition and get the satisfaction of doing the work myself so however long it takes me I’ll get it sorted
I get this, totally. For some the joy is riding and not having to know the machine inside out. But for people like us the pride is knowing that we overcame the challenges, learnt new skills and what we end up with is the fruit of our labour.
Unlikely but while you have the swinging arm out check the uj carrier bearing. The uj should be an interference fit. Ie make sure the bearing hasnt siezed and the uj is not slipping in inner journal.
Thanks I will do .I’ve now stripped the gearbox and ordered new bearings but the existing ones looked ok hopefully the new ones will reduce the whine but I haven’t seen any thing in gearbox or clutch that would squeal the wheel bearings are all new I’ll get the bike back together and hopefully it’s ok at least the above items are all good 
I bet it won’t… this whine develops either on IVth or Vth gear, depending on prevalent speeds used in bike’s first youth. That’s my guess. Had two police bikes, and municipal howls on IV, stradale - on Vth:) And in my opinion sound comes from micro-cracks formed on the cooperating surfaces, and it’s invisible for unaided eye. Good news is you may entirely ignore it and even embrace as a very-Guzzi-specific feature:)
Thanks I’m renewing all the bearings as some were not quite right can’t wait to test
Hi I had a V50III from new at 37 thousand miles it became dificult to put into gear and after stripping the gear box down I found three bearing races (roller bearings) had lost/destroyed a lot of the rollers. I replaced all the bearings in the gearbox and this solved the problem I hjad no sreeching though. Good luck.
thank you I have renewed all the bearings but not fitted the gearbox yet