I’m new to the club and forum and new to my 1981 850 T4 - I bike I’ve wanted since the late seventies!
I’ve given her my first look over and overall she’s in good condition but for a small drop of oil dripping from the sump drain bolt.
The previous owner had changed all the oils prior to collection and I assumed at first the crush washer hadn’t been changed. However looking more carefully, the leak is coming from above it .
There is a small slot (about 8 mm by 2 mm wide) in the bell housing. I can’t quite see if it’s leaking from here or from a sump bolt almost directly above it.
I’ve read that some Guzzi models have a valve in a breather tube which exits centre top of bellhousing and connects to a breather box that sits above it. Apparently problems with this valave can cause a similar leak. I can see this breather tube but don’t know if my my 850 T4 would have this valve, or if this is a complete red herring for my issue… Any thoughts?
Breather valve? Possibly, and easy to remove and clean/replace, but oil from that ‘slot’ generally points to oil coming through the crank seal which isn’t exactly a rare occurrence. I think? there might be a way for gearbox oil to get in there too (really not confident about this) and both would require substantial spannering to address, so… keep an eye on just how much oil comes out (and how much is where it should be) and accept tgst an oil drip from a Guzzi might not be the end of the world (o;
It will be either engine oil (from main bearing seal 80% chance, 20% other sources) or gearbox oil (80% input shaft seal, 20% conical seals on clutch pushrod).
All will require frame crab and engine/gearbox split.
But not as hairy as it sounds…with practice (and you will get practice) this is a 4 to 6 hour job.
First step is to poke yer finger in and identify what type of oil is actually leaking…(clue…smell it).
Probably not. If not, it’s almost certainly engine oil (the smell test’s a good one too), and the constraint is when the oil starts getting on your rear tyre, which you probably don’t want.
You can budget for £1k or so for someone to do it, or an entertaining couple of weekends doing it yourself.
It’s definitely easier to get help in getting the bike off the engine (and on again) but the rest of the job is pretty easy, presuming you’re happy with spanners. You’ll need a means of stopping the crank turning as you remove the clutch and flywheel, and you’ll need something (ideally a turned tubular drift thing) to push in the new seal. And finally you’ll need a clutch alignment tool to reassemble it. I also made a wooden cradle to support the engine nose-down. I made all the necessary tools myself, but I do have a lathe, which helps. You’re welcome to borrow them, if you’re near enough to Folkestone.
Should have also mentioned, the cross bolts which hold the frame & engine together can be complete b****s to remove. Penetrating oil now will pay dividends in a week or two.
Once you’ve done it a couple of times (don’t ask…) it’s quite easy.
Oh yes, the infamous long front engine lower through bolt.
Penetrating oil is your friend. If this bolt has never been removed (likely) you are in for a lot of fun. Heat is good as well.
Be aware that perseverance is required, but they all come out.
Eventually.
They tend to seize where they go through the bottom of the timing chest cover. Once safely removed, I replaced mine with SS bolt and lots of grease. Then made sure it was moved every 6 months or so…
Just be aware that you may end up destroying this bolt during your efforts to remove it but whatever you do try not to burr the threaded end over while you are persuading it to come out and play.
Where it goes through the crankcase is a very snug fit. Wooden or plastic drifts will help.
Thanks for your reply. Yes I’m keeping a tray underneath and emptying it daily. Sp far at at the end of a day there’s a circle about the size of a 5p piece.
“… not as hairy as it sounds…with practice (and you will get practice…”
I had a few projects in my late teens and early twenties but none since then. However, this will be the path I will take as this was always meant to be a bike I would work on and gradually improve. I just wasn’t expecting a significant job so soon!
I’d rather hang onto £1000 and experience the screaming, kicking of tyres and expletives but hopefully build some knowledge along the way.
Thanks Simon for the offer of borrowing the tools you mentioned. That is much appreciated.
In answer to your questions:
The clutch hasn’t slipped but I haven’t yet given it some beans until I was happy with it after a few local runs.
The smell test. I’d forgotten about that one…it’s definitely gearbox oil, not engine.
My obvious next question: Is Haynes the best service manual for this model?
I notice it only goes up to 1978. I believe my T4 had a production run from ’80 –’83 and not sure how many changes were incorporated. 850T* production history seems a bit thin on the ground!
As said, engine oil and gearbox oil smell differently. To quote the quaintly translated factory manual, “if it smells bad it’s gearbox oil”
You say coming from the bell housing drain hole slot, but could still be from higher up. I would be looking at the breather hoses first, they can get in a poor state and/or the hose clips loose. Oil from there can leak down past the metal pipe in the top of the bell housing and appear at the slot in the bottom.
Don’t forget the pushrod seals. They tend not to last well and the gearbox oil seeps down its length and out into the clutch hub. Eventually that’ll come out the weep slot in the bottom of the bell housing. Guzziology’s multiple O rings are available from Gutsibits as an upgrade.
I’ve used an endoscopic camera to confirm by viewing the puddle of oil in the bell housing in the past.
Sorry, bad English. The camera just confirms your weep is coming from inside the bell housing, not that it’s from the pushrod seals.
I should add that when I went to sort out the weep from the bell housing on my machine ( '77 so similar age ) I found it was a combination of all the above. The seals are well over 40 years old now and the rubber had hardened and worn so they weren’t working as well as they should. That’s the crankshaft seal, the gearbox input shaft seal, the pushrod seals and the breather pipe. That breather hose thing is real. The hose fits to an aluminium stub pipe which passes down through the casing into the bell housing cavity. If the hose clamp isn’t sealing perfectly, or if the hose perishes, then you can get a little oil coming down outside of the ally pipe. The hole in the crankcase is pretty crudely cut, so it just seeps down ( if it isn’t crusted up with 40 years of oil and dirt ) and into the bell housing. I sealed that up by using a slim spatula to slide grey ThreeBond all around inside the joint between the pipe and the casing. I also got a circular hose clamp because the worm drives don’t tend to clamp evenly. Mine was weeping near the drive. Seems to have worked a treat.
I’d check the level of the gearbox oil. I’ve found that if you don’t allow the oil to flow out until it has found its own level it has a tendency to flow through the mainshaft and drip out of the bell housing.
