Breva 750 Gearbox..... Again

[Muzz]

So, after developing yet another whine at about the 25,000 mile mark i have just taken the box out yet again after draining grey oil at the last change. I thought it was alloy as it did not appear to be magnetic. After letting the oil settle there was a fair amount of black sediment it the bottom.

At about the 12,000 mile mark I had it apart after developing a massive whine in top and found broken studs, faulty selector forks and damage to shafts and bearings due to the hardening disappearing off 5th gear.

This time the whine is through all gears, but louder as the gears climb up. Apart now, and the same set of gears have decided to start shedding their hardening.
They are the 2nd set in from the front of the box. Harpers list them on their web page as #2 (Gear 5a) on the primary gear shaft and #23(Gear 5a) on the driven shaft.

The box has ALWAYS had the full amount of gear oil in it and changed regularly. The oil gutter and the plastic shroud are fitted. All bearings were replaced at the 12,000 mile stripdown.

My question is, why is 5th gear failing on a regular basis? Has the casing of the box been drilled slightly off and loading up the gears? When I replaced the first lot of gears was I given anther faulty set from the same batch?

I love the bike, the motor is brilliant and has never missed a beat, nothing has gone wrong with it other than the gearbox.

Any ideas from the experts greatly appreciated.

[sign216]

Muzz,

Sorry to see that this has come up again.  Breva transmissions from 2003-2004 had many problems, almost like there was derelict employee in the assembly line. 

How about replacing the whole transmission with one from a later year (if it'll fit).  That way you'll also get whatever improvements Guzzi made, and avoid whatever issue is dogging you.

Joe

[malik]

What a bugger. Most peculiar. I haven't heard of that problem before, and I'll ask around. Motociclo did have a V7 customer who was going through clutches every 10,000 km. and there was an older big block (an SP, perhaps) that had problems with the final drive for years - not fixed until the whole drive was replaced with new, and nothing since. That implies that sometimes something to do with the casing can be slightly off, & replacing the internals doesn't fix the underlying cause. WHY are those gears wearing so badly so quickly????? Good luck.

[Muzz]

Muzz,

How about replacing the whole transmission with one from a later year (if it'll fit).  That way you'll also get whatever improvements Guzzi made, and avoid whatever issue is dogging you.

Joe

I had thought of that Joe and have been looking for over a year now to see if one pops up. So far no luck. NZ is not a large country of course and Guzzis out here are not the most common of bikes on the road.

To that end, do any of the experts know if the V7 range box will fit in? I suspect that the 6 speed wouldn't but perhaps some of the V7 - V7ll might.?  I don't want the hassle of changing driveshafts or swingarms.

I know that early on a group of (early) Breva owners had problems with a jamming pre-selector fork which Guzzi quietly changed the design of without telling anyone. (Mine had the later pattern one fitted but it still jammed prompting one of the gearbox drops). Has anyone heard of generic problems with the Breva box other than the pre-selector fork? I haven't personally which is making me think of a mis-alignment in the box itself.

The box itself is an absolute beauty to use, changes beautifully and smoothly. It just shits itself on a regular basis.

[malik]

The driveshaft for the V7, the V65, Breva & Nevada is the same, and likely the swingarm apart from the colour as well. The Parts manuals for the gearboxes have different numbers, but other than some minor differences, look the same. (The carbed Nevada has a bottom drain plug that the later ones don't). I do know that, other than the colour, the 2007 Breva box fit seamlessly on the V7C, and is still running fine after 50,000km (on top of its original 23,400). And I didn't notice any change in gearing. The unknown small block gearbox I picked up from Yowie's estate looks to be identical, but it hasn't been tested (or dismantled) yet.

I had better get a wriggle on and fix the V7C gearbox (it has a wiggly selector shaft when we put it back together), fix the Nevada's box - the bearings sound positively unhealthy, and check out the box from an unknown small block. When I get to replacing the clutch on the Special, I'll check that the other boxes at least fit.

With all the people going back and forth between here and there, getting a box over shouldn't be a problem. If you find one in Oz, we can arrange that, at least.

Mal.

[Muzz]

Thanks for that info Mal. Will keep in touch.

I did note on the Harper site that the 5th  gears shown come in two different counts, but from looking I can't see anywhere which model has which. Will count the teeth on mine later.

[pete roper]

Muzz, I got your PM. Gimme a bit of time, I'm flat out like a lizard drinking right now.

Pete

[Muzz]

Muzz, I got your PM. Gimme a bit of time, I'm flat out like a lizard drinking right now.

Pete

 

[Muzz]

Pete, I took the box around to Kev's last night and let him have a good look at it. He confirmed that everything looked mint other than 5th. He too has no idea what would cause it.

After discussion, at this stage I will take the casing of that munted one you sent over some time back and put the innards of mine in it. This may eliminate the case angle as I think from memory the one you sent over had been run without oil. The 5th in the munted box is in much better nick than mine but we thought it best to try to get a new 5th gear set. Will do that today. The transfer gear in the munted box is a much better fit on the primary gear shaft than mine and seems to be in at least as good a condition as mine, which was a very loose fit on the shaft.  That could be a cause of the whining as well.

[Chuck in Indiana]

Strange stuff. I have a Baby Beaver transmission in the AeroLario, and it's pretty darn good. Certainly quiet enough, shifts fine, no false neutrals.. <scratching head>

[Muzz]

and it's pretty darn good. Certainly quiet enough, shifts fine, no false neutrals.. <scratching head>

The same. All good until it lunches 5th. Even then it shifts etc perfectly. <shrug>

[Muzz]

A further question for the experts if I may.

Having spent a very pleasant evening at Kev's (Steamdriven) perusing my gearbox and the munted one that Pete Roper had sent over earlier we have decided to meld the best parts of the two boxes in to one. The main thing is we will use the case out of the munted one in case my one is drilled  incorrectly.

What we did find in my gearbox is that the idle gear that fits on to the primary gear shaft is a very loose fit, and always has been. If we take the gear off the munted box and put in on the primary gear shaft the fit is noticeably better. The gear when fitted on it's original shaft is a perfectly snug fit. 

If I use the primary shaft out of the munted box it does of course have first gear as part of the shaft.  The condition of that gear is about the same in both shafts. However, the gears that run on it show different wear. The munted box had been run without oil and it shows especially on the lower gears. Do you think I can get away with using the first gear out of my gearbox running with the shaft out of the munted one.  I rarely use any power in first, it's usually second or third so it would not get much loading. I realise it could well sing like a cuckoo but my question is, could it result in premature failure? I would use the matched pair of idle gears as the condition of the gears are about the same in both boxes.

The difference in the fit of the idle gear is such that Kev wondered whether my gearbox just happened to be fitted with a whole heap of parts which bordered on the edge of the tolerance band and unfortunately added up to one which is miles out.

[pete roper]

Flinging together a 'Frankenbox' is always risky and it will undoubtably sing like a canary but it's probably worth a try. Otherwise source one from the US. Pinball usually have a few on offer.

Pete

[Muzz]

Flinging together a 'Frankenbox' is always risky and it will undoubtably sing like a canary but it's probably worth a try. Otherwise source one from the US. Pinball usually have a few on offer.

Pete

Most of it will still be out of my box Pete, but I will need a 5th gear set.

Just taken the cluster sets apart and the wear on the 5th gear caged roller is showing the same opposing side brinelling on the shaft, the same as I showed you when the first lot collapsed. The shaft that came from the munted one has an even polish all the way around. This all in 12,000 miles on a new shaft, gear set and caged bearing. Makes me think that something is wrong with my case.

Currently waiting on Pete Kelly at MotoKiwi to flick me a price on a new 5th gear set.   Actually, would you be able to flick me a price on what you could do a gear cluster for?  Still haven't heard back from Pete yet.

Will take the offending bits in to my son's work tomorrow and use his wash bath to get rid of all the black powder sitting in the case. Might as well get some use from all the help I give him.

[pete roper]

You got part numbers? If I'm really quick I could bring them over in a month when I come over to the North Island to do these wretched rollerisations for two blokes. That was supposed to be Michael's gig but....
Might save a bit of GST.

[Muzz]

I might have. Will have a look first thing in the morning as its quite late here and it might take some looking. Thanks.

[Unkept]

I wonder how hard it would be to fit a V9 / V7 II/III six speed gearbox? (V9 one may not work with the rear drive?)

https://www.ebay.com/itm/2017-Moto-Guzzi-V9-Roamer-Transmission-Gear-Box-194miles-2A0004211/263457392633?hash=item3d5748c7f9:g:bFYAAOSw9V1aaQPx&vxp=mtr

I know the mounting points are different, no doubt the linkage connections... but the V7II uses the same rear drive and driveshaft as the V7 Classic / Breva 750.

[Muzz]

The casing on the V9 looks similar, but who knows with the drive shaft length.

[Muzz]

After careful consultations with Steamdriven and armed with publications also supplied by said master mechanic I duly assembled Frankenbox.  I am not expecting it to last, but what I am looking for is just how long it takes to disintegrate.  If it lasts a reasonable time with all the munted bits in it I can then conclude that Luigi indeed excelled himself and was able to actually misallign the drilling the casings.

I did my level best to make sure everything worked before it went together.  However, when I fired it up I have obviously got something wrong as it tends to make a clacking noise moving the bike and neutral is "not quite" neutral. It does appear to have 5 gears but again, "not quite".  I was anal taking the gears off the gear shaft and putting them in order on a rod, then re-assembling it all in the same order.

Poop, bum dunnycan.   I have had a couple of glasses of a very nice Sauvignon Blanc, wiped away my tears, got my various stands and chocks ready and and now am in the process of motivating myself to strip the whole shebang apart again and try to find a fault of which I have no idea on.  Sigh.

[Chuck in Indiana]

Well, a couple of hours, and you'll know.  I've never seen inside a small block transmission..

[TimmyTheHog]

Well, a couple of hours, and you'll know.  I've never seen inside a small block transmission..

+1 with  ...I like Pictures :D

[Muzz]

Well, a couple of hours, and you'll know.  I've never seen inside a small block transmission..

I speak it like a native,

Took all the rear stuff off last night and am getting ready to haul box off motor soon.  Have arranged to take the box complete around to Kev's one evening and we will strip it together.  A second pair of eyes is good,  also, his engineering knowledge is much better than mine.  He did say last time that he thought Luigi saved up all the dud bits he could find and put them all in my gearbox.  Even the "non-jam" later model pre-selector fork that mine was fitted with managed to jam up.

[Chuck in Indiana]

 

[Muzz]

Part of the fun Chuck is getting it back together in one piece.

The early pattern pre-selector fork could have the fork pushed back out of the way so that it could be taken out without disturbing the cluster. The later pattern one does not allow you to do this, which means that in order to re-assemble you are trying to fit two gear shafts with gears and the selector forks assembled as a unit in to their selective bearings , all the while fitting as they go in the retainer for the selectors (which is also the base for the indexing system) and the pre-selector fork assembly.

This is somewhat of a challenge.

If anyone has not read Nick Webb"s write-up on the smallblock gearbox on This Old Tractor it is well worth reading.  He re-wrote the Guzzi manual in a real world scenario, as distinct from Senor Whitegloves who does the official Guzzi stripdown and whose efforts are woefully lacking in what you need to know. 

Trust me, I are a doctor.........

Edit: One thing I have found use is the use of a very heavy duty nylon zip tie to hold the clusters/selector package together.  I don't pull it up tight but being fairly solid it still stops everything flying apart while trying to juggle the five elements. Once everything is in place I use a pick and carefully release the zip tie with a prick rather than cut it, as things can turn to custard really quickly and if things are still held together disaster can sometimes be averted.  Works for me.

[Frenchfrog]

Just a thought Muzz...your selection issue wouldn't have anything to do with a bad adjustment of the selector hexagon on the back of the box would it ?A little goes a long way on that one and it's easy to disengage the spring too.

[Muzz]

Just a thought Muzz...your selection issue wouldn't have anything to do with a bad adjustment of the selector hexagon on the back of the box would it ?A little goes a long way on that one and it's easy to disengage the spring too.

I know about that one.  Bolt correct and spring engaged.

It almost sounds as though one or more of the dogs are engaging when they shouldn't be.

Hopefully we will find out, Sunday afternoon we will take it apart again.

[Muzz]

Sunday afternoon was spent at Kev's (Steamdriven) as we went through the box.  I had put a washer on the wrong side of one of the gears.  I had mis-read the parts diagram and what the diagram says is a washer is actually a washer pack consisting of two washers and a wave washer.

Late this evening I fired the bike up with Frankenbox fitted and there are five gears.  That's the good bit. 5th gear is LOUD, I mean really LOUD.  It came out of the box that had been run without oil, as it was in better condition than the one that had destructed in my box.  Says how good that one was.

So, I have a bike that is mobile. but sounds like a cop siren.  I will drain the oil regularly, filter it and throw it back in.   I will be looking to see if any second hand boxes come up, a bit of a long shot as there are not too many of those around.  Malik reckons that the V7, V7C and V7ll all fit, which gives me a bit more scope.

[sign216]

Sunday afternoon was spent at Kev's (Steamdriven) as we went through the box.  I had put a washer on the wrong side of one of the gears.  I had mis-read the parts diagram and what the diagram says is a washer is actually a washer pack consisting of two washers and a wave washer.

Late this evening I fired the bike up with Frankenbox fitted and there are five gears.  That's the good bit. 5th gear is LOUD, I mean really LOUD.  It came out of the box that had been run without oil, as it was in better condition than the one that had destructed in my box.  Says how good that one was.

So, I have a bike that is mobile. but sounds like a cop siren.  I will drain the oil regularly, filter it and throw it back in.   I will be looking to see if any second hand boxes come up, a bit of a long shot as there are not too many of those around.  Malik reckons that the V7, V7C and V7ll all fit, which gives me a bit more scope.

I remember when a Loud 5th gear was a smallblock "thing."  Not anymore.  How old is that second hand gearbox?

Joe

[Muzz]

I remember when a Loud 5th gear was a smallblock "thing."  Not anymore.  How old is that second hand gearbox?

Joe

Most of the "2nd hand box" is out of my bike bought new in early 2004; 1st, 2nd, 3rd and 4th and one gear shaft are from this box.  However, all the bits have spent some time running in hardening dust. The cases, 5th gears, the gear shaft and the split caged needle bearing and the transfer gears are out of the box Pete sent over some time back.  At the time we used the pre-selector fork out of it as my later pattern "non=jam" model had jammed.  This box had been run without oil.  It does have an earlier serial number than mine but it was still fitted with the later pattern pre-selector fork.

We used the transfer gears from Pete's box because the one that splines on to the end of the gear shaft is a nice snug fit; the one from my original box wobbles around like a ship in a gale.

Much of this trial is because of our suspicion that my original box has been drilled out of line, hence the cases change.  The wear on the gear shaft is showing that the gear is trying to run sideways, and the fact that the 5th gear collapses every 12,000 miles certainly gives credence to this theory.

In my phoning around NZ, one thing that stood out was that no one had needed to do a major gearbox overhaul on these later smallblock boxes.  <shrug>

[malik]

So, I have a bike that is mobile. but sounds like a cop siren.  I will drain the oil regularly, filter it and throw it back in.   I will be looking to see if any second hand boxes come up, a bit of a long shot as there are not too many of those around.  Malik reckons that the V7, V7C and V7ll all fit, which gives me a bit more scope.

I'm not sure about the V7II box. It's a 6 speed isn't it? And the engine was tilted forwards a few degrees too. I do know the Breva box works perfectly in the V7C. When I do the clutch on the V7S, I'll try the other boxes for fit, just to double check. The injected Nevada box should also be the same.

Mal.