Gearbox cluster compatibility

[72degrees]

Finally getting round to rebuilding one 350 engine and addressing the worn gear bushes. Used ones being sourced from Mdina (asked for the most unworn they have!) but may try to get new ones machined up by cloning those. That might be needed to allow for the one that seems rather loose in its gear (1st on layshaft), or perhaps the gear(s) really need replacing as the bush 'hole' has worn (plating fix possible?) Just how tight should the bush be in the gear anyway?

So that got me trawling ebay.it and threw up several used complete 'geabox' listings for 350s. Some just '350' , some K1/2 and some Kanguro. Now the question is, I know there are at least two versions (as shown in the parts list PDF I have). Can you put a complete later cluster in earlier crankcases?

[hombre]

I've fitted a Kanguro gearbox (X1) in Sportcases once, not the very first ones because it already had the plain main bearing. Maybe its of help...

[72degrees]

Possibly, thanks. More research needed. Staring at the Ebay photos doesn't show the subtle differences. The 4 and 4A versions in the parts list definitely have different part numbers for some gears, but perhaps so long as the shafts are the same spacing and length the whole cluster might be interchangeable. One way to find out - if rather costly.

[Steve Brown]

Pete, if you want to come and look I have a 350 gear cluster or two spare. I have also swapped later Kanguro clusters into my 76 Sport without any issues. I didn't even check to see what the differences were. I'm in South Leicestershire near Lutterworth.

[72degrees]

Pete, if you want to come and look I have a 350 gear cluster or two spare. I have also swapped later Kanguro clusters into my 76 Sport without any issues. I didn't even check to see what the differences were. I'm in South Leicestershire near Lutterworth.

Thanks Steve. It so happens I see someone has one for sale in this months ATG. Just enquiring what year it is. This engine is a 77. The 375 is a 76. The box on that isn't too good either (sometimes drops out of gear) so a mix and match with that may not help.

The bushes arrive from Mdina tomorrow so I'll see how 'wobbly' they are first.

[Steve Brown]

I'm sure the year won't matter. My original 350 Sport gearbox was occasionally jumping out of gear. On inspection the dogs were rounded but not much else was worn. This bike had done well over 100,000 miles and the low mileage Kanguro cluster had dogs intact with a clear 'undercut' to them. One day it will become viable to get the worn dogs re-profiled. It's only a small amount of precision grinding by a specialist.

[72degrees]

Well the used bushes from Mdina Italia have arrived and are noticeably less sloppy than mine, but having only stripped one engine to this degree I'm not sure how much play is acceptable. Still rather 'wobbly' to my feel. Gears all selected and stayed in OK but there was a lot of noise from the area behind the clutch where the layshaft 1st gear pinion is.

If only Morini included bush dimensions in the workshop manual.

Should the bushes just slip in to the gears or should it take some pressure?

Might as well try and get it as good as possible before closing the cases again.

[Steve Brown]

They are a floating bush. Ok, some are splined to the shaft but should be an easy oiled fit with no binding. If you want to compare I have as said a couple of clusters to look at.

[72degrees]

I decided to take my shaft, gears and two sets of used bushes to a CNC machinist locally who made me a custom small end for a Gilera 98.

He agrees that there is too much play and is going to quote for making new ones from suitable material. Once the machine is set up he can run off as many as the small length of 'stuff' he has to get can make. Usually not an eye watering price so I *may* have some available soon. Watch this space, though in the case of one, the excess play was more bush/gear rather than bush/shaft (he confirms the shaft us not worn or ridged) so might require tweaking.

[72degrees]

Oh and for future reference the nominal dimensions of the bushes in question appear to be as follows.

25.01.11 1st gear bush on driven shaft ID 17 OD 21 L 12.5

25.01.12 2nd gear bush on driven shaft ID 20 OD 24 L 17.5


The other plain with spiral 25.03.09 (5th gear bush on main shaft) seems OK on my box as do all the 'splined' bushes.

With the ease of running off items with CNC it seems odd that nobody, anywhere, seems to be reproducing these bushes given the thousands of machines out there.

To be fair, this engine had led a very hard life such that the conrod eyes had gone oval, so perhaps they are never usually needed. The box did work OK but while I am in there again I thought I might as well improve the shining hour.

The new L5-alike cam, looks by visual inspection to be not hugely different to the one in there. I will check the timing once back together enough to do that, as somewhere (in the Forgotten Error thread?) I have a note of what that is.

Just need to replace a couple of oil seals. The cam one got a bit damaged parting the cases and the gear shaft one looks dodgy too. Will treat it to all new crankcase screws and nuts (plus the copper washers on the 'hidden' ones) and a new oil pump seal 23.02.18 and then it's just a case of some fresh Threebond a left cover gasket and try and persuade it all back together.