Thumper Club Forum
Technical => Project Progress => Topic started by: themoudie on June 12, 2023, 01:39:07 PM
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Just to keep you on your toes, I thought that I might post, perhaps infrequently, snippets and details of this rebuild of a 1975 Ducati 350 MKIII that I acquired in "big lumps" from a leaking shed, the roof of which it was holding up, having previously been rescued from a skip in Edinburgh as the then owner was emigrating! ???
First conundrum when stripping the engine is the removal of the alternator rotor. This is usualy achieved using a bell shaped extractor, with a 60mm OD x 1mm pitch thread that threads onto the hub of the rotor and then using a central screw against the end of the crankshaft, eases the rotor off the crankshaft taper. Not this one! ::)
I had not seen a plain brass rotor afore and with my rotor extractor not fitting, resorted to making up my own puller, using bent M8 threaded rod and nuts, to hook behind the rotor; a piece of M10 threaded rod, with nuts to act as the central pressure screw and a piece of 65mm x 35mm x 3mm MS box section, drilled to keep all the threaded bits at the correct distances apart. I was able to "pop" the rotor off the taper on the crank, with relative ease.
What I found behind the rotor was that I was the pround owner of an early Spanish 'Motoplat' generator/ignition set up, with 4 rubber insulated wires, 2 x yellow for the regulator/rectifier charging the battery and a single red and single blue wires for the the ignition CDI/coil. The rubber coating is perished, exposing the tinned, multi-core cable beneath! :( Usually, Ducati used 'Ducati Electronica' components, but the fitment of this Spanish component would suggest that it is one of the last 350 MKIII engines built by Ducati and assembled in Spain in the MotoTrans factory, under license and where these engines continued to be manufactured until 1983 in the production of the MotoTrans 'Forza' and 'Vento' 350cc models. The latter being a stotter in it's later form. ;D
So, rather than re-using an unknown quantity 'Motoplat' generator, with dodgy insulation, I am going to have to resort to an 'Electrex' replacement set-up that'll not be cheap! ::)
Good health, Bill
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Good luck! I actually think much of the interest in these projects is unravelling what a series of previous owners have misguideldly done. Better than Inspector Morse!
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Aye Ian, that's why I like my family genealogy, it takes me to all sorts of places across the globe and all sorts of human situations! ;)
Good health, Bill
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Crikey Bill that all sounds a bit complicated to me, but good luck in figuring it all out. As I age I realise more of my own limitations and rather than assuming I can tackle complicated jobs (be it bikes or buildings) I look at the bits I know I can do and then find some talented chap, or chapess, to do the other bits. This way I am finding less frustration at not being able to do a job and more pleasure at doing the bits I can do.
You sound to have taken on a big job there but I bet you will end up with a very lovely bike.
Ian
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Interesting Bill, I look forward to seeing and reading more about it!
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Interesting Bill, I look forward to seeing and reading more about it!
Me too. Best of luck with it Bill 🤞
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Thank you for your interest. Wait until I start the re-assembly shimming of everything on it's shafts and then the shafts into the crankcases, that's when the "fun" really starts! ::)
Good health, Bill
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Stripped out the stator tonight that uses 4 x M5 x 15mm slotted cheesehead screws to hold it in place. They had been stud locked and spring washered in place! :(
A ½" drive impact driver head was too big to fit in down the side of the stator. So, I had to resort to a ½" impact driver, with a ½" to ¼" converter, ¼" extension, 8mm ¼" socket and wide slot impact driver bit. Hit with a 2lb hammer! ;D
The Motoplat Electronica encapsulated stator, from 1975, so 48 years old, showed cracking of the potting material due to stress from the wires and some of the wrap covering one of the generator coils is coming away.
Finally, the Motoplat stator wires, are showing perished insulation on the exposed ends of the stator feed cables that have been exposed to sunlight. Those wires exposed in the engine as they pass through the stator backing plate and within the outer cable sheath appear to still be in good condition.
However, as these Motoplat systems have a known short life expectancy, 30K miles, before going "PHUT", :( the whole lot are for re-cycling and replacement with modern Electrex components. The brass rotor when polished up will make someone a grand fridge magnet or paperweight! ;)
Good health, Bill
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The brass rotor when polished up will make someone a grand fridge magnet or paperweight! ;)
Good health, Bill
Err…. Last time I looked, I don’t think one can magnetise brass 🤦???
However with all the stress of impact drivers etc you’re having I think we can all let your little slip go amiss Bill 😁
Cheers Michael NOT a magnet expert
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Don't they use brass tools in perfume factories to prevent accidental sparks from detonating the highly volatile base liquid that perfume is made from?
Ian
P.S. I'm not a magnet expert either Michael and I have no idea why I would possibly know anything about perfume!
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Michael I have no idea why I would possibly know anything about perfume!
Oh come on Ian. You gave the game away when you let it slip (see what I did there😉) about your blue alter top 😁
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I'd forgotten that my secret is out!
Delores the confused
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Ever the purist Bill ... this could get expensive!!!
if it's anything like my 'bargain' #10 then there are surely many more horrors yet to reveal themselves .... just saying ...
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Aye Steve,
Ever the purist Bill ... this could get expensive!!!
if it's anything like my 'bargain' #10 then there are surely many more horrors yet to reveal themselves .... just saying ...
Oh, don't I know it! ;) But, the SRX Mono cost £1,000 to rebuild the engine alone and another £1,000 for the rest of the chassis bits and pieces. :'( :'( :'( On the plus side we both use it and have been putting on 3K to 5K a year since it was back on the road. On a good day somebody might part with £2,500 for it, but I suspect ~£2,000 would be nearer the mark in the current climate.
As for the 350 MKIII, purchased about 20 years ago for £450 and sat in the dry, so no further deterioration. However, the engine could swallow £2,500 nae bother and the chassis another £1,500 and with clean 350 MKIII's now fetching £4,500 to £6,500, depending on how "original" or "BLING" the machine is. Being mine, the machine will be rideable, clean and modded to make it as easy to run as possible, not pimped to hang on a wall, or gawk over in a pub! ;)
Having to use 10mm threaded rod to prise the crankcases apart, along with nylon felling wedges and a 2lb hammer! ::) ;D ;D ;D
Bit hot for troshing, so take shelter and work "Como un español" or "Como una española", depending upon your gender in these PC times! ;)
Good health, Bill
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Being mine, the machine will be rideable, clean and modded to make it as easy to run as possible, not pimped to hang on a wall, or gawk over in a pub! ;)
Good health, Bill
Well said 👍.. best of luck with it Bill. Looking forward to seeing, reading your progress with it over the coming weeks/months/years 😉🤦???
Cheers, Michael
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Making steady progress working through the disassembly and cleaning of engine components.
I have attached an image below that I hope is self explanatory, showing the components attached to the upper bevel camshaft drive shaft. You don't see that many shims in a Jap or British motor, let alone on a single shaft and a single bearing! ::) Ducati at its best.
When I pressed the Self Aligning bearing out from it's bushing, the two large diameter shims appearred from between the bearing outer race and the bushing! :? The inner shim against the bearing is quite dished across its width and I wasn't expecting to find shims between the Self Aligning bearing and it's housing.
I may, MAY, use an alternative 350 cylinder head to the one that originally came in the tea chest, with other parts. So, questions asked of more learned souls than I on a Ducati singles forum! :-\
When re-assembling a new bearing into this bushing should I insert these two shims before inserting the bearing, or should I omit them from the assembly?
And, what do I need to measure to ascertain the correct shimming, if required?
N.B. this is probably a late 350 engine assembled by MotoTrans, or using MotoTrans components, assembled by Ducati! ::)
There is no indication of these shims that I can see in either the Clymer, or Haynes manuals.
I may be some time at this one! ::) ;)
Good health, Bill
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And there I am struggling with a simple Triumph engine! Good luck Bill.....
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Have just come back from a Shelsley Walsh evening meet-there was a 70's Ducati single and a Laverda Jota there-very nice too!
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Thank you Ian, I'm no sure about the "simple" bit, you appear to have cracked the holding pushrods, compressing piston rings whilst lowering barrels conundrum succesfully. ;)
Just been out for a canter on the 450 afore watching tonights "Who do you think you are?", plenty of urge left at half throttle (60mph) and getting 20 miles to the litre (89mpg) consistently, E5 or E10, with Millers Oil VSPe Power Plus added, so far so good.
All the best with the Grumph build.
Thank you xbally for the compliment. Like all machinery getting on for 50 years of age, they require "attention" and can be cantankerous, but give me a lot of pleasure.
Good health, Bill
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Like all machinery getting on for 50 years of age, they require "attention" and can be cantankerous, but give me a lot of pleasure.
funny that.... i said that about SWMBO .. i'm currently living in my workshop .. might get repatriated in a week or so ;D
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You asking for a skelp round the lug there! ;D Lucky, you wus allowed to stay in the dry workshop and not put out to grass, like that old dicker! ;)
Cauli's and broccili coming out our ears and the rasps/blackcurrants as well.
Good health, Bill
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Yes my1996 Ducati Monster 750 has turned into something of a cantankerous money pit.....last 2 years on and off the road with one problem after another.......Spent last Friday trying to cure fuel starvation problems to no avail. Now have to fit another fuel pump and correctly moulded OE fuel hoses in an effort to get it running something like again. Like the older singles its a great visceral experience to ride...when it's going well.
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Thought that I should check clearances in the cam drive upper bevel, after finding extra shims, not mentioned in workshop manuals i.e. the ones at the back of the upper bearing, inside the bushing. (See image attached to July 12, 2023, 10:57:21 PM posting)
I mic'd up the components and they measure as follows:
Depth of bushing (internal) = 11.20mm
Depth of bearing (overall) = 11.00mm
Shims = 0.23mm and 0.21mm
Raised inner rim of tower = 0.10mm
Gasket = 0.10mm
So, no wonder the second shim was being squeezed from between the bearing and the back of the bushing. Trying to squeeze 11.44mm of bearing/shims into 11.20mm of bushing + say half the depth of the gasket after torqueing = 0.05mm, means 0.29mm of pre-load on the outer bearing track!
The gasket surrounds the rim of the tower and is of the same depth, so when the tower is torqued to the cylinder head I would have thought that would provide sufficient load to the outer bearing race to hold everything snug, with only the 0.21mm shim in place behind the bearing in the bushing.
Engineer's comments welcome.
Suspect worn tooling, mismatching Spanish/Italian components and clumsy assembly at the factory! :( Sounds familiar to those who have studied the UK motorcycle industry debacle and actual Italian "engineering", rather than the "rose tinted" gloss! :(
More micrometer work at the assembly stage. ;)
Good health, Bill
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come on Bill, you know you love the challenge ;D , all i can say is ... i won't be getting myself a ducati any time soon, or any italian bike for that matter ;D , ok, my Son's 350 morini is a lovely bike, both to look at and ride, but ye gods did we have a game sorting out a missfire ... which only happened once the bike was warmed up ... yours truly was called up as Son figured it was an electrical issue, i had it here for 2 weeks, went through everything, timing, quality of HT, etc etc, even got my oscilloscope out to watch the advance/retard curve on both cylinders, so it wasn't electrical, while i had it i went through the fuel system with a fine toothed comb and found no problem there, but ... i did find, that after a 30 min bimble around the lanes that the front pot was a lot hotter than the rear (unusual, as you would, if anything expect the opposite) so out of interest i got out my trusty 'colourtune' and found that the rear cylinder was not firing consistently, we'd changed the plugs, so i changed them again ... to no avail. not having ever checked compression 'on the fly' (nor know how to) we took off the rear rocker cover and found that the exhaust valve rocker was nipping up when hot ... seems Son had over tightened something or mixed up some shimming ... funny old world .... (well, the world of old italian bikes may not be quite so funny )
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Morning Steve,
Thank you for the info, I too have been through that rigmarole with the Morini and although it is clear what steps are required to make adjustments in the Morini manual, it can all get a bit shoogly as you tighten the rocker pillows (support blocks) and if you don't give them enough room they nip up. Old BMW 5, 6, and 7 series have a similar set-up and most people give them a bit of slack, "just in case", hence the castenet symphony! ;)
Mine is definitely lack of electrically induced advance, caused by an incorrect voltage coming from the trigger coil to the CDI circuitry and the advance, which is switch like and not a smooth curve, not being triggered. The advance is not extreme for an "old school" 125 4 stroke single, with 11:1 compression, of 36° BTDC @6,000rpm, it just won't rev above 2,500 - 3,000rpm, coughs and splutters and then dies! :(
Out for a canter today sometime, after doing some chores about the place.
Cheers, Bill