1980 500W first time project introduction

[3potjohn]

You should try swearing in Spanish.Most colourful.
John

[park3164]

I dropped by his workshop yesterday (reckon it is an essential service reason in the current restrictions) and was told the bike had been sworn at again in proper Maltese. Crankcases are now split and further damage reports to follow. I will get pics on the weekend. That flywheel shaft sure was rusty and pimply even to my novice eyes.
Inside the cases were not as bad as they could have been, tho small amounts of fine metal grit and some issues. The dreaded obsolete clutch near side engine bearing may be ok,same for the plain crankshaft bearing in the RHS case, but the sprocket shaft crankcase bearing is no good. Big end bearings and crank/conrods may pass muster too. Gears appear quite good. I rarely have a whisky but having a single malt last night seemed appropriate as the worst of the depths have been reached (pending further checking). Task this week is now to add to my shopping list

Fiona

[Ming]

Sounds to be good progress, well worth a single malt. I always revert to proper Anglo Saxon swearing as the French language is far too polite, judging from the swearing of builders I have heard during work on our house.

[park3164]

Well, this didnt work out well. I was planning to get some photos to put up, but shortly after the crankcase was split we have gone into severe covid lockdown, and now there is not access to lots of trades for a month or who knows when. Meanwhile, it seems it would be prudent while the cases are split, I should think about sources for replacing as many engine bearings as I can even though the sprocket shaft one is the only obvious dud.
So the questions that many no doubt have previously asked - what are the current suggestions if any for replacements for the clutch shaft obsolete bearing? I have noticed references to a modification to a SKF bearing in the past. There is access through contacts to facilities that can modify and reharden bearings (for a price of course).
And what may be involved with a timing side roller bearing conversion that is important to know, so I can pass the info to the engineer doing the work? Looking through the forums I've noted evguru recommending it for the 500, and some mention of issues with the oil feeds and such need be catered for. Or should I just default and try for a replacement for the plain bearing - if there are suggestions for what might do the job.
Any way, for now the default during lockdown , apart from online homework, is the brake refurb and the rewiring - till trades come back on line.
TIA as usual for any advice,
Fiona

[EVguru]

First undersize plain main bearings are available from Mdina. I'm leaning away from the roller timing side bearing conversion unless it's a pre-plain bearing 350, or a tuned engine.

The two FPAC (four point angular contact) bearings need to have their ID precision ground in the as hard condition. Any engineering shop that has a cylindrical grinder with an internal attachment should be able to do the job. It could even be done in a lathe if you have a set-tru (other adjustable run-out chucks are available) three jaw and a toolpost grinder. You can hard turn bearings with the right insert, but holding the correct fit tolerance is quite difficult with that method. Vintage Bearings in the UK will modify, or even make obsolete bearings.

The purpose of the larger main bearing journal on the crank is a bit of a mystery. The journal diameter for the primary drive gear is the same as on the 350 and quite a few 500 crankshafts have had the main bearing journal ground down so that a standard FPAC bearing can be used. I have a 501 bottom end that came from Germany that even just uses the ordinary deep groove ball race, the same as the 350. There's many a larger capacity engine design that doesn't use such generously sized bearings as our Morinis.

The modified FPAC on the gerbox imput shaft makes much more sense as it allows the use of a larger diameter shaft.

[park3164]

Thank you ever so much Paul, it's just brilliant to have such information available. I will pass it onto the engineer doing the work as he was wanting specifics and will understand the detail more than I. He has a quite a collection of lathes and mills including a recent purchase which will precision cut to one tenth thou of an inch, so should be no probs for him to do this.
And next total novice question. Doubling checking terminology here - on the measure twice cut once theme, before I order pistons from Mdina from halfway around the world. We have noted the discrepancy in the blue book and Harglo manual re piston to bore clearances (blue book states 0.2mm, Harglo states 0.4mm); and that the Harglo figure is the one relied on and refers to bore diameter vs piston diam. The .2mm in the blue book seems to be referring maybe to piston/bore radius not diameter or a total error? This discrepancy is confusing.
So - what exactly does the Mdina oversize piston +.2 and +.4 refer to? Blue book style half units? Increased piston diameter 0.2mm and 0.4mm?
I'm told I need only a light rebore done and about 0.5mm increase diameter of bore and piston ie to 69.5mm diam not 70mm (according to standard rebores of 0.5mm or 1mm I'm told). But that 0.5mm increase would mean 2nd oversize straight away for only a light rebore if it I order the seemingly nearest size of +.4.
I appreciate your patience with my steep learning curve here. As well as the recommendations which language is best to swear in

Fiona

[MickeyMoto]

Hi Fiona,

Just to add to the confusion, my Blue Book states piston clearance of 0.050 to 0.055mm at centre of ring travel. Max wear is 0.10mm. The bore should be tapered with +0.011mm at the bottom and -0.01mm at the top.

Pistons should be 0.2, 0.4 and 0.6mm oversize.

I'll photograph the relevant pages and attach later.

*Edit pictures added. Hopefully they are readable as reduced in size.

[park3164]

Thanks mickey moto, a great help. I should have personally checked the manuals again - that 0.05-0.055mm translates to around 2 thousandth inch; which is what the old engineer works in from doing old British bikes. Harglo manual still confuses and lists piston clearance at gudgeon pin height as double, 0.1-0.12mm, or 4 thousandth inch. That's where I got a 2 and 4 from for clearance, mea culpa big time but relieved that I double checked before ordering.
This and seeing in Harglo the oversize pistons are for bore sizes + 0.2 or +0.4mm makes much more sense. I'm mainly the parts finder for this project, and passing on questions as best I can. I appreciate the advice and the patience of folk on this forum
Fiona

[harrymuffin]

Regarding your bearings, the 500 drive side bearing was a modified QJ306 and the reason it was used which is fairly obvious to any engineer, is because of the extra loading any bearing would have to put up with, in going from the 350 fixed race ball bearing was to use larger split inner race with extra ball. This was modified by SKF by having the inner race increased by a couple of mm to fit again ,for loading purposes, a larger shaft dia, than the 350. I have had a number of the QJ306s modified and fitted to 500 engine, with no problems. I had a hell of a time to find a bearing stockist who would do the modification, SKF are just not interested (see below), the tool room that does the grinding researched for the correct bearing fit on the shaft, from an original Morini special bearing.
For the timing side bearing then the ideal bering is the NUP304ECP which has the rollers assembled on the inner race with the outer race being loose and shrunk into the aluminium crankcase housing and therefore floats allowing expansion and contraction which was the original problem with the 350 engines, the bearing fretted in the housing becoming loose. The crankshaft has to be reduced in diameter and does not require grinding or hardening after modification. The diameter can be reduced on any quality lathe by a competent turner, using the correct type of stellite type tool. I have done this myself on my own lathe, after Adrian first did the mod on our deliberation years ago, but you have to know the diametal 'fit' when turning to obtain a transition fit of the bearing on the shaft light tap similar to the drive side. This methd was common on motorcycle engine especially Velocette on their KTT and production OHC engines and what was good enough for them is more than good enough for a 'cooking' Morini engine. Personaly, I would not bother, as the modification is only worth a BHP owing to less friction, so best find a Vintage bearing relignining specialist who would be able to recast a suitable bearing material inside the bearing bush(?) and machine to size for you or you do it as I have had to do with some of the bushes supplied by NLM. I think someone in the club reguarely had this recon. done on his 350s
The gearbox special is more of a problem in that the most suitable bearing requires machining on the O/D and I/D but the bearing tried out by Adrian Crimp about 18 years ago is still working and that is a 3206 which if you look at the design loadings and speeds is more than suitable for this application, again just the I/D needs increasing in size. The firm that supplies and modifies these bearing is relatively local to me and located in Brierley Hill, which is not much use to you, but if you want more info let me know and I will pass on to you relevant information. Last thing, you can chose to use any make of bearing as long as it is reputable, SKF is owned by an investment firm who are there to asset strip, so FAG or one of the Jap bearing companies, they bought up the English bearing makers, but stay well away from Chinese crap, in my last day job we had a lot of problems with their stuff, falsified certificates wrong materials etc, mind you the Japs steel manufacturers after coppying them got found out.
Hope this is of help

[park3164]

Thank you harrymuffin. There is a contact in heavy jet plane maintenance so such bearing modifications may be feasible. I'll pass this on to the ones with the knowledge. I may be interested in following up with your vintage bearings stockist especially if they have some modified stock on hand, but will see what the guys say here first. I've seen Brierly Hill mentioned in bearing posts - is that UK Bearings?
Fiona