Crankshaft roller bearing conversion

Camel, Sahara, Kanguro, Coguaro
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tremoto
Posts: 22
Joined: 18 Feb 2009 12:53
Location: Londra

Crankshaft roller bearing conversion

Post by tremoto »

Help required! After many happy years riding since my last rebuild, (give or take 20 years) the crank in my 501 has developed play with the death nell signs of a leaky seal replaced several times to no avail!

The crank was originally refurbished by an engineer with an undersized plain bearing as when it was measured it was found to be beyond the pail. Now that I am in this position could anyone tell me what roller bearing type and size would work with my engine considering the crank is possibly no longer serviceable without adding more via metal spraying.
etc and engineering needed?

Any thoughts deeply appreciated on this intractable situation.
mbmm350s
Posts: 666
Joined: 22 Jun 2018 10:18
Location: Reading UK
Location: Berkshire UK

Re: Crankshaft roller bearing conversion

Post by mbmm350s »

Hi,
I have no direct experience of this on the 507cc motor but
I think this is a difficult/expensive solution to convert to a roller bearing. For this to work the crank needs to be ground a long way to make
the correct fit for the inner race.
Then the outer race needs to be held in the correct precision fit in the crankcase.
Since the original design was not for a roller bearing (or even deep groove ball bearings as per early 350s/250s) the precision of fit needs to be carefully established.

take a look at this thread
viewtopic.php?f=7&t=208

And Morini tom raises some issues with this on the 507cc motor
viewtopic.php?f=4&t=2797

if you enter this into your search engine (chrome)
roller bearing conversion site:http://www.morini-riders-club.com/forum

then more threads are returned

hope this helps.
Mark
harrymuffin
Posts: 292
Joined: 07 Apr 2014 16:06
Location: west midlands

Re: Crankshaft roller bearing conversion

Post by harrymuffin »

This conversion was sorted by me and Ade Crimp and he carried out the conversion on his 500.The crank main bearing does not have to be ground as it can be turned down with the appropriate cutting tool. The journal although tuff is not through hardened if at all and has a treated depth of tuffness of about 0.050". Any compent machinist would be able to turn this to the required size and I beleive this is what Ade Crimp did with his conversion.You have a choice of three types of roller bearing, a lip on the inner race, a lip on the outer race or no lip on the outer race with the caged rollers attached to the inner race which is my prefered choice. The inner race needs to be an interference fit on the now reduced diameter inner journal, I could look up the BS standard but cannot be bothered at this time, but would suggest a fit of 0.002" which is along the same guidleines that Velocette used on their drive side main bearing KTT engines. The outer race should be a tight fit in the aluminium case and should be fitted by heating up the crankcase for it to drop in and not drifted in as some people would do and therefore wonder why the fit becomes sloppy. If you use the N206 bearing then it will allow differential expansion between the crackcase and cranckshaft ie it will float as the lateral movement of the shaft is restricted by the drive side bearing. If your outer race is not a tight fit/sloppy then you will have to sweat and wipe the outer surface with soft solder which should give a tight fit and because any clearance you may have had would be in the thous of an inch and be comparable with the original running clearnce of the plain bearing anyway. Or. loctite tite with a low retension retaining compound. I think you will find without checking that the standard plain bearing retaining holder is common on the 350 and 500 engines. The crank journal would be reduced to the original roller race diameter. If you do not want to reduce the journal diameter the the NU1007 bearing is available. It is the outer diameter of the bearing that restricts choice as the housing in the crankase is 62dia.
If you do not want to go down this route then you can have the journal reconditioned by having it submerged arc welded and then ground back to standard which has been standard practice since the process was developed before the war. I can vouch for this as it wa nornal when recovering crankshaft bearings on slow speed marine diesel engines where the ship would have to be cut open to get the crank out and easier to weld and grind in situ in the cranckcase, the bearings can be up to feet in diameter. I have had this process done on a six cylinder car engine with no problems. Talk to Coventry Metalling and Boring as they did mine but there are a number of firms that do this recovery process.
tremoto
Posts: 22
Joined: 18 Feb 2009 12:53
Location: Londra

Re: Crankshaft roller bearing conversion

Post by tremoto »

Thanks guys, I had been considering building up the crank back to a serviceable level but I need to digest the solid information you have given me and most importantly split the cases to mull over the engine contents. So it's probably is best at this stage to look into this route. Much appreciated information and contacts.
tremoto
Posts: 22
Joined: 18 Feb 2009 12:53
Location: Londra

Re: Crankshaft roller bearing conversion

Post by tremoto »

Forgot to ask, where are folks sourcing big end shells etc from these days. I see Mdina Italia are now listing some sizes now.

Cheers
morini_tom
Posts: 920
Joined: 05 May 2006 13:47
Location: Northampton

Re: Crankshaft roller bearing conversion

Post by morini_tom »

I have now done the roller modification on 3 501 cranks. Short story is I had one bad experience but I don't blame the idea of the modification for that, more it's execution in that instance.

The first was on a very tired engine and the roller bearing at least was still going strong many thousands of km later when I decided to replace the engine with a fresher one.

The next engine, I made the mistake of deciding to have the crank lightened/balanced at the same time as having the main bearing ground for the roller mod. Unfortunately, the place I used thought that it would be a good idea to lighten the crank by drilling all the Mallory plugs out and then attempt to balance it. End result was a very shiny and light crank, which unfortunately had also had it's gallery plugs welded up at the same time. It wouldn't have been so bad except that it was a brand new crank to start with, and I had used this particular specialist because they had an excellent reputation for doing crank work. That was the crank which I posted about on the forum that had blued up and pushed the oil seal outwards. I never followed up on that post, but upon teardown I found that the outer race of the main bearing had cracked radially, and the inner race had walked outwards and probably also spun on the crank. The crank journal was undersize for the main bearing inner race, and to add insult to injury there was absolutely no fillet radius on the crank. In short, that crank was always a ticking timebomb. I won't say who the specialist was but needless to say I will not be using them again.

When I rebuilt the engine I made sure I used a machine shop I know and trust (Automotive Services in Northampton. Cannot recommend them highly enough). I measured the drive side journal diameter and bearing inner on the CMM at work and then replicated that fit when the timing side was ground for the roller bearing, which should stop the inner race walking this time. Additionally I had a generous fillet radius and used a shim between the crank and bearing inner to move the bearing off the fillet. FInal mod was that as well as plugging the oil feed hole in the timing side crank journal, I made up a longer gallery plug for the timing side which seals the now redundant passageway down to the roller bearing. I figured that the dead end passage could allow sludge to accumulate and drain back down to the big ends over time. That engine is still going strong, although it's probably only done 5k km or so.

The roller bearing I have used is NU206ETVP2.C3


Other things to be aware of are that you will need to also plug the holes in the crank cases which previously held the plain bearing cage. I had mine welded up but you could also drill and tap some small screws with sealing washers.


Regarding other bearings, the drive side main 4 point angular contact bearing is obsolete (633250C) but you should be able to modify a QJ306MA. These are obtainable from bearing stockists although I have some of these (unmodified) on the shelf so happy to pass one along at a favourable price.


The drive side gearbox input bearing (633245A) is also now obsolete but again, I am sure there is a 4 point angular ontact bearing which could be modified. That said, I've never needed to replace that bearing.


Big end shells are difficult. I searched for ages and ages and could not find anything satisfactory. Alex Luzzi had some second oversize shells, so you could try him if that is the size your crank needs, but it would be a shame to waste a life and grind an otherwise good crank to second oversize as cranks are also in very short supply now. Harrymuffin should be able to advise further on the other options of modified Fiat shells.
harrymuffin
Posts: 292
Joined: 07 Apr 2014 16:06
Location: west midlands

Re: Crankshaft roller bearing conversion

Post by harrymuffin »

Big end shells from the original FIAT 500/Multipla fit the 500 big ends and are slightly wider which is an advantage as the already overloaded big end is given a better chance of survival. The keeps on the shells have to be moved but have had no problems on customer engnes or my own. You get four complete big end bearings for less than one half a bearing from what used to be NLM, don't know about the mob in London.
Regarding gearbox and drive side obsolete bearings, Ade Crimp again persuaded SKF to modify standard bearings and they do have official SKF bearing numbers.
rossguzzi
Posts: 433
Joined: 23 Jan 2019 14:21
Location: Perth W/Australia

Re: Crankshaft roller bearing conversion

Post by rossguzzi »

Some very interesting reading here.
This sort of work is far above my ability. Hope I don't need it for a very long time.
What would the expected life of a 500 motor be if looked after ? It's a bit scary the thought of parts not available any more.
Vitesse
Posts: 218
Joined: 05 Jan 2019 13:42
Location: Barnacle
Location: Crowcombe

Re: Crankshaft roller bearing conversion

Post by Vitesse »

rossguzzi wrote:What would the expected life of a 500 motor be if looked after ?
Would that be akin to the guy going to the doctor who merely says that he needn't worry about the Best Before dates on food anymore? :D
tremoto
Posts: 22
Joined: 18 Feb 2009 12:53
Location: Londra

Re: Crankshaft roller bearing conversion

Post by tremoto »

Yes, really good info and will have to consider options with all thats been said. Once it is stripped, possibly next week if I can sneak the time a fuller understanding of what is required will be found. An incidental note one bearing holder allen head has vacated the scene unknown. Never seen this before and I am sure is purely intrinsic to my issues. Cheers Morinisti !
mbmm350s
Posts: 666
Joined: 22 Jun 2018 10:18
Location: Reading UK
Location: Berkshire UK

Re: Crankshaft roller bearing conversion

Post by mbmm350s »

What would the expected life of a 500 motor be if looked after ?
From the factory 100000 Km would be minimum. Nikasil engines should last longer.

but today it depends on the skill of the engine builder and availability of quality parts.

And that might be an advantage of the roller bearings - a regular standard part with easy replacement
once the conversion is done.


However a lot of the wear is done when not using the bikes
They are left for months if not years in damp sheds, mouldy garages and even cellars*
where corrosion caused by combustion acids in oil eats bearings, cylinders, valves;
In storage belts degrade, carbs gunge up, batteries die etc couple this with with occasional short journeys
a recipe for shortened engine life.

I think we should just ride them while we can and fix them when they eventually wear out.

Mark
EVguru
Posts: 1528
Joined: 01 Aug 2006 11:13
Location: Luton
Contact:

Re: Crankshaft roller bearing conversion

Post by EVguru »

Big end shells from the original FIAT 500/Multipla fit the 500 big ends
The Morini 500 has a big end journal diameter of 35mm.

Fiat shells are listed as fitting the 500, 126 and 126p
https://www.historic-cars.net/historic- ... 0-Fiat-126

The 126 manual I found online lists a big end journal diameter of 44mm
http://mailbox.com.pt/ficheiros/pdf/MANUALFIAT126.pdf

It appears that the shells from the four cylinder Fiat 600 might be the ones to use. Those for the 600D might be larger.
Paul Compton
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
morini_tom
Posts: 920
Joined: 05 May 2006 13:47
Location: Northampton

Re: Crankshaft roller bearing conversion

Post by morini_tom »

If speccing shells from alternative sources be very careful with rod diameter.

As Paul says, it’s a 35mm journal but the rods when bolted and torqued up without shells are actually 1.5inch bore (38.1mm) so could very easily be mistaken for 38mm.

I measured brand new rods, shells, crank and main bearings on a CMM to be sure of the fit when I built my 501 up.
harrymuffin
Posts: 292
Joined: 07 Apr 2014 16:06
Location: west midlands

Re: Crankshaft roller bearing conversion

Post by harrymuffin »

!960s Fiat Multipla big end shells fit and are slightly wider, as discovered by Ade Crimp of Bristol University and obtained from a firm in Bristol 'Piston Broke', they seem to stock a lot of obsolete stock if they are still going. I have had no problem with fitting them to my own 500s and other peoples and still have some left over.
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