Beltomatic assemblies

With the engine all in pieces and waiting for parts to arrive, I decided to occupy myself with overhauling the Beltomatic (I love that word) drive assemblies;  after-all, its all very well making the engine run sweetly, but if the power isn't going to transmit reliably then the whole thing is a waste of time.

This is an ingenious piece of design and engineering that requires springs and counterweights and bearings and sliding bits.  I only hope it performs as well as it looks like it should.

There was nothing particularly complicated about stripping it down.  There is a retaining circlip on the primary assembly that wasn't compatible with my circlip pliers, but nothing that a couple of screwdrivers and a little patience couldn't handle.  I was surprised to find that the needle rollers on the primary drive are held in an alloy cage, and even more surprised to see that the cage was still in good condition.  There were a number of "compensating washers" taking up the lateral movement in the assembly - I have no idea what the factory setting should be for this slack or if my compensating washers are still appropriate, and so I shall reassemble as found and see how she fairs.

After a complete strip and jolly good clean down (its amazing how much the accumulated crud can restrict the ease of flyweight movement) I spray painted the drive plates with Smooth Black Hammerite.
Definitely a job worth doing as the assemblies feel so much more free now, and I am confident that all the parts that will require lubrication can now get it.

Engine Gasket Set

Now committed to a full engine rebuild, I went in search of a gasket set.  And sure enough I found someone out there who makes gasket sets for old motorbikes.  Of course there is!  I often wonder what it might have been like to do a project like with without the use of the internet (and then my mind usually wanders to the next question..... what will it be like to do a project like this in say 25 years time, when [internet] technology might have evolved into something we cannot even begin to imagine!)


I noticed on the Klamotte website that they sold gasket set for DKW Hobby engines but there was no mention of Manurhin.  As I wasn't sure if there might be some subtle differences,  I emailed them to ask if the Hobby Gaskets would suit my Manurhin.
Their response? "Hello, I´m sorry, but I don`t know this engine"
Really!??


Fortunately, fellow Manurhin owner, Roy, had already told me that this gasket set was suitable so I went ahead and ordered anyway.


So, for 21 Euros plus 4 Euros shipping, I now have a engine gasket set.  Just got to get those bearing changed now and it can all go back together

Engine casings

Now most of the bearings are out of the engine casings, I can give the casings a jolly good clean and inspection.
Generally the casings appear to be in good condition, but I was a little worried to see signs of 'chattering' on the insides of the crank casing.

I wonder what might have caused this?
Will new bearings solve this? and has the engine been damaged now because of this wear?
Do I have to get them machined smooth again?

Plenty of things for me to be thinking on over the next couple of weeks while I am away from the garage.

Bearing extraction

So I managed to get the crankshaft bearings out of the engine casings with a little bit of jigging and extracting, and I think Ive found a chap who can supply new bearings to suit (I will get round to seeing him over the next couple of weeks).
The only bearing left now to extract is the one that came out of the casing still firmly attached to the crankshaft, and I am buggered if I can get it off.  The trouble is that it is so closely up against the counterweights that I cant get an extractor or a purchase behind the bearing.  I've tried some heat and clamping in a vise, but no joy (actually I'm not convinced that heat is going to help because I cant heat it without heating the shaft too, which seems to defeat the point)

So what to do?
Well, I decided in the end to leave it for a while, let some penetrating oil do its job and spend some time incubating on the problem while I overhauled the clutch assemblies.
All suggestions on how to remove this bearing will be gratefully received :-)

Crankshaft machined

A while ago while out in our local curry house, I bumped into an old friend.  He owns a successful engineering company, and I was quick to ask him if motorcycle engines were something he ever had the pleasure of handling.  His answer was simple - "NO - too much hassle" (and to be fair to him, if your business is tier 1 engineering supplier to the auto manufacturing trade, nobbing about with private one-off jobs probably is more hassle than its worth) - "But, if you want to drop it round, I'll have a look at it for you.... as a friend".  And so I did.

It turns out that the sheered pin in the crankshaft was hardened, and so the only way out was to spark erode it out.  The Manurhin workshop manual calls this little pin "a magnetic cotter pin" - im not sure why 'magnetic' but my engineer friend and I decided that a new pin made from a piece of silver-steel would be tough enough to do the alignment job and yet sacrificial should anything fail (I'm relying on the tapered shaft to do all the securing of the flywheel)

Note only one hole was spark-eroded.  It looks oval at the top, but its a good true 2mm dia hole deeper down

Normally when updating this blog I would put a link in to the supplier or source of information, but in this instance, I'm not sure if Richard of RPS engineering in Birmingham would be overly grateful to receive a little queue of scooter tinkerers asking for fiddly-piddly machining jobs.  Its not really what his CNC machines are cut out for.