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Fork swap question

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900Rebuilder

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Beeston
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M900
Hi All,

Just got my wheels back from the powder coaters and have stumbled upon a snag. Tim has been helping me with lots of helpful advice via DM's but I thought I'd also put it out there to see if anyone else has had the same issue.

On my early M900 I've done a 916 fork leg swap and achieved this via the usual boring the top yoke and shimming the bottom along with having some basic risers made which then enable for the Renthal FB's to clear the adjusters as the legs are longer than the 900's. Maxton also re-valved them for the M900's weight.

Trouble is whilst my wheels have accepted the correct 916 diameter bearings for the 25mm spindle the bearing location in the hubs are different to the "standard" wheel that most Ducati's of that era ran so will most likely require some custom work to make fit which I'm not in a position to do easily. I suspect that the wheels that came in my box of bits are very early or may even be 900ss or 888 etc.

Markings on them are as follows:

Brembo
17 x MT 3.50 DOT E
Cagiva Elephant logo 03-89

Does anyone know what wheels these are from as I believe the "bike" or box of bits in reality were originally fitted with Marzocchi forks if that helps?

The front wheel of Louise's 620ie looks like a perfect fit but cant be robbed unfortunately 😂

Any help gratefully received - Ben
 
So I'm thinking that your problem might be that the new bearings while being the same OD as the originals, but are thicker needing deaper seats to achieve similar alignment. Without machining the wheel hub the two locations where the wheel's alignment can be altered. First via the spacer on the left hand side (an easy fixable unless the speedo drive is an issue) and the second point is the step in the spindle that fits up against the outside of right hand bearing. Only a small amount of wiggle room with the location of the spindle, beyond that it's making a new spindle.
 
Last edited:
Bitza said:
So I'm thinking that your problem might be that the new bearings while being the same OD as the originals, but are thicker needing deaper seats to achieve similar alignment. Without machining the wheel hub the two locations where the wheel's alignment can be altered. First via the spacer on the left hand side (an easy fixable unless the speedo drive is an issue) and the second point is the step in the spindle that fits up against the outside of right hand bearing. Only a small amount of wiggle room with the location of the spindle, beyond that it's making a new spindle.
Click to expand...
The bearings are the stock 916 size and no difference in width its that they fit further in on the RH side and the speedo drive won't fit as the LH bearing is in further where as the 916 wheel has it closer to the fork leg.
 

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Ben, Sorry I'm having difficulty getting a clear picture of this. If the new bearings are the same width as the originals it's hard to see why they should fit further into the hub, especially with the inner sleeve that fits inbetween the bearings inner races. However with the set further in won't making some spacers overcome the issues? Best of luck with it, if you are really stuck I do still have my old wheels, newer pattern with spokes getting narrower towards the rim, front 25mm spindle front for speedo drive, rear 17mm spindle. Downside in need of repaint.
 
I'm no engineer so not really sure how to fix it as the original 20mm spindle spacer is around 5-7mm narrower than the 25mm 916 version indicating that my wheel has a different layout hub. Agree on the spacer front but have no access to measuring correctly or manufacturing them.

I'm most likely going to switch wheel's once I've tried the 620ie one in my 900 to check that wheel / hub fits ok.

I also have an S4 rear wheel so I'm contemplating sourcing a matching front but haven't seen any for sensible money yet. If I go for a 3-spoke I'll be in touch as my coater is good value for money so colour is not an issue.
 
Just twigged, sorry for being dim. So your problem is basically down to the early (20mm spindle) front hubs having the bearings set closer together, compared to the slightly later (25mm spindle) hubs.
I'm thinking this ought to be spacer sortable. You don't really have to be that accurate, a vernier caliper measure will suffice. Use the brake caliper brackets to work from for centrality. You'll have a bit of wiggle room with the spindle too. Make up the righthand spacer first, checking wheel is central and that there is sufficient spindle thread protruding. Then simply measure gap between the outside of the speedo drive to the fork leg, for the left hand spacer. If I lived closer I'd give you a hand.
I'm sure you 'll find a way to sort it whatever.
 
Thanks 😎 you've finally twigged my issue (that wasn't meant to be patronising btw). I'll need to get my calipers connected up next and think I'll need some Hel adapters to join my radial master cylinders to the traditional style hoses.

One step forward one step backwards
 
Bitza said:
I'm thinking this ought to be spacer sortable. You don't really have to be that accurate
Click to expand...
916 doesn't have a spacer on the RH side, rather a step in the spindle which sits up against the bearing. The spindle is actually free to move in/out on that side with the position being determined by the speedo drive/spacer on the LH side so, as long as the LH side is correct the spindle will compensate to some degree (limited by the amount of thread on the spindle).

Obviously the mounting face for the discs on the hub need to align with the calipers though.

Looking at the pictures etc. it seems to me a thicker bearing (if available?) or spacer under the bearing to bring it outwards on the RH side might work, notwithstanding the correct length spacer tube between the bearings.

Failing that, a wheel from a compatible model, I would think any wheel of the era designed for the 25mm spindle with mech speedo etc. should fit?

I'm using an MHE front wheel in my Monster with 916 forks and was a straight fit.
 
I think that I'll be going with the correct wheel option as is the easiest one for me with no direct access to engineering support to produce bearing spacers etc currently.

I went to test fit the wheel from the 620 this weekend but realised the jack and axle stands etc are currently holding the jeep up and as I've been tasked with gutting our lounge for a total overhaul I ended up hacking off plaster and lathe strips for most of the two days.

Going to Stafford next weekend so might pick up a wheel there who knows? Ideally I would move to the 5 spoke now as that's my long term plan anyways (money allowing) and I'm beginning to think that my M900 speedo might not work with the 916 drive so may need to delete the drive entirely and run another / newer unit anyways (I want to keep the M900 style however).
 
I agree, the correct wheel will be better and likely cheaper in the long run when you take into account engineering, messing about etc. plus you can recoup something by selling your current wheel, which sounds like it might be rarer so sought after?
 
You just can't beat a dry build before you even think of any finishes, be those painting, powder coating or plating.
I must have had at least 3 complete dry builds on the Commando, probably nearer 5, before I was happy to get going on the finishes.
I'm looking forward to seeing how you get on with fitting a centre stand and a floating rear brake.. :ROFLMAO:

I also spent a lot of time and different ideas on the 750SS without doing anything invasive like cutting the actual bike. Good job, as I declared it a non-viable project and had a perfectly good bike to sell at the end. DaveR still rides it.
 
Mr Gazza said:
You just can't beat a dry build before you even think of any finishes, be those painting, powder coating or plating.
I must have had at least 3 complete dry builds on the Commando, probably nearer 5, before I was happy to get going on the finishes.
I'm looking forward to seeing how you get on with fitting a centre stand and a floating rear brake.. :ROFLMAO:

I also spent a lot of time and different ideas on the 750SS without doing anything invasive like cutting the actual bike. Good job, as I declared it a non-viable project and had a perfectly good bike to sell at the end. DaveR still rides it.
Click to expand...
True but where's the fun in being sensible? Regarding the centre stand I bought that maybe 8 years ago and only bought the rear brake as it came up so it will be an either or situation if needs be. Same on the cutting thing though as nearly cut the rear end off before deciding to keep it whole which has turned out to be a blessing in disguise.

Biggest mistake I can own up to is having multiple projects on the go simultaneously which means you achieve a large amount of nothing on all of them. Also I think on reflection I may have been battling some low level depression which has hit my motivation over the past 3-4 years without actually realising it was that bad.
 
I get the 'dry build' thing but I've been doing so much of it recently, that I'm getting sick of it. I can't remember how many times I've fitted and then removed to repair/alter and then refitted various body panels on my Land Rover build, made worse by the fact that some are a 2 man job due to size/weight so I need to wait until a suitable strong person is available - Hopefully the next strip down is for paint and final build?

Also means I've lost my nice (no longer) clean and spacious bike workshop as it's the only place I can realistically work on something that size and be warm in the winter, so my bikes are relegated to cold/damp/dusty garage space. :(

I bought it knowing there was a lot to be done but I definitely bit off more than I ever intended to chew, having already gone 100%+ over budget, taken a year longer than planned and with the end still not really in sight. I won't be beaten though and will finish it but thereafter I'll not be taking on any more car projects and, for now at least, no more bikes either.

Getting back to your Monster, I agree on the 5-spoke wheels, I've never really felt at ease with 3-spokes, there's just something 'wrong' about them which is one reason I fitted 10-spokes to my 916 (plus the huge weight reduction).

I've still got the original 3-spokes and forks/brakes etc. so that, if I ever need to, I can return it to original but not whilst I'm riding it.
 
Thanks DD

On a minor positive the bolts and rear brake plate I ordered Friday from Molnar have arrived and should make the fit of the 900ie lump in the carby frame much more robust, especially as the design allows you to fit a socket onto each end and they are not as recessed as the original Allen bolts are.
 
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