Shocks

The Cagiva era Morinis
nickst4
Posts: 185
Joined: 31 Oct 2011 06:55
Location: Diss, Norfolk, UK
Location: Norfolk

Re: Shocks

Post by nickst4 »

Good job, Tom! That's one very special Dart you have there, packaged even tighter than the original! By the way, do you think the Mito front end was a big benefit? Maybe it has twin discs?

Hopefully you'll find the shock is good and will give feedback to Wilbers so they have a Dart spec on record. Presumably the narrower spring you asked for doesn't have any negative aspects because they simply adjust the gauge and/or the number of coils to give the required rate. For a given gauge, I assume a narrower spring would be stiffer because it is a shorter length of metal that needs to flex more for a given stroke.

Nick
EVguru
Posts: 1528
Joined: 01 Aug 2006 11:13
Location: Luton
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Re: Shocks

Post by EVguru »

nickst4 wrote:Good job, Tom! That's one very special Dart you have there, packaged even tighter than the original!
That's my fault. I showed Tom the exhaust on an early Freccia C9. They has the system packaged inside the bodywork like that.
By the way, do you think the Mito front end was a big benefit? Maybe it has twin discs?
It has 38mm stanchions rather than 35mm and comes with a 17" front wheel, so there is a much better tyre choice. The caliper is the same, but the single disc is 10mm bigger. I never had an issue with Dart brakes which compared just fine with the cast Iron 300mm disc and 4 pot caliper on my Gilera CX. Tom had already adopted the Mito front wheel (with Dart disc and bushes to suit the smaller spindle), but felt something was wrong with the front end. When we stripped it down the forks were quite sloppy and it appears that the re-chrome had been ground undersize by 0.1mm on one side and 0.2mm on the other. I already knew that the Mito bottom yoke was compatible with the headstock and a good set of used forks (I recall Tom used Planet forks) cheaper than another re-chrome.
For a given gauge, I assume a narrower spring would be stiffer because it is a shorter length of metal that needs to flex more for a given stroke.
All other things being equal, yes, not so much for the length, but for the tighter radius.

http://www.planetspring.com/pages/compr ... ulator.php

Stock springs often have quite a lot of turns of quite thick wire, which an equivalent performance spring would have fewer turns of thinner wire (of a much more expensive alloy) for the same rate, but a lot less weight.
Paul Compton
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
morini_tom
Posts: 919
Joined: 05 May 2006 13:47
Location: Northampton

Re: Shocks

Post by morini_tom »

Yes it's pretty tight! I knew it'd be tight when I installed the 501 but then the exhaust system just took the biscuit! The one saving grace is that the rear exhaust port is high enough up that the header can go over the top of the frame cross member (you can just see this in the photo). Still no room to get a c spanner to the nut though! Initially I had a 2 into 1 made in the same vein as the original dart system but the bike never ran right and I couldn't get equal lengths, so I started looking at how to route a 2 into 2 with a link pipe. Conversations with Paul began reasonably sensibly- but talk of modifying an excalibur 500 system to fit went out of the window when Paul reminded me of the freccia's tucked in pipes. Difficulty routing an exhaust out of the left side (sidestand) and my dislike of twin stacked pipes was all the excuse I needed. Some time (and a lot of cash!) later and Alex at NLM had done a great job of working out just how to make it a reality.

The choice of front end was as Paul says fairly straightforward. Some years ago I fitted a Mito 17 inch front wheel to the dart forks by turning up some top hat spacers. This gave me the advantage of wider choice of front wheel (although not as good as I first thought as all the good rubber is then unavailable in a narrow enough size for the rear! - I did look at fitting a Mito rear wheel but decided that one step too far). It was a good, relatively cheap modification as the original brakes and forks were retained and the Mito speedo drive interfaces to the dart speedo ok (never checked the resulting speedo accuracy but can't have been too far out).

Then about 4 years ago I started to become unhappy with the feel from the front end. The MRC trackday at Cadwell that year convinced me that the forks had to go (they'd felt fine every other year). Closer investigation showed two things- firstly they were flexing and secondly there was as Paul says a pretty terrible size issue going on. Given the extra power of my bike, and the abuse I like to give it, it made sense to try to go bigger on the forks. The difficulty here is that I didn't want to have to cut the bodywork to make space, and I wanted to keep the bike looking as standard as possible. Mito mk1 forks did just the job (not Planet as Paul says). The bottom yoke was a straight fit, and the top yoke just needed a bit of trimming on the mill. I had to machine some longer top caps so I could drop the forks lower (not unlike the standard dart forks in that respect!). Other than that it was pretty straightforward. The dart switchgear went on with only a little modification, and the cagiva supercity wheel dropped straight in, the bigger disc mating to the dart caliper held in the mito forks.

Because of work commitments I've not used the dart as much as I'd have liked since the fork mod (couple of thousand kilometers probably) so I've not really spent any time trying to set it up properly. The one trackday I've done in that time it felt a lot more positive up front but has a tendency to understeer in sweeping 'on power' corners. Now I've got the wilbers on it, next year I'll fit new tyres (not sure what yet) and then begin trying to improve the setup.

The steering lock is terrible now too as the bars are yoke mounted clipons as opposed to risers, so the bodywork limits things somewhat. It's only really a problem at junctions, on the move it's fine. I'm probably spoilt for steering lock too as my other bikes (Vincent and a 1200 Corsaro) have loads of lock!

There's a better photo of my bike sans-bodywork on the readers bike page of the club website:
http://www.morini-riders-club.com/photos/readers.html

I've just realised it's been almost a decade since I started modifying my dart, and I have a sneaking suspicion it won't stop just yet!

Tom
nickst4
Posts: 185
Joined: 31 Oct 2011 06:55
Location: Diss, Norfolk, UK
Location: Norfolk

Re: Shocks

Post by nickst4 »

Thanks Tom, and Paul. Apart from the delicious bodywork, improved motive power and jaunty exhaust, I feel the 501 has lost a bit of the original character because of the now-conventional front 'guard, but that's just nit-pickin'!

So, you have a Vinnie too, Tom? A twin, I hope: one of the most beautiful (probably THE most beautiful) engine of all time, in a package that makes it the most impressive feature. I wish! How does it compare with your other steeds? If I sold all ten of my oddball bikes I'd still be short of the price of a ratty one, so that'd be a very silly move I think.... :roll:

Nick

Dart 350, Duke ST4, Monster 750, Suzuki VX800, Sachs b-805, Cagiva Alazzurra, Cagiva Canyon, MZ Skorpion Tour, Yamaha SRX600, Honda NTV.
morini_tom
Posts: 919
Joined: 05 May 2006 13:47
Location: Northampton

Re: Shocks

Post by morini_tom »

You're not wrong about the front mudguard. I always liked the manga style of it.

When I first put the 501 together I did make a carbon front mudguard for it, but it was a pretty tatty handmade job and when I ground-up rebuilt the bike when I did the mito front end I opted to take the mito mudguard. In the fullness of time I might have another go at a carbon front guard (It does fit with the 17 inch wheel and with the mito forks but painting a plastic one would look wrong on my bike). Here's a picture of me at Cadwell, not long after I put the 501 in (2 into one pipes and I think 16 inch front wheel still):

Image

Yes, I'm lucky enough to have a Vincent twin in the garage. It makes a great stable-mate for the Morini. They're all different but they compliment eachother perfectly. I can't think of any aspect of motorcycling I'd want to do that these 3 can't deliver (other than a bit of off roading but I'd never get that signed off!)

Image

Tom
nickst4
Posts: 185
Joined: 31 Oct 2011 06:55
Location: Diss, Norfolk, UK
Location: Norfolk

Re: Shocks

Post by nickst4 »

Chinese Red, no less! You're obviously a man of substance! If you ever feel inclined to permit others to ride the Vincent, I'll be first in line... :lol:

Nick
MickeyMoto
Posts: 2415
Joined: 22 Nov 2008 17:41
Location: Even further oop North

Re: Shocks

Post by MickeyMoto »

Shouldn't the Morinis be red and the Vincent black?
morini_tom
Posts: 919
Joined: 05 May 2006 13:47
Location: Northampton

Re: Shocks

Post by morini_tom »

I'm not sure I'll ever bring the Vin to a Morini event but you never know!

Yeah, I'm in a bit of a muddle with the colours but It's good to be different, isn't it :)
nickst4
Posts: 185
Joined: 31 Oct 2011 06:55
Location: Diss, Norfolk, UK
Location: Norfolk

Re: Shocks

Post by nickst4 »

morini_tom wrote:I'm not sure I'll ever bring the Vin to a Morini event but you never know!
:)
Northampton isn't so far away from Norfolk, though... :wink:

Nick
dr j
Posts: 23
Joined: 07 Jun 2012 12:09
Location: Sharpsburg MD, USA
Location: Hagerstown MD USA

Re: Shocks

Post by dr j »

Nick, Tom, and Paul,
Thanks for all the information on the rear shocks for Darts. Very helpful stuff. I appreciate it.
Jarl
1985 Morini 350 K2
1990 Morini Dart 350
Moto Madcap
Hagerstown Maryland USA
Bonneville Land Speed Racing: BUB 2012- four 350cc Modified Pushrod class records (best is 97.961mph)
and BUB2013-four 350cc Altered Pushrod class records (best is 98.319mph)
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