Skorpion 660 Lightweight Build

[jpmsteadi]

Just went on a small test ride. Holy cow, the FCR is fantastic. The new main body fixed the problem. It pulls so well, even from being able to count the thumps. If anyone is close to atlanta and wants to give it a try sometime, let me know. Very worth the 250 bucks I've spent on the project. Now to make it work perfectly (and build a more permanent mount solution.

I got in the new seat and plastics today. Unfortunately The plastics and seat don't mount straight up. I was hoping that the tour vs sport was just in the seat and plastics and not a rear subframe issue, but it seems like it is. I am okay with permanently getting rid of that god-awful seat, so it seems like its time for the grinder to come out to play.

[Tramcard]

When the Skorpion was first designed for MZ it was meant to have a Rotax air cooled engine and be as compact as possible. I do not think too many exotic metals were proposed although the original frame was meant to be glued together. The Germans could not get their head around that.

Whole bike was designed in the UK by Seymour Powell design agency as part of a series of design programmed on BBC TV in the 1980s. Seymour and Powell are the designers and bikers. Frame was designed by a small setup called Ticraft who specialized in specal motorcycle racing frames. It is no longer around as the guy who ran it retired.

MZ rather bloated the bike that went into production. Cost was the real factor as the Rotax engines were expensive (much the same one as used on Harley Davidson military bikes). Seymour and Powell were not too happy with the production machine.

[jpmsteadi]

Really interesting information! Perhaps me going to more exotic metals would make them happy!

If anyone has a tour, I would love to get a measurement of the four little nubs that come off the frame to support the seat.How far back they are from the front seat and how much they are proud of the frame.

Thanks!!

[breakwellmz]

Hi.

Well you`ve been busy jpmsteadi looks like the motivation is back!
A bugger about the amount of wear in your carb.
I took the black 3D printed piece to be one of these until i read it - A silicone Hose Straight Reducer, they come in a big range of sizes and i`ve found them very useful at times.
You have a HUGE amount of room around the intake/head area on a Skorpion compared to my Mastiff due to the very different frames, i`m envious!
Keep up the good work mate!

[Puffs]

Yes indeed, a busy man & a busy thread. Good to hear of your progress & positive results!

On the shock: OK, so the shock's stroke is about the same, but then the transmission ratio in the linkage is quite different. But if you can sufficiently adjust the basic damping to the spring rate by adapting shim stack, you'll be OK. And then you have a nice shock with a dail-in fine adjustment. Conventional wisdom is: ride hard --> damp hard.

JB Weld in the carb / slide body? Does that keep?

[breakwellmz]

Re your shock mods, i came across this - http://hajokootstra.blogspot.com/2016/0 ... rbrug.html

[jpmsteadi]

Supposedly the JB weld does keep, but I think I will try and do a stainless insert. Could be a fun mill project anyway. The carb is already broken,so.......

Fascinating article there. I might order one of those other linkages and try it! They are super cheap on ebay.

[jpmsteadi]

So based on the excellent blog linked to above (https://hajokootstra.blogspot.com/) I have order a linkage set from a 2001 GSXR 1000. Its the one he is using and seem to transform the linkage from a very progressive rate to a slightly progressive one, more in line with what the modern shock I am going to be using wants. That in combination with the dogbone adjustment should result in a rear suspension linkage that is both the right height and can benefit from the R6 shock more. It will likely still need a stiffer spring and some revalving, but hopefully it will be closer and a more incremental adjustment. I will post pictures and report when that comes in.

I have also reached out to the neatherlands company that the blog gentleman used to source a set of andreani cartridge internals for the 41mm paioli forks. I had been considering an R6 front fork swap, and still might go that route, but it is tempting to get a set-up that slides right into the forks. The andreani cartridges are most likely even better than the R6 forks and allows me to not have to fuss around with the swap. I really like the fact that they separate out the compression and rebound into the different legs; that is a very modern very nice feature. If they don't get back to me I plan on taking apart the forks and measuring everything really well, then calling a local vendor and seeing if anything they have will fit.

I rode around about 60 miles yesterday. the FCR really wakes this motor up. It seems to be running very rich other than right off idle, so I am trying a needle that has a slightly smaller straight diameter, but putting it in half a clip lower (so making the diameter richer, but the overall needle slightly leaner). I am not going to go too lean until I get the O2 sensor on the exhaust to monitor it better. Unfortunately the tig I ordered is a bit backordered.....

[jpmsteadi]

On a slightly different mod note: The MZ runs at such crazy different temps constantly it will make getting really good jetting hard (I have seen it swing from almost 200 to 125-130 just by riding at 45-50 mph for a mile or so). So as many people have done, I am going down the road of putting a bypass thermostat system on it, like it should have had from the factory (in my opinion).

The donor I have chosen is a KTM 390 duke. I was looking for a plastic thermostat that was inline, not attached to the engine or radiator. Plus the 390 duke's lines are larger than the MZ; it should flow plenty of coolant. The parts came in. Here are some pictures of it and showing it mocked next to the current cooling system. The thermostat is so nicely labeled! The bike has been ridden today and I don't really want to tackle this with hot coolant, but it will be done early next week.

[breakwellmz]

It`s a mystery to me why MZ didn`t fit a proper thermostat, i`ve had the standard one apart and there`s not much in there!
That thermostat looks a lot neater than the one i picked up to fit to the Mastiff, i gave up on trying!
Do your cooling fans come on as they should?

[Puffs]

On the cooling of the 660 I can't say much (other than that it would surprise me if Yamaha hadn't sorted that out properly), but on the suspension issue: good to hear you're reducing the stroke to be more similar to what the R6 shock wants. The R6's track record in the SuperSports class suggests they must be doing something right.

On the forks: best make sure F & R are compatible (in both stroke & damping), otherwise it might turn out to ride a bit like a camel.

[jpmsteadi]

It`s a mystery to me why MZ didn`t fit a proper thermostat, i`ve had the standard one apart and there`s not much in there!
That thermostat looks a lot neater than the one i picked up to fit to the Mastiff, i gave up on trying!
Do your cooling fans come on as they should?

I have put on the Tusk universal fan kit from RockyMtnATV. It has an adjustable temp to turn on and has a readout for me to keep an eye on the temp.

I'll keep you updated on how the thermostat works. It seems like it should be a pretty easy job. And hopefully by keeping the temp at a nice 195ish I will be able to dial in the carb jetting better. The stock carbs seem to be jetted so rich in order to run 120-220 degrees.

[jpmsteadi]

On the cooling of the 660 I can't say much (other than that it would surprise me if Yamaha hadn't sorted that out properly), but on the suspension issue: good to hear you're reducing the stroke to be more similar to what the R6 shock wants. The R6's track record in the SuperSports class suggests they must be doing something right.

On the forks: best make sure F & R are compatible (in both stroke & damping), otherwise it might turn out to ride a bit like a camel.

I am sure that the cooling system works fine, but because it has such variance it runs richer than is ideal.

The 2006 R6 shock with the 2000 GSXR1000 linkage fits really well. Some slight sanding of the linkage to make it fit onto the frame end, but not too bad. Once I get the mill in I will clean it up a little (not that anyone is looking at i

In order to size the dogbones correctly I started with measuring the stock shock and linkage height from the swingarm to the frame with the wheel off the ground, no load. I then installed the new linkage and the R6 shock, but didn't install dogbones. I put the rear wheel up on blocks of wood until I got the same measurement from the frame to the swingarm as the stock shock. I think measured the length the dogbones would need to be to give me that unloaded height. It came to 145MM. I put a new hole in the GSXR linkage and installed them.

I am now getting about 1.5" of sag with me on it. Almost perfect from the spring that came on the R6 shock. I have ridden around several miles, starting with the shock set at full soft, then going five clicks up on all three adjusters. It is so much more compliant and comfortable, and, even though I haven't ridden it very hard yet, feels very controlled. Makes the forks seem harsh though. For an current cost of about 75 bucks, this seems like a steal in terms of performance upgrade.

As for my forks plan, I think my plan right now is to just let the stock forks ride until I get the shock and FCR completely sorted. No need to start on another big project while the other two aren't completed. I am currently looking at doing a 1999-2001 R6 front end swap. I have found reports online of it basically bolting on with a DRZ-400 steering stem bearing kit. I have not measured anything to confirm that though. That generation of R6 forks is still right side up (looks wise I prefer that) and are supposedly fairly nice cartridge forks. Going the cartridge inserts into the OEM forks is tempting, but it would also be nice to go to a fork that so many people have made so many things for. Finding replacement parts and the like would be much easier going to a large OEM.

[droy]

jpmsteadi

Thanks for the documentation and keep it coming.

two shock question - your riding weight (in lbs) and did you check static sag? Static sag on my CBR1000RR shock conversion is about 3/4-inch

[jpmsteadi]

jpmsteadi

Thanks for the documentation and keep it coming.

two shock question - your riding weight (in lbs) and did you check static sag? Static sag on my CBR1000RR shock conversion is about 3/4-inch

I weight about 145-150.

The static sag is the 1.5" ish, measured at the axle to the rear subframe. The free sag is basiclly nothing. maybe .25"