God Help Me ...

[morbidelli17]

I've always wanted a 660 Skorpion for race use. So I went ahead and did it - one came up for sale here in Southern California, and I snapped it up. Screw my therapist - what are his lap times, anyway?

So I've got questions galore, but I promise I'll try to use the search function first. Right now, the biggest question is this: The bike came with what the owner calls a "Stage 1" cam. I suspect we're talking about the Megacycle 280-x2 cam, but does/did anyone market something specifically called a "Stage 1" cam for this critter? My first thought is to drop in an 11:1 piston, but I want to try to make sure I don't have piston/valve clearance issues. Bad for lap times.

Thanks in advance, and best to you all.

[basser23]

Congrats on the purchase..it'll be fun....
The cam you are refering to MAY be from Hotcams for the Raptor..they have what they call a Stage 1 cam..ask the previous owner if that is indeed the one.
These were meant to bump the mid and upper power a bit,and supposedly not require changing the valve springs...
Chip

[morbidelli17]

Thanks much. The problem is the previous owner didn't do any engine work, but bought it from a guy who did the work. I am told it is stock except for the cam. Will look into this Hotcams thing, and thanks.

Next question: Anyone tried to get a 2nd gen SV650 rear wheel onto the stock swingarm? Jesus, I could not believe how much that rear wheel weighed!

[basser23]

There have been numerous posts regarding performance for these bikes,and one of the ways is to lighten them up starting with the wheels...heavy!!!
Bill Jurgenson recommends wheels from an SZR or TZR to lighten up. Also listed are wheels from the GS 550E, supposed to fit.
I would imagine that the SV wheels would be similar...probably need spacers,not sure of axle diameter either.Let us know how you get on.
I am thinking along those lines too.
Chip

[morbidelli17]

Thanks. As soon as I get this thing back from the exhaust system guy, I'll do the measurements on the rear wheel. Mine came with a spare set of rims. I could not believe the weight of that rear wheel. Think I'll leave the front be for a bit; ultimately, I'd like to put a GSX-R front end on it, and that way I can swap front rims between this bike and my SV.

My name's Michael, btw. Thanks for the input, Chip.

[Bill Jurgenson]

Almost ANY wheel would be better than the Grimca crap MZ used.
The tragedy of it is that the prototypes had both the fork and Brembo wheels and brakes from the TZ250. Then some fool had the idea that the Skorpion had to be sidecar-ready so they went fro the those lead-heavy and supposedly stronger wheels. Ther are not strong, however, on the contrary, the front rim dents much more easily than a much lighter Brembo as I know from personal experience.

In the states, the easiest way up front is to fit an early R6 fork complete with wheel and calipers. The early R6 had a 41mm USD fork so it goes right into the original yokes. It is adjustble and has a much better wheel. Of course there are other good 41mm forks out there.
For the rear, the swing arm from the same model R6 can relatively easily be modified to fit the Skorpion. That gives you a better aluminum swingarm and a much better and plentiful rear wheel.
This sort of change over gives you modern usable widths for racing: 3.5" and 5"
At the Yahoo MZOG (MZ owners group) you'll find photos and info on this reworking of the swing arm.

There are no wheels that fit plug and play. Unless you change everything as above, you will need to make spacers.
Be sure to get the rear caliper and plate that goes with the rear wheel you eventually decide to use. That ensures that the wheel, rotor and caliper will fit easily and be easily replaced. You then only need to make the spacers to the swing arm. The entire unit cushdrive/wheel/brakeplate+caliper can remain as is.
Don't bother to try a Ducati Monster rear as it is not possible to fit and AND get the chain to line up - I tried.

Personally, I would go for Marvic magnesium wheels, at the front there is one with the requisite width for the caliper(s). The rear wheel only has a bearing housing on the left. The right bearing is carried by abolt-on adapter ring for the rotor.
I used Marvics myself in my racer and the difference in handling and acceleration and braking is otherworldly. Of course any lighter wheel is a big improvement.
here is the rear wheel utilzing the rotor and Paioli brake plate from Yamaha:

The front is completely uncomplicated:

I made a new hollow front axle that needs no spacer at the left and does not protrude from the fork leg. the previously used Yamaha 17mm front axle would have worked of course. The right leg has M16 thread so the Yamaha axle turns right in. The 25mm Ø left fork clamp is the same as Yamaha uses. Since none of the Brembo wheels fit the RSU fork together with the speedo drive, a replacement spacer is needed to take of the vacant space. I simply make a a 78mm long single spacer from 25mm aluminum tubing drilled and reamed out to 17mm to fit the Yamaha axle. The Yamaha axle is hollow, too.
I have fit many sets of Yamaha SZR (Brembo) wheels to Skorpions (by no means only mine but all three of my street bikes had them) as well as three sets of TZR wheels (front 3", same as SZR and FZR400; rear 3,5", the wheel used in the prototypes) which I now use myself on the street with 110/70 and 130/70 tires just like the prototypes had.
I also had a set of Brembo TZ250 wheels (3,5" and 4,5") which I used for the rain tires.
Originally my racer also had the SZR wheels with which I used SuperCorsas in 110/70 and 150/60. Since the 150 Super corsa is only 143mm wide, it works very well with the 4" rim which is actually too narrow for a 150 tire. Not my opinion, that is what the tire makers say.
And that is BIG reason for going to other wheels. Apart from the SuperCorsa which is very narrow and the Bridgestone BT003 Racing which is available in 140
there are no racing tires the be had to fit the3" and 4" rims.
No intermediates, no rain tires, no slicks, all of which are 120 & 160 or larger.
Simply put, you absolutely need 3.5" front and 5" rear (or 5.5) to mount the available tires. that is what makes fitting the R6 parts so practical and within the frame of setting up a track bike economical. Besides there are plug and play mag wheels to fit the R6 and even carbon fiber wheels...

Or you go the other way and fit the sizes ( roughly 2.75 and 3.5) used in modern 125 GP racing for which there are also tires abundant.
In keeping with that, try to radically reduce the weight. I got my racer down to 122kg with the half faring ready to race.
My street legal Skorpion weighs 152kg gased up and ready to go.

[basser23]

Michael,
Good to know your name...As you can tell from Bill's post,you have hit the mother load of information on the Skorpion!
check out his blog spot and web site..
He is an absolute wealth of info on what works and doesnt on these bikes..
What sort of exhaust system are you going to run? I am looking for a system 2-1 for mine with larger headers,havent found one as yet
although Offtheroad.de has a system for the new 660 that may fit...let us know cause there are some of us that would like to change
this. Tim Barker made 2-2 at one time...
Thanks,
Chip

[morbidelli17]

Exhaust is being fabbed by a guy in Southern California named Mark McDade. He's using the header pipes from a big, ugly, 2-2 that had megaphones leading into aluminum canisters that extended beyond the rear wheel. On aesthetic grounds alone, I couldn't be seen rolling with that. It'll be a 2-1, high-mounted canister on right, and (ahem) very little internal restrictions. I'll post up detailed pics when I get it back.

Thanks for all the advice I've gotten so far. Seems to me that with a short time frame (three weeks until next race weekend), I think I'd be best leaving the motor alone for a few races. It's got the exhaust, the cam, K&N filters and probably a jet kit; that'll have to do for now. I think I'll just get the shock rebuilt, change fork oil, get the new bodywork and seat on, and get a decent chain and sprockets.

I'll hopefully have time to play with the wheels before the next race. I'm not gonna put $1800 wheels on a $1200 motorcycle, but I'm not afraid to cut spacers, and I've got some SV stuff laying around. I kind of have to run Dunlop, and they make a 160 rear they claim fits the stock rim, but if I have to run the stock fromt rim, I'm stuck with either running street rubber or squeezing a 120 onto the front. The guys who race these things here seem to have no problem running the 120 on the stock rim, but I'm not too crazy about the idea.

Thanks again for all the input, and best of luck to all of you this race season.

[Bill Jurgenson]

http://www.Offtheroad.de/
I assume you mean this one:

It will probably fit without too much trouble.
I use one like this which fits almost as if it was made for the bike:


but this one will not fit the XTZ head. The ports of the aircooled head are almost parallel, unlike those of the XTZ. I don't know how strongly the ports of the XT660 are splayed but they are angled as well so it shouldn't be a big problem. You will have to move the radiator out in any event.
The also supply headers which the combine with 2 cans to make a 2 in 2:

The headers will present no problems but the connetcing pipes will need extensive rebending to make them fit a road racer.

I would pester Tim Barker who is in the exhaust business and has experience making racing systems for the Skorpion and the SZR.
I used a Barker 2 in 2 myself.

here is another tip: you can get a very good quick release gas cap from Newton
Get the Aero 400 A48S undrilled. The flange is the exact right size so you need only to transfer the pattern of the MZ ring to the Newton and drill the holes and screw it down. You are rid of the damned lock and it is much lighter and prettier as well.


I added the tank vent long ago because the integral one in the tank was crap in this particular tank.

BTW Tim Barker had a few carbonfiber tanks ($$$$) probably still does.

You can get absolute top quality rear sets from Gilles Tooling for the Skorpion. It is the model AS31GT MZ01. This is my doing, I pestered them and lucked out in that they were interested. Over here, Gilles is sorta the Rolex of rear sets. Almost too nice to ue. All parts available individually (crashes), two different pegs, fixed or rolling shift nose, fully adjustable pegs, adjustable shiftlever travel, etc etc etc.


here with fixed nose and new style peg.
and the other side:

[morbidelli17]

I Bill!

I think the one I have is indeed the Barker system. But the megaphones are old and corroded, and the canisters are mounted much lower than yours. I'm thinking my system will look something like the one on the XT bike.

This is why I join Internet communities when I get a new bike. Thank you all very, very much for the help.

[basser23]

Michael,
Told ya Bill is THE man....
The system on the XT660x is the one I was talking about...interested in the one you settle on...
Tnx
Chip

[morbidelli17]

Spent the day sanding, priming and painting the tank. I'm actually going to use a wrap on it, but when I do that, I always put a matching coat of paint underneath. It too a few minutes to get all the crap out of the tank (which, it turns out, is an Acerbis plastic number; go figure). There was, no lie, a dead fly floating around in there. Some new high-tech octane booster?

Anyway, does anyone know the axle diameters front and rear for the 1995 Skorpion. Mine is water-cooled, unlike some of the critters I've seen here ...

[Bill Jurgenson]

all the original plastic is from Acerbis just as it is for who knows how many other companies.
The tank of my SZR is from Acerbis and so is the tank of a Triumph. The fine quick release tank cap from TWM for a Triumph fits pefectly on my SZR tank.
Lots of "connections" out there, e. g.
Paioli gehoert Brembo;
Marchesini gehoert? - yup Brembo
and Brembo?
Brembo gehoert Yamaha.
btw, Oehlins also belongs to Yamaha.

Showa belongs to Honda.

neither here nor there.
the tank is the best part of the original plastics and really pretty good. Otherwise I would not have kept it.
My friend had an aluminum tank made by Sauer.

As for the Barker pipes, they cannot possibly extended beyond the rear wheel originally simply because nothing may extend beyond the rear wheel by international race regulations.
google european supermono (ESA)
all serious big bore contenders including OVER and Slipstream run some sort of 2 in 2 extend as far back as possible.
Length is necessary for such a low RPM large capacity cylinder to make use of the resonance.
To a certain extent, larger Ø and taper can shorten the caculated length and that makes the 2 in 2 better as the combined section of the two headers and megaphones larger than a reasonable 2 in 1 could be. Dyno tests consistently show that the 2in 2 works better.
So be aware that your cosmetic "improvements" will rob you of power the 2 in 2 was made to get.

BTW, if the cam really is a Hotcams, throw it away - far away.

[morbidelli17]

I have no doubt that the 2-1 will make a bit less power, but it's a trade-off I was willing to make. Not only are aesthetics important, since I'm slow, but I was concerned about ground clearance as well. This is the bike as I bought it. With apologies to Caliphotography, whose thumbnail I copied, these pipes are so long and low (and looked like they were about to shake off) that I just didn't feel comfortable with them on the bike.

Didn't know the Acerbis was standard - that's really interesting. And it's pretty light, at least compared to the SV tank.

Anyone have those axle dimensions?

Take care - M

[samandkimberly]

Almost ANY wheel would be better than the Grimca crap MZ used.

Don't bother to try a Ducati Monster rear as it is not possible to fit and AND get the chain to line up - I tried.

Bummer - I just picked up a pair of early Monster wheels today. 3.5 front/4.5 rear.

Sam