New member with a trackday-skorpion-tour

[basser23]

Ok Jan...there are 2 requests for those rear sets...
by the way...love those fairing stays...look very strong

Shiny side up!
Chip

[billr]

I want to think that most MZ Skorpion guys are Yamaha fans too, since it uses that beautiful 660 engine. As Bill knows, I bought the MZ
racebike for my son. I found this for myself this week, so the next time you see me in Nashville Bill, I'll be on this sweet little 400...

Very, very nice. That'll be a fun ride.
Bill R

[Bill Jurgenson]

Let me add a few points; I do have little bit of experience. no special order.

Many of us use LiFePo akkus in their street bikes (as do I) with no problems at all, on the contrary.
You may or may not have problems with the rectifier (Regler) but those will be problems with that rectifier and not the fault of the battery. The rectifier in the Skorpion and SZR is notorious for crapping out and being generally undependable. Some people I know never go any distance without a reserve unit in the tank bag. I replaced the rectifier in my persent Skorpion three times, the last time with one from Ignitech which is much better. I have supplied two different riders in the last 8 weeks with new rectifiers because their rectifiers had shot the battery dead. And I replaced the rectifier in my blue bike once as well.

When I was racing, I used my own CNC milled rearsets

here still with the lever bought from Metisse. You also see the PVL magneto I initially used, once I had gotten rid of the starter crap and the battery, too, since it is a magneto.
A bit later I got wise and reversed the shift pattern (I use first gear up only now), using a simple old MZ ET175 lever facing backwards:

This was the last version of the bike before I retired it.
You see that the mag is gone, replaced by a SilentHektik constant loss battery igniton. You can also just see the Mecdine speedshifter connected to the lever by that vertical Ti rod. Wheels are Marvic mags, slicks are Bridgestone, 120/70 and 165/55.
This bike weighed as you see it 125kg ready to race with 5ltr in the tank. The previous version without the lower fairing and without a battery was 122.
My present green road bike and my blue one I sold both weighed around 150kg in street registered form, the present green one weighs 148 with full tank.

back to the rearsets, once I jettisoned the Metisse parts (too expensive and difficult to get individually but when i first bought them, the company was just around the corner), I used MuZ Replica pegs and the brake lever from the SZR.
I used this setup on the street as well since we had milled several sets of brackets:

this one is welded. We used all the sets due to breakage in spills on the track. This last set is still in use on a friend's Skorpion.
In the meantime, I use Gilles AS31GT-MZ01 rearsets:

which are obviously adjustable and made for the Skorpion. A number of Skorpion riders have bought these. All the parts can be had separately (crashes), they are light and beautifully made. Having made two different models of rearsets myself, I would not have made them myself, had the Gilles been available. Mine were definitely not cheaper(selfemployed, my time costs money) and nowhere near as good.
my first set:

These later went to Chris Hunsicker in Phili. There were better as road pegs but also heavier than the second design.

I mentioned the weight.
150 kg is very conservative. It is rather easy to get a Skorpion down to 150kg in street going trim. there is no reason a racer should weigh that much. Throw out the starter and freewheel and the magnets inside the flywheel. You are running constant loss anyway. Get an Ignitech Sparker programmable ignition. When you put in another cam, throw out the decompression unit. By all means replace the gear for the balancer shaft on the crankshaft with a solid one or you will be looking for trouble in short order. Change the timing chain tensioner to manual.

exhausts.
Over here in Europe, the Holeshot is a no go. There are very few tracks where that kind of noise is allowed in training and only a few more for racing save professional stuff like MotoGP.
Been there, done it and I retired the bike two years ago. It has gotten worse. Mine was LOUD! Ask Chris.
I am not sure how ESA manages in Holland. Here in Germany they run only at Oschersleben and that is one of the two tracks left where such DB levels are possible.
Sachsenring is 88db. You can't even ride a stock Ducati there and a Suzi without the airbox restrictor is too loud, too. Hockenheim is offically 98, Assen is I think 92.
Any of the straight thrus save a SR Racing has at least 106 out of the box, the Holeshot a lot more. I measured several. My bike had 128 but then the Bimota I ride is out of range = way over 130. Bimotas seem to be exempt from any restrictions...
As it is, the problem is less the can than the system. It is imperative to make (have made), or get second hand a system with large headers such as the Remus Cup system for the Skorpion. These had 32mm inside diameter instead of the original 28 = 32 outside. That is sufficient if you are not looking into all-out tuning and engine life measured in hours. A 2-2 system is potentially better because the combined volume of the two cans can be much larger than a single can could possibly be and each still be rather small.
The system I run on my SZR is very good and I am one of the quietest at meetings

but 1) the Termignoni system is no longer made and scarcer than hen's teeth and, 2) the SR Racing can is big and, 3) it wouldn't fit the Skorpion anyway. What I have on my Skorpion won't fit, either:

there is a similar system with large headers for the XT660:
http://www.off-the-road.de/XT-660/Exhausts/OTR-SR-2in1-system-e-marked.html
but like what I have, should be adaptable to the Skorpion without much trouble.
These guys also have a pair of larger headers for the XT660 engine which will fit the Skorpion as they are:
http://www.off-the-road.de/XT-660/Exhausts/OTR-Racing-Headpipe-XT-660-2004-2006.html
Then two separate cans.

[wrecckah]

hi Bill,

thanks for the explanations

i've read your blog and many many posts with much interest. One day, i would like to own an Mz which is as sorted as your bikes.

As it stands now, my budget allows very little...it is a cheapskate trackday-funbike, and for now, it has to stay one

- the wheels will be swapped for lighter items for sure, that's step one. i've got some friends in the supermono-world, and they are already looking around for me
- i need to change the exhaust because of ground clearance, that's step two. I love the stealth sound of the original can, and i would not like to make the bike any louder, but i can clearly see the potential weight-gain...so it's a no-brainer. gotta throw the big can off. I see that you pointed to exhaust systems for later 4-valve XT660 engines, do these headers fit the 5-valve head? If so, i might have more options, because i'm an aftermarket motorcycle parts dealer, and i could get some brands very cheap.
- the gilles rearsets are wonderful, and i could get them for reasonable money as i am a dealer of gilles too, but it is still too much for this project now...my own rearsets will cost me 30 EUR i hope.
- then some carb-work (cheapo carbwork), some more weightloss, and job done for next season.

If all goes well, i might consider more engine mods (cam, bigbore, ignition box, etc...)

One question: did you run aircooling on your trackday bike? (air/oilcooling, with small oilcooler) ? Is that enough for track use? If so, the junking of the radiator and overflow could mean a big weight-gain.

cheers, and thanks,
Jan
PS fantastic looking bikes you got.
PS there's another skorpion for sale near me, for next to nothing..i might pick it up for road-use the bug has hit me

[basser23]

Jan,
on Bill's air cooled bike...way many mods and head change too I think....think he built it using an xt600 barrel and soforth....
30 E for your reasets? I'll take a pair:)
Chip

[wrecckah]

Hi Chip,

so is it then possible or not to ride on track without watercooling with a semi stock engine?

30 EUR is what i paid for the blocks of aluminium let's see how they will turn out, more info in a couple of weeks.

cheers,
jan

[basser23]

Jan,
I wouldn't ride a stock motor without a radiator at all.....it would probably seize or blow the head.....
Chip

[wrecckah]

that's exactly what i do not understand

an engine gets hot, and needs cooling, check. i get that.

a modified engine with more performance gets hotter, and needs more cooling...how come that highly modified engine only needs that tiny oilcooler?
that barrel has got more air-cooling surface? that's enough?

thanks for explaning to this numpty
cheers
jan

[basser23]

Jan,
As i understand,the XT600 was designed as an air cooled motor with an oil cooler...much more fin area than our XTZ's..
plus the water jacket is not there so there is no insulation to the air flowing over the fins....look at a Yamaha 450 motocross bike.
Water cooling no fins......some are used over here in a F450 road race class...that uses a standard motocross frame,the rest is pure
road race....about 220 pounds wet with 55-60 hp......very interesting....
Bill is 100% spot on regarding the exhaust....duals flow more,so I'd ditch the stock headers and pick up on some of the headers from
Off thre Road and add cans....

Chip

[Bill Jurgenson]

So many questions, comments.

first yes, the high-up XT660 headers do fit the the XTZ head. They praobably also fits past the frame just like the XT system on my Skorpion does.
Maybe a bit of gentle force is required.
Of course, the two separate headers would also fit, if one wants to make a 2-2 which is what I would do for a racer.
I have two wheels from a RGV here which can be made to fit. They don't belong to me, but I don't think the owner is asking much for them. They are light.
If you are at all interested, I'll drag them out and check on the sizes (3,5" front and 5" rear I think) and find out how much he is thinking. He bought them for his Skorpion racer but decided against using them. He does have my Marvic mag wheels and at least two sets of Brembo wheels.

To my engines
I raced the 5-valve water-cooled engine, That should be obvious from the photos on my site and even those posted here. I use the standard Skorpion radiator without a thermostat and covered the radiator as necessary to get the engine warm enough. No oil cooler. I never had trouble with too hot, more likely with too cold. You don't need the over flow regardless whether street or race. Throw out the fans, too, of course. And you will not need an oil cooler, either. The bikes running oil-in-frame do need an oilcooler because there isn't much oil in the frame and the steel tubing is also not a good cooler. The OEM plastic oil tank is really pretty bad, but it will do and there are sure enough Skorpions out there racing that use it. I used it, too. You change the oil very frequently with a race engine anyway. and you also make sure it is warm befor really revving it.

People do race the aircooled engine, things like Andy Duncan's special which he has sold or those OVER SRXs (drool!!!!) and I imagine they are relatively stable thermically. The Bimota is air-cooled and I have no problems with that at all, not even with the rear cylinder.
I know from my engines (this year's and last) that the problem is getting the oil hot enuf and not that the oil is too hot. I stupidly put on an oil cooler last year and regretted it. The oil temperature never really got even as high as the oil needs as I found out the hard way. Let along too high. And too cold is for modern oils at least as bad as too hot.
This year I have no oil cooler but I do have my new own-design oiltank (extensively discussed on my blog) and the oil temeprature is just right, even in this year's very hot summer. Stop and go city riding did no harm at all.
As for my various parts, last year's engine was built up from a TT cylinder, bored to 98mm with a Wiseco flat top and TT head with modified ports and a Megacycle 266/2. Bottom end was the same as this year's and the year before last: always the XTZ crankcase with my one-off welded crank with Carillo and with my own one-off timing gears and rollerchain. This year is a XT600E cylinder milled out to take a XTZ 100mm barrel bored to 101 with a Wiseco flat top and a late SRX head with the wider bolting pattern to match the cylinder with a Megacycle 266/4 and the same RD beehive springs as last year. Same TM40-6 flatslide, too. But that has all been covered on my blog.
.
As for the weight issue, the air-cooled engine is at least as heavy as the water-cooled one.

First place to save weight is to get out the angle grinder and hacksaw and go after that seat frame. there is quite a bit that is totally unnecessary, even for street legal.
And of course the wheels are rediculous but you are planning to change them anyway.

30€ for the aluminum for the rearset brackets. OK. What about the pegs and the levers? What about the worktime involved?
Maybe you don't figure your time. I can't do it that way, cause my time costs me money and I can earn something in that time, probably more than I save by doing something like making rearsets. Where there was absolutely nothing to be had, it was different. And with my timing gears or welded crank it is also different; they can't be bought for any amount of money.
Or fitting wheels to the bike. Of course I can farm the work out but that will be just as expensive as if I do it - or else it is not up to my expectations. But I would never make my own rearsets when I can but the best there are and specifically for the Skorpion for reasonable price. Same for the Gilles GP light clipons.


keep me posted.