MZ/MuZ Riders

Hello fellow bro's!
my name is Vince i live in FLorida U.S.A.
just bought a 2002 skorpion touring 660cc.

i want to circuit race in a single cylinder class here in southern united states, can anyone help me with modifications?
this is a 660cc single water cooled,dry oil sump (yamaha raptor quad ATV motor?) yes???

Can i use off road titanium fmf exhaust and silencer for the quads will it fit the heads>
1) what is the best exhaust for max torque/horse power?
2) induction 2-carbs or g with mikuni flat slide big single??
3) obviously strip it all down for weight savings but is there a place that sells a small fairing or does anyone have an upper fairing for sale?

what is largest rear radial tire i can use without chain interferance?

thanks you
VInce AKA poppanitrous

audipost@gmail.com

Its not a Raptor engine it's a XTZ Tenere, SZR engine even though most parts are interchangeable, especially tuning parts such as cam piston or carb setups.

Dont worry too much about the exhaust unless you are looking for that last ounce of power, any slip on will do just fine as long as it is less restrictive than the stock one. At any rate you would want to put the bike on dyno if you are going racing and that will make it possible to get the best out of any setup that you have.

Carbs are essential since the stock carb and an half is a pain to set up, not to mention the limited supply of jets avalianble. That being said it is possible to reach 60 Bhp with the stock carbs and a lot of engine work and many, many hours on the dyno...
Can't say which is best, one or two carb setup, go for what fits your budget it will be a big improvement regardless. My guess is that a 2 carb mikuni setup is easier to install as it is essentially a bolt on job.

You will need at least "hot" cam/valvesprings and a head job if you want to see any significant power increase, modified CDI and a big bore comp piston would definatley be on my shopping list as well.

Dont forget to upgrade the suspension/brakes, power and speed without control can be a bad thing you know...

For body work,go to Beasley fiberglass, they make all the stuff you need,from fairings to seats,fenders....
As far as exhaust,M4,Holeshot, come to mind,there are builders of
dual systems such as Barkers.
Good luckl
Chip

i am going to race AHRMA supermono 2 (660cc is allowed in supersport trim) i canto go with aftermarket carbs.

i have cash in hand to purchase if anyone can sell me or find:

2 fresh "stock" carbs

aftermarket rear race shock adj.

used race plastics.

a link to a place that sells
racing compund brakes and lightened rotors

audipost@gmail.com

thanks
Vince

Searching for SZR, XTZ (Tenere) or MuZ/MZ carbs on e-bay (worldwide) is your best bet to find carbs.

Jets are not in abundance, especially for teh right hand side CV carb, drilling jest as per Dynojet will be a must if you are going to tune the stock carbs.

Yamaha single specialist http://www.kedo.com lists the avaliable jet sizes for the stock carbs. Adding the mod as per Competitive solutions kit should help with throttle response. http://www.tunebike.de/English/Carburet ... retor.html they also supply drill bits for the jets.

You cant really go racing without removing or raising the rev limiter, modifying the stock CDI (7200 rpm limit stock) as per http://www.tunebike.de/English/Mechanis ... ition.html (there are others that supply the same service as well) or installing a Sparker programmable CDI http://www.ignitech.cz/english/aindex.htm

I will allow myself a couple of comments.
1) do not waste money on modifiying the DENSO ignition box (it is NOT a CDI). for only sligtly more you can get an Ignitech Sparker TCIP4 which is fully programmable and plug and play for the XTZ/SRX engine. I will be glad to help if needed. I use nothing else in the meantime and have supply 30 of these to SZR and Skorpion riders.
The issue with the DENSO box is not so much the rev limiter. The spark advance is way too much for anything approaching higher compression. It goes all the way up to 37º. My race engine went only as far as 28º. The extreme advance is very bad for the smallend conrod bearing and is in my opinion the main reason why these tend to go bad in the big Yahaha single.
2) not any exhaust can will do. Actually the stock Lenhart & Wagner can is very good at top end. On the dynomter it was only 1hp down against an open BOS titanium can when we tested my 59hp street engine. The BSM can was 4hp down! Its major handicap is its weight. It is built like a brick shithouse and should normally outlast the bike easily. I have no experience with the Holshot cans but they should be OK. You should look for a completely different exhaust system since the headers are much too restrictive. Changing only the can will basically only get more noise, but not more performance.
Call Tim Barker at Barker Exhausts. He raced a SZR and made several exhaust for skorpions as well.

3) do NOT lighten the starter freewheel clutch like it is shown in the pictures at tunbike or you will definitely get a broken freewheel like this:

Mathias didn't believe me and that is what he got.
I know from personal experience that that is exactly what you get. That is why I do it this way;


4) replace the drive gear on the crank for the balancer with a solid one from Slipstream tuning. Or, if you can take it, remove the balancer entirely.

5) Stay away from HotCams cams. The only good cams available for the 5 valve are Megacycle. If you don't want to take my word for it, ask TIm when you call him. If you do go for a hotter cam, definitely use the KibbleWhite Spring set with titanium retainers made for the XTZ engine. These are very good and not too expensive. The slightly more expensive alternative is RD Springs. I am running their new beehive springs in my 4 valve "bastard" engine.


6) the Stock valves and guides cannot be beaten and larger valves are no help; they are big enuf. The stock conrod is more than good enuf until you get around 75hp.

Bill Jurgenson wrote:I will allow myself a couple of comments.

2) not any exhaust can will do. Actually the stock Lenhart & Wagner can is very good at top end. On the dynomter it was only 1hp down against an open BOS titanium can when we tested my 59hp street engine. The BSM can was 4hp down! Its major handicap is its weight. It is built like a brick shithouse and should normally outlast the bike easily. I have no experience with the Holshot cans but they should be OK. You should look for a completely different exhaust system since the headers are much too restrictive. Changing only the can will basically only get more noise, but not more performance.
Call Tim Barker at Barker Exhausts. He raced a SZR and made several exhaust for skorpions as well.

Just out of curiosity Bill, did you dial in the carbs for each exhaust when you did the power comparison between the diffrent cans?

I have dynoed my bike at app 60hp with the stock carbs dialled in for a no name ZX-9 slip on (very loud indeed), swapping to the stock exhaust would make the bike allmost a non runner above 1/2 throttle.
Currently I run a BSM Vamire (dB plug removed) and it runs just about the same as with the ZX-9 exhaust, there is a noticeable top end power loss when I put the dB plug in.

I run mine with stock carbs and a renegade with Db killer and haven't noticed any difference in terms of power loss but then I haven't dynoed it either. But when I removed the Db killer the power seriously drained away, the noise was nice but the DbK went back in straight away