o2 sensor

[hb1rd]

I was thinking my primary side of my carb is lean and my secondary is rich .I want to put an o2 sensor to see if this is true.
I have a couple of questions before I can do this .Is the stock exhaust all stainless and has anyone ever tried this for jetting set up

[BlueRidgePanther]

Stock exhaust is entirely stainless. I use an o2 sniffer on all my bikes when I'm setting them up after changing something in the engine. Since I've never really done anything to my MZ's engine aside from a pipe swap, I can't help you much on this one.

[Bill Jurgenson]

you are thinking right.
Left is on the lean side.
This in particular because of the mandatory CO2 tests at vehicle inspection every two years.
The right side is very rich, the main reason why the motor guzzles some much gas.

Standard jets are 120 left and 160!! right.

just for comparison: a Mikuni TM34-b65 set up for a stock motor will have 115 left and 120 right.
I am running 125 both sides in that carb on my green bike but that is a pretty heavily tuned engine.
The OEM L&W exhaust, especially the smaller headers, can't manage more.
Despite going like a bat out of hell, shifting into 4th at 150kph and fifth at 170kph, I am getting 5,5Ltr/100km which, if I didn't goof up, should be about 44mpg.
Not all that good in absolute terms but pretty damn good for this engine.
Running the TM42 with the BikeWorx kit on my other tuned engine, I had a 140 main jet street and 145 track.
The 80+hp race engine using a TM38-B65 had 140 both sides.
The 2004 Raptor 660 (same engine, same hp rating) which uses a single barrel 40mm CV carb has a 140 main jet.
The KTM LC4 has that very same carb, too.
You can get some idea about how much too big the right jet is. THe right jet alone is larger that anything normally usable in a single carb like the TM42.

Under normal usage, the jet size right side is not all that important. In any slider carb, the needle determines the actual size in use until it is out of the needle jet. This being a CV carb, this doesn't happen until rather late or only under heavy-handed mindless twisting in an RPM range high enuf for the slider to get pulled up. This happens from about 4000rpm upwards which is why this carb cannot possibly get "good" milage.

Here some various carb sizes for comparison:

Picture 1.jpg (45.91 KiB) Viewed 1399 times

Keep in mind that the Bikeworx kit delivers a plus of 5hp desite being much smaller in area than the stock carb. This carb setup is used in racing, too. I used it myself and I am pretty sure that Chris Hunsicker is using it.
The TM34B65 is also much smaller than the stock carb, despite delivering much better performnce and much better mileage.
A TM32B65 would be ideal if such a thing was readily available. There actually is a dual Keihin CR 32 (round slide) for the SRX which is ideal but doesn't fit under the tank of the Skorpion without serious modifications.
go figure...