MZ/MuZ Riders

Hey guys, I did a search and found some helpful threads yet I'm still fighting some demons here.

A little background. Bought a '95 Skorp in non running order. Factory dual carbs in a box, TM42 (HS/HSR as Harley calls it) installed but sat for two years with fuel in it. Also had a stock and Dale Walker Holeshot pipe. Owner used to swap them back and forth but couldn't remember what jets were in it due to not being ridden in 2+ years.

So I tear this thing down, get a rebuild kit with new o-rings, needle valve/seat etc and toss it back together with Holeshot pipe (that's what I'd like to run). I took note of internals as follows:
140 main
35 pilot
idle screw 1.5 out
#96 needle (one richer than stock) on second position from top (second leanest)
Results: Lots of stumbling up to 1/4 throttle especially in low RPM range. Very rich idle-1/4. At full throttle it is hard to get north of around 5-6k. 1/4-3/4 throttle feels OK but not like it should.

After some research on here I bump the main to 147.5 and drop pilot to 25.
Results: Idle up to 1/4 seem good, maybe just some fine tuning left. Still trouble getting north of 5k in 4th and 5th gears. 1st now starts to pull wheel off the ground, but won't quite stand on end. Bumping main again to 150 didn't have much effect either. I realize some of my efforts with the main might be a waste if the needle and position are too far off. Should I track down a standard #97 needle before going further? I'm wondering if it is dumping so much fuel that it is just too loaded up by the time the main comes into play, though plug only looks slightly rich.

Can anyone recommend a baseline jetting/needle for a Skorp with Holeshot/single 42 combo? I'm trying to avoid buying $40 worth of jets and an hour each evening tuning when I can be riding!

P.S.- this is my first streetbike and I am loving it (minus this little issue)!

ETA- I had a Raptor 660 a few years back, essentially the same engine, so I have a rough idea of what these engines can do. Right now I am nowhere near there.

I put the same carb on my Baggie, and you can find some posts here on what I did. My intake manifold is around 5" long, due to the framing of the Baggie, but I don't think it would affect the proper jetting. I spent a while jetting it, and looking at my notes this is what I ended up with:
Needle- 96 in the top slot.
Main- 147.5
Pilot- 30
Screw- 1-1/4 of a turn.
There is a big difference in turning the screw a small amount. My notes say with a 27.5 pilot I was at 7/8 turn.
You can download the Mikuni tuning manual, which says to mark your throttle in 1/4 turn increments with a piece of tape. That helped in figuring out what was wrong, as with the wrong jetting it will run good at some positions but not others.

Alright, so I now have the -96 needle in the top (leanest) position and took a long shot by throwing a 152.5 main in there. Seems like she is really waking up. Power delivery is much smoother and it PULLS hard at wide open which it never did before.

I have a -97 needle on the way that I am going to try running at the second leanest position as I have read that it where most people tend to settle in. I'll give it a shot as I can always go back to -96 if the results aren't positive. I am also going to switch the pilot to a 27.5 as I am running the 25 now at 7/8 turns to keep it from decel backfiring through the carb, it needs a tad more fuel. As for the main, I've tried the Mikuni "roll off" method and it exhibits no signs of a lean of rich condition so I may be spot on @ 152.5. Just for kicks I will pick up a 155 main and I already have a 150. I will run them back to back, changing on the side of the road, to see if either make a positive change in either direction.

Quick question though, the bike still does not like to pull smoothly if you are below about 4k RPM, especially in 3rd or above. Is this a normal characteristic of this engine or possibly the exhaust that is on it (Holeshot Comp)? I've had this engine before, but there are no tachs on quads so I guess I just never realized it.

I dont know about the single carb TM42,but on the dual carb version,stock,(jet kit) mine pulls very smoothly from 3k on up,so you are getiing close!
Which manifold do you have? There was a guy...morbidelli17, on here that had a FCR41 on a rhino manifold that worked very well for his race bike.....

The manifold looks to be the one sold by BikeWorx back in the day. Complete kit with manifold, carb and K&N filter.

As far as accel from 3k in higher gears, I may be chasing something that can't/won't be fixed with jetting. It may just be a characteristic of the pipe/carb combo. I'm OK with it if I know that is where the powerband is meant to be on this setup, but if it isn't correct I need to get it straightened out.

You may be correct...just dont grab a handful of throttle at once,roll on shud give smooth accel...

Mine pulls strong right off of idle, strong enough to stand up in the first two gears. I spent hours on the jetting, as I could get it running good, but the next time I rode it, it would be rough at lower throttle levels. I am sure you know that the main jet only does anything at 3/4's or so of throttle. Most of my tinkering was with the pilot jet and needle/clip position. My carb is around 5" from the head, so it may have a little difference than yours, but these motors do pull good from idle. It is very similar to the Raptor, which has to have great bottom end to be a good 4 wheeler. I put in a stage one cam and 12/1 piston after I jetted it, and it didn't require any changing. My exhaust is a straight through design, pretty loud with no back pressure.

Harold- Are you running the single carb conversion? If so do you by chance remember jetting/needle positions you ended up with?

My settings are in a post above.