Pilot jet settings??

[Fil]

Hi guys,

How far from lightly seated should the pilot jet (mixture) be set?

The manual suggests 2.5 turns out, but my bike was set at about 5.5 turns.

As you unscrew the pilot jet, does this enrich the mixture or make it more lean?

My bike is standard (until my Dynojet kit arrives) apart from a BSM Future road legal exhaust and a drilled airbox.

[DAVID THOMPSON]

out makes it rich
my rt125 is fine at 2 turns
my saxon tour has a piece of **** bing and it will get replaced soon
some of the fellows with the 660 motors say they pop and bang
and complain a lot if too lean
try 2.5 but you will wind up richer than that i think
but 5 may let the adjustment screw fall out
read this past post
http://www.mzriders.com/viewtopic.php?t=918

so you dont have to hunt for carb parts

[keithcross]

There are reference to taking this screw out to 7½ turns without problems. Saying that my carb has never been adjusted from new and I have no problems with the same mods as fil. When the bike was put on teh dyno the mixture was OK, maybe a little rich, but OK. There were holes in the power curve that a dynojet curve should sort out though.
I have posted copies of the dyno reading for my bike on my album. See
http://www.mzriders.com/album_personal.php

Keith

[cat]

Hi guys,

How far from lightly seated should the pilot jet (mixture) be set?

The manual suggests 2.5 turns out, but my bike was set at about 5.5 turns.

As you unscrew the pilot jet, does this enrich the mixture or make it more lean?

My bike is standard (until my Dynojet kit arrives) apart from a BSM Future road legal exhaust and a drilled airbox.

It's not the pilot jet, it's...I keep forgetting what they're called - something that CV carbs have, that works the opposite to air screws (in terms of in/out rich/lean).

Keith, you don't think this would help with the dips in the power curve? Is it more the midrange, the needle?
(I still think it's too much (the Dynojet kit) to pay for a Ti needle and a couple of drills.)

[keithcross]

The dyno operator looked at teh curve and the Dynojet catalouge and said that the needle in the kit should get rid of the holes. £140 fitted and checked/adjusted on teh dyno.

Keith

[cat]

The dyno operator looked at teh curve and the Dynojet catalouge and said that the needle in the kit should get rid of the holes. £140 fitted and checked/adjusted on teh dyno.
Keith

People report good results with the tunebike.de kit, but it does not have a needle - only that collar thing.

[keithcross]

Cat

People do report good things about the tunebike kit, however I tend to listen to the operator of the dyno I use. He has a great deal of knoweldge on tuning bikes. The company prepare track day bikes and even modified my sons 1100 Goldwing to produce lower BHP figures without resorting to buying a kit.
It was a shame, but he had to have the power reduced due to having a restricted license. Went in with 73 RWBHP, came out with 31 RWBHP. Still managed 100mph with a long run up though

Keith

[cat]

Cat

People do report good things about the tunebike kit, however I tend to listen to the operator of the dyno I use. He has a great deal of knoweldge on tuning bikes. The company prepare track day bikes and even modified my sons 1100 Goldwing to produce lower BHP figures without resorting to buying a kit.
It was a shame, but he had to have the power reduced due to having a restricted license. Went in with 73 RWBHP, came out with 31 RWBHP. Still managed 100mph with a long run up though

Keith

Well, generally, carb kits (Dynojet and others - like JD) have needles; custom needles to fine-tune for the application, instead of the generic needle, 'best fit', from Keihin or Mikuni. I'm guessing that tunebike.de use that collar/sleeve thing to try to get the same effect as a different needle.
So it does look like a case of 'you get what you pay for' -- getting custom needles made is obviously expensive, especially if it's Ti.

[Fil]

It's not the pilot jet, it's...I keep forgetting what they're called - something that CV carbs have, that works the opposite to air screws (in terms of in/out rich/lean).

Keith, you don't think this would help with the dips in the power curve? Is it more the midrange, the needle?
(I still think it's too much (the Dynojet kit) to pay for a Ti needle and a couple of drills.)

Hmmm, not sure what you mean cat - the only screw on the carb I'm aware of that can alter the mixture is the one I believe is called the 'pilot jet', and this sits in the primary carb. I think the only way you can alter the mixture in the secondary (CV) carb is by changing the jet/needle.

Carbs are not something I claim to be any kind of expert in, so I hope that someone with more knowledge can clarify this for us!

I'll let you guys know how I get on with the Dynojet kit once it arrives (it's in the process of being made in the States as they have no stock in the UK...).
I can't wait to remove and refit my carbs for the third time ...

[keithcross]

The pilot jet screw, which we are talking about (I think) is located on teh primary carb (left hand slide type carb). It can be found towards teh front of the carb, and is shrouded in part. It can be seen quite clearly if you look at the carbs from underneath.

Keith

[cat]

Hmmm, not sure what you mean cat - the only screw on the carb I'm aware of that can alter the mixture is the one I believe is called the 'pilot jet', and this sits in the primary carb. I think the only way you can alter the mixture in the secondary (CV) carb is by changing the jet/needle.

Carbs are not something I claim to be any kind of expert in, so I hope that someone with more knowledge can clarify this for us!

I'll let you guys know how I get on with the Dynojet kit once it arrives (it's in the process of being made in the States as they have no stock in the UK...).
I can't wait to remove and refit my carbs for the third time ...

ok. I see Yamaha calls it the "pilot screw".
Not the pilot jet, that is inside, inaccessible from the outside. It is situated just to the left of the pilot screw. The pilot jet itself, being a jet, is not adjustable. The pilot screw probably adjusts the amount of air passing across the pilot jet and so the amount of fuel passing through the pilot jet. (I'm not sure, not clear about that. I'll look up something about it later today. I do know it's not called an air screw because it does not work the way an air screw does on a "normal" carb, where turning the air screw out opens an air passage in the idle/off-idle circuit. Although Yamaha calls it a pilot screw, what I was referring to was some generic term that I'd come across recently - which I'll try to find.)

I think the only way you can alter the mixture in the secondary (CV) carb is by changing the jet/needle.

The parts diagram for the Yamaha XT600 shows what looks like the same carbs as ours. It has a "pull-knob" choke plunger instead of cable-operated. The secondary carb in the Yamaha diagram has a normal removable main jet but the diagram of the carb on the MZ shows an odd-looking thing that has to be drilled - although it is obviously removable.

The XT600 parts diagram is more useful than the diagrams of the MZ carbs available on the www, which have German terms that machine translators don't recognise, and incomplete parts lists.

[cat]

Although Yamaha calls it a pilot screw, what I was referring to was some generic term that I'd come across recently - which I'll try to find.)

"Fuel screw", I think it was, but I've gotten sidetracked into reading all sorts of stuff about CV carbs, especially about cutting the spring - or not, the drawbacks. (This is another advantage of the Dynojet kit over the tunebike.de kit - you get a lighter spring.) "Pilot screw" seems like a better name than "fuel screw", because it does have a similar effect to changing the pilot jet size.

I found a good basic article on CV carbs, that won't give you a pain in the brain:
http://members.aol.com/roundr1/CVK40.html

Fil, are you getting the Dynojet kit (E9204.001 - MZ Skorpion 1995-97, I suppose?) from TTS, or where? If you say it's been made up in the US, then I guess not even Dynojet themselves have stock. Given that I already have to do the shipping, I should probably get one direct from Dynojet, if that's possible. It seems like it's worthwhile even with just a modified airbox. ...Although...

I can't wait to remove and refit my carbs for the third time ...