MZ 125 UPGRADE GUIDE TO 150CC KIT

[jbthumper]

my question on the 28mm carb too...because our motos are on high compression pistons...they can't really burn too much petrol,right?it was design for high power n fuel economy,right??
right??right??right??

I take it all back!!!(feels funny when quoting my own post)
Just fitted my bike w/ a 28mm flat slide today...but my carb is 2nd handed and pretty much old(has no air mixture screw)...
not tested the fuel consumption yet....but accelleration has been better...u can hear a louder air suction sound from the air box when idle compared to standart carb....still need some adjustments though....

ptong...
for me...my high air flow filter WAS our normal filter...i tore the fiber by cutting the sides using a cutter...measure and cut the fiber according to filter size...paste by using sillicon on the edges...put multiple layer if you want to filter better...BUT DO NOT take my word for it...i'm NOT going to be responsible for any machanical failure resulting from this modification

[jbthumper]

I NEED HELP!!

i tried smaller main jet(90) but too lean,can't even do a half throttle...(due to high air in flow)now i have a 140 main jet and that problem went away...BUT i can't get a stable idle with the carb...i'm running on 15 pilot jet(is it too small??)...needle circlip is on the third...

i checked the spark plug...it appears black!!but not wet(no gas resedue)....
is it because of not enough fire power??
do i need to change to a hotter plug??(eg CR7)
i pray you,please help...i've been on it for 2 days now


I thank all in advance.

[micheleen]

Is this with the 28mm carb fitted ? What make and model of carb is it ?

Black plug is definitely too rich, have you done a full throttle under load check? You really need to check plug colour at full throttle, half throttle then idle and adjust jetting/needle for each position in turn to set the carb up properly.
Shout if you need more info on this.

Alternately find a bike shop with a dyno/exhaust gas analyser though this would probably cost a bit

Cheers, Mike

[jbthumper]

Is this with the 28mm carb fitted ? What make and model of carb is it ?

it's mikuni... almost identicle to the one offered for the carb upgrade kit(28mm)...

i've also tried each needle position...they don't help...(sigh)

Alternately find a bike shop with a dyno/exhaust gas analyser though this would probably cost a bit

I'm on a tight budget


FYI:i'm not using the standart muffler

[micheleen]

Is there a model no. on it anywhere ? I believe the TM series are flatslides and the VM's (like the original carb) are roundslides.
Is it like this one ? Page 2 has an exploded (:shock: not literally) view of one.

Cheers, Mike

[jbthumper]

it's TM flat slide...as stated in my post above

hey!very informative site you got there

[micheleen]

hey!very informative site you got there

It's one I found a while back when looking tuning info

OK, first thing I suggest is that you carefully check all over the carb for adjustment screws, I haven't come across any carb so far which doesn't have some sort of air adjustment. There'll only be two adjustment screws, one for air and one for idling speed so you should easily tell them apart if you twiddle them while the engine is running (note what they were set to first though
).

Not that it affects idling at all, but I would have thought that a 140 main jet is too big even with the 28mm carb, a full throttle test and plug check would show that though.

Hope this helps , Mike

PS If there DEFINITELY isn't an air adjustment screw we can fall back on Plan B

[jbthumper]

nope,DEFINITELY no air adjustment screw....i've tried the 140 main jet with 15 pilot jet...in idle it gives a bit of a problem(pops after 1 minute) as for riding with load....i've tried....A OK...but feels a bit lean on top,though...

I call for Plan B

[micheleen]

Plan B it is then
Take out plug & clean it up. Replace then start up and let bike idle for a while, you only want to be running on pilot jet so don'y rev it or use the choke.
Switch off engine and check plug colour, if it's black try a smaller pilot jet, if it's light grey try a larger pilot jet, yellowish grey-brown is the colour you want . Then adjust idle speed to suit.

Cheers, Mike

[jbthumper]

hmm...is there a pilot jet that's smaller than 15?? because i even had a tough time finding the size 15 one...(but i've heard of size 12,though)

OR

can i change the air jet??because i haven't checked it yet...i'll do it today.

[micheleen]

Yes if the problem is too rich at idle then you could increase the air jet size instead of reducting the pilot jet.

Cheers, Mike

[jbthumper]

will give it a try

[ptong]

Still wondering if the 28 mm carb will make any difference except to potentially provide a great deal of tuning issues for no performance benefit. I mean unless you have wider ports etc it shouldnt make any differenc eto performance should it?

Also thanks Dave for the reply on the costing issues, that makes sense.
Still think the decals look cheezy though.

[micheleen]

I think the 28mm carb would help a bit, especially if you have a less restictive exhaust on. That does then mean, as you say, that the head is the next bit to work on

Cheers, Mike

[jbthumper]

i think the tuning issue only applies for me (just my luck)
i'm using an older version of the TM. That's why it's so damn hard to tune it....

but doing head mods...that, i have second thoughts about...