bringing a 125 SM back from a coma

[djsbriscoe]

Hi,
Can you not loosen the carb clips on both sides and then operate the throttle/move the handlebars?
This will allow the carb to rotate and ease any tightness in the way the cable is routed. This is what I do on my RT125 when I remove/replace the carb.
It may help a little.

David.

[OSPRNG]

I am sure i have read somewhere that there was a factory modification of the addition of a zip tie under the tank.
I will see if i can find that as well.

Jamie

i did some more browsing and i came across this from mxsteven http://www.bikepics.com/pictures/801899/
this is exactly how i anticipated securing the throttle cable along the frame. so will try that this weekend and hopefully it works.

[OSPRNG]

this cable is driving me nuts.

i have tried securing it along the frame with a zip tie, then two zipties.
with the tank off i confirmed that the black hose does not move at all in this way.
put the tank back on and fired it up, all the way to the left drops throttle, all the way to the right revs it up.

tank off again, tried to 'shove' the cable back down the frame as much as possible to similate it being done so by the handle bars,
and reset the zip ties to make sure it doenst move work forward even when the handle bar is all the way left.
confrimed it doesnt slide anywhere with full tilts. tank back on, readjsuted the throttle which now revved right away.
seemed to be fine. no revving up from center to all the way right.
all the way left still dropped it.

with the tank still on i tried to shove/pull the throttle cable, as well as the choke cable. choke doenst seem to have any effect despite move so thats ok.
shoving the throttle cable in definitely revs it up.

there are no kinks in the routing of it. i think the throttle cable is sliding inside the hose, which is why securing the hose itself doenst secure the throttle.

could the throttle cable have been cut too short?
here, both the choke and the throttle cable run along the right side of the spine. should they be ran on opposite sides?
both cables run over the tank knobs.. should i have them run under it?

[DAVID THOMPSON]

try some kind of small tank with enough fuel to test ride it with out the regular tank
that cable is hanging up or being moved by some thing
maybe the electrical wires around the fork neck going to head lamp
or all else it has a burr on the cable inside the outer cable
my bike is a rt so nothing to compare it with
dave

use a tank from a weed eater on it so you can see what the cable is doing when the speed changes

[Jamie]

You should get three Private e-mails with all the info I could find on the factory notes.
Have had a quick look at the throttle cable and it is routed to the right of the tank, along with the clutch.
I will take the tank off tomorrow night and get you some pictures.

Jamie

[djsbriscoe]

Hi,
Sounds to me like there's a mismatch between the correct length of inner cable and the correct length of the cable cover/outer cable. I'd buy a new replacement from grahams if I where you. Maybe someone fitted a non OEM cable.
Here are the cable lengths from the parts book.

Throttle cable (part number 3923012000)
outer cable/cover length=850+3mm
inner cable length = 70mm at each end + 850+3mm (total length = 140+850mm)

Choke/starter cable (part number 3923013000)

outer cable/cover length=910+2mm
inner cable length 50mm at each end + 910+2mm (total length = 100+910mm)

I hope that's useful.

David.

[OSPRNG]

thanks for the replies guys.

i measured the throttle cable i have and its per above spec precisely. the outer cover hose is indeed too short however thought i'm not sure it has any efefct on the cable movement.
the advisory in one of the datasheets mentions zip tieing the cables, which i'll give a shot.
i've also tried a couple of other routing paths, the last one seems to be good but ive yet to test it (too late here, dont want to wake the neighbours).
plus i ran out of the grease on the handle bar end of the cable from the repeated removal and replacements.
will report back next week.

meanwhile, happy holidays to anyone celebrating.

[OSPRNG]

i have completely disconnected the throttle and choke cables and routed them the best way imaginable (tried about a dozen different paths and reassmbled the bike each time for a full test).
none of them did anything better. i'm starting to wonder that maybe routing is only half of the problem here, and maybe some reasonable movement in the cable is being exagerated by something else in the scheme of things.
i cant imagine Jamies pictires providing a path other than one of what i have alreday tried, but heres to hoping.
no mechanic in the area is willing to take a look at this ("MZ? who the heck makes them?")

[borisattva]

i have completely disconnected the throttle and choke cables and routed them the best way imaginable (tried about a dozen different paths and reassmbled the bike each time for a full test).
none of them did anything better. i'm starting to wonder that maybe routing is only half of the problem here, and maybe some reasonable movement in the cable is being exagerated by something else in the scheme of things.
i cant imagine Jamies pictires providing a path other than one of what i have alreday tried, but heres to hoping.
no mechanic in the area is willing to take a look at this ("MZ? who the heck makes them?")

you mentioned you had to adjust the throttle cable by the grip to get it to start.
maybe it is now too tight. try loosening it up and see if the revs change with the handle bar movement.
if they dont, try adjusting the idle screw instead of the throttle nut to deal with the starting issue.

[OSPRNG]

you mentioned you had to adjust the throttle cable by the grip to get it to start.
maybe it is now too tight. try loosening it up and see if the revs change with the handle bar movement.
if they dont, try adjusting the idle screw instead of the throttle nut to deal with the starting issue.

THATS IT!!
after letting it in warm up and rev steadily, i started loosening the throttle cable nut and what do you know,
the handle bars gradually lost their effect on the throttle.
i picked up the idle speed with the screw and now this beastie is officially back from the intensive care unit

thanks for the help and patience everyone

[stephendacosta]

A throttle cable that does not have enough adjustment slack in the outer cable will increase the RPM's on a right turn. Back off the adjuster to have 3/16" of play and turn up the idle adjustment, if needed--Steve

[stephendacosta]

Sounds llike you ar getting it sorted out. Sometimes an unintended increase in throttle while turning can be caused by not enough free-play in the adjustment.
Check to make sure the outer cable has a little slop at the adjuster. It should take about 5k for it to break in completely. Power will increase gradually.-Steve

[OSPRNG]

haven't posted in a looong while so just wanted to provide a conclusion.

with the cables and carb sorted, i drained the bike for the winter.
in the spring i brought it in to a local mechanic to get the fluids replaced and have a general 'look over'
in the process they ended up playing around with the carb to the point that i could not start the thing when i came by to pick it up.
it would start with choke fully closed but would stall shortly after opening.
turns out that they set it to around 1000 idle rpm (manual requires 1800)
adjusting that didnt help things much, but opening the idle screw 5 turns did, so hey decided to drill a wider hole to compensate without requiring the screw to loose.

i can start the bike now, but i have to have it choked off for about 10 minutes even in warm weather to prevent it from stalling out.
once it does 'warm up' it flactuares from 1700 to 2100 while on this idle.

i've been riding it almost every night for about 30 minutes at a time. the pipe gets very hot and is at this point very dark, with some rainbow tint.. is this normal, or is the carb now set to run the engine too rich?

after a while of riding the idle seems to stay around 3k unless i drop it down by turning the thumb screw on the side.
its seems to be a lot louder than it is fast so far the neighbors haven't complained, but i definitely can take warm it up for a night ride.
i plan to keep this around to get enough flight hours and then move on to something a bit more powerfull/highway worthy, maybe a yamaha wr250x for the fuel injection.

unless of course MZ comes around and surprised the world with a more powerful line of motards

thanks to everyone for the help in getting this bike sorted.

[DAVID THOMPSON]

the drilled out jet is not the solution
there is something screwed up in the carb or plugged up
read this post and click on picture to enlarge it and see the safety wire
viewtopic.php?t=918
every time i have had a problem with mine
it has always sorted to crap in the carb from dirty gas
most of the time any more i open drain screw in left side bottom of carb and get rid of a load of water
this happens almost every time i go on reserve fuel side of fuel tap
dave

[OSPRNG]

problem they said was that this is a non standard mikuni carb, so if i wanted to replace it with an undrilled one i woulnd't be able to do that.

nice idea with the wire !