MZ 125 SM running fault.....Any ideas!!!!!!

SM, SX, RT, FunX, and models re-branded as ATK in U.S.

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MZ 125 SM running fault.....Any ideas!!!!!!

Postby kood1983 » Tue Jun 14, 2016 8:47 am

Hi,

I hope somebody can help here i've run out of ideas.......... its a bit long winded but please have a read !!! :smt023 :smt023

Right i bought an MZ 125 SM (52 plate) which had not been started for over a year and was sold as a none runner due to the owner not been able to get it started however when i collected it it started but cut out after a few seconds so i thought buzzing its something and nothing to get it going properly..............how wrong was i...........

I started by cleaning the carb out literally no screw left untouched i set the air mixture screw to the recommended 2 turns out as i've seen mentioned many time on here but on cleaning it out there was no real debris found.

I refitted the carb and got the bike started but even though it would tick over like a clock it would not rev up it just sounded like it was getting starved of fuel and would cut out so out came the carb again and i set the float as per the owners manual just to see if that was a problem but tbh it wasn't out of adjustment a lot so once again i refitted the carb and nothing had changed it would still not rev up but would tick over perfect.

Sometimes on start up i could here a knocking sound but not always so i drained the oil and found quite a lot of copper filings in the oil and filter almost like glitter so just as a temporary measure i cleaned out the filter and replaced also with fresh oil if say the engine is in need of a rebuild due to knackered shells / bearings i would of thought it would still rev up but the knocking would get louder like with a car engine if its shells or bearings are knackered it would still rev up but would sound like a bag of nails.

Anyway.....

So its all back together now with fresh oil etc once started the knocking is still there now and again but it will still not rev up so i got some of advice off a friend and they said check the timing so i did as told and checked the timing the inlet cam was slightly out also the exhaust but again not massively out so i set it as per the manual also followed a guide on here and set it bang on............

But now it struggles to start and when it does it makes one hell of a racket some serious knocking going on i havent even tried to rev it due to the noises it makes now but tbh i dont think it would rev even if i tried.

I'm coming to the end of my tether with it now i'v tried everything thats been mentioned by friends and from what i can see on here in relation to its issues just to mention also the filler cap on the tank is not blocked also its been run on normal unleaded not super unleaded as i've seen mentioned on here they don't like fuel with ethanol added to it and i've also checked for spark and there is no problem there either.

Can anybody shed any light on this please??

Any advice would be greatly appreciated.

Thanks in advance.

Gaz.
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Re: MZ 125 SM running fault.....Any ideas!!!!!!

Postby DAVID THOMPSON » Tue Jun 14, 2016 11:47 am

never heard of any one loosing the balance shaft but theres always a first time
Dave
Dave 2002 MZ RT125+1995 Saxon Tour(500cc)
1997 MZ 660 Traveller+6/13/09 WV USA
"IN the end times the IDIOTS will be in charge
of everything"
"I like the road less traveled if it's PAVED!"
wd8cyv at yahoo dot com
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Re: MZ 125 SM running fault.....Any ideas!!!!!!

Postby kood1983 » Tue Jun 14, 2016 2:42 pm

DAVID THOMPSON wrote:never heard of any one loosing the balance shaft but theres always a first time
Dave


Hi Dave,

What do you mean balance shaft.......are you referring to the crank shaft??

Also would you say with the symptoms i have described are pointing towards stripping it down and inspecting??

Cheers Gaz.
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Re: MZ 125 SM running fault.....Any ideas!!!!!!

Postby DAVID THOMPSON » Tue Jun 14, 2016 5:16 pm

item 10 is balance shaft

if there is trash in oil ita time for a take apart
Attachments
crank MZ 125 SX SM 06-2008.pdf
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Dave 2002 MZ RT125+1995 Saxon Tour(500cc)
1997 MZ 660 Traveller+6/13/09 WV USA
"IN the end times the IDIOTS will be in charge
of everything"
"I like the road less traveled if it's PAVED!"
wd8cyv at yahoo dot com
User avatar
DAVID THOMPSON
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Posts: 5149
Joined: Sun Nov 23, 2003 11:01 am
Location: Parkersburg, West Virginia USA .questions answered MZ 95 up, BMW 1953 to 1979 and ham radio WD8CYV

Re: MZ 125 SM running fault.....Any ideas!!!!!!

Postby stephendacosta » Mon Jun 20, 2016 10:04 pm

Time to see if the motor will rev up with the fuel enrichner(choke) on.
Stephen DaCosta
1995 Skorpion Sport; ten-MZ 125's;2009 BMW G650GS;1981 GS450 Suzuki Roadracer
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