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PotatoHead202...
Scooby Slapper



Joined: 10 Feb 2020
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PostPosted: 21:48 - 11 Dec 2022    Post subject: CZ125 Reply with quote
Almost got my 1989 CZ125 back together now. Managed to get it started a week ago whereby it started on 2nd kick but the throttle cable wasn't long enough (now has a jikov carb rather than the damaged AMAL) and a lose ignition connection so started, revved high due to the tight cable but then died.

Got the wheels and suspension back on now and tried again today. Again, started 2nd kick but seems to be intermittently puffing back through the carb (smoke). Now, the airbox isn't connected, no airfilter and was running from an auxiliary tank with the cap on. A friend reckons he got the timing spot on however..... Any ideas where to start?
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blurredman
World Chat Champion



Joined: 18 Sep 2010
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PostPosted: 16:45 - 12 Dec 2022    Post subject: Reply with quote
Definitely put the air box and air filter on.



Pics or it didn't happen! Smile
____________________
CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S, 1979 MZ TS150.
Current: 1973 MZ ES250/2 - 18k, 1979 Suzuki TS185ER - 10k, 1981 Honda CX500B - 91k, 1987 MZ ETZ250 - 40k, 1989 MZ ETZ251 - 52k.
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 17:34 - 12 Dec 2022    Post subject: Reply with quote
Is the exhaust on and baffles in? You need those for it to run correctly.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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jaffa90
World Chat Champion



Joined: 06 Apr 2016
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PostPosted: 18:52 - 12 Dec 2022    Post subject: Reply with quote
Does this engine have reed valves for a one way system?
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 19:32 - 12 Dec 2022    Post subject: Reply with quote
jaffa90 wrote:
Does this engine have reed valves for a one way system?


It'll be the most bare-bones basic, piston-ported, air-cooled single you can imagine.

In fact, my first thought was IS the ignition timing right or has the mate got advance and retard mixed up? These engines will run backwards.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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jaffa90
World Chat Champion



Joined: 06 Apr 2016
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PostPosted: 01:56 - 13 Dec 2022    Post subject: Reply with quote
Could be a scored piston / rings / cylinder causing blow by ?
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WD Forte
World Chat Champion



Joined: 17 Jun 2010
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PostPosted: 02:20 - 13 Dec 2022    Post subject: Reply with quote
Could be all manner of things but as above, not running with the stock air inlet + filter + zorst is going to lean it out so wont help

Add on a carb swap with no mention of size and jetting compared to prior one to complicate things
Points timing, gap and and condenser condition and associated wiring
could cause problems too.
easy to check timing though

Still, its a simple enough bike, I had one for a while years ago
but not a fan.
My lad had an MZ ETZ 125 which I had bit of soft spot for
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 03:07 - 13 Dec 2022    Post subject: Reply with quote
WD Forte wrote:

Add on a carb swap with no mention of size and jetting compared to prior one to complicate things


Although it is SUPPOSED to have Jikov carb rather than an Amal. A worn Amal concentric is an utter bag of horrors when it comes to getting a motorcycle running well. At least a Jikov has a proper starter enricher and accessable slow running circuit. Not to mention a throttle slide that moves and seals properly in the throttle body.

Another question is, has someone pissed about with the port timing, either on the piston or the barrel? It was common to open out the base of the piston port (I've even sen one with about 3/4" sliced off the skirt to turn a rectangular port into a semi-circular cutout. The overtsize Jawa "race" pistons were short with a cutout rather than a port) and chamfer the inlet side of the piston crown nearly down into the lands with a hand file to gain more peak revs/power.

Hell, I've even seen one running only 2 of the 3 rings and the head lapped in to the point the piston was almost hitting the plug electrode. As you'd imagine, this does nothing for the idle performance.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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PotatoHead202...
Scooby Slapper



Joined: 10 Feb 2020
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PostPosted: 21:10 - 13 Dec 2022    Post subject: Reply with quote
Exhaust is all connected and is original AFAIK. Not entirely sure on the jetting of the carb - was just advised by the Czech dealer it would work. AMAL is in broken pieces and struggled with parts. Apparently they were originally fitted with Jikov but the importer swapped them.

I'll add that it didn't seem to do it when revving- just at idle.

Was an attempt to get it started prior to fitting the airbox (had it blasted and coated).
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Suzuki V Strom 1050XT, Honda CBF500 ABS,
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Old Thread Alert!

The last post was made 3 years, 308 days ago. Instead of replying here, would creating a new thread be more useful?
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