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Discussion Starter · #1 ·
I took my Z50AK4 outdoors today for the first time since September. I've done a complete top end overhaul. It's now running a CT70 cylinder, ATC70 head.



Still running on the original Z50 carb (barely), choke on, ok, mid choke poor, no choke = stall (no doubt carb is not large enough).



While running I found a few things:



Relatively difficult to turn over, is the CT70 Kicker a direct swap?



The exhaust needs more work (badly carboned up; smoke rolling out of it was insane! I thought the engine was coming apart! Removed exhaust to confirm. You're ideas to cure please)



There is a Squeaking sound in rhythm with engine rpm - The only time it's not present is while kickstarting, no air cleaner, throttle open, choke open? Thoughts?
 

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LoudFastUgly said:
There is a Squeaking sound in rhythm with engine rpm - The only time it's not present is while kickstarting, no air cleaner, throttle open, choke open? Thoughts?


False air, check if the intake manifold is plane.

(simple check, spray some wd40 or brakecleaner at the connection to the head while the engine is running.)



It is quite normal that an engine does not run idle if the air cleaner is removed.
 

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Doubt it's that the 50 carb isn't big enough, it's that the 50 carb is jetted for a 50. The 70 will need richer jets to run right. Of course the 70 will be limited by the smaller carb, but the reason it needs the choke on is that a) it's jetted too lean with the 50 jetting and b) it might have an air leak, as stated above.



Don't know my kicker swapping tooth-count info, but others here do?



I got a memory card and will get you pics of the 70 carb if you're still interested...lemme know.



Regarding the noise, my stock 50 makes a pulsed sucking sound with each intake stroke, clearly audible with the filter on but more noticeable with it off (it runs fine either way). Could this be what you're hearing?
 

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LFU said:
...is the CT70 Kicker a direct swap?...
That would depend strictly on which CT70 you got the kicker from. The 3-speed auto trans models use a 22T pinion, which is the same as the one in your Z50A engine, but the 4-speed CT70H models use a 24T pinion,which will not mesh with your Z trans.
 

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Discussion Starter · #5 ·
mexicanyella said:
Doubt it's that the 50 carb isn't big enough, it's that the 50 carb is jetted for a 50. The 70 will need richer jets to run right. Of course the 70 will be limited by the smaller carb, but the reason it needs the choke on is that a) it's jetted too lean with the 50 jetting and b) it might have an air leak, as stated above.



Don't know my kicker swapping tooth-count info, but others here do?



I got a memory card and will get you pics of the 70 carb if you're still interested...lemme know.



Regarding the noise, my stock 50 makes a pulsed sucking sound with each intake stroke, clearly audible with the filter on but more noticeable with it off (it runs fine either way). Could this be what you're hearing?


Pics man, pics!
 

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i put a carboned stock z50 pipe on my lifan 125, i think it cleans it's self with all the pressure coming out of it. hehehe ;) jeff just sent out my mini gunz if that explains why it is on there. but any ways i heard you can havem boiled/steamed clean, i imagine at a machine shop.
 

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Discussion Starter · #7 ·
Let's see, lots done since last post.



I took my pipe into work and ran it through a machine called a "Hotsy" hot water/steam cleaner. No real difference realized. I'm starting to think that this pipe is not worth the effort. I can't wait to get it running right and put some real heat into it and see what happens.



I've tried every chemical cleaner in the house, oven cleaner to drain-o, no luck. I don't want to try a solvent (explosions make me nervous) yet.



I setup the valves today (.003"), runs much nicer (had them way too loose). Diagnosed the squeak (intake leak at gasket) and tried to setup the carb. The carb adjustments don't seem to make any difference as to how it runs, honestly I have an 18mm KLX110 carb on the way for trial and we'll see how that goes. Trying to set up a 3 year old slightly oversize carb should hopefully go better than trying to setup an undersize 35 year old carb.



I flushed the engine oil twice, seems to be aerated for some reason, but better with each flush. We'll see what happens here.
 

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sound like you may have a clogged up jet in the carb.

Take it apart and clean and needle out the jets and reset the base idle and air mixtures.

See if that helps it.



The carb may not be large enough to support the engine at high load or RPM's

but it should at least idle and run to the midrange ok with that carb.
 
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