Honda CH125 (Elite) 1994 won't cold start

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XGamer23
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Honda CH125 (Elite) 1994 won't cold start

Post by XGamer23 »

Hello folks,
so for a few months already, my Honda has been giving me troubles with cold starting.

It will start if you spray starting fluid or gasoline into the intake, and keep spraying for 3-4 second and then it will run on it's own power. After it started ,it runs great, normal and pulls nicely (so all is normal). It starts the first second when it is warmed up, but as soon as it's cold again, it won't.

I removed the carb, cleaned it and took it back together and there was 0 change. Everything is the same.

It has one of those additional intake passages for additional fuel when the engine is cold, and a limiter that blocks off the passage when it warms up. It works fine. I tested it on 12V and it pulled the pin in and out when it had to. Even though it doesn't really matter, since when it's cold, the pin is inside meaning that fuel can pass through, and when it's hot it goes out and blocks the additional fuel off (simply, a choke). But to be sure, I did test it that it goes in and out just fine. You can also crank it for like 5-10 minutes and it will start eventually.

So, the only thing I forgot was to clean the fuel cock assembly, and the filter inside of it, but I'll do additionaly. Also, I tested it without the air filter, same issue.

I'm out of ideas what to do else. As I noted, the engine runs just fine when it turns on, but won't start when the engine is cold, meaning the automatic choke doesn't work properly. I did test the small passage for fuel with compressed air, and it seems to be clear and clean in both ways. As I noted, I hope it's the fuel strainer under the tank, in the fuel cock since it's never been cleaned or looked at.

Here are some pics of the carb, and a video showing how it nearly started: https://imgur.com/a/1tuB46P
Here are schematics of the scooter and it's parts: https://www.cmsnl.com/honda-ch125-spacy ... partslist/

Thanks in advance for your advice!
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flybd5_juan
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Re: Honda CH125 (Elite) 1994 won't cold start

Post by flybd5_juan »

Did you clean or replace the air filter?
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Re: Honda CH125 (Elite) 1994 won't cold start

Post by XGamer23 »

flybd5_juan wrote: Sat Aug 22, 2020 3:36 pm Did you clean or replace the air filter?
Yes I did clean it. Also I tried without it, since you can't really spray any fluids down the intake unless you remove the air filter.
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Re: Honda CH125 (Elite) 1994 won't cold start

Post by flybd5_juan »

When this happened to me on my Aero 125 it was the bystarter. Changing it solved the problem. It's the only thing in the engine starting formula that is affected by heat. The other problem I had was a leak in the carb bowl, the screw that controls the overflow drain always let the fuel out.
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Re: Honda CH125 (Elite) 1994 won't cold start

Post by XGamer23 »

flybd5_juan wrote: Sat Aug 22, 2020 9:24 pm When this happened to me on my Aero 125 it was the bystarter. Changing it solved the problem. It's the only thing in the engine starting formula that is affected by heat. The other problem I had was a leak in the carb bowl, the screw that controls the overflow drain always let the fuel out.
Doesn't the bystarter allow fuel flow when it is cold, meaning that the pin is stuck inside of the bystarter. When it gets hot, the pin goes into the small hole to block off the additional fuel meaning that the choke is off?

I hope that that is the issue, but it simply doesn't make sense. I'll try removing it completely and then try to start it.
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Re: Honda CH125 (Elite) 1994 won't cold start

Post by flybd5_juan »

From Wikipedia (which is not always accurate, or even close to it, but this is...):

"A choke valve is sometimes installed in the carburetor of internal combustion engines. Its purpose is to restrict the flow of air, thereby enriching the fuel-air mixture while starting the engine. Depending on engine design and application, the valve can be activated manually by the operator of the engine (via a lever or pull handle) or automatically by a temperature-sensitive mechanism called an autochoke (OR BYSTARTER). Choke valves are important for naturally-aspirated gasoline engines because small droplets of gasoline do not evaporate well within a cold engine. By restricting the flow of air into the throat of the carburetor, the choke valve reduces the pressure inside the throat, which causes a proportionally-greater amount of fuel to be pushed from the main jet into the combustion chamber during cold-running operation. Once the engine is warm (from combustion), opening the choke valve restores the carburetor to normal operation, supplying fuel and air in the correct stoichiometric ratio for clean, efficient combustion."

This is a typo:

"The other problem I had was a lean in the carb bowl..." I meant to say LEAK.
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Re: Honda CH125 (Elite) 1994 won't cold start

Post by XGamer23 »

flybd5_juan wrote: Sun Aug 23, 2020 10:26 am From Wikipedia (which is not always accurate, or even close to it, but this is...):

"A choke valve is sometimes installed in the carburetor of internal combustion engines. Its purpose is to restrict the flow of air, thereby enriching the fuel-air mixture while starting the engine. Depending on engine design and application, the valve can be activated manually by the operator of the engine (via a lever or pull handle) or automatically by a temperature-sensitive mechanism called an autochoke (OR BYSTARTER). Choke valves are important for naturally-aspirated gasoline engines because small droplets of gasoline do not evaporate well within a cold engine. By restricting the flow of air into the throat of the carburetor, the choke valve reduces the pressure inside the throat, which causes a proportionally-greater amount of fuel to be pushed from the main jet into the combustion chamber during cold-running operation. Once the engine is warm (from combustion), opening the choke valve restores the carburetor to normal operation, supplying fuel and air in the correct stoichiometric ratio for clean, efficient combustion."

This is a typo:

"The other problem I had was a lean in the carb bowl..." I meant to say LEAK.
Eh, I feel dumb now. The whole time I thought that chokes just put in more fuel, rather than limiting air...

I might have to replace by bystater, even though it works fine. As I noted above, I connected it outside of the carb to 12V directly, and after a minute or so, the pin extended outside, and disconnecting it from 12V, made the pin go inside again. I mean, it works.

Also, it says "to restrict the flow of air", shouldn't that mean that the pin should be already extended when the engine is cold, and be pulled back when it is hot? It really confuses me.

Somehow, the definition and my case, don't really fit in well together.
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Re: Honda CH125 (Elite) 1994 won't cold start

Post by flybd5_juan »

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Re: Honda CH125 (Elite) 1994 won't cold start

Post by XGamer23 »

flybd5_juan wrote: Sun Aug 23, 2020 1:27 pm You need to read this.

http://hondaspree.net/wiki/index.php5/B ... at_It_Does
Since my electric bystarter device with the pin works fine. I assume I'll have to re-clean the carb all over again and look out for the special places for the bystarter?
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Re: Honda CH125 (Elite) 1994 won't cold start

Post by flybd5_juan »

The orifice the bystarter pin goes into might be plugged.
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