Chinese 125cc ATV not starting

[Notallthere]

Hi everyone This little monster came to me as a non runner and to sort it for a friend. Had it in bits thrown the service bits at it but nothing, it struggles to turn over unless you put your hand over the intake then it spins like a demon. The valves are adjusted correctly and I am just lost where to go next.

[Gwbarm]

When you put your hand over the intake do you feel correct suction or does it feel weird.

[Notallthere]

Feels as it should. All I do is a 95 percent close-our and away it goes.

 

[EugenM]

Hi,

Sorry for asking (I'm struggling to understand some of your expressions, unfortunately I didn't learn english in school). What do you mean when you say that is turn over only when you put your hand over intake...is it starting only that way? Or is not starting at all?

[Notallthere]

19 hours ago, EugenM said:

Hi,

Sorry for asking (I'm struggling to understand some of your expressions, unfortunately I didn't learn english in school). What do you mean when you say that is turn over only when you put your hand over intake...is it starting only that way? Or is not starting at all?

It is struggling to turn over with the air intake fully open. But if you cover the opening by 95 percent it then spins over freely 

 

[EugenM]

can you post a picture of the carburetor?  Does it have an automatic or mechanical choke?

[Pod]

On 3/26/2023 at 2:30 PM, EugenM said:

Hi,

Sorry for asking (I'm struggling to understand some of your expressions, unfortunately I didn't learn english in school). What do you mean when you say that is turn over only when you put your hand over intake...is it starting only that way? Or is not starting at all?

Check your electric choke on the carburetor

their is a black cap on it and it is retain in place by 2 Philips screw. Take it out… turn the ignition on you should slowly see the needle extending. If not working properly change it it about 10$ or even go for a new complete carb kit for about 30$. You’ll find everything you need on amazon

[Mech]

It sounds to me like a weak starter you are describing. When you put your hand over the carb it can't suck air so doesn't have compression so there is little resistance to turning over.

I presume it spins nicely enough with the pull or kick start, or if you turn the crank by hand ?

[Notallthere]

Hi yha new starter and battery and it's a Chinese 125cc so key start only. It is like it has to much compression ?

[Notallthere]

3 hours ago, EugenM said:

can you post a picture of the carburetor?  Does it have an automatic or mechanical choke?

Manual choke and it's not on the engine and the mo, but still has the problem.

[Notallthere]

On 3/26/2023 at 6:34 AM, Gwbarm said:

When you put your hand over the intake do you feel correct suction or does it feel weird.

Hi yes fine if you put the hand over the intake it sucks you right in.

 

[Notallthere]

4 hours ago, EugenM said:

can you post a picture of the carburetor?  Does it have an automatic or mechanical choke?

Hi manual choke and still have the problem with the carb off. If I take the plug out it spins like a good one.

[Notallthere]

Hi all the engine spins by hand with around 70psi compression, take the plug out then it will spins freely then once back it barely turns over, Adjusted valves so there all good . New battery New starter, it's like the start decompressor is not working. It's not very often I get stuck on a engine but.

[Mech]

Well if it has a de compressor then certainly check that's working. Other than that it might have a bad battery cable, or solenoid, or earth cable or connection.

Cables can get bad connections where the wire goes into the terminal. If you have jumper leads try jumping straight from the battery negative to the starter or engine, preferably the starter because starters can have bad connections to the engine sometimes, Then use another jumper from the battery's positive to the starter's power terminal. That bypasses the earth connections and the cables and the start solenoid. If that works, try jumping one cable at a time.

[Notallthere]

Hi Mech

First place I started with new starter and cables as the old cables had corrosion, I have tried the spare battery and jump leads and it's the same hard to turn over until you close off the intake. How do you test the auto decompression as not sure how it works.

[Mech]

I'm not sure Notall. Most have some moving parts.. A pin that comes out or a ring that turns.. If they are mechanical. I think you'd have to pull the cam cover off to look.

Your one might be operated by vacuum and that might be why putting your hand on it works so well. If i't s a diaphragm one there should be a fairly large diaphragm somewhere obvious.. I think.

Have you tried the jumpers off a good battery straight to the engine and the starter motor ? To eliminate the starter solenoid.

Do you know the make ?  We might find some manual for another model that's made by them, that has a de-compressor..  It might tell us something.

[Gwbarm]

I think you are right your compression release is not working, if it will run, try this, cover the intake hit the starter as soon as it starts to turn over remove your intake cover, it should start. Not sure on yours never worked on 125 but all the ones I have repaired have been quite troublesome inside the engine.

[Notallthere]

Hope the photo's help  

21 hours ago, Mech said:

I'm not sure Notall. Most have some moving parts.. A pin that comes out or a ring that turns.. If they are mechanical. I think you'd have to pull the cam cover off to look.

Your one might be operated by vacuum and that might be why putting your hand on it works so well. If i't s a diaphragm one there should be a fairly large diaphragm somewhere obvious.. I think.

Have you tried the jumpers off a good battery straight to the engine and the starter motor ? To eliminate the starter solenoid.

Do you know the make ?  We might find some manual for another model that's made by them, that has a de-compressor..  It might tell us something.

I really hope the photo's help and yes I have tried a spare battery with jumper cables and direct to the new starter motor.

 

[Mech]

Seems it's made by a company generally known as Highper..  Which may or may not also be Hyper..

But either way there's not much info on them, not even a parts supply to look at pictures, which would perhaps help identify a de-comp.

Perhaps if you show us some pictures of the top of the engine.. If there's a vacuum de-comp it would be obvious I think.

[Notallthere]

Hope these help I just don't believe what a pain this is when I can sort out a V8 in minutes.

[Gwbarm]

That metal piece at the top of your second photo looks like it could be it is the spring in tact and does it move or is it stationary, never seen one exactly like that if that's it can't tell a whole lot from the photos, good photos just can't really see much.

[Mech]

Yup that thing at the top of the second photo looks like it could be a de-compressor.. What's over the other side under that ribbed cover ?

It may be that it works automatically, when the cam turns slowly it catches and does something that holds a rocker down(on the exhaust valve), but once the cam is spinning faster, or perhaps after it's done one full rotation, it releases a valve to restore compression.

You should try moving it by hand and/or watch what it does when you turn the engine over slowly.

[Gwbarm]

That looks like a pop rivet holding it on, that could be rather annoying if you have to replace the spring, but looks can be deceiving.

[Mech]

I think the lever is attached to a shaft. The "rivet" is a stamped join between the shaft and lever. There's another rotating part behind the lever. The part behind the lever looks like it may poke at the rocker on the right.. It might hold the rocker up.. 

[Gwbarm]

I figured it had to be something more than it appeared, I v been mostly impressed with the Chinese engines, but occasionally I will see one and say, really, you didn't do that.