Notallthere

Right sorted the two rings on the left are the directional bearing and when it rotates the lobe gets stopped at the top by that silly thin piece that goes between the two shafts. So the cam rotates and the decompressor stays put, so the side of rocker is lifted and released by the flat on the left. So now have to work out why it's missing the decompressor when the two rocker arms are the same apart from the rough casting on the one, but they do have the same casting number on them. Thank you all for your help and input.

Cheers

On 4/3/2023 at 9:14 PM, Mech said:

One of those rockers looks like it's better made than the other. I wonder if it's not genuine and causing the problem. It looks like the other rougher rocker has a bit of over-hang to the side. I wonder if that's meant to get held up by that bump on the sprag clutch thing.

Mech there isn't any problems with anything catching or interfering with each other.

That's a good eye. I will have a look in the morning cheers Mech.

12 hours ago, EugenM said:

Mech I thought the same thing, but if you search on the internet you find countless pictures of this type of cylinder head and  doesn't seem to be anything missing from there 

https://www.motorkit.com/en/spare-parts-yx125-140cc-/23933-cylinder-head-for-yx-and-lifan-engines-125cc-with-27-and-23mm-valve.html

Yep that's the same head spot on. 

I also see that there's a manual decompressor for it. I wonder if it could be fitted to mine. https://www.motorkit.com/en/spare-parts-skyteam-125cc-engine/23195-lifan-yx-125cc-engine-manual-decompressor.html 

12 hours ago, Mech said:

One rocker looks nicely made !

The ring with a notch has a one way bearing. Totally lost on this one.

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

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.

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.

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.

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.

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.

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.

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

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 

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

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.

Hi Squily Than you for your reply. New starter, new head and new plug. It's better since the head went on but when it fires it stops the engine dead with a clunk. The valve aren't hitting and it spins over really well but with the plug in it does struggle. Even with a car battery hooked up (Strange or what).

1 hour ago, jftucker1981 said:

Dont buy chinese

If I could afford anything else I wouldn't 

Hi Yes tried the fully charged car battery and had the head off with no damage to see. It does act as to much compression it's at 120psi and the crank is free and easy to rotate. I know that some engines have a auto decompresser on start up ? I have been looking for what to set the tappets to because all the same engines have a different gaps.

Cheers

Hi all

I am pulling my last bit of hair out with this little GY6 125cc atv. Is there a decompressor on start up ? I put a new starter on and with the spark plug out and the battery direct to the starter it spins over a treat, but spark plug in it pulses or does not turn over at all. Please any help

Hello all

I have been given a Chinese 125cc ATV. It has come with a few issues, The main one I am scratching my head with is the starter is not spinning the engine properly but ok with no spark plug. I have changed the started with no change to the slow turn over. It's not the battery but the power lead to the starter does get hot. Any advice so I can get away from throwing parts at it.

Cheers all

Hello 

I hope everyone is well today and to say hi to all. I have been playing and working on all sorts of ATV over the last 20 years.

Cheers

Mark