gear issue on a lifan 125cc

[BamBoozled]

Hello, I've got a couple of issues on a lifan 125cc engine....
The first and second gears seem to work fine on all throttle positions there is lots of power but as soon as I change to third or fourth gear the bike jolts to a slow speed and revs very high but it has some pulling power just insane revs and very little speed I have no Idea as to why this may be as it is a new engine the gears when I check them with bike off sound and feel like there selecting fine I even tried to roll the bike to check its in gear all solid as a rock..

the second issue is the gears don't stop anywhere I mean I can select every gear fine but it wont stop in natural the gears just go back around again surely that is not normal?

[BamBoozled]

Just an update to my post I have found out through modern technology i.e taking a photo of some Chinese writing from a sticker on the engine and using an image translation app that you can change gears from 4th to natural when the bike is stationary


anyway that's one thing out the way just trying to figure this 3rd and 4th gear lack of power and high rpms I've been searching around here there and everywhere online and came across clutch slipping video and it looked almost the same anyways I've now made sure the clutch cable has some slack and adjusted the clutch by opening the little shiny metal circle clutch cover so that's all good haven't had a chance to test it yet to see if the issue is resolved my guess is a nope. as i did check the cable a few times trying to diagnose this before and the clutch arm wasn't pulled at all but it didn't have the slack that was suggested i.e coin width in the lever gap so maybe.. anyway will update this post when I've got a chance to test.

[Rickwales]

It doesn't make sense that its clutch as it would slip in all gears. And that would not explain jumping out if gear either.
Sounds more internal and maybe selector issue.

[BamBoozled]

oh right thanks for the reply man fair yeah that is true.

but it doesn't jump out of gear it seems and feels like it goes into all gears just 3rd and 4th have very little power so it obviously is in the gear to even move... but 3rd and 4th gear make the engine scream at high rpms and give minimal power and say like I'm in 2nd gear and going like 20mph change up to 3rd bam the bike slows forcefully "like engine breaking" then once slowed down it gives a tiny bit of power and will move the bike but the rpms are crazy high

if it is selector how can it change to 3rd and move the bike if it wasn't in the gear at all... and also when the bike is stationary I can flick through all the gears fine I can hear it click in place I'm assuming the noise of that star thingy its confusing

[Rickwales]

Could be a woodruff key has sheared off and a gear is slipping on the shaft.
Only certain thing is that you will have to get gearbox out and investigate.

[BamBoozled]

yeah I was just hoping I didn't need to do that as I don't know a huge amount
about what I'm looking for in there apart from the star thing and it is a brand new engine that I brought and fitted as I brought the bike as my first ever non running project and my first motorbike the old engine ran once with some easy start so I cleaned all the carb out after that and then I accidentally put the float inside the bowl on upside down and the bike didn't start again and without that issue another came up where by I opened the cam cover to check timing and found this little lump of silver metal so I ended up just saying screw it..

Brought the lifan and fitted it up didn't run until I brought new coil and wiring and also realised the float bowl to the carb was upside down from taking it apart before and now after all that only 1st and 2nd gear work just turned into a savage project should of been done after a new engine.

here is a couple of photos attached of when I got it and after just to show

Pretty sure its an SR125-SSR PF2 Origanlly with perimeter frame.
New fuel tank as petcock was snapped and was premolded to the tank could only find the same tank from Australia
new plastics new fuel hose
new engine

[Rickwales]

If its a brand new engine then ypi should be able to send it back and get it replaced.

[BamBoozled]

Yeah but I've had it for nearly a year now Its taken me a fair while getting the time to work on it sat not running for months in my flat after I fitted the engine in and then I had some free time to play around working out why it didn't run the old coil and wires gave no spark so order a new cdi coil and htlead got the spark then still didn't start then I open the carb trying to figure it out and the bowl was empty of fuel and I was like huh that isn't right then realised the float was on upside down change it around and started first kick and it sat again for awhile and just got back into it and taking it out to break it in and tune the carb up and then ran into this weird issue

I had it out today its just a weird one with these gears because they definitely change in and out fine 3rd and fourth are just so loud and like a 2stroke I just cant run them and it 2nd is starting to be like that now too so I was just riding it in 1st could it not be jetting or tuning or something like that? i change the main jet today from the standard #95 to a bigger #97.5 runs alot richer as the engine was getting seriously hot and sounds nicer to me more deeper less loud but i'm just using 1st gear really I can change to 3rd and 4th and run them just the bike is so loud and it doesn't sound right or feel right sounds like it over revs for the gear and not enough go for the amount of revs but they work?? I don't understand it.

[Rickwales]

What oil have you put in it

[BamBoozled]

it had the oil that came in it for the first few runs I just changed it to 10-40w semi-synthetic