Lifan 140CC engine seizing? Need advice

[ALIKA T3]

Aloha all!

Today I've been driving the monkey to the autoparts store down the valley,a 2 mile drive each way.

On my way back,I drove pretty slow,considering I was being a bus.

I got to park the bike near my car in the street and the engine just stopped doing a rubber squishy chirping noise.
That didn't sound good to me at all.
>>>I tryied again ,the engine started right away and died just after with the same heart breaking noise.
It sounds like it comes from the top end,but I didn't really have time to investigate before the engine stopped.

>>>I let the engine cool down and tryied to start again to diagnose the problem,knowing that I might cause more damage,but I really can't open an engine just hearing a noise....
Same thing happened with engine cooled down 20 minutes.


*******I've been driving it for a while now,and the only change I made recently is the oil by-pass hose,I bought one at TBparts to be shorter than the piece of hose meant to connect an oil radiator that I used.
And I added a skid plate,which may cause problems of cooling maybe?

I have no freaking idea,that sounded like a valve seizing to me,coming from around the exhaust flange... but I never opened these type of engines,so any input will be valuable.

Mahalo nui loa


By-pass hose isn't pinched


Skid plate installed recently,bent up more than originally to not hit front tire when braking.I think it's a 200CC model....


I always check oil level with the original dipstick,the temperature one is too short to be accurate.Another lame part from China

[PlanetMinis.com]

[jetskibruce]

I think you are looking at the right things. Check the new hose, be sure it flows like the old hose. Less air flow with the skid plate. And how is your jetting. Lean engines run great but run hotter. Your pipe is not too discolored but you may be able to go up a jet size. The oil still looks nice and clean, not burnt. How is the valve clearance? A little tight? Might be an issue.

[ALIKA T3]

I think you are looking at the right things. Check the new hose, be sure it flows like the old hose. Less air flow with the skid plate. And how is your jetting. Lean engines run great but run hotter. Your pipe is not too discolored but you may be able to go up a jet size. The oil still looks nice and clean, not burnt. How is the valve clearance? A little tight? Might be an issue.

Hi Jetskibruce!

thanks for your interest

I'm gonna take the hose apart to check it out.

I have no idea of how to tell if the jetting is good or not,I have no experience with these.It's the one from factory,the bike is running great,that's all I can tell.
What should I look for?
The oil is brand new,it has about 200 kms,it's Castrol Act'evo 4T,recommended by DRatv.com
Where do I check the valve clearance?
Is it behind the cover on top of the engine? I remember my Honda 125CG had it there I think.
I'm gonna make some search online to find out if you're not online anymore...

Bye and thank you again!

[T Bolt USA]

Buy a CRF50 Repair Manual
Start with externals
Pull the ignition cover off
Drain the oil and Pull the clutch cover off

[jetskibruce]

Yea, search the site. Lots of information about valves. Probably some for your exact motor. Factory jetting is probably close, but high flow air cleaners and pipes can use some bigger jets some times. I do pop on and off the site, I have been enjoying this web site since I bought a used china clone 50 a few months ago. I rode it up the street today, I should take a new picture I look here because I have worked on motors since I was 16 but here you can get the answers to all kinds of specific questions for these bikes and engines. Search, search, first though.

[bobbob1015]

It doesn't sound like a heat issue at all...more along the lines of plugged delivery lines....I would start at the oil pump just put the bike on it's side (gas off , clutch side up) and pop the clutch cover off.. You will see the oil pump in the bottom right, should have a little screen right on the bottom of it. pop that out and clean things out... might have metal shavings and such those are normal as long as you don't have chunks..if that's good it might just be the hose you had in there before? If things are working out so far...but either way I like to get in to clean out that screen at least once a year..its your only filter unless you run higher end motor/clutch.

[ALIKA T3]

All right people!

thanks again for your support.
I'm back at home for a smoothie,the girlfriend whistled at me for it.

I checked the valve clearance:I got 0.08mm at intake at full play,I can get a 0.09 and also a 0.10 shim halfway through the gap only,so my guess is 0.08 is the correct gap since it was the only one that fit through completely.

At exhaust,it's a tiny bit tighter with 0.08mm,but it was a PITA to crawl under there .

I was kicking the engine with ignition off,and it has spitted some oil on my tire,so I guess oil flow is good
I heard the same chirping noise,and it seemed that it was back flowing into the carburettor.In fact,I found out that the adaptor plate is loose on the engine.
Man,vibrations are gonna make that bike falling apart ,I've put Loctite on blinker reflector plates already,the light bulbs were falling apart,I've put lock washers all over,and also noticed today that the engine has some play in the frame too.....

So I'm going back down to the bike when I'm done with the smoothie,tighten that carb flange and let you know

[ALIKA T3]

ALL good!

false alert,i've been riding it up the hill,it's fine.That was the loose flange under the carb.

thanks again for your help,I learnt more about the engine by the way

Bye!

[jetskibruce]

Man,vibrations are gonna make that bike falling apart ,I've put Loctite on blinker reflector plates already,the light bulbs were falling apart,I've put lock washers all over,and also noticed today that the engine has some play in the frame too.....

I think that is why they are called "Thumpers" LOL

- Glad it is back together. It seems like a great way to get around the island.

[olyelr]

Well 'cmon, what kind of smoothie did she make ya?


Glad you figured it out, Alika!

[ALIKA T3]

Aloha guys!

haha,I almost wanted to take a picture,but I changed my mind....it seems that I should have eh?

Blueberries,açai purée,apple-bananas from the back of the valley where lives my co-worker and buddy,apple juice,and a few frozen mixed berries (strawberries,raspberries and other stuff I don't know)
The thing that makes you stop doing mechanic right now

Thank you again for all the help!!

As for going around the island,it is a great mini bike,but I think the rpm's are too high for cruising with a decent speed,I should replace the front sprocket for the Hawaii Con 2012

Have a great day,I'm going to work riding the bike today