lifan motor trouble

i just got a used lifan 120cc motor and put it in a stock crf50 frame. im using the stock 50 pipe with a gasket and K&N air filter. my problem is that it takes about 15 to 20 kicks to start it and when i ride sometimes it bogs out a little and dies after about 2 minutes of riding. anyone know why this is happening? is it because of the smaller stock pipe? or maybe something else cause im not too familiar with chinese motors

I'd say it's most likely the filter being too free flowing & making it go lean, hard to say without actually seeing/hearing it though.

What colour is the plug & how is starting after it's hot?

If it starts better hot then you're likely running a little lean, better cold or with filter off, more than likely running rich.

If you reckon it's going lean try moving the carb needle up a couple of notches (clip going further towards pointed end)

now the motor wont even start

after about 15 kicks it starts for a couple seconds then dies. the only thing i can think of is cleaning the carb and maybe moving the needle and trying again. if there is anything else i should do please let me know

I had this same problem with my kids pit bikes after about two seasons use. They needed the valves adjusted. After the adjustment, one kick starters. I'm willing to bet they are way too tight and don't allow the valves to fully close. Try this, take the spark plug out and put your thumb or finger over the hole to check the compression. If it hardly pushes any air out, that's it. If it has good compression, then it's either fuel or ignition.

i took the spark plug out and the compression was really good. how could i check my ignition to see if thats the problem?

The only check I can think of without knowing the setup on these bikes is to simply take the plug out, earth it against the head & kick the engine over to see if you have a spark (would be worth using a new plug anyway if you don't know how old it is)

Also cleaning the carb would be a good start, if it's sat with fuel in the jets might be gunked up.

As previously asked, what colour is the plug tip? (picture would be good)

It's hard to diagnose non-runners at a distance & without any history of previous trouble but I'll try & help as best I can. Maybe someone on here that lives close by wouldn't mind taking a look for you too?

Is it one of these motors? 2206532.jpg

A mate had something similar, they're based on a honda engine & I think some parts are interchangeable.

The problem he had with his was bent valves due to over revving, it did seem to have compression but when I took the head off they were obviously bent & not holding enough pressure. (when it did run the engine was really sluggish & not willing to rev)

i checked the spark and it was good. the other day when it was running and i would let it idle it would slowly start to rev for no reason and now the bike wont even start at all. heres a pic of the plug. its pretty much just black.(not a very good pic sorry) and a pic of the engine as well.


the other day when it was running and i would let it idle it would slowly start to rev for no reason and now the bike wont even start at all.]

Sounds like a vacuum leak.

I would buy a new plug and try it anyway. It's the cheapest part to replace and it will eliminate that possibility as well. Super easy fix if it works.

how do i fix a vacuum leak? or atleast check for one?

Spray ether or carb cleaner or something flammable (carefully) around joints on the intake manifold and carb while the engine is running. A change in rpm of the engine indicates where the leak has sucked the flammable liquid into the engine.

I'd start with a spark plug first, however.

If it doesn't run at all, then you have different problems.

does choking it have any effect? try holding your hand over the back of the carb. make sure you have fresh gas as well

we had one that has fish oil caked in the main jet

Perhaps it's come to the end of it's Lifan. I hope it had a full Lifan.Lifan's pretty short,If you don't stop and and smell the burning oil every now and again you could miss it.What is the true meaning of Lifan? ect.ect.who's next?:thumbsup:

Sounds like the needle isn't right. (Too rich)

And a vaccuum leak. Move the clip 1 notch towards the top and make sure the boots are tight.

My 90 did this until I got the carb dialed in. Went through a few plugs in the provess. Then 400 miles of 1 kick starting until I sold it. As soon as mine would start the bog, I'd swap in a new plug and make a carb change until I got it right. As soon as I had it dialed in, it quit that weird floating idle and fouling plugs.

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