Vibration issue after 1000 km

[zapkin]

As some of you may know, I purchased an American Lifan 2007 GY-5 in January. Last week, I rolled over the 1000 km mark and the bike started developing a strange vibration when the gears are engaged and I am driving on the road.

It was barely noticeable when engine was cold, but as the motor warms, the vibration gets worse.

The first thing I did was check the engine mounting bolts and all were nice and tight.

Within a couple of days, the vibration became very annoying.

 Just the other day I took the bike into the shop and they did not seem to take me very seriously, even suggesting that the wheels’ being out of true was the issue. They checked the chain, made an adjustment, and adjusted the clutch. The bike had cooled down some, so when I left the vibes seemed less.

Saturday, I started the bike and there was a weird humming coming from the motor as I let it warm up. I then took the bike for a ride and the vibes were even worse. I parked it.

Sunday, I took the bike for another ride. Once warmed, the bike started with the vibration again. So this time my brain clicked and I thought I would see what happens when the clutch is pulled in at about 45 miles per hour...what do you know? The vibration disappeared. This tells me that the tires or rims are not to blame. Right?

Today I took the bike into the shop. I know they are not taking me seriously and it is annoying as hell. I posted about the issue on the American Lifan website and they said no problems were reported with the trannies in these bikes. If you are curious about this, I suggest looking around on the chinariders.net site and you will find issues with trannies in these bikes...but anyway I will take their word for it and be confident that the transmission is not to blame.

I do not know what is wrong with the bike, hopefully something simple.

Now on to the good news: I received my air filter and #115 jet from rabbit in about a week. I installed the filter and noticed an immediate improvement in idle and throttle response. Right now with the clip down all the way and with the air filter on the bike runs better than ever...BUT...there is that leg and hand numbing vibration that seemingly came from nowhere.

 

[Martin]

... and I thought I would see what happens when the clutch is pulled in at about 45 miles per hour...what do you know? The vibration disappeared. This tells me that the tires or rims are not to blame. Right?

Probably, but not necessarily. When you pull the clutch you also take away the tension from the chain and from the rear hub. Check that there is no freeplay in the rear swingarm, wheel and hub. If it's all tight I guess it most be an engine problem.

Oh, one more thing. I had this annoying vibration thing for almost a year. I check all motor bolts again and again. But on close inspection i found that one of the mounts had a fine line in it. When I removed the bolt, the mount fell off! After welding it back on vibrations were all gone.
 

[zapkin]

I did check the sprocket bolts and all were tight. Could this be an issue with the rear hub? or wheel bearings in the back?

[countrycruiser]

Zapkin,

I know little about this bike but I wonder if you could some how get the rear whell off the ground and do a visual on it while the rear is spinning???

[Jim]

Zapkin, I replied to you on the american lifan site...

But I also wanted to reply here...


I believe that the reported transmission issues you mentioned from china riders were actually with the non counter balanced engine, as far as I remember.

And I thought I could mention a few things on my gy5 that vibrated or rattled... (it was unbalanced though, and is now sold)...

The muffler insides broke apart and that made a heck of a rattling noise
The battery box cracked
The motor mount bolt broke


All of these were repaired, and this was the non balanced motor. The only one that caused significant vibration though was the motor mount, but as far as I know, they've been redesigned for the balanced engine, and I haven't heard of them actually being an issue.