Yesterday I took a ride at my favorate lakeside road here.

The problem is it seems that the bike doesn't run smooth enough, since it's a second-hand and till now I can't find another one here, so I don't know it's a problem or it is what it suppose to be.

I can feel there's a force pushing and pulling the bike when you holding the throttle steadly. I cleaned the carb and this problem had been reduced.

Besides, the vibration is so strong, when cruising at 80kph at 6th gear, I can feel the pulse of vibration, it isn't comfortable. My last bike is a Hwak GT 650, but it's smoother than the SH. Is this right?

Now the bike has 41100km on its speedometer, don't know if a jet kit would make some changes.

 

That doesn't sound right to me. Are u sure it's engine related? If you pull in the clutch, does the bike still feel rough? Is there a particular RPM where it's twitchy? have you had a professional tune-up recently?

 

I'm sure it's about the engine.

The pushing and pulling force has been reduced, but not eliminated.
The vibration feels not like a problem, just not feel comfortable.

There's almost no experienced mechanic here, and they always don't feel wrong with my bike.

 

Sounds to me like maybe timing is off, or carbs are out of synchronization. The SH is one of the more smooth V-Twins that I've ridden - so something isn't right. I don't do much of this work myself, maybe one of the others can add some insight.

 

I've sync the carbs.
Maybe the timing...

 

Adjust your chain.
I bet it is too loose.
My '03 did that at about 1500 miles & it was my chain adjustment.
Stopped after I adjusted it !
I never would have thought that could do it but a friend suggested I check it out. He was right!

I just saw you have 41,100km - Wow thats about 25,500 miles.
Have the chain & gears ever been replaced?

Here's a pic of a really worn sprocket.
Does yours look like this?

 

I've replaced the chain and sprockets, they're like new now.

I will check the chain adjustment first, it's easier. Thanks!

 

Mine had the same problem when i bought it..... it turned out that the chain was too tight and the rear axle was waaaaaaay over tourqed.

 

If these tips do not help you, I would be looking at the tuning a bit more. An engine that surges like that is sometimes lean on the fule setting. If it is doing it at constant throttle perhaps your needles need richening up a bit.