Help with vibration

[joecass]

I did some porting to my BBR 48CC engine and opened up the muffler and now that it revs faster when I get to 20mph it vibrates a lot. Its hard mounted and I tried pushing on the tank and the muffler when its vibrating and that did not help. Are the crank shafts not Balanced that well in these engine or maybe they have a lot of runout? Im thinking about pulling the crank out and checking it.

 

[Deleted member 27811]

There is a ton of info. on here about that exact topic and some one in here can set you motion about this subject. It's hard to balance these single piston engines, but it can and has been done by many. (carry on)

 

[Tyler6357]

Are you using a stock pipe?

 

[joecass]

Yes but I cut the baffle out and that help me gain power

 

[joecass]

Has anyone done this mod? Would the depth and drill bit size be the same for a 48cc engine?

https://motoredbikes.com/threads/vibration.50519/

 

[FNTPuck]

Has anyone done this mod? Would the depth and drill bit size be the same for a 48cc engine?

https://motoredbikes.com/threads/vibration.50519/

No the depth and size would not be the same because the rod and piston are different size/weight.

If you are really determined and brave you can start small (maybe half diameter and half depth) and slowly go up until vibrations are reduced in your cruising RPM range. If you go too far though, you will need a new crank which is not expensive but kind of a pain to change.

 

[joecass]

So if you take to much off you can make the vibration worse or you make the crank week and unreliable?

 

[FNTPuck]

So if you take to much off you can make the vibration worse or you make the crank week and unreliable?

Since you cannot truly balance a single cylinder for all RPM ranges, by drilling the crank/lightening the piston/otherwise modifying the rotating assembly you are changing where in the RPM range it is smooth and where it will vibrate. If you currently vibrate at 20mph and screw something up, you might now vibrate at 15mph (or even worse at 20).

 

[Lukesky36]

i used the stock pipe it used too turn into a tuning fork and vibrate the s**t out of my hands and the whole bike i stuck a banana pipe on it and since then i get a lot less vibration also make sure your not 4 stroking it will cause uneven running and vibration the more you break in the motor the more smooth i find the engines get and im talking 1000 miles break in

 

[joecass]

Do you know what size main jet it comes with mine has no number stamped on it?