Last weekend i drove my 2005 L7 against my friends 2006 L7 on the go-kart track.. My bike is a standard 47cc and my friend`s a standard 49cc bike.
Now the vibration on my bike is very heavy and my friends bike is as comfy as can be, almost no vibrations!
Anyone knows what the reason can be? Engine mounting is equel in my opinion. Possibly the flywheel or the crank?
Could be a badly balanced crank, could just be dodgy quality from the factory. I mught help is you check all the mounting screws & bolts and that there in no excess play anywhere.
Mmmm, a badly balanced crank is very likely. Engine mounts are all fastened so thats not it. I have not opend up the engine yet cause its running ok.
I might do that when i install a head kit.
I think i`ll try the flywheel mod first though, and see if there is less vibration.
A good second hand (or even new) crank & flywheel are aprrox sod all $$ from ebay so its not the end of the world, and its very easy to take it all apart and rebuild it.
if it wasnt vibrating that bad before check the top engine mount the weld probably broke... same thing happened to me but ill live with it lol
good luck
more likely than anything its your engine i found the same thing for a while in my friends cag vs mine if it has a stock big bore motor in it then it will vibrate like crazy b/c the crank is balanced for the small piston/head. Mine vibrated like crazy i had the stock bb my buddy had the normal 39cc and his was smooth check your motor maybe a big bore. you may not have noticed it lots of people don't. may sound stupid but its happened before
I`ve checked the top engine mount, thats not it. It vibrated since the start. I noticed that it was vibrating more then my friends new bike (wich has a BB as standard) when i rode both on the track, so i know now that these bikes CAN run smoothly.
It`s not that my bike is unrideable, but i now wonder if it is damaging for my engine, especialy because i want to change to a 44mm headkit. If these vibrations kills my enginecases, crank en bearings it would be a waste of money.
That depends on which bit is currently out of balance. If the crank is too heavy then, yes, a heavier (44mm) piston will help to balance it out. However, if the current piston is to heavy for the crank then swapping to a heavier the 44mm piston will make it hugely out of balance! If you've got the parts you could just try it and hope it makes it better, it's sods law it won't tho. If you do - don't go mad with the revs either cos if it is more out of ballance it is trying to rip itself appart, and most likey will at high RPM's.
I`ll have a go with the lightened flywheel mod first. Don`t think that it will do much harm because the flywheel isn`t balanced in the first place?
Mayby i`ll notice some difference.
Then i`ll have a go with two extra engine mounts to reduce vibration even more. I`m hoping to test these improvements on the track in two weeks time. I`ll post my results then.
Oke, I`ve been riding with an extra engine mount. This actualy helped, because i could tell it reved out more. Still vibrating though.
Now after a few races on the go kart track it started vibrating more and i think it has finaly destroyed the crankbearings...
So i orderd a Head kit with a new crank witch i am going to install next week. I`ll post the results when i`m done.
Just one question, does anyone know wich type of crankbearings i should order?
So, i took my engine apart to install the new head kit with a new crank.
The old crank was indeed out of balance a lot.
Installed the new kit and some new bearings and went to the go-kart track just to discover that it had the same problem still!
So i had my flywheel and the one from my friends bike checked. His flywheel is ok but mine was not balanced properly. I had mine machined , so we will see if this is the solution to the vibrating problem.
