Atomik 125 proX heavy vibrations and lack of power

[tom152]

I have an atomik 125 proX its was running ok but was getting really hart to start and had small vibrations in the top end. the other day my girlfriend stacked and the pin inside the motor to engage the clutch came loose. so I had to take the clutch side crank case off to fix it. while the motor was out of the bike I decided to change piston and rings, as well as clean the head up a bit. Iv now put it all back together and re-set the timing. but now its running really rough with lots of vibration, any ideas what could be causing it could the timing 1 tooth off be the reason. or should I be playing around with the carby first, like I said before the bike run well, I had good spark and the carby was working well???

 

[my67xr]

hi,
welcome to Miniriders,


it might be a timing issue,
did you align the mark on the cam sprocket to 9 o'clock in the head ?
and was the fly wheel lined up so the T or TDC marking was at 12 o'clock ?

otherwise the valve clearance may be set too tight ?
did you set them to .003" on the intake and .004" on the exhaust ?


be sure to drop by and post in the introductions thread too !
http://www.miniriders.com/general-chat/20824-introduce-yourself.html

 

[tom152]

Yeah the cam sprocket was lined up with the notch at 9 o'clock and magneto with the T at the notch at 12 o'clock. Not sure about the valve clearances what would be the easiest way to work out what the clearances are?

 

[my67xr]

pull the little covers off the head, 1 is infront of the manifold, the other is under the front of the head
here is a video link explaining how to do it.
it will basically be the same process as this, but use the clearances i posted above.
you need a set of feeler gauges, a 14mm spanner to turn the engine over, a 9mm spanner for the rockers' locknut, and a pair of pliers to adjust the square headed stud.

[video=youtube;QJciyJRJh8Q]http://www.youtube.com/watch?v=QJciyJRJh8Q[/video]

 

[my67xr]

btw, have you checked that the flywhees'l locknut is tight ?

 

[zwebx]

btw, have you checked that the flywhees'l locknut is tight ?

also if its a slinger motor check to see if thats tight

 

[GooseMan]

You must spread some Reputation around before giving it to my67xr again

Lol I get this message alot!

 

[tom152]

Iv set and re-set the valve clearances, the motor has really good compression and starts 1st kick, when it is idling it runs reasonably well but when i rev it there is a loud rattling and still a lot of vibrations. its sounds like the valve screws are hitting the caps and on the intake cap there is a small mark so suggest this is happening but no other evidence. the noise defiantly sounds like its coming from the front of the engine. all other nuts and bolts are tight, and clutch and gears are working fine, the bike had been running well, so Im really unsure as to why im having the sudden problems

 

[my67xr]

so when you set the valve clearances, it may not have been at TDC, it was possibly 180 degrees out ?

 

[tom152]

I was sure to turn the magneto so that the T is at 12 o'clock and cam sprocket at 9 o'clock not at 3. if the dot was at 3 o'clock I turned the magneto another 360 degrees so the dot was at 9. If the timing chain was 1 tooth off could this be a possible cause of the running problems.

 

[rotn50]

I have found with quite a lot of engines that when doing the timing the notch on the cam sprocket at TDC will sometimes sit just above or below the notch on the case at 9 oclock, I have found that timing it with the cam notch above the notch on the case is better than below, that's only if your engine is like that when being timed.