tapping noise

[Fattmungus]

my gearbox packed it in a while ago and it seems that since i got it rebuilt ($500 later) my bike will make a tapping sound occasionally. it only seems to happen when it is hot (the motor i mean not weather). it sounds like the tappets, cos it is a light metallic sound. i assume that if it was tappets, it would be more loud when its cold and be less noisy when hot. has anyone experienced this before? im gonna check the tappets this week as part of maintenance. so i was wondering if anyone has experienced anythin like this before?

 

[z50kid]

are you talking on ur pit bike yer?

 

[Fattmungus]

yep. the bike in my avatar pic

 

[benox]

I dont know if this even makes sense to what your talking about, but does your bike have a 138 in it? My bike + Sydneys are both 138's and have this tapping noise coming from the head.

If that was so retarded, and so not in relation to anything your talking about, just ignore this post

 

[crazzy #1]

hmm... dont make sense buddy, does the sound have to do with the gear box or the engine? ur not so clear about which one it is

 

[Fattmungus]

its a 125cc. the standard motor for the bike. genuine thumpstar. well the sound is relative to engine revs so i dont think it is in the actual gearbox itself, otherwise it wouldd be relative to the wheel speed.

 

[Ruby]

Cam chain slack?

If it was me, I would have spent the $500 on a new complete Lifan 140cc engine and had change for carby and IRK.

 

[coolmodee01]

my guess is timing chain
does it run rough?

 

[Fattmungus]

it still seems to run fine. i can start my bike up cold e.g. after a few days and there will be no noise. it only seems to appear after i ride it for a bit. if its hot and i stop riding, i can hear it when its idling. then if i turn my bike off and start it again, it is there. if i rev it while its sittin there i think its still there at high revs. i dont know bout high revs when riding cos its too loud. does my motor run a chain tensioner? and wat sort of life can u expect from a timing chain?

 

[pegleg]

I think that you should do your valve clearances, and this should be done when the engine is cold.
If they were done when they were hot previously, they could be way out.
and as Benox said, if this makes no sense whatsoever or sounds retarded, just ignore the post...lol

 

[crog]

I have had the same problem with my brothers bike.
It sounds like it's coming from where the cam chain is!
I must check if there is any slack in that. But it hasent done it for a while and how do you check your valve clearances?
cheers

 

[Sidney]

Yeah like Benox said. My bike made a tapping noise and I thought it was abnormal, took it to the machanic and got the tappets adjusted and it made no difference so I rekon it's just normal.

 

[Fattmungus]

well (in the case of my 125) you take off the two valve caps on the head, and the top plate. then u make sure the rocker you are checking is on the back of the cam lobe. there should be a little bit of up and down movement between the rocker and the top of the valve. if not, then thats probly the reason you are doin the clearances. anyhoo, u put a feeler guage between the rocker and the top of the valve to get the clearance. the adjustment is made by undoing the nut on the rocker and turning the threaded adjuster clockwise for less clearance and counter-clockwise for more clearance. once u get the right clearance make sure the nut is tight. reassemble and yeh all done. i knwo this is a vague description but im sure somewhere on this forum there is an in depth discussion on setting them. i have heard that the clearances should be .004 thou (0.1mm) on both? does anyone know if this is correct for my thumpstar 125? yes i know there is USUALLY more on the exhaust but not always.