[Nick-G]

I recently installed a tb108cc stroker crank on my crf50.



It has a tb race head, piston, and cylinder along with hv oil pump.



My problem is when I start the bike up it knocks very loud it kind of sounded like the piston was making contact with something so I took the head off and piston and valves show no signs of contact at all.



Anyone have any ideas it seems to be getting worse and I can't figure it out.

 

[fiddy4ever]

Adjust your valves. Mine always seem to come loose over time and they will start knocking when there loose.



Intake valve set it at .003



exhaust valve set at .004

 

[Nick-G]

Adjusted them both more times than I can remember. I even kicked it over without the rockers with the valves sitting closed all the time and it still did it.

 

[firepower354]

Try a second base gasket. I bet you're hitting the head.

 

[doopsx3]

+1 on the base gasket

 

[Nick-G]

Tried a second base gasket still knocks.



Its kind of a slow knock and I can only hear it at idle.

 

[doopsx3]

when you had the top end off, was there anny sign of the piston hitting anywhere...it may be slight

 

[Nick-G]

piston and valves looked perfect no signs of contact anywhere.

 

[crf50187]

post a video and pics of the piston

 

[XRshfifty]

forget a bearing when installing the stroker crank?

 

[Branyers]

What clutch are you running? Are you sure the noise is coming from your top end?

 

[Nick-G]

forget a bearing when installing the stroker crank?

I don't have any extra parts laying around that I am aware of.

What clutch are you running? Are you sure the noise is coming from your top end?

100% positive its coming from the cylinder/head of the engine.



The most confusing part is the knock literally goes away as rpm's increase. It is really loud at idle but if I turn the idle screw to raise the idle it nearly goes away.

 

[530mini]

Is the flywheel tight? Do you hear it if you turn the crank by hand? I just built a tb108 with no problems, but I have left the flywheel nut loose before and makes a noise as you describe. HTH



Derek

 

[fulp428]

its a head gasket just had mine do it took it apart and head gasket was torn put a new one on and ran like a champ!

 

[dood]

I recently installed a tb108cc stroker crank on my crf50.



It has a tb race head, piston, and cylinder along with hv oil pump.



My problem is when I start the bike up it knocks very loud it kind of sounded like the piston was making contact with something so I took the head off and piston and valves show no signs of contact at all.



Anyone have any ideas it seems to be getting worse and I can't figure it out.

Your crank could be hitting the oil pump drive shaft. Or you could have a bad rod bearing right from the factory.