yzf250 knocking noise after rebuild.

I have freshly rebuild my top end on my 2009 yzf250, new intake valves piston and rings, cam chain. I put it all back together ran mint, but after starting it up for about the 3Rd time a loud knocking noise from the engine appears, the bike is still running fine although a very obvious loud knocking noise. valves are all inspect aswel. note, the knocking id only at one certain compression stroke its past TDC its a short stroke but quite a difficult one, never had even put it in gear so i dont think it is the trans. i also ripped out the cams a couple times thinking that was the problem and once i put it together it ran mint for about 4 seconds then knocking came back. I originally thought it was the exhaust cam decompression sticking but after inspection was not making the nosie. I took the flywheel off and checked if I had put it wrong, but no. have just tore apart the clutch side cover and all teeth are fine. I am at a point where I don't know what to do next. please any advice is much appreciated.

Edited by Kieran Black

If the noise was not there before Your work, I would look for something that was done wrong during the rebuild.

Loud knocking noise, any way wrist pin clip came out ?

 

 

 

 

thanks for replying, yes that's exactly what I have done back tracked. the noise was definitely not there before rebuild but I have gone over everything. as for the wrist pin, that could be something as my new piston kit came with circlips with no plyer hole so I just used the old ones which had them. I didn't think this would matter as they fitted alright in the slot? 

 

Edited by Kieran Black

NEVER re-used wrist pin circlips!

 

Most designs don't have 'plier holes'.

 

 

 

okay this could possibly be the problem, it would be impossible for the clip to slide into the bottom end ? the noise was more of a knock though not a rattle of a clip. the bike still runs so obviously the pin is still in tact, yet if the clip was loose that could cause the pin to move around within the slot ?

If in doubt, dis-assemble the top end and replace the circlips.

I've had a circlip fail on an ATC200X 3-wheeler,

the wrist pin slid out and wore out a 1mm groove in the cylinder.

 

Apart from consuming a lot of oil and smoking/spooging like mad,

it made no out of the ordinary noise while running.

7 hours ago, Kieran Black said:

okay this could possibly be the problem, it would be impossible for the clip to slide into the bottom end ? the noise was more of a knock though not a rattle of a clip. the bike still runs so obviously the pin is still in tact, yet if the clip was loose that could cause the pin to move around within the slot ?

The knock noise that You hear, if a clip did come out, would be the wrist pin hitting Your cylinder wall .   Not good ! 

Sounds also like, You might have put the wrong used clip in the piston,  from the info I see, the motor would come apart again and look for what was done wrong. 

Good Luck and I hope You post again with the out come ! 

 

 

 

 

I can't belive it, you guys were right. I am beyond pissed of garking on the cylinder, might just be salvageable. more worried about the circlip which I cannot find. this is a bloody joke. thank you guys for reply because I was about to take it to a shop, but now it's just my own fault. thank you 

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