Front cylinder knock

[Oldgit]

Hey chaps.

I had an issue where the chain tensioner came loose, causing the chain to flap around a bit (sorry, I don't know what the chain from the engine to the gearbox is called). I tightened the tensioner but since then there is a knocking sound from the front cylinder.

2004 XB12R.

Any ideas what it could be?

Cheers

 

[Theycallmecrash]

Either its the chain again, due to the tensioner having stripped thread in the primary cover. It sucks but it happens.

Other possibilities, low on oil and lifters are making noise. Ive noticed valve noise sounds like its from lower front cylinder. Lifter could be bad, could be an ignition knock. Hard to say cause i cant hear it.

 

[Oldgit]

Thanks for the reply Crash.

Its not the chain, I checked the tension. Pretty sure the oil level is good, I'll check it anyway.

The sound is like a bag of marbles has been thrown in there. I've used a hose to listen and its definitely the front cylinder. It still runs fine though, but sounds awful.

 

[flismvdub]

I have a very similar sounding problem. loud knock that intensifies under load. It used to go away once i let off the throttle, but now it is there all the time.
I tore down the front cylinder and replaced the lifters but on start-up it sounds the same. Sounds like its coming from the lower case. I checked the sprocket nut but that was fine as well. Let me know if you find anything out..... my next step will be to tear into the engine.
Thanks

 

[UMDterp13]

100% Bad front rod bearing, both yours are 04/05 motors I guess?
text/call me and I'll send you video of mine so you can compare it.
Jeff - tree oh one 919 nine 391

 

[Oldgit]

Mines an 04 motor yes. I'd text/call you but I guess you're in the USA? I'm in the UK so that would work out expensive

Interested to see this video though. Any other avenues available?

flis - mine knocks when idle from cold, and doesn't improve at all.

Cheers

 

[Oldgit]

Jeff - I did some more messing around with the bike. The oil is definitely OK, ie its just over the bottom of the sprocket. I listened thru a tube and the loudest knock is from the middle of the "V" where the cylinders meet. Moreso from the front cylinder than the rear. I recorded the sound, not sure how to get it available on here.

Assuming its an issue with bearings, how easy is it to repair once I have the engine out? Are there tolerence issues or special tools required?

Cheers

 

[Phixer]

This is mostly likely the big end gone on the front rod. This requires a replacement crank as they are too expensive to split and repair.

I have the same problem with one in the shop right now. It's about £600 for a new crank assembly.

 

[UMDterp13]

Used motors are about $1000. If your mechanically inclined, I suggest that. I pulled all parts from a salvage 08+ and swapped into my 05 12r.