Ok, what i have is a yz400 99 model. Here is a short background to what happened before i go on with teh story and ask for some help. A few of us went for a ride, i droped the bike in the river and it was submerged a fair bit. Motor was still running went it came off on me and i was pushed of and didnt have a chance at getting it switch off, so it stalled by itself(guessing water went in?). Anyway, after pushing it to dry land, and getting rid of all teh water, upon starting the bike, it started making very laud noise, very similar to rod knock, or piston slap etc.. mates told me most likely piston or rings gone, just get a rebuild kit and replace it, so that is exactly what ive done. Bought a wisco oem spec piston kit, and while at it, checked some freeplay on my rod and it seemed fine. Anyway, i ended up getting it all in and finished. Started teh bike, and voila! all good, no noises or anything, thought i fixed it and that was it. After a few weeks, mate asked to go for a ride and i thought id start teh bike again, check oil and just overall look over it. Upon starting teh bike, within 2-3min, BANG...a few little noises and oops, thats SAME exact noise i had before came back!!! I was devestated, couldnt figure it out! and so i thought must be big end/rod noise. So i started searching the forum, and found some issues with a crank balancer keyway that was talked about? so i looked at mine and here is what ive found... I am guessing these are teh gears that are talked about when saying balancer shaft and crank shaft gears? Upon further inspection, ive realised i have no keyway on my balance shaft but just splines! so cant be that, right? So next i looked at teh crank shaft spline, and that had a keyway! see picture^^^ Trying to figure out if this is what you guys were talking about, and went ahead and removed teh shaft and tried to see how much play it has... well, it has very minimul play in it rocking it left to right, im guessing this is ok??? How much play should i have here? Then i thought! why not check my timing... well, lucky i did, have a look at teh pictures... So i timed it right? As you can see by where the dot is on teh gear, you can see its not lined up perfectly with the cylinder head! seems to be one tooth out on teh exhaust side? am i right? Next is the intake side, same thing, out by one tooth or so by the looks of things! So, conclusion that im getting to is, is this where my knocking noise would be coming from? i mean, if its advanced too much or what not, it would create wrong timing/firing and would create such a bang/knock! im hoping its that anyway... Question next is, why did it jump on me? obviously, it was running good until it jumped after a few minutes after starting it and thats when the noise came about. Now i just have to check the chain and the chain tensioner.. can anyone tell me how to check the tensioner please? I mean, i had it removed before and by just looking at it, i couldnt see anything wrong, how much force/tension should it have? I just hope i havent done any valve damage, but ive rotated teh engine by hand and nothing hits, so its a good sign. Please give me some opinions and specs to look for now, and any help is appreciated greatly, sorry for the long read, hope this helps someone out one day cheers Danny EDIT: ive just realised i have not timed it properly, as ive noticed teh marking on teh timing gears ( exhaust- E, and intake-I) are 180deg out, so i shoudl have turned teh crank one more revolution! i wonder if teh markings are parrallel to each other? off to rectify and recheck this. EDIT2: Ok, went and turned teh crank shaft onather one revolution, and the dotted markings still remain the same, the intake cam is one tooth out easy. Also noticed, my tensioner isnt doing much at all, i was able to install the tensioner by hand all the way into teh hole, without turning that screw on teh inside of it so the rod can be pushed back inside, wich means, there is stuff all tension on the chain bracket!