For a while now - i.e. since i bought the bike - i've been wondering why it had had no bottom end. I've been told 125 2T's have no bottom end etc., but it wasnt until i rode a mates KX125 that i realised my CR125 had something seriously wrong. After returning the bike to stock jetting, checking float height and needle condition, rebuilding the gearbox etc I have just pulled the head off and apart. The pistion and cylinder look in great condition (except for the carbon on he piston cause it is running crap. So looking at the powervalve is about the only thing i can think of. What I found odd looking up from the exhaust port was that I could see above the powervalve when it was in the static position (i.e. closed). As it turns out I cant actually see a way to adjust the CR125's powervalve, so it seemed particuarlly odd to have such a gap above the powervalve (as this would let the petrol air explosiion decompress too early off idle.
So after much head scratching I pulled out the box that contains the 'spare' engine that I got with the bike - which was the one that had a big end bearing blown. I started looking at the head, and noticed that the edges of the exhaust port looked much sharper, and almost a different shape. I sat it next to the head that i have just pulled off the bike and it looks like whoever "rebuilt" the engine has taken a dremel or the likes to the exhaust port, and bored it out so the powervalve does not actually fit any more (hence the gap above it). Furthermore, i notived that the powervalve flaps in the current head also have holes drilled in them (bout 1mm dia. in each flap) for god knows what reason. I dont think this is a standard feature!
So quite interesting really, whoever 'rebuilt' that engine is a bloody butcher, and the guy i bought it off trademe obviously either did it himself or figured that out and offloaded it!
So my question is therefore who reconditions motorcycle heads in the manawatu region, and what does that cost? the old head that i was comparing the current one to looks ok, except it seems to have a few vertical marks (not scratches though) in it, and a couple of patches where it has some build-up on the surface. everything else looks great though, so im hoping i can get that one reconditioned (properly) and then the bike should be a great runner!
Im acutally quite happy i figured out what was wrong as its the first bike i';ve really pulled to bits and only paying 2k for it, i dont want to be paying a shop to fix the thing cause its so easy. and it will be good when its running properly too as the rest of the bike is in mint condition!
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