Racing my K7 GSXR600 on the weekend. Go out for qualifying, bike running great, take pole by 1.6s and pretty confident about the days racing. Go to start the bike to form up for race 1 and it is a little hard to start and sounds a bit rough. On dummy grid I notice a bit of smoke so call it quits and go back to pit. Strip bike down and find a plug is fouled. Give it a bit of a clean, start back up but still smoking. Call it a day and come home. Borrow a compression tester from a mate, cyl 1 90psi, rest of cyls are 145 or so, pretty consistent. Not sure what has caused the drop of compression on #1 so only thing to do is drop engine out and take head off. Being a bit of a noobie (only just bought this bike after riding 125's for 4 years) I am a bit hesitant but after good advice from my mechanic (who is about 1000kms away) I take the head off and find what is in the pictures below. Major signs of scuffing on the bore, not sure what has caused that (ring failure?) but also sign that the piston has been touching the head (left side at around 9 o'clock) and also a small mark where the left side inlet valve has just touched piston lightly. This could indicate something worse, maybe big end? So next step is strip the bottom end. Something I am a bit scared by quite frankly. Although looking like it could be cheaper to buy a complete replacement engine. I see plenty going on here but not sure what shipping to New Zealand would be! So has anyone else seen this before? Engine had 1 meeting on it since my mechanic gave it a once over and replaced the valve retainers. In qualifying bike seemed to be running fine, but 30 mins later when I start the damage had been done. Pretty gutted to say the least, was getting ready for our championships starting mid January. The budget was already tight so this has compeltly cocked everything up!!! :down:
if your finger nail catchs on the ridges on the bore the wall is pretty much done and only a overbore will work if its not to deep. the pistons show signs of blow by which is indictated by the white ring around the piston
I thought the ring on the left side of the piston was from the piston hitting the head? Top and bottom is from blow by, hence the oil smoke/fouled plug and scouring on cylinder wall. There is two tiny shiny bits on the left inlet valve pocket, hard to tell if the valve has any damage to it though. I have found a bottom case/cylinder and crank, rods and pistons with 1000miles on ebay for $300USD. Might be the best solution I think. Only other logical option is 4 new pistons and clean up cylinder, but then there is chance I would loose some compression?
You need to look at the connecting rod bearings before you start buying parts. I'm guessing that the rod bearing spun/failed and that allowed the piston to move up just a bit in the cylinder, touching the valve and head. Good luck with it.
Just by looking at the pics my guess would the rod bearing failed which allowed the piston to contact the cylinder head and valve. My next step would to remove the oil pan and look for debris. Be sure to check the oil pump pick up screen also.
I'm curious to see what the side of that piston looks like. To my very very untrained eye, it looks like it might have seized. please post up more pics when you get the motor apart.
I would really like to pics of the piston removed from the bore. If the newer GSX-R's get too much race time on them the piston can just explode. It is also possible you caught it in the early stage of self destructing.
Yeah that is coming shortly. I have nearly split the cases, I just need to work out how to detach the selector shaft from the drum. I haven't removed the clutch and it's a little fiddly. Will post some pics when I get it out!
So what do you think the cause is? I could just get the cylinder honed and a second hand piston off a mate, $200ish and I have a running engine again. I'm just worried another cylinder could do that too?
You can't hone it. Clearance is 0.0015" max. It's not a Triumph Bonneville with cast iron jugs. Honing will make it so sloppy it will just rattle around and break, plus you've damaged the coating severely. You need to replace the cases or have the set recoated. To be honest, mate, I never figured out the exact cause in either of the two 600s. One was overrevved, as I told you, and got hot and melted. It's still apart. The other one was recoated and raced again, no problems. I think there is a material fault in some of the pistons, but I have no sure data to back that up. Recoating is about $600 here. When they do that you have basically a brand new set of cylinders with perfect clearance. Millenium Technologies, the KWS sponsor, does awesome work. I do realize where you live...
Yeah I am either going to buy a second hand set of cases or another engine. My only concern is that it was caused by detonation from either lack of fuel or too much advance. If that is the case then I could put it back together with a new engine and it would do the same thing. So frustrating not knowing the cause!! Every time I find something it just raises more questions.
(I believe you but) that's crazy!!! It seems like it wouldn't take much expansion to cause some trouble!
I was under the impression that it is possible to clean off the alu with acid and then get the bore lightly honed with the correct nikasil bore honing device and it would be usable. Probably not optimal but not going to blow up because of it? I am probably going to buy a new engine, but I am just worried that it was caused by fueling. If that is the case then there may be a faulty injector etc.
If it's fueling, it would be a rich condition washing all of the oil off the cylinder walls, right? Wouldn't a lean condition show up as an eroded piston? I always thought that too lean would cause small deposits of aluminum to appear on the plug and the top of the piston to be light gray and dished. There are oil jets under the piston to cool it down, so if it was too hot on the skirts it must be because there was no oil at that piston for a long duration. Or the wrist pin seized up (lack of oil) causing the piston to rock in the bore and make contact with the wall. Or, it failed like Rick mentioned previously, I wouldn't know without the engine in front of me.
that's what I did on my TZ250. (but then again it didn't rev to 17K RPM) I would think it would work as long as the piston to cylinder clearance was still with in spec. If you have deep scratches on the cylinder wall then your compression will not be optimal. clean up the cylinder and put a ring in the bore and check to see if touches the cylinder all the way around. It wouldn't hurt to check it out since you have it all apart anyway. muriatic acid will eat the alum off the cylinder. I would try it the piston might have touched the head when it got hot and expanded.
what kind of fuel management system are you using? did you drain and refill the cooling system at all prior to this track event?
I think you are a little tight there on you clearance. The service manual lists a service limit of .0047".
You need to look again! maybe .047mm but not .0047" If you tried to run one that loose it would sound like a diesel if you ever got it to start.
