By:Pyndon
Amazing what work you can get done in three hours.......
Now I gotta get to work, first a good rub and a scrub to rid all dirt before the operating theatre!
2 more hours in the shop tonight. Did the last bit of cleaning and commenced the strip....
I could not clean between the cylinders very well until I'd stripped the coolant hoses and starter off. When I did, it was only too clear to see where the leak was stemming from.
Rear Cylinder:
Front Cylinder:
Interesting that on the first picture you can even see a gap under the head...weird
So I stripped the rear cylinder to take a closer look....
Followed shortly by the front cylinder....
A quick clean and a closer inspection revealed the cause of the oil leak.
Rear cylinder crankcase face....
Front cylinder crankcase face.....
As for what caused this, I have no idea. Clearly nothing to do with a blocked breather hose or increased crankcase pressure. Looks more like abrasive wear or some type of corrosion. Every nut/bolt was checked on removal and was torqued correctly, nothing loose or untoward
Yeah I'm a little frustrated that it's not an easy fix but I'll be totally honest here. As I sit and write this, I really don't have no issues with it whatsoever. I can honestly say that this engine has been flogged to death for 68,000miles and has probably done more tough hard miles than most others. I have got my money's worth out of this bike (engine) twice over and I think it's going to be happy for an engine rebuild.
It's also interesting to note that both cylinders have done the same at about the same time in life so maybe it is just wear and tear?
The solution - a set of new cases I guess. Has anybody got any lying around?
We'll get it sorted soon, I'm having withdrawal symptoms already
Now I need to tear it down further, I'm going to do a full engine overhaul. New bearings, etc. and generally check everything over while I'm in there.
Obviously before now I had only identified the problem with my motor being damage between the base gasket and crank cases causing some type of corrosion between the two. The samples have currently gone for analysis with a corrosion expert and we are waiting for results.
What I can confirm is that the cylinders were unfortunately attacked in the same way and as a result, these have gone for analysis too. Although they were not as bad as the crank cases, they were bad enough not to use.
Pictures of the cylinders….
In addition to this, the front cylinder showed signs of the Nicosil coating lifting from the casting and in one case chipped off slightly. This is something I was glad to find before it becoming a real issue. It was not noticeably affecting performance or oil consumption so I think I caught this in good time. FYI – I have seen this happen on a number of Yamaha R6 engines after less than 10,000miles so it is a common problem and is thought to have been much improved over the years through improved processes etc.
This was on the front cylinder, you can see where the coating has become polished where it is lifting and the chip is also clear.
Wear wise on the cylinders; if it wasn't for the damage they are perfect. Perfectly round and when measured in parallel with the pistons, they were in spec with a running clearance of 0.06mm (wear limit is 0.1mm). So, if it wasn’t for the damage, they would be great. Astonishing considering what the bike has been through. If they were not damaged as a result of the corrosion or peeling, I would have given them a quick freshen up with a flex-hone and ran them again.
Moving onto the pistons, I have run the bike on some pretty crappy fuel over the years with the places I have been and have just got back from Africa so it is hardly surprising to see the amount of gunk built up on them. Not an issue, just need a good clean.
Skirt warn perfectly smooth, no scoring.
What was interesting is the amount of blow-by evident from the lower oil bypass on the piston. The brown indicating the blow-by indicating that the rings are on their last legs. Hardly surprising really considering all the silt it swallowed in Baja It will be interesting to measure the end gap.
So, giving the pistons a quick measure, they came in a 99.936mm and 99.949mm front and rear respectively. Wear limit is 99.93mm so both clearly in specification, close to the limit but usable. This probably explains the increased engine noise over the years. Decision is made to continue to use these pistons.
Piston rings however, will be changed regardless. The blow-by evidence was as a result of what I expected. The piston rings were close to their limits, end gaps of 0.483mm and 0.457mm front and rear respectively. Wear limit is 0.5mm. New rings will be fitted for sure. More compression = more power = happy Pyndon
Cylinder head wise, looking pretty good really. Inspected the valves and there is minimal evidence of ‘cupping’ and the clearance have been pretty stable so I was happy to see this. I stripped the heads and gave everything a good inspection. Results though would suggest that a light lap with fine paste to clean up the seats and they should be good to go back onto the engine. Good news there. All the cam journals are good.
Right, onto the bottom end. First of all start stripping the flywheel side.
Here I have used a straight edge to try and indicate the amount of wear on the output shaft. It is about 0.127mm on each spline and it’s only going to get worse over time. I’m throwing a new output shaft in for the sake of it while I’m in there, they are available and not that expensive. I think all the hard work in the sand that this bike has done has attributed to this wear. Acceptable in my book, I’m sure it would go on for miles more but I’m not willing to try it.
Once this side of the motor was stripped, there was evidence that the left hand upper main bearing shell had moved. It had drifted out of the casing slightly, not enough to cause a problem but I noted it nonetheless. I think it will be worth measuring the case bores to check for wear once I get torn into it.
Next up, clutch side strip down. Everything looking good here, it wasn’t long since I put a new outer basket in as a result of a re-design (posted in this thread) and everything else looks good.
It is extremely pleasing to note that this engine has done 68,000 hard miles and is still on the original clutch plates! I measured them and they are still within spec and showing no signs of deterioration. These will be going back in on engine rebuild. This is excellent to see.
Off with all the pulleys and gears.
No signs of movement of main bearing journals at the right hand side.
Out with the balance shaft…
Now split the cases…I love this bit, it’s like opening a Christmas present
Closer inspection of the bearing shell movement, no problems just need to investigate why. Maybe the cases are wearing slightly? Will measure later.
Crank removal and then onto the gearbox.
The crank is sweet; no signs of scoring or excess wear at all. Moving onto the gearbox, I removed the lubrication rail first and was amazed to see it spotlessly clean inside and out!
Shift forks showing no signs of excess wear at all…..
……and to me, this looks like a brand new gearbox! I’m very respectful of the gearbox on my bike but don’t think I don’t beat on it. I’ve ground a fair few gear over the years, even the type that make you cringe and look back to see if you left anything on the road. You would not think so looking at this though. Absolutely no excess wear on the drive dogs whatsoever, the area any mechanic looks first! Gears / teeth are like new too.
I was keen to check the wear on the shift fork rollers as I have seen other have these fail in the past. While they feel ok, there is a little play in them and since they are so low cost, I think I will replace all three anyway for peace of mind. I’d kick myself if I had to go back in again for one of those little fellas failing!
Engine bits parked neatly to one side, it was time to have a closer inspection at the components and casings.
First of all I checked the roller bearings in the casings. Surprisingly, the only one with any feeling of roughness was the smallest shift drum bearing. It was not damaged but if I was using these cases again I’d replace it. The others were all super smooth.
The main bearing journals were all in pretty much the same condition. They looked fine although I was not measure them to confirm tolerance in conjunction with the crank shaft.
Crank shaft measured 49.9745mm left and 49.9872mm right. Near as damn it both in the blue band but the left possibly more a warn yellow.
The main bearing bores were 50.04mm and 50.05mm left and right respectively.
Link the two together and this gave bearing clearances of 0.0655mm and 0.0628mm left to right hand side respectively. Wear limit for these is 0.08mm so they are well in the wear limit but just outside of the upper tolerance band of 0.055mm. Again, if this was going back together, I’d probably run them again but given I may be using new cases, I’ll throw new bearings in and try to tighten up the tolerances a little. Should help keep the engine noises and wear at bay.
I haven’t pressed the bearing shells out yet but when I go I will measure the case bores to give sight into the shell movement if possible. I have had Honda CRF450 main bearing bores oval on Supermoto bikes before and cause the roller bearings to ‘float’ in the cases so I won’t rule it just yet.
So moving onto the oil pumps. First up for inspection is the suction pump. All in all not too bad at all. A few signs of debris being dragged through the workings but nothing too much to cause concern.
Inner to outer rotor clearance is 0.0762mm and the wear limit is 0.2mm so well inside this.
The clearance between the outer rotor and the housing was 0.127mm and the limit here is 0.4mm. Again, well within limits.
Finally, the axial clearance was 0.076mm and the wear limit here is 0.24mm. Again well inside the specification.
To be honest I was kind of hoping to find that the oil pump was wearing out and this was the reason why I was suffering so much cam-chain slap in hot temperatures but now I am not convinced. All the contact surfaces are showing signs of wear but nothing that would make me want to take action. Given that I may fit new cases, I will probably throw new inner and outer rotors in to set out on the right foot anyway.
So moving onto the pressure pump side and pretty much the same here really. Nothing out of the ordinary.
Inner to outer rotor clearance is 0.0762mm and the wear limit is 0.2mm so well inside this.
The clearance between the outer rotor and the housing was 0.1016mm and the limit here is 0.4mm. Again, well within limits.
Finally, the axial clearance was 0.0635mm and the wear limit here is 0.24mm. Again well inside the specification.
And that’s it really for now. The cases and cylinders have gone for a thorough going over and analysis to identify what has happened.
The cases….
After talking to a number contacts at KTM and racing colleagues around the world, I am getting a warm feeling that something good may come of this one.
I must emphasize that I am absolutely happy with the performance and durability of this bike and its engine despite what we are finding here. Everything identified in this thread or this post is aimed at helping others and if this latest issued is resolved as a result of what I am doing here then everyone will be a winner in the long run. I hope that I can get my bike up and running soon and KTM and everyone else reading this thread benefits from it in some way or another.
Until next time, I must progress some 950 engine rebuilds……my garage benches are starting to look like something you would see in a factory in Mattighofen.
Better than Christmas here today, look what was on the doorstep when I got home.
Now, into the shed...
OK, it’s taken me six months getting this engine build done but now it’s done and it’s time to share all the intricacies, niggles and issues along the way. I could have just opted to replace the engine cases with the replacement cases for the 2003 motor but instead I opted for the 2010 cases for a number of reasons. First off, the lubrication system built into the new cases has been improved as well as additional longevity built into them i.w.o up rated bearings etc. All of this will be revealed within this write up and hopefully it will help others understand the differences between the years and act as a picture reference file for others when rebuilding their engines in years to come.
Well, the oil in the air box was worse than I thought. The motor was using oil and oil was dripping from the air box if I left the bike on the side stand after a ride. I was really struggling to see how it could be worse, especially with newer rings etc, how could it be breathing heavier, it's just had a Pyn rebuild!. |