Full Engine Teardown and Rebuild

Work in progress, missing pics.

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.

So, while I was waiting for the new cases and cylinders to arrive I thought I may as well strip, inspect, clean and re-build the cylinder heads. The gunk on top on the piston, and the gunk inside the SAS chamber was a good indication of the places
I had been riding recently, like Africa where the quality of the fuel is so poor.

It’s difficult to capture on camera but you can see here the wear on the internal valve springs caused by the two springs rubbing together. Not a concern, just wanted to highlight the wear after 70,000 miles.

The heads were fully stripped, inspected and cleaned. All the valves and guides checked for wear etc. Everything was in good shape, all I decided to do was to re-lap the valves into the head lightly just until I was confident that the seat was 360 and clean again. Incidentally they didn’t take much and are still not down to the smallest shim sizes, pretty impressive.

Another through clean of all the components and time to put them back together. New valve stem oil seals were fitted in the process.

Remember me saying about the main bearing shell wondering out of the engine case in an earlier post? Well, when the new cases arrived I saw they had three threaded holes around the main bearing bores, something the earlier cases did not have.
Old cases…

New cases….

It would appear that they have identified the wondering shell problem and resolved this issue. They have designed a retaining plate for the shells that screws over the top to hold them in position. You don’t get these with the cases, so if your upgrading ever, make sure you order them or you’ll have to wait another week like I did.

With the crank all measured and very little wear apparent, I selected the correct shell sizes (still red size) and pressed them into the new cases using the KTM tools. This is a heart in mouth process, pressing those shells into $1500 cases has the potential to go very wrong if you are not meticulous. You cannot and should not do this without using a press and keeping everything perfectly in line, they are tight!

Once installed, always check the installed dimensions as per the manual to ensure the clearance is good.

Fitting the new main shell retaining plates (use Loctite)…

I had previously identified wear on the countershaft sprocket splines and since I was into the engine I thought it best to replace the shaft with a new one. They are not an expensive item surprisingly so worth doing on a high mileage bike like this.

Simply remove everything from the old shaft, taking care not to over-stretch the spring rings, inspect everything for wear and re-assemble to new shaft in reverse order.

Surprisingly, there was no evidence of wear on any of the gear dogs or teeth. I was really pleased to see this, these gear stacks are bombs.

Next it was time to strip and inspect the big end shells. When I stripped them down I did notice quite a bit of visual wear on one shell.

I identified this uneven wear to be due to the fact that the shells were not aligned properly during installation.

I did however check the clearances with plastigauge and the clearances were in tolerance. Regardless though, while I was in there, I replaced the shells (red size again) to match the crank and ensured they were aligned correctly. I re-checked the clearance with the new shells and then fitted new rod bolts.

New shells….

New clearance..

New Bolts….

It is also important to note that the cam chain oil jets and clutch oil jets DO NOT come installed in a new set of crack cases. It is therefore important that you remove them from the old cases and re-install them into the new cases. Size 60 for the cam chain and size 30 for the clutch jet. The piston / cylinder jets have changed on the new cases from once jet to two (one at the front and one at the rear) for improved lubrication and cooling.

You can see the new jets here, the brass jet and the steel tube jet, these come pre-installed in the new cases.

What is extremely interesting to note, and something that I was not aware of, is the new dowel arrangement they have designed into the engine casings. This is almost surely as a result of the problem I have had where the cases are moving in the centre of the cylinders and allowing contaminants to get into the gasket area. They have now included two small dowels to prevent case movement in this area, a positive step in the right direction.

Incidentally though, you do not get the dowels with the cases, so make sure you order a pair up front or as with me, it’s job stop for another week. The bolt length in this region have also changes as a result of the new dowels.

The gearbox stacks themselves were in great condition as were the shift forks. I had already installed the new (stronger) shift drum earlier in the bikes life but it would definitely be worth replacing the shift drum on any early bikes for the new one. The early ones has a habit of breaking if you snatched a gear. Another small item that does wear out is the shift fork bushings. These are a tiny item that cost nothing to replace. Although mine were showing signs of wear I’m sure they would have been fine however, I was not doing to take that risk, and I’ve seen them fail before so I replaced all three during this rebuild.

With the crank re-assembled and the gearbox prepared, before installing them into the cases you first need to install the oil pump. Upon inspection of the oil pump, all the rotor clearance tolerances were good, even though they all showed signs of wear. I took the decision to use the same rotors and housings during the rebuild as they are quite a spendy items and they were in spec.

The only thing I did change, and this was very interesting to note, was the pressure pump housing, piston and spring. We all know about the 950 cam chain clack when the engine is hot, well, my opinion is that this is caused by low oil pressure (as many of us know) hence why the oil light flickers. Well, when I inspected the pressure relief piston and spring on the oil pump, I began to see why mine clacked so much.

The minimum spring length spec is 42mm, my spring was down at just under 41mm, thus reducing blow-off pressure. Also, the piston and housing was extremely warn, obviously leading to oil leakage from the pressure pump.

Not the best pictures but trust me, they were scored up pretty bad.

The new pressure pump housing has a different (concealed) spring retaining mechanism. Interestingly, although the parts manual does not show it, when you purchase the new housing, you get the piston, spring and retaining mechanism all included so you don’t need to buy them all separately as I did. Ah well, I have spares!

The new spring installed measured at 42.59mm and this along with the new piston and housing should help prevent leakage and improve oil pressure.

Another thing I noticed…..and yet another weeks delay while I ordered more parts, was that the gearbox oil rail has been re-designed to include an o-ring at each end. Again this is to prevent oil leakage at each end and help maintain oil pressure. While the early ones can still be used, I really wanted to eliminate all oil losses and try and put a stop to that annoying can chain clacking. So I ordered the new part which was amazingly, just a few cents. This part, as well as the new pressure pump housing can all be retro-fitted to the earlier cases so if you’re ever in there, I would highly recommend for the cost.

With the oil pump installed (be sure to follow manual as the rotors fit in specific ways), the crank installed and gearbox and shift mechanism all installed, it was time to close up the cases.

Before doing so, I applied Graphogen paste to all the shells (including big ends on assembly) to protect the shells on initial start-up prior to oil pressure building. I also put a drop of oil on all the roller bearings to give them some lubrication from the off.

With the cases all closed up and the gasket trimmed to the base gasket face, it was time to start building to it. Gear selector shaft assembly, gear position sensor etc.

Then came the next show stopper (which is why this build’s taken so long – all the unknowns!) when I discovered that my balancer shaft does not fit the later cases. They changed the left hand bearing from a ball bearing to a cylindrical roller bearing. In the new engines, the balancer shaft acts as the inner bearing race and is a smaller diameter to that of the old engine. Thus, the shaft would not fit, bummer!

On the later engines, they updated the balancer shaft assembly for a number of reasons. First off was the bearing issues, by replacing the ball roller with a cylindrical roller they could improve longevity however, you cannot just replace the shaft and use the remainder of the assembly from the old engine because they also changed other stuff too. They fitted a split gear on the later engines to reduce noise from the balancer shaft gears (stops it chattering back and forth with the valve train). As a result the precision diameter at the right hand side of the balancer shaft is 1mm longer and the threads are 1mm shorter. You cannot even use the early nut, the entire assembly has changed (apart from the right hand cam sprocket and woodruff keys).

Split gear assembly….

So, another halt to the program while I sourced the parts required. Fortunately I had an SE motor in the garage with a gearbox issue. Since the balancer parts are pretty pricey, I decided to rob them from that motor and put a call out for some used parts in OC (to which I got not reply)

Anyway, having robbed the donor motor, I got the balancer shaft, cam chain rails and cam chains all installed and was able to continue with the build. The split gear assembly is a tricky little fella to remove and install without the correct tooling so be aware.

Moving onto the ignition, I noticed another wondering bearing. The starter drive gear that drives the flywheel had a drifting bearing.

You could even see the witness mark on the flywheel…

Obviously this was not a problem as it’s probably been like this for years but I knocked it back in before reassembly anyway.

With the ignition system, flywheel and starter gears all installed I fitted a new gasket and closed this side up, with the 70K miles grafted and brown ignition cover.

I next installed all of the clutch side components.

Upon inspection of the crank support bearing it was apparent that this was out of tolerance so I installed some new shells into the clutch cover.

Then installed the clutch cover assembly.

With the cylinder head, cylinders and pistons all assembled, I began to install the rear cylinder assembly. Incidentally, I installed new piston rings since the old ones were verging on out of spec but the pistons were spot on. De-coked and re-installed into the new cylinders, obviously checking clearances first.

Another frustration, when I installed all the new 12.9 grade studs into the engine cases (important to replace the early grade 10.8 studs), I installed them with Loctite and torqued them to the required torque. Upon installation of the cylinders, the small M6 studs were not long enough to fit the enclosed nut and washer as per the parts manual. The stud that screws into the engine cases is the one on the right in the picture below.

As a result, and not wanting to have the stud loose in the cases, I made the decision to use a nut with a built in washer face and install it with high temperature sealant to prevent contaminants getting into the stud orifice. Not ideal but should do the trick.

It then came to installing the front cylinder and I came up against metal to metal contact. It turned out the this was the culprit….

The front cylinder can chain guide bolt was sticking through into the area that the cylinder needed to be, weird. I checked the parts books and the cam chain rail and bolt are all the same on all years of bikes so this was a mystery. I checked the rail assembly and it all seemed 100%. The only thing for it was to chop the bolt down 2mm. So I removed the cylinder, ignition cover and thankfully was able to rotate the engine enough to get the said bolt out. I cut it down and re-installed, no further issued although it still bugged me as to why this would be? On the early engines, they had cut outs in the cylinder walls which would have prevented this from happening. My only thought is that my engine had a particularly long thread on the said bolt. Anyway, removed the obstruction and continued.

I had the same issue with the M6 stud and took the exact same action here that I did with the rear cylinder.

Once both cylinders were installed, despite having the dowels in the cases now between the cylinders, I thought it good practice to seal the ingress point with a small bead of high temperature sealer. I have done this now on all my 950’s with the hope that even if the tiny movement is still there, no contaminants will be able to sit in the corner and work their way into the mating surfaces.

With all the ancillaries installed the motor was finally complete.
finished engine
Time to now install the motor into the bike, which is not easy on your own. I find it useful to remove the rear swingarm and wheel and set the bike down on the centre stand.

Drag the engine into position and install the lower rear engine mount bolt.

Then install the engine hangers to the motor (after installing the oil lines, as you cannot get them in after the motor is up in the frame).

Then simply pivot the motor (only having to lift half its weight) on the rear bolt until you can get the upper engine hanger bolts in.

Raise the bike onto the centre stand as you would normally and continue with re-assembly.

I chose to have a few parts powder coated while the bike was in pieces too.

Since me headers were cracked, I thought it a good opportunity to try out the new GPR exhaust system and give some feedback to the forum on how that goes. I hope to get the bike on the dyno once it is run in so it’ll be interesting to see how she goes (before / after comparison).

Did a lot of shock work too to get a full travel 320mm bike. Unfortunately ran into a few more issues with that so still not in a position to post but will do so once resolved. Shock box…

Continued build…

New Iron Man sprockets.

SE swing arm with chain guide and integrated Scotoiler.

G-IT bash plate to match new exhaust system..

New blinkers

So I have 450miles on the bike now since the rebuild and I have to say, all the improvements with the oil system would appear to have paid off. I’ve ridden it pretty hard and get no cam chain noise whatsoever. Clearly by reducing leakage and maintaining oil pressure the problem has been solved.

The only thing I am seeing more of is oil in the front intake trumpet. Now, I still have the early 03’breather hose on the bike without the one way valve thingy. I can’t think why the engine would be breathing heavier than before the rebuild but maybe it is? Anyway, I’m getting oil in the airbox and I need to fix this. I’m guessing the latest check valve in the breather hose will cure this.

That’s all for now, here’s to the next 70,000miles

Additional note about changes to cases / parts:
I can confirm that 08′ will have all these developments built in, dowels on cases, longer centre crankcase bolts, oil jet changes, bearing changes, balancer shaft changes, split gear drive on balancer shaft (reduces engine noise), gearbox oil rail seals, updated pressure pump housing assembly, uprated shift drum etc etc.

Most changes were included in 2005 models with the exception of the longer crankcase bolts between the cylinders which came in in 2006. Almost everything else was in 2005.

You must also note that when fitting the later crank-cases, you can no longer fit the old cylinders (03 & 04 cylinders), the cylinder skirt is different – buyer beware.

Also worth pointing out that they changed the shimming arrangement on the gearbox main shaft to remove lateral movement of 2nd and sixth gear. I measured all this up and realized it was to prevent 6th gear on the main shaft rubbing faces with 2nd gear on the output shaft and maximize 6th gear dog engagement. This is something that is not apparent to most (including dealers) but it seems the shims to do this became available on the 2007+ fishes. 2003 = 1.5mm shim, 2007+ = 1.5 to 2.3mm shims.

And I just fitted myself a new pre-filter kit too

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!.

1.2ltrs of oil in just 700 miles which bad bad enough to need to get to the bottom of it

So, I did a few searches on this place to see what I could find. Fitting a one way valve was an option but surely it would just hide a different problem, I wanted to know what was causing it.

A mention from an inmate and some extensive searches found that a couple of people have had leaky seals on the end of the balancer shaft. Low and behold this was the only seal I did not change when I rebuilt the motor. I checked the gasket kit and there it was, sitting pretty in amongst the remains of the gasket kit. So out it came and 40 minutes later the bike had been stripped, seal changes and put back together.

The seal was bad for sure, it had gone. It was square off and was very brittle and cracked in a few places. It is the original seal that came on the bike in 2003 and I’ve lost count how many times that cover has been on and off.

Anyway, I’ve replaced the seal and the bike now has 1000miles on since the rebuild. Today I removed the air box lid expecting the worse and would you believe it, the front intake trumpet was DRY.

So, I still have no check valve in the breather and all seems well so far. Fingers crossed that this was the cause of the problem.

On a different note, the motor feels strong! It’s also so much more quieter than before, all those clangs and rattles have gone, it actually sounds like a newer 990 now. It has that lovely whine to it like the newer motors, that must be the split gear on the balancer shaft.

At first I didn’t like it, I was so used to the old motor and it’s noises that this just felt wrong, but now, I’m beginning to love it.

Ride on