by JohnNicholas on 05/31/2010
Here is the story of my rebuild of my 2005 KTM 200 EXC, twostrokemotocross.com inspired me to have a go and do it myself.
Since starting racing as a 10 year old in 1984, I have had two dirt bike ambitions I really wanted to fulfil, first to ride a 500, second to rebuild my own motor. Well the first was ticked off last year in the dunes at Lancelin, north of Perth, Australia, thanks to the kind Kiwi who said in response to my request for a photo of his gleaming 2001 model CR500, ďTake it for a spin if you like.Ē Needless to say I took the offer up, let me tell you holding that baby wide open in 5th in a pair of shorts and sandals was quite a thrill. I have a neat little scar on my left calf to remind me of when the curve in the pipe branded me on that great day! Anyway, after 5 heavenly minutes I figured I would be wise to hand it back while I was still in 1 piece.
On my return to England I was reunited with my 200, which has since seen another yearís hard use. The routine Iíve been following is do the top end myself every 100 hours, get someone else to do the mains every 200hrs. Almost immediately after the 200hr full rebuild I drowned it good and proper, it seemed like I pumped a whole gallon of brown water out of the old girl, which was pretty depressing, but she seemed to shrug it off, but when I recently drowned it again in a huge mud hole at the 380 hr mark, I figured it was time for a strip down. When the next day I landed off a log and there was a horrible squealing noise that lasted about 30 seconds my mind was made up. Later in the day it boiled over when I had to scream it to get up a sandy climb in a wood, so I knew I had to get to work. I had followed the CR 250 rebuild on the site with interest, and done lots of google searches about splitting crank cases, so armed with my workshop manual I set to work.
I bought a KTM clutch holder and primary gear holder as well as the inner ring tool, for removing and fitting the bush that slips on the crank and sits in the roller bearing. As their rotor holder is $160-00 here, no joke, and the shift roller holding key was out of stock, I asked my friendly neighbour Phil the farmer and his cousin Steve if they could help me out and 1 hr later I had a DIY rotor holder and key blank. The blank took about 20 minutes of filing to get a good fit and I was good to go.
I opted to take the motor out before removing the primary gear nut and clutch hub nut, they both came off with the motor sat on the bench, with me holding the motor in 1 hand and a breaker bar in the other with no problems. I did remember the primary gear nut is left hand thread! At this point I discovered the source of the horrible noise, the intermediate starter gear had spat a tooth off, which had done some pin ball action before shredding the water pump drive. New parts were duly ordered.
This motor doesnít require a crank case splitter , the cases eased apart with no problems, I tapped away gently with a plastic mallet and used the tabs on the cases to prise them apart by hand. I was a bit concerned about putting the tranny back together so I took lots of pictures and made running notes as I disassembled it. Actually there was nothing to worry about, the important thing is to make sure the stop discs on the end of the shafts donít get forgotten, and keep a grip on the lower end of the whole assembly when removing it so gears donít come flying off.
I had decided because of all the water thatís been in the mill I would replace all the high speed bearings while I had it in bits, I opted to leave the gear shift and kick start roller bearings and the shift drum bearing in, as they showed no signs of corrosion and donít lead too hard a life. I was pleased to see that the cylinder looked just as it did 100 hrs before, you can still see all the original hatching marks, and there isnít any sign of wear. The piston with over 100 hrs on it had just a few signs of blow by.
I took the crank and rod assembly to my KTM dealer for assessment, using the time honoured technique of grabbing hold of the rod and giving it a damn good yank in two directions, mechanic Nick determined that the big end was at the end of its life so fitted a ProX kit, considerably cheaper than the factory parts and just as good so they say.
With that sorted and a bag of new bearings in my possession it was time to get the old bearings out and stick the new ones in. At last I would have a 2 stroke engine in pieces on my kitchen table! I started out by applying localised heat with a hot air gun, this worked fine for the main shaft and countershaft bearings, but the crank bearings were much tighter and I didnít want to start whacking them too hard.
Next I put the cases in the oven for about 5 minutes then tried again. It is possible to get a socket on the inner race of the ball bearing and drift it out from the outside in, this worked fine without the need for too much force. I had the case sat flat on a large wooden chopping block. Next up was the roller bearing side, there is no clearance to get a socket on to the bearing on this side, so I used a drift and worked my way around the bearing, hitting the ends of the rollers. Several rollers quickly fell out, so I was then able to hit the bottom of the race. Not pretty but it worked fine. I think for next time I will make a draw bolt and sit a big piece of plate across the case and pull the bearing out from the inside to avoid having to hit anything.
Installing the bearings was straightforward, I heated the cases up and dropped them in, the crank shaft ball bearing started to go I out of square but the lightest of taps got it out again and I got it right the second time. I made sure they were all the way home by tapping in with a socket on the outer race and went back up to the workshop for reassembly.
The workshop manual instructions were very clear, and I got the gear assembly in to the right hand case at the second attempt, it was a little bit fiddly. Putting the shift forks and drum back in was straightforward. Then it was time to stick the left hand case on. I sat the right hand case on a big pile of rags to allow for the shaft end sticking out and popped the left side on. I tapped away gingerly with the mallet again and got it seated without difficulty.
Then I put the bottom end back in the frame before replacing the primary gear and clutch hub. At this point I have a confession to make. Following the details in the manual, I torqued the primary gear nut to 180NM using a pretty gnarled old wrench Iíd borrowed from Phil, it was only later, looking up the engine mounting bolt setting in the ownerís manual that I noticed the figure for the 05 model is 130 NM. The workshop manual was written in 02 and I didnít check for revisions. Lesson learned.
I figured too tight could not be a good thing so whipped the clutch cover off and slackened it off then went to torque it to 130NM. I got to the point where I was thinking the wrench should have clicked but it hadnít, so I slackened it off and inspected the thread on the crank and the nut, to my horror there was damage to the thread and not the nut, but it was fairly slight, and with a 4 day riding trip to France 2 days away I had no choice but to stick it back on. From the amount of force I was applying I was pretty sure there was over 100 NM of torque so just had to cross my fingers. Maybe the wrench was under reading and that initial go at 180 started the damage, the nut certainly went on square, I put it on with my fingers to start with so it wasnít cross threaded. I hope that next time I pull it apart it can be fixed on a lathe, going a size down on the nut.
The rest of the rebuild was a routine affair, so with the whole bike back together I prepared to fire her up. I had, of course, turned it over by hand at every stage of the build to check nothing was amiss. Well itís fair to say I have never heard so many strange noises from the motor, I was a bag of nerves as I warmed it up. A friend pointed out that itís only because I was listening so hard! It turned out the noise that really freaked me out was the very bashed about pipe touching the bash plate and creating a harmonic at mid rpm. Iíve put about 40 hrs on it since and itís running perfectly, so I think Iíve got away with it.
At the same time I set about a much needed fork service, and took the shock to the shop for a rebuild, the seals were completely shot and the whole bike felt like an old sofa. I purchased a motopower fork service dvd which was brilliant, I made notes as I watched it in the house then went up to the workshop and set to work. The process was easy and straightforward, instead of a seal driver I used a piece of 6inch roofing lead rolled around the slider with a nice smooth edge filed on to it instead and it worked fine.
At this point I have to make confession number 2, my note taking failed me and I put the seals in the wrong way round. Díoh! What I know as a result is that over 4 days riding each fork leg lost 250ml of oil, and I got a good insight in to the effect of an increasing air gap on the feel of the whole bike. As a result Iím running and 10mm larger air gap (120mm instead of 110mm) and for the trail itís perfect. I can also vouch for the fact that the seals work a whole lot better installed the right way roun! They were undamaged as a result of being in the wrong way round.
I really enjoyed the whole process, I got a huge sense of satisfaction and achievement from doing it, and it confirmed to me that it is indeed true that you can service your 2 stroke at home with some basic skills and a decent tool kit. Sure the bottom end needs doing by the shop because the crank has to be balanced after driving the pin out, but this is not an expensive job. I saw on Thumpertalk a guy talking about his sonís KX80 with 1800 hrs on it, so hope I can maintain my bike in good condition for many a year to come. I only have to look up clips of the World Enduro Championship from 2005 on utube to remind myself that itís me that holds the bike back, not the other way round, if I ever get a bit of new bike envy. The motor is bog stock, the suspension has been revalved and sprung for my weight and I have a Scotts damper fitted which has really calmed the whole thing down. I ride some rocky terrain up here in northern England and never ever felt comfortable at speed on rocks until I fitted it. It is a great piece of kit. An Enduro Engineering seat recently replaced the original which was getting seriously uncomfortable over the course of a day and is a big improvement.
It sits me slightly higher than the original which I prefer too. I also have a 12.5 litre tank. Overall I love the package, itís super light, plenty fast enough, and always fun. One of our mags over here always complains about the fierce power delivery of the 200, saying you never know if it will wheelie, spin or drive. Well excuse me, get used to it! Thatís my idea of fun, why would I want to ride something with a dull, linear power delivery. My bike is more challenging, sure, but more rewarding. I had a go on a friendís 04 WR250 and never want to repeat the experience. I think Iíd have had more fun pedalling. Maybe the tester doesnít know what the clutch is for!