2017 KTM 250 EXC Engine Top End Rebuild

my bikes 945 hours now I had intended to overall the top end at 150 hours but the weather's not so good this weekend so I'm gonna do it now so this video is gonna show how to replace the piston and rings okay I've taken a seat and tank off I've cleaned out all around the engine and the frame so no dirt can drop down while I'm working on the engine and I decided to do a compression test and it's written about 210 psi which is pretty much the same as I measured before in previous tests which indicates the engines doing go condition but just going on the number of hours the engines done now I think it's good time to change the piston rings and so I'm gonna go ahead and do that this is the KTM piston kid I purchased you can see the part number there this is what's included a new piston kit of CNA piston rings and you can see there the part number for the piston a new wrist pin and circlips two rings for the head and small embry and then you get a very selection of basic askers different thicknesses and also the side cover gaskets when doing any major work on the bike it's a good idea to disconnect the battery so I'm just going to remove the ground terminal and that way I can be certain that if any wires touch the frame or anything like that it's not going to result in any damage or blown fuses and I'm gonna remove the silence where it makes removing the pipe a bit easier it's just held on with two two bolts so it's pretty easy to do okay next I'm going to remove the pipe there's a couple of pipe springs and two bolts to remove use a spring puller to remove the springs then the pipe is held on with bolts here and here so you have to remove those and then you can just let the Pope off the next step is to drain the coolant and you've removed this bolt and the coolant to come out I've already removes the radiator cap if you leave a radiator cap on and will drain very slowly so I've got a bucket and a funnel and I'm just going to remove the bolt and drain it into the bucket once the coolant is drained you can replace the bolts and then this needs to be talked to ten years and meters so make sure you have the copper washer on okay the next step is to remove the engine braces that's one on each side and the bolts are t45 so initially just loosen them and then you can remove them the boss one tip I have when working on a job like this is to use trace and organize your paths into different groups then when you come to a reassembly and it'd be a lot easier to figure out what goes where and next I'll take the other engine brace off the next thing I'm going to do is remove the coolant hose so from the head there's a hose there and then between each radiator at bottom there's a cross hose which if you remove this it'll make it a lot easier to remove the cylinder as I removed more parts I'm also cleaning those parts some of them I couldn't access properly before when I was washing the bike and you don't want any of the dirt dropping down into the engine when you take the new cylinder off so I'm wiping with a cloth and also using compressed air to blow out dust etc next you can pull off the vent hose okay I'm going to replace my spark plug so I'm going to take the plug out if you're going to continue using the same one you can just leave it in next you can loosen the head bolts and you want to do it in a crisscross pattern so start with one bolt and loosen it and then go over to the other side and work in a star pattern and it prevents the head being warped damaged and the same when you're tightening it you want to do a crisscross pattern then you can go ahead and take the head off I usually it it's stuck a little bit so you can use a soft mallet and just tap and it should come off fairly easily so in this case the o-rings have come off with the head one other thing is note that there's two pins and make sure those are located in the cylinder and you don't lose those the next step is to remove the power valve linkage which is located behind this cover so you need to remove these three bolts once you've removed the three bolts you can remove the cover just slide it out and it should come off pretty easily the power valve linkage has a ball joint and it's held in place with a retainer clip the first time you take it off it's actually a little bit difficult to understand how the retainer is held on but if you have a pick tool shape like this you can put it underneath the retainer and the retainer has a loop on the end so you can position that the pick in that and twist it round so you pull it round like that and then it just drops down and it's good idea to have a cloth in place in case it just drops out because otherwise it could drop down inside the case once you've removed the retainer you can pull the power valve link off the ball carefully so I use a screwdriver and carefully pry it off then you can remove the gasket and you also need to remove the power valve cover on this side to access the cylinders stud nut so this is the same this is talks t25 so I just removed the three bolts on the cover and take the cover off now you're ready to remove the cylinder and the cylinders held on with four stud bolts so you need to remove the nuts you can see inside here inside the power valve cover you can see one of the stud nuts on each site is in sight there isn't much room what you can do is lift the control arm up and that will allow you to fit a ring spanner on there so you want to loosen all of the stud nuts a little bit and then fully remove them afterwards then once you've loosened all the stud nuts you can go ahead and fully remove them okay now I'm ready to lift off the cylinder I've got the piston down pretty much as far as it'll go and it just lifts up on the cylinder and lifts it off you might have to wriggle around with the tubes a little bit okay now with the cylinder off I've put a cloth around the crank just in case I drop anything so it doesn't drop down inside the crank cases and I'm ready to take the piston off there wrist pin is held in with circlips each side and I'm going to use a flat bladed screwdriver and pry the circlip out and then on the other side of the piston this sight the circlip is still installed but using their Tokyo Frog piston pin tool I can insert it into the wrist pin and I'll just chip it's quite stiff I can't push it out manually so what I'm going to do is support the piston with one hand so what you don't want to do is hammer and not support the piston because it looked at quite a bit of force on the crank and maybe damage that so I've got the piston supported with this one hand with the tool in the wrist pin and then I can tap it out and then you can just lift it off okay so this is what the piston looks like after 145 hours you can probably see those some light scratches where marks but they're very superficial and you can't feel them at all and there's no significant wear on the piston you turn it round you can see it's pretty similar on this side as well few light wear marks around these areas but no major damage the wrist pin itself you can probably see it's slightly discolored and but there's nothing you can feel on it and then the Rings you can move them fairly easily so they've had a lot of carbon buildup in there and then the piston top it's got a little bit of carbon deposits on there but nothing very significant and this is the exhaust side of the cylinder there's no major damage at all just some very superficial marks okay then it inside their power valve it's a little difficult to see but it's relatively clean and I'm not actually going to bother disassembling it I think I can use it for another 150 hours before it really requires an overhaul there's very little deposit on it so I'm just going to leave it like that I'll wipe it out and then reassemble the cylinder okay I finished cleaning this cylinder now I cleaned off all the gasket sealing areas and then cleaned it out with a clean cloth and some wd-40 so it's looking very clean now both inside and outside so ready for reassembly every time you overhaul the top end is a good time to check the crank for play so pull the crank in to the topmost position and then vertically push and pull if you can feel any play at all it would indicate the crank bearings need replacing in this case I can't feel anything so it's fine to clean the head I'm just using some parts cleaner and just wipe it out you can see the deposits come off pretty easily then for the more stubborn deposits I'm using some carb cleaner this is a foam type and then a stiff brush and I can see it coming off pretty easily okay that's cleaned up pretty nicely before you reassemble the engine it's important to remove any old gasket which might be left on the sealing surfaces and you can see around the front there's some gasket material here left so I'm going to use a razor blade and carefully scrape it off but it's a good idea to put a rack down in the case so you don't get any debris falling down in and then carefully using your razor just scrape scrape the old material off the piston kid I bought came with a selection of bass gaskets and there are all different thicknesses the thickness of the base gasket will adjust the cylinder height and have an effect on the compression and squish so it's important to get the correct gasket thickness in my case I'm going to be reusing the Spock cylinder so on all I needed to do was measure the stock base gasket thickness and they use the same thickness if you're going to be using a different cylinder you'll have to calculate the X dimension and one other method is measuring the squish one thing to notice that the base gasket that was fitted on my bike I thought it looked like one gasket but when you look carefully it's actually to place it on top of each other so I just measured the thickness of each of the gaskets so as a point two and 0.35 and then find the same thickness gaskets in the kit and place them together and use those [Music] and the kit comes with a new small M bearing and I've applied some two-stroke oil to it thank the piston kit comes with a new wrist pin and also circlips one issue with these circlips is they're very difficult to install without damaging the piston so I'm not actually going to use these I'm going to use these ones which are called easy clips and you can use some needle nose pliers to compress the circlip and easily put it into the piston before you install the piston it's a good idea to install one side there so clips into the piston while you still have it on the bench so it's a lot easier so using my easy sir clips and compress it using some needle nose pliers and then you can install it into the piston and I just felt it clip into place and it's important to position the open end of the circlip either at the top or the bottom my preference is to actually have it at the top and think if you have it at the bottom these openings the open end of the circlip kind of rests in there so I don't think it's quite so secure so I prefer having it at the top like that and make sure these so clip is fully engaged in the groove and before installation I'm going to place them to stroke all so the wrist pin you don't need a lot just a thin film and also I'm going to apply some to the the piston and rings I know some people apply or don't apply any oil and install it dry but I think it's a bit better to have a film of oil on everything initially okay so now I'm ready to install the piston and one very important thing with the piston is to get it installed the right way round so if you look at the top of the piston there's an arrow on one side and this should be pointing towards the exhaust and then I have the wrist pin partially inserted and I can slip the piston over and then checking the alignment carefully push the the wrist pin through the bearing and it should push him fairly easily and you can see there it's installed now then you can grab your second circlet and using your pliers compress it and I'm going to have the gap up of the top so make sure that the gap is right at the very top and it's fully inserted into the well fully seated in the in the groove okay we're now ready to install the cylinder and at the back of the piston is where you need the ring caps and if you look carefully in the ring roofs those two pins in there and you need to get the ring gap to align with those pins so rotate the Rings make sure it lines up correctly and then compress the Rings with one hand and then grab your suin that with the other hand and being careful not to scratch the the piston install the cylinder just take your time make sure it's lined up and definitely don't force anything okay once you have the piston installed inside the cylinder check that the piston moves freely so you can use the Kickstarter to do that and if the Rings aren't installed correctly and catching on the cylinder it'd be pretty obvious they'll tend to lift the cylinder up and as you can see it it goes very smoothly so there's no issues there okay the next step is to install these stud nuts so you got four and you shouldn't talk them down in a crisscross pattern respect for these nuts it's 35 Newton meters but the front nuts you're not going to be able to get a torque wrench on there easily so I'm just going to do that by hand okay have nuts on all of the studs now so I'm going to tighten them in a crisscross pattern so this one first and then the opposite side and then come back and do this one and then the opposite corner and next I'm going to tighten them to spec once you have the cylinder talked down you can check the X dimension the X dimension is the distance between the side of the cylinder and the top of the piston and on 17 model pistons they're actually domed so if I move it up I think you can probably see the center section of the piston is higher than the side section so in this case the X dimension is the measurement from the top of the cylinder to the sight of the piston and that needs needs to be between 0 and 0.1 millimeter so I've put the bike in gear in third gear and I can use the rear wheel to move the piston into top dead center and then hold it in position while I do the measurement so I've got my straightedge and I can see there's a very slight gap and I've got a 0.1 millimeter feeler gauge and that won't actually fit in the gap so I know the X dimension is between 0 and 0.1 millimeters so swithin spec and I can leave it like that if it was a larger gap or smaller gap what I've need to do is take the cylinder off and use a thicker or thinner base gasket to make the adjustment the next step is to install the power valve sight cover gasket make sure it's lined up correctly and it's fully seated then you can install the power valve linkage so just push it on to the ball make sure it clicks on properly and then this good idea to use a cloth around the the gap on the bottom in case the retainer pops off while you're installing it and the retainer goes on from the bottom so feed it up and then just press it round and it should clip into place okay next we can install the cover so lining up correctly push it on and then the fasteners you need some Loctite on them I'm using a medium strength lock type just a small amount and the torque on these is very low so the spec is 4 Newton meters so if you don't have a small torque wrench be very careful not to over talk these okay so next I can install the power valve side cover on the other side I've applied some mediums Frank love tight to the bolts and these tote to the same four new Newton meters as the other side the next step is to install a head and you need to use the new o-rings that came with the kit I've smith some silicone grease on the earrings and that helps keep them in the groove on top of the cylinder while you're installing the head so I think that's a good idea and confirm that the Rings are seated nicely in the groove if they're poking out obviously is not going to seal well you know I have problems with water leaks etc so this is an important step and I recommend using some some grease the next I can install the head and there's two locating pins which you need to position correctly so make sure those go into the head properly and then you've got six head bolts and it's important to use new copper washers okay once you have the head bolts finger tight and you can use a wrench and going in as a star pattern start to tighten them so initially just snug the bolts down then when you've snugged all the bolts down you wanted to fasten them to talk which is 27 Newton meters so again do this in a star pattern okay I've just done a compression test with a new piston and I'm getting 210 which is pretty much exactly the same as what I had before so everything looks good anyway and I'm gonna put in a new spot but I like to use a little bit of anti-seize on the threads so I've already put some on now ready to reconnect the coolant hoses then you can reinstall the spark plug cap the next step is to reinstall the engine braces and use these bolts which are held in place with Loctite but you can see there's still quite a bit of old Loctite left so I like to run them through a die before installing them then on all the engine brace bolts I use a medium strength log tight and then you can install the brace on the bike and the long bulb goes out into the engine and the two shorter ones go into the frame then all of the engine brace bolts need to be talked to 25 Newton meters next I'm going to add coolant the recommended coolant is this one the M 3.0 made by motor X and I'm just going to fill it up using this funnel then once you've felt that the kunta and I typically tip the bike over just to get rid of some of the trapped air and the radiator and then on these 79 year bikes there's a air drain on top of the head which once you've felt the coolant system up you just loosen this off and it allows any trapped air to escape and there I can see some water coming out now so can retighten it and then recheck the level in the radiator so I'm just going to add a tiny little bit more and that should be good and install the radiator cap then reinstall the vent tube so I've still got to put the pipe the tank and the seat back on but other than that that's the engine rebuild complete as I think you saw it's a fairly straightforward process and really the trickiest part was putting the cylinder butt back over the piston and not damaging the rings but just take your time and be careful and I should go fairly smoothly you didn't need a few tools to do the rebuild but once you have those you can certainly save a lot of money by doing it yourself

Channel: Tokyo Offroad

Views: 1,625,331

Rating: 4.8048444 out of 5

Keywords: KTM, 250EXC, Rebuild

Id: _dzYPpK3IVU

Length: 30min 57sec (1857 seconds)

Published: Sat Nov 18 2017