2011 350sxf 100 hours re-freshing the bike - Page 3 - KTM Forums: KTM Motorcycle Forum
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post #21 of 41 (permalink) Old 12-14-2016, 10:17 AM Thread Starter
Join Date: Oct 2015
Location: Toronto, Canada
Posts: 91
Next the piston can come off.
I had an oil burning problem and was expecting to see a very back oil scraper or comp ring but they looked okay, as well as the overall condition of the piston. The pads were worn off as they should be and I could have probably used a new piston much sooner (at 150 hours now), but other than some oil consumption the bike was still very powerful, fast and snappy so waited until now (winter time).

To take the piston out, make sure to put a good sized rag around the con-rod blocking any possibility of something falling into the bottom end. This is very important because if something falls down there its a full engine rebuild including a bottom end tear down.
Using a strong pick or very small tipped screwdriver, remove the piston writst-pin circlip on one side only. Push the wrist-pin through from the other side to get it out. It was very snug so I used the handle-end of a small screwdriver covered with a rag to push it out of the cod-rod making sure not to mark or damage the wrist-pin. You can look at the top of your piston to note the part numbers from Vertex. It also shows the arrow that points towards the exhaust side so you know which direction it installs for later (the new one should have an indicator also).


Finally, you can take a look at the con-rod condition and for excessive play in the rod bearing by checking side to side movement feeling for click or shift at the bearing. I'm not familiar with what wear to look for in the bottom end and I am just assuming it should be okay as it's outside the scope of my top end build and far beyond my knowledge or skill.


Last edited by serialize; 12-14-2016 at 10:19 AM.
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post #22 of 41 (permalink) Old 01-22-2017, 12:26 PM Thread Starter
Join Date: Oct 2015
Location: Toronto, Canada
Posts: 91
So the piston / rings install went very well.
Total cost was $571.00CAD thats for the piston/rings vertex high-comp kit and the machine shop charging to re-cut valve seats, clean all the head parts, re-set shims, and hone the cylinder (also confirmed measurements for roundness, taper, and bore to go with the A piston).

The job is not bad at all if you have a clean place to do it where you can leave it all out and work through it. I would say this took me 3 days work at an extremely casual but meticulous pace (I have horrible OCD and can't get a speck of dirt on anything, all parts must be fully cleaned and inspected and super accurate installation and measurements and it's very overboard but hey it's winter and it's a nice was to spend my time).

The most specialized tool i used was a torque wrench and everything else was done by hand. For the Locktite 5910 the manual recommends for the lower case seem under the base gasket was a waste at $90.00 which I regret spending when it was two tiny dabs (pea size) for $90.00 when ThreeBond 1211 would have done just fine at $15.00.
The one and only specialized tool that would speed things up and make life somewhat easier would be the piston wrist-pin circlip install tool from KTM but I was able to do both circlips with a thin screwdriver (mind you i ruined one circlip of the new ones and re-used an old one).

Last edited by serialize; 01-23-2017 at 04:46 PM.
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post #23 of 41 (permalink) Old 01-22-2017, 01:12 PM Thread Starter
Join Date: Oct 2015
Location: Toronto, Canada
Posts: 91
Here are the overall steps I did for the install.
This is considering you have the bottom end set to TDC and using the bottom end locking bolt from the teardown of the top end (which I did).
So at this point everything is off and the conrod is exposed ready for the new piston and crank is at TDC.

Mount your piston rings onto the new piston. I went with the Vertex OEM replacement high-compression "A" or "I" piston as KTM calls it.
I followed exactly the instructions from the Vertex website on installing rings.
Start with the oil ring (the squiggly one), put it on in the lower groove of the piston and make sure the ends do not over lap. Also put the gap to the side of the piston. Next put your bottom oil scraper ring on into the same groove as the oil ring just slip it underneath. Put this scraper ring's gap to the intake side of the piston about a centimeter or so off centre of the intake direction. Then install the top oil scraper rings into the same groove as well just sitting on top of the oil ring, and put the gap 180 opposite of the bottom oil scraper (just off centre from the exhaust side of the piston). Next mount the compression ring, make sure the letter marked on the ring is facing up and install in the upper groove of the piston.

Install the piston with rings into the cylinder while still off from the bike/con-rod. Make sure the triangle marking on the exhaust side of the piston faces the exhaust side of the cylinder. Using some assembly oil or 10w40 motor oil and a q-tip, oil all the rings on the piston, also oil the side pads so they are lubricated when you install in the cylinder (i even put a thin layer of oil on the cylinder wall). Flip the cylinder upside down on your clean work bench and install the piston from the bottom being very careful of the rings not to snag them. The end of the cylinder inner sleeve gives to rounded half circle cut outs which lets you use your fingers to compress the rings enough to slip it into the cylinder (this was surprisingly easy I though would be much more difficult but with the cut-outs it's a nice straight forward install). Try to push the piton evenly into the cylinder.
Once you are in and you slid it up and down just enough to feel that it slides nicely and rings are not grabbing then bring it down to it's lowest poition of being exposed from the bottom but not letting the rings get out. This way the hole for the wrist pin is accessible. While the cylinder and piston are still off the bike make sure to install one of the spring clips for the wrist pin and make sure its the one for the side of the piston on cam chain side. This is the side you have little access to when the cylinder goes back on the bike so you might as well install the spring clip while it's off the bike and you can get at it. Set the "hooked" end of the spring clip into the groove it has on the piston (notice one side is a sharp right angle and the other is more shallow and better follows the shape of the hook of the spring clip. slip it in this way). then hold and press with your finger tightly towards the groove in the piston where you are aiming to pop it in to seat it. With a nice firm and committed motion, try to do it in one shot "pop" it into the groove with a thin flathead screwdriver. Carefull not to stab your hand/fingers as i almost did. Once it's popped in make sure to check all around the spring clip to make sure evenly seated into the groove. Also, what I did to make sure its nicely in there is I lubed and installed the wrist pin and pressed against that side of the spring clip to make sure not moving and properly snapped into place. This one went in perfectly. Take the wrist pin back out so you can move on to installing the cylinder and piston onto the bike/con-rod.

Last edited by serialize; 01-23-2017 at 04:47 PM.
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post #24 of 41 (permalink) Old 01-23-2017, 07:03 AM
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Location: Rum City, Qld / Australia
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Great thread mate, this is going to help a lot of people.
I have been following it, I didn't really want to make comment and ruin your progress, but I believe you should get a pat on back.
Well done

current bikes
2002 ktm 520sx
2004 ktm 525exc
2005 yamaha fz1
1982 Honda xr500
1994 Yamaha dt200
1970 Yamaha dt250

2005 ktm 525exc
1996 ktm 360exc
1994 Honda cb400
2002 cbr954 Fireblade
2002 honda xr250
1998 honda xr250
1997 suzuki rmx250
1993 yamaha wr500
1993 suzuki dr350
1993 honda xr200
1978 honda mt250 elsinore
1982 honda xl185
1981 honda ct185
1985 yamaha dt100
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post #25 of 41 (permalink) Old 01-23-2017, 09:59 AM Thread Starter
Join Date: Oct 2015
Location: Toronto, Canada
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Originally Posted by DW View Post
Great thread mate, this is going to help a lot of people.
I have been following it, I didn't really want to make comment and ruin your progress, but I believe you should get a pat on back.
Well done
Thanks DW! Appreciate the feedback.
Over the years I have had the pleasure of getting so much useful information on web forums for motorcycle repair and maintenance. I'm hoping this can help others too. Might not be the only way of getting this job done, but it's my experience and what worked for me and can be a starting point for others if nothing else.

Been trying to keep up with the post it's been a little crazy though have a very active 2 year old and a new 2 month old up a nights .. LOL

BTW: Have a few pics to post. Photobucket not working for me anymore and curious if anyone has good/easy photo upload site I could use (the google one doesn't share the image only the link to it, the old photobucket link lets the image show in the thread).

Last edited by serialize; 01-23-2017 at 10:03 AM.
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post #26 of 41 (permalink) Old 01-23-2017, 10:25 AM Thread Starter
Join Date: Oct 2015
Location: Toronto, Canada
Posts: 91
Using you crank case sealer (ThreeBond 1211 will do just fine in my opinion - I used the REALLY expensive Loctite 5910) put two tiny dabs on the bottom end surface where the cylinder and base gasket would sit right at the point with the two lower case halves meet. Only a tiny bit of sealer is needed here right on the seam the base gasket takes care of the rest. The KTM manual has a good picture and shows the point to seal also. Next mount the base gasket.
Installing the cylinder/piston combo onto the con-rod is best done with a helper/second set of hands if you can get someone to hold it while you install the wrist pin. WEAR EYE PROTECTION, the spring clip could possibly fly out and that would be terrible to catch it in the eye. My wife was nice enought to hold it for me while I lubed the wrist pin with some oil and installed it through the piston and connecting rod. She also hanged around and held it for me to make it eaiser to install the spring clip into the wrist pin holder groove of the piston. This can be tricky, and please make sure to keep that rag plugged and blocking the hole to the bottom end of the engine don't want to drop that spring clip down there. I ruined one spring clip, it got ovalled and even though it went in an seatefd it's not good like that and could fall out. I did not have any spare spring clips, although next time I'm doing this top end job I am going to buy a couple of spares. I reused the best of the 2 old ones i took off the old piston which looked good. I find the best way that worked for me was to try and put as much pressure as i could with my fingrer that is holding it into the groove trying to get it as close to the seating position as possible and then a nice committed motion with the screwdriver to pop it in (each time I did it nice a firm and fast "pop" worked better that when I hesitated and screwed up the spring clip and had to pull it back out again). Once you have it in there and nicely seated in the groove, gently from the other side (where you originally installed the other spring clip while still off the bike) use something to tap lightly on the wrist pin back towards the spring clip you just installed to make sure seated correctly and doesnt move or come out of place (I used a 1/4 inch socket externtion with a rag on the end not to mark the wrist pin). Now you have all the hard stuff completed and the rest is easier and more straight forward. You can slide the cylinder down the piston gently into place on the base gasket.
Keep in mind you want to somewhat TIME this step for the drying time of the case sealer below which is 2-4 hours so you want to get the head on and bolted down prior to 4 hours passing (the rest after that can wait a little but try and get the head back on and bolted down before drying time is done to avoid possibility of leaking).

Crank Case Sealer (Loctite 5910 or ThreeBond) went here in 2 small dabs

Last edited by serialize; 01-23-2017 at 04:58 PM.
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post #27 of 41 (permalink) Old 01-23-2017, 10:55 AM Thread Starter
Join Date: Oct 2015
Location: Toronto, Canada
Posts: 91
Installing the head is next. First, carefully mount the head gasket. Check the bottom of your cylinder head make sure both locating dowel pins are nicely in place and seated evenly. Then put on the cylinder head, and this you kind of have to angle it as you slip it over the chain and chain guides until you can get the clearence low enough to get past the upper frame of the bike (it's really low on this bike and almost no clearence, so much so when you install the spark plug wire on these things you litteraly have to slightly bend it to fit in the whole, not sure i like this but it's the way it is). When lowering the head down onto the head-gasket and cylinder make sure again to line up the locating dowel pins nicely and evenly seat the head down with even pressure pressing downward. Get it nice and evenly seated on top of the head gasket. Then carefully mount all the washers and 14mm mounting nuts to bolt it down. Using a torque wrench follow the KTM manual instructions which are very good for the 3 step tightening instructions.
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post #28 of 41 (permalink) Old 01-23-2017, 03:04 PM Thread Starter
Join Date: Oct 2015
Location: Toronto, Canada
Posts: 91
The rest of the work will be to put the cams back in the head and time the motor as well installing the tensioner.
Putting the cams back in I found the intake cam I like putting first since you have to slightly position it so that the black plastic breather tube on the camshaft seats in nicely into the head (you'll see what I mean when you put it in the plastic to should fit in nicely and not get pinched down when you put on the cam bridge). Line it up with the flats on top so that it's pretty close to being in the correct timing position. Then put in you exhaust cam and do the same,. have the timing marks up as best you can. Install the cam bridge and be careful to have the locator dowels line up correctly to mount it and also be careful of that same black plastic breather tube being seated correctly and doesn't get pinched down by the cam bridge. Don't bolt it down yet, go on the opposite side of the motor and check the timing marks. The flats of the cam lobe should line up perfectly to the marks on the cam bridge which are 2 dots at each cam having the dots perfectly visible from the "flats" of the cam. If not lined up carefully adjust the cam on the chain until they do. With the bottom-end of the engine having the crank locked at TDC and also the timing marks of the cams lined up correctly the engine will be in correct timing. Tighten the cam bridge bolts (criss cross pattern starting from the outside then in) and do this mindful not to move the cams or chain and possibly skip a tooth and get out of timing. Once tight check that the timing marks are still lined up. Next the time chain tenioner needs to be installed. Set to the "locked" position by compressing and then install it and the retaining bolt (big 24mm bolt). Remove the smaller 17mm bolt to be able to release the tensioner to the correct chain tension by pressing the back-side of the tensioner until you hear/feel it pop out and extend to put tension on the chain. Go back to the cams and double check there is sufficient chain tension, you should not be able to move the chain by just using your fingers. Also take a look again and make sure the timing marks still line up perfectly to where you set them before intsalling the tensioner.
If all is good put back the 17mm tension access bolt.
NOTE: for the OEM KTM Hydraulic chain tension these can fail and it's a very good idea to replace it now with a new one. I changed mine becuase it was compressible by hand and that should not be the case it's becuase the spring became too weak and it's worn out and needed to be replaced. If this part fails the top end would fail and could cost you valves, piston, cylinder and head parts and in worse case even the bottom end timing drive gear if the chain balls up down there. It was a $50 part and at 150 hours I was happy to replace it.

Last edited by serialize; 01-23-2017 at 04:42 PM.
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post #29 of 41 (permalink) Old 01-23-2017, 03:17 PM Thread Starter
Join Date: Oct 2015
Location: Toronto, Canada
Posts: 91
Final assembly of the valve cover and manual test.
Firts before putting anything else back together at this point I did a manual test. Remove the engine locking bolt from the bottom of the motor that you used to lock it at TDC. This is just to manually turn over the motor with the rear wheel and just watch the cams and chain make sure all working correctly and smoothly and also listening to the bottom of the head and cylinder make sure no noises of valves hitting the piston (this is to make sure engine is timed up). If something went wrong this way would be much less damage than if the engine were running. It might be easier to get a helper at this point and get someone to turn the engine over for you using the rear wheel while you have it in top gear (5th) and you can watch the cams and listen to make sure no noises. I went through a few rotations of the crank it all went nicely and considrably felt the strong compression which is great.
Put back the spark plug aluminum inner tube, set the valve cover gasket and reinstall the valve cover. Put back the upper radiator hose if you removed that like I did to get the extra space/clearence. Reinstall the spark plug wire. Put back the instake tube that came off the back side of the head (I used a little hourehold spray cleaner as a lube so it slipped back on easier.

Last edited by serialize; 01-23-2017 at 03:22 PM.
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post #30 of 41 (permalink) Old 01-23-2017, 03:20 PM
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Originally Posted by serialize View Post
BTW: Have a few pics to post. Photobucket not working for me anymore and curious if anyone has good/easy photo upload site I could use (the google one doesn't share the image only the link to it, the old photobucket link lets the image show in the thread).
I noticed photobucket doesn't work anymore at the image upload screen.

I think this site if fine, and it's free also.


2012 Yamaha Super Tenere
2008 KTM 950 Super Enduro R

Past Rides
'14 Honda NC700X
'11 Husaberg TE 300
'08 Husqvarna 610 TE
'06 Ducati 1000S Multistrada DS
'04 BMW 1150 RT
'03 KTM 450 EXC
'02 KTM 640 LC4e
'01 Honda XR650R
'00 KTM 520 EXC
'98 Honda XR600R
'95 KTM 620 RXC
'90 KTM 500 MX
'88 Yamaha TT600
'86 Yamaha XT 350
'84 Yamaha IT465 (STOLEN)
'83 Kawasaki KDX 450
'83 Honda CB1000 Custom
'82 Kawasaki KDX 400
'77 Yamaha DT200
'70 Honda CT70

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