Time to rebuild ! Piston choice and others
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  1. #1
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    Time to rebuild ! Piston choice and others

    Hi

    So i decide to open my engine recently whith 250 hours since last rebuild, i start to have some metal shavings in the short screen. Find out that was some damaged dogs, and worn teeth. So i had some luck to find a polaris outlaw 525 tranny fo replacement, and thanks to this forum i was able to know they are the same as ktm, except, i have to order a spacer to put in front of the sprocket.
    Anyway, i have to put a new piston on it, and im realy interested to put a wossner piston, i find one at realy good price whith the ref : 8547DA but it was listing for KTM SX 525 (03-06). So i decide to contact wossner to know exatly the reference, and wow ! i was realy shocked whith the customer services. So i first send an email to the info customers, they reply me whith the catalog, and a contact form, so i use the contact form they send me, and then they reply me, "we do not sell to you country", ok... I reply them to know if they can just tell me the reference, and no more answer from them... I contact the dealer on ebay ho sell the piston, he say "As far as I see this piston don't fit to your ATV", i checked the catalog from wosser, they have two ref. 8547DA 94.95 mm, and 8637 both listing on "KTM SX-EXC525 Racing 2003 - 2007". I checked ktm parts catalog, and far as i know ktm 525 sx 03 -06 ref is 59030007000 II, and ktm atv 525 piston is 59030007000 II, so the same...
    Sory for the long story, so can anyone tell me what reference for wossner piston ktm 525 stock compression.

    In case of no compatibility at all, the seller on ebay propose me vertex piston, doe anybody know how reliable they are compared to oem or wossner

    Thanks

  2. #2
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    So i did a little search last night, i send a email to wossner USA, and thanks to them they respond me (not like wossner germany). They tell me that the reference 8547DA is for 94.95 mm piston, listing for KTM SX-EXC520 '00-02 / SX-EXC525 R '03-07 / Betamotor RR525 '05-09. But they dont have listing for ktm/Polaris 525 atv on the wossner catalog. So i check on ktm parts catalog, and prox catalog, and this bikes share all the same piston, so normally there's no problem using it. Now for the reference 8637DA, this is for the high comp 12.50:1 94.95 mm piston.

  3. #3
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    My other concern is the rocker arms bearing, they never been change since a buy the quad, and they have 1000 hour easy on it. They seem nice for now, but i know when they fail, it cause a lot of damage. When i was checking on ktm parts, i see they dont sell only the bearing, but only the complete rocker arm , but when i check the parts for ktm 520 exc 2002, the rocker arms have the same reference whith the quad, but they listing the bearing separetly ref : 59036061090. Does anybody already change this bearings ?

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  5. #4
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    Quote Originally Posted by NeSta75 View Post
    My other concern is the rocker arms bearing, they never been change since a buy the quad, and they have 1000 hour easy on it. They seem nice for now, but i know when they fail, it cause a lot of damage. When i was checking on ktm parts, i see they dont sell only the bearing, but only the complete rocker arm , but when i check the parts for ktm 520 exc 2002, the rocker arms have the same reference whith the quad, but they listing the bearing separetly ref : 59036061090. Does anybody already change this bearings ?
    Glad to see you’re taking this on yourself.
    You will need some special tools. Hope you know about that.
    The wossner piston will work, but you have to feel hand a hair off your combustion chamber. You can email Travis at thumper racing to get the details. He can send you a picture and highlight what you need to take off. Vertex is a good option. Should work fine. I would use a CP, if you can get ahold of it.
    While
    You’re in the top end, go ahead and fix the soft intake valves if you haven’t. The head go a long long time once the intake valves are fixed up.
    While you have that bottom end apart man just replace all the case bearings and get the crank rebuilt with a welded pin. Set your axial clearance either at or just under .020”.
    The rocker arm rollers aren’t a weak point or anything. Unless they roll harshly or having pitting go ahead and leave them.

  6. #5
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    Thanks for the information.
    When you say, i have to feel hand a hair off my combustion chamber, did you mean porting the head ? sorry my english is not to good. Does it mean, i cant just put this piston without this ?
    Concerning the head, i ordered a full set of prox valves, intake and exhaust (Ktm here in europe, goes wild in the priçe this times) Hope there are good. I read here in the forum, that the best is kibblewhite valves, and have cut the angle valve seat, but finding here, in Portugal ho does this, is very hard, so for now i have to stay whith the standar angle. i change all case bearings to be sure, and i´m going whith a Prox Connecting Rod, hope is good too. My actual connecting rod is a ktm whith 250 h, its seems realy good, no play at all, but i prefer not risking.
    About welding the pin, i dont know because, i never had issue whith the crank, i stay whith stock compression, and stock cdi. did 525 had a lot of spreading crank issue ?
    Now for axial clearance thanks for the value, that was something i was looking for. I had some good luck whith my last build, because when i spoke whith ho rebuild the engine last time, and ask him if he check this, he tell me "Doesn´t need to be checked" . So i will order the tool for this, or maybe see whith the shop ho going to balance the crankshaft, if he can check this for me.
    I will take my time to do this rigth, i have a friend of mine ho is mecanic going to help me to, but is more experienced with japanese bikes, any help is welcome.

  7. #6
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    I've never run a Wossner piston in my quads so I can't help there. Only OEM or CP. KTM has used Vertex as a OEM supplier on some of their bikes so those should be a quality part too. Pro-X rod kit should be good as well. Crank spread seems to be a problem if you ride in the upper end of the RPM. I had the transmission wear out similar to you and started finding metal flakes in the filters. When I tore it down one of my main bearings had started to gal. I don't know if this was from metal contamination from the transmission or crank spread related from years of racing motocross. I put in a new OEM crank for the price of a rebuild and didn't worry about welding it. If you ride in the low-mid RPM range more it probably won't be an issue for you. If you ride near the rev limiter often you might consider welding the pin.

    Axial clearance must be checked on these engines. It's true that it's not an issue on most Japanese engines because they run ball main bearings or one ball and one roller bearing. These use two roller bearings and if they don't have enough clearance they will destroy themselves in short order. The races on the crankshaft are press-fit and you need a special tool that you heat up that allows you to take them off. Behind those races are different thickness shims that need to be changed to adjust the clearance. To check the axial clearance you have to bolt the crankcases together around the crank then measure side to side movement. When I do mine I use a dial indicator.
    Mine:
    2017 Husky FX 450
    2009 505 SX
    2008 525 XC-modded for mx (currently 450 cylinder)
    Dad's:
    2009 450 SX
    2008 540 XC

  8. #7
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    that wossner thing is stressing me out lol , i already order the piston, worst case, if i dont find, i will return it, and change to the vertex.
    Strange thing about the metal i find before i tear down the engine, was the metal shaving was in the short screen, and not in the long screen, maybe i'm wrong but i was thinking the long screen was for the gearbox, and short screen for the rest of the engine, but i didn´t find anything else damage, will see.. But thats sucks cause here in europe each gear is aroud 100 euros now, before, not a long time ago, it was aroud 50 euros, i had luck whith the polaris transmission.
    Another thing about the axial clearance, sorry maybe a dumb question, but does the value change when your changing the connecting rod ? And where are suposed to be the shim ? in the ktm part description, its seem they are in the timing chain side, but in my crank they are in the other side, does it matter ?
    i dont know if i going to weld the pin, i dont race anymore, it will be just trail riding and some hill climb, so maybe it will be good, it hold very well until now, even when i was racing in some high rpm it hold very well, the only thing strange that happen to me once, was the shaft seal behind my shift lever blowing out at the end of a race, never know why.

  9. #8
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    The crankshaft has to be disassembled to change the rod. I would think anytime the crank is broken down and re-assembled there's a chance it doesn't get pressed back to the exact same width that it was. My crank had shims on both sides of the crank. I put them back on the new crank in the same arrangement. If I recall there was something about making adjustments only on one side. I'd have to check the service manual to be sure though.
    Mine:
    2017 Husky FX 450
    2009 505 SX
    2008 525 XC-modded for mx (currently 450 cylinder)
    Dad's:
    2009 450 SX
    2008 540 XC

  10. #9
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    It’s only an extra small fee to have the pin welded and it’s added assurance. Just do it. These cranks rock back and forth and once the pin is welded with axial clearance set a little more loose they handle revs fairly well AS LONG AS you don’t have the dirtbike cdi.
    Quad97, manual states to only put them on one side but RFS builders have been doing them on both sides for a long time.
    In theory I don’t see how either one is necessarily wrong or right. All it does is change the alignment of the rod and wristpin where they connect. As long as axial clearance doesent allow for the crank to flog over far enough for the rod to tap against the piston itself I’m willing to bet either one ever poses an issue.

  11. #10
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    It’s only an extra small fee to have the pin welded and it’s added assurance. Just do it. These cranks rock back and forth and once the pin is welded with axial clearance set a little more loose they handle revs fairly well AS LONG AS you don’t have the dirtbike cdi.
    Quad97, manual states to only put them on one side but RFS builders have been doing them on both sides for a long time.
    In theory I don’t see how either one is necessarily wrong or right. All it does is change the alignment of the rod and wristpin where they connect. As long as axial clearance doesent allow for the crank to flog over far enough for the rod to tap against the piston itself I’m willing to bet either one ever poses an issue.

  12. #11
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    Do you weld the pin all around, or just put some welding points ? Youngwildandfree when you tell me about the wossner piston issues, does it concern the 11:1 stock compretion ? or is it just for the high comp ? I search in the the forum, and what i understand, if im correct, is the dome of the wossner piston (High comp ?) is a litlle taller than he should be, and sometimes he can hit the head ? I send a message to thumber racing here in the forum, but i don´t know if he comes here anymore, i will try to send a message in is internet site, to see if he can send me a picture.

    Thanks you both, for the help ;-)

  13. #12
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    So i ask to thumper racing, and he reply me (Thanks a lot). So i let the information here, in case someone one day need it. You only need to modify the combustion chamber, for the wossner piston 97 mm, and 99 mm 12.5:1 compression . If you use stock 95 mm 11:1, and 12.5:1, you dont need it.

  14. #13
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    I’ve seen people weld it all that way around and I’ve seen people just do two sides.
    To be honest I doubt it matters.

  15. #14
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    In another brand that I had a stroked crankshaft in they TIG welded the pin in three spots about 1/4-3/8" in length.
    Mine:
    2017 Husky FX 450
    2009 505 SX
    2008 525 XC-modded for mx (currently 450 cylinder)
    Dad's:
    2009 450 SX
    2008 540 XC

  16. #15
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    Ok thanks for the information.

  17. #16
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    Not that I know of right now, but I guess we got an answer here from teh comments posted

  18. #17
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    Good job to this taking this

  19. #18
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    So i send the prox conecting rod to put in the crankshaft, but i have a doubt about the two copper washers ho came whith the connecting rod. maybe im wrong but you dont use it whith the atv engine ? Theres no washers at all ? because in the part catalog they appear.
    Last edited by NeSta75; 10-14-2020 at 06:08 PM.


 

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