How To Rebuild the Top End on a KTM 85 SX

KTM 85 SX Top End Rebuild Parts
www.rockymountainatvmc.com/Sa...
Learn how to rebuild the top end on your 2 stroke motorcycle. This video demonstrates how to easily replace the piston, rings and gaskets on your KTM 85 SX 2 stroke engine. We walk you through step by step on how to successfully rebuild and install the top end on your dirt bike.
KTM OEM Hard Parts
Cylinder Head O-ring Gaskets
0770800021 O-RING 80,00X2,00 VITON
0770540020 O-RING 54X2 VITON
GASKET SET CPL. 85/105SX 04
Part# 47030099100
47030035020 CYLINDER BASE GASKET 0,20MM | As Required
47030035030 CYLINDER BASE GASKET 0,30MM | As Required
47030035000 CYLINDER BASE GASKET 0,50MM | As Required
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[@nou943]

piston pin puller? you mean a flathead and a rubber mallet?

[@caywoo]

lol

[@dylangreen9819]

Or just a socket?

[@samuelcooper5140]

Yh ns aye aha

[@motomich9787]

Hahahaha good obe

[@jonoj7666]

Didn't have my service manual with me but this vid having all the torque specs saved the day. Thanks heaps 😀👍

[@peterhellmuth4340]

Hi great video I was just wondering if you had a video or pic how the power valve on the side goes back on and how the spring goes cheers

[@nickross6138]

Great video very detailed thanks

[@danmartens1282]

Any chance rmc has a video on internal power valve adjustments ?

[@ryanmayer1087]

Dawg I put 178 hours on my piston on my 2018 ktm 125sx this season and there was no cylinder wear and the piston was in great shape. I don’t believe anything anymore lol

[@Donniekabab]

Doing the piston of my ktm sx150 2018 at the moment. I notice in this clip you do not lock the ball socket to the power valve shaft. My 2018 has a lock spring at the ball socket. Disassembling no problem but reinstalling damm I am not succeeding for hours now. Is it required to mount this lock spring?

[@yesmatem5356]

I had a tip end rebuild and it’s really crisp sounding now is that ok

[@philipp4109]

I blew my piston on my 85 after 4 years of riding Almost every day

[@mattlaidlaw8521]

my ktm 85 just had a full engine rebuild all bearings crank piston ect after 3-4 hrs not even that kaboom completely blew the piston wrecking the head cylinder piston crank bearings and case hate this 🙃🙁

[@devinborchert6108]

Definitely not rebuilding every 10 hours😂

[@davidbeauvais1364]

That’s like throwing money in the toilet.

[@Motofumes159]

My 85 sx has 248 Run hours on it and it’s on stock top end It has lost a bit of compression but she still runs great

[@nicsminibikes]

Do you have a video of rebuilding the bottom end of a KTM 85 sx?

[@tremontweaver8845]

How do you put the power valve back together

[@dirtmoto2780]

Every 10 hours??? My kdx topend can last 4-5 years easily.

[@johnnyaltomare2422]

Dirt Moto right I thought that was ridiculous. I own a an 03 yz and it’s only been rebuilt twice...

[@jonthelamb4549]

Every race is just a waste of money

[@nakkisampyla4460]

Dirt Moto depends on if you ride it 10h or 100 or 200 hours every year 😂

[@rsturborolphy6760]

All depends on what your doing with a bike . If your in composition then probably do the top end every meeting the last thing you want is a dud engine come race day and let's face it if your racing 2 strokes you need money either way 😂🤙

[@leviingramunique4262]

That's why your bike is probably clapped

[@tgsubie]

So you do no honing of any kind to the cylinder or piston sizing, not even mentioning it. This forces me to ask, for the common 85, would it be acceptable to replace the piston with a completely stock size piston?

[@Will24three]

how about a break in procedure video for 4 and 2 stroke.

[@tomjones7129]

Shandon Williams I've never owned a brand new bike but just put a full tank though it of slow riding

[@tylerm9508]

Just do a heat cycle and run a high mixture for the first tank and your good

[@rsturborolphy6760]

Isnt it worth just putting a small beed of sealant round the base of the barrel? Now about to do the top end on my 09 85 . Ktm need to calm down on the production of the older bike parts getting hard to find bits for even earl 09 bikes. Got a quote on a barrel and piston...£600 ....my 98 cr125 top end is half of that 😂

[@Iatolaazzahola]

Top end replacement schedule is directly related to riding conditions and who is maintaining the air filter. I like the video. but why not go into servicing the power valve when you have the jug off? Critical maintenance area.

[@logannicholas-xc5qi]

What size piston is standard on a 2016 tc86

[@jarenwilson2343]

I have a 1994 yz 80. I ride it several times a week wide open In a field and it has a stock piston 😂

[@mustafanajm965]

Thank u for the video i have question please i have this bike im going to repair the top end but what the different between oem top end and vertex top end please help thank you

[@rmatvmc]

Either one is a good option. I'd just get the new parts installed and call it good! -Charles

[@blackdevilteam5503]

What does gilardoni means on the side of the cylinder?

[@DYLLY0456]

That motion pro puller is just the company wanting money for unnecessary tools. Just ask someone to grab the piston for you and hit the wrist pin out with a mallet

[@user-zc7lj1qw7o]

You forgot one very important checking big end bearing for any play

[@aynsleybordycott5506]

How do u do a topend on a 2001 ktm sx65

[@davidofqwerty]

Hi what should the compression be in the cylinder after a top end rebuild thanks alot

[@rmatvmc]

It depends on the bike and your specific bike should say in the service manual. But it should generally fall in the range of about 130-190 psi. Hope that helps!

[@davidofqwerty]

@@rmatvmc cheers pall thanks very much

[@speedtoad6167]

No honing cylinder or cleaning power valve? Interesting.

[@IDive2]

what should the compression range be for the ktm 85s?

[@rmatvmc]

KTM doesn't give any specs for compression on the 85, they prefer a cylinder leak down test be done to check engine wear. But your compression should be 120+ on an 85cc.

[@dsr3405]

Can you do this step-by-step

[@user-ow9jq6er3f]

Hello im getting a 2016 85xs that has a 105 big bore kit on it and it needs a complete rebuild top and bottom what would you suggest as far as a complete rebuild kit and what size of piston would i need

[@rmatvmc]

Awesome, congrats on the new bike! We sell the KTM big bore replacement piston ( www.rockymountainatvmc.com/parts/ktm-big-bore-kit-replacement-piston-kit-p ) but unfortunately it is currently out of stock. We would still recommend taking out your piston and measuring the cylinder before you order the new piston to make sure you get the correct size. For the bottom end, you can use either the Wiseco ( www.rockymountainatvmc.com/parts/wiseco-bottom-end-rebuild-kit-p ) or Hot Rods kit ( www.rockymountainatvmc.com/parts/hot-rods-bottom-end-kit-p ). Then you should just need gaskets for the top end. We have OEM part numbers in the description of this video or you can get a gasket kits or individual gaskets. You can check out all the engine parts for your bike here: www.rockymountainatvmc.com/parts/dirt-bike-engine?v=2016-ktm-85-sx-17-14&page=All

[@jesseanthony4816]

Dude I beat the absolute shit out of my ktm85sx and decided to do a rebuild on it since it was starting to loose compression and found out it has the original piston in it from 2004 kind of impressive tbh

[@grantas222]

Doing a rebuild on my 04 85sx, it also had the original cylinder and piston😂 it had an air leak and ran lean, spark plug melted and scratched the cylinder

[@onenessseeker5683]

@@grantas222 where did it have an air leak.. I think mine has one

[@grantas222]

@@onenessseeker5683 the carb boot

[@zvinz7598]

2:42 come si chiama quel pezzo sferico che si stacca? Italy please

[@tomsharpe8181]

Will this be relatively the same for any other 85's? Specifically a yz85?

[@r.jjetskivids5810]

Tom Sharpe yeah

[@zane4964]

Tom Sharpe yep pretty much exactly the same except check what the torque specs are for the yz85. Also the yz85 does not have the power valve.

[@tomsharpe8181]

ENDURO SK knew it didn't have a power valve so didn't know if that affected it someway

[@r.jjetskivids5810]

Tom Sharpe yeah with a power valve there is just a extra step to unhook it before taking the cylinder off.

[@icantcomeupwithaname8925]

Tom Sharpe yeah the only difference is no power valve and the torque specs are different 22ft lbs for the head and 20 ft lbs for the cylinder.

[@ryanbruno8117]

Is it the same thing for the TC85

[@SolveigRuokonen]

Yes they have same engine

[@nathansharp2478]

What size piston will I require for a 2007 ?

[@rmatvmc]

If you haven't had to bore your cylinder, it should be a 47mm. You can enter the model of your dirt bike on our website and see all the pistons and sizes available for your bike. www.rockymountainatvmc.com/ Hope that helps!

[@tink0801]

I hit the piston pin with a flat head screwdriver if I'm replacing it

[@rmatvmc]

The wristpin is not the problem. It's applying un-wanted side to side force to your connecting rod. You do not want to throw the connecting rod out of spec, leading to bigger problems down the road. We do not recommend hitting it out. Thanks ~ *Vinny*

[@KurumaDesigns]

I do that too james but I make sure to hold the connecting rod firm before hitting so I don't hurt the conrod bearing.

[@jaxslaps1011]

i just use very slight taps on the handle of an 8mm t handle and i hit it with the arm of another t handle i also try to hold the piston while i do it, or the connecting rod, infact i just did but i wasnty as careful as the crank siezed this afternoon.

[@trevordean2314]

Is this the same as a husky 85?

[@jesse9705]

trevor dean yeah

[@kaigreenwood4033]

Yes

[@libiyamullaney9672]

The two back bolts where the base gasket is how do yoy get to them ?

[@aaronkarg8485]

10mm wrench that I filed down on the bench grinder to make it thinner. Good luck torqing them too. I noticed he didn't show that!

[@RacingAddicts]

Use a crow foot to loosen and torq the 2 bolts.

[@Ryan-ls1pz]

How often do you rebuild the bottom end on an 85?

[@heavenly_seahorse]

Ryan Morgan 250 h

[@nemanjadraca4012]

Just rebuilt my 2015 ktm85sxs bottom end and top but I have kinda low compression it doesn’t even have 5 min of run time on the complete motor could it be a air leak? Or the size of the gasket used on the head?

[@rmatvmc]

It could be caused by both of those. Did the piston and rings fit correctly in the cylinder?

[@nemanjadraca4012]

Rocky Mountain ATV MC yea it was a tight fit

[@nemanjadraca4012]

They fit right but my compression is soft not as hard unless it’s cuz my timing is off because the kicker catches compression a lil lower when u kick instead of at the top almost as if it’s a decompression lever idk

[@nemanjadraca4012]

Rocky Mountain ATV MC the rings also Wer not snug at all but I put the up right and the gap was in between the spot it’s spose to be

[@MotoKid-ty2yr]

how do I do that torque foot pound thing

[@rmatvmc]

Using the BikeMaster Adjustable Torque Wrench | www.rockymountainatvmc.com/parts/bikemaster-adjustable-micrometer-torque-wrench-p Check your owner's manual for exact machine specs, once the wrench clicks while tightening you have reached your foot pounds needed.

[@saifulbmrt8436]

Is gut

[@danmartens1282]

How do u torque front nuts on cylinder?

[@rmatvmc]

The best way is to use something like the Motion Pro Torque Wrench Adaptor. You can check that out here: www.rockymountainatvmc.com/parts/motion-pro-torque-wrench-adaptor-p

[@jonthelamb4549]

First step should be wash the bike and take your time doing it

[@user-pd6sg4vc1j]

Сколько масла в коробку?

[@hayden9373]

Will this be almost the same as a KTM 125sx?

[@hawkgamer3354]

the exact same for the same year for different years it will be slightly different

[@hawkgamer3354]

no parts lists on google might be useful to put it back but it would be good as a refrence to come back to 2 strokes are fairly simple when you know a bit about them

[@ktmkid3259]

Does it matter what year

[@rmatvmc]

Not so much. Very similar process for all years. Always refer to your bikes specific service manual for proper procedures though. thanks

[@ucelo5913]

If I don't use the bike for competition / pushing it to the limits ¿how often should i rebuild the top end?

[@martialartsfan882]

Alejandro Ucelo probably once a year then depends how often you ride

[@jakewaggoner4196]

There are guys that have about 100-150 hours on their lightly used trail bikes. lol. Some people replace the rings and leave the rest but it's all torn apart and 2 stroke top ends are cheap, you might as well replace it all. My 03 Cr250 Wiseco top end is $150 (USD).

[@danblades5893]

Id say every 50 hours or every 6-8 months

[@garethbullivant6620]

Does anyone know how long it takes to run in after the rebuild is please

[@Kapteeniupponalle]

1h calm driving

[@onenessseeker5683]

I put a new piston in & hit the power band almost straight away.. to make sure she's good & get a real good ring seal.

[@user-ys1eo2fc9x]

What oil are you using ???

[@rmatvmc]

I believe we used the Motorex Cross Power 2T oil for the premix.

[@robayre482]

What oil did u use to lubricate the piston ?

[@jonthelamb4549]

Rob Ayre 2 stroke oils what you use in your gas your just preluding so it's not going to break right away

[@brodiefrancois.6542]

forth

[@Steezy_Mx]

Every 10 hours for top performance.

[@motoxwade2246]

SECOND

[@alexmccormack9719]

6th

[@joeyday6029]

how ironic

[@mattlaidlaw8521]

EVRY RACE R U MAD 😂😂🤣🤣

[@tobybrasherharding164]

First

[@byronbridges6898]

it sais 40 to 80 hrs what are you talking about dude its a top end you would have to be destroying the bike to do it every race.

[@30626a]

2 day ride and you need a new piston. Sounds like a shit manufacturing to me

[@splasx]

This is kinda of a lie you should be rebuilding every 60 or so hours

[@rmatvmc]

It all depends how the bike is ridden. More serious racers will replace top ends way more often than someone riding around their yard or trail riding.

[@Iatolaazzahola]

@@rmatvmc the schedule also depends on who is maintaining the air filter. Good air filter maintenance is what keeps the top end happy.

[@Ryan-ls1pz]

How often do you rebuild the bottom end on an 85?

[@johnnyaltomare2422]

Ryan Morgan you rarely have to rebuild bottom ends... most of the time you rebuild a bottom end is because your crank is seized or something like that

[@Ryan-ls1pz]

Thanks

[@rsturborolphy6760]

@@johnnyaltomare2422 or a bit of ring has popped down to say hello 😂🤙

[@johnnyaltomare2422]

Mr megane r26 f1 right right😂👌🏼

[@rsturborolphy6760]

Ibe got a road registered cr125 with a endurance display soon as I've done near 150 miles on the road a new piston goes in without fail it ain't worth the wait for it to give it . You can get away with a nip but anything snaps and its normally all bad news 😂