How To Rebuild the Top End on a KTM 85 SX 

lol

Or just a socket?

Yh ns aye aha

Hahahaha good obe

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

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

That’s like throwing money in the toilet.

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

Yes they have same engine

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 🙃🙁

trevor dean yeah

Yes

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

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

Every race is just a waste of money

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

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 😂🤙

That's why your bike is probably clapped

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*

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.

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.

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

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).

Id say every 50 hours or every 6-8 months

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!

@@rmatvmc cheers pall thanks very much

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

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.

Tom Sharpe yeah

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.

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

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

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.

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.

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

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

@@onenessseeker5683 the carb boot

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!

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

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

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

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

Rocky Mountain ATV MC yea it was a tight fit

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

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

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

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

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!

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

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

Ryan Morgan 250 h

1h calm driving

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.

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.

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

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

Thanks

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

Mr megane r26 f1 right right😂👌🏼

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 😂