Is the KTM 790 Engine Reliable? Shocking Damage Found Inside!

Added: 2026-05-12

[00:00:00]In this episode, we’re tearing down a KTM 790 engine.

[00:00:04]This machine is the DNA behind the CFMOTO 800 series.

[00:00:09]It’s also the root of the Kove 800.

[00:00:13]In fact, others have been copying this engine design lately.

[00:00:18]So, you tell me—is it a masterpiece or what?

[00:00:22]This one uses a slipper clutch.

[00:00:27]European bikes using Japanese FCC clutches— even BMW does it.

[00:00:34]This clutch... the whole assembly uses an anodic oxidation process.

[00:00:40]Uh, the clutch plates actually look fine.

[00:00:44]Because of the deep partnership between CFMOTO and KTM, CFMOTO’s 800 engine is essentially this exact machine.

[00:00:56]Just with a different badge.

[00:00:58]The internal components are identical.

[00:01:02]You can check my August teardown video of the 800MT.

[00:01:08]As for the fault with this unit, the owner reported abnormal noise and a misfire (cylinder drop).

[00:01:16]Hearing that, I started suspecting the hydraulic tensioner was acting up.

[00:01:24]Take a look at the camshaft bearing cap.

[00:01:27]There are some slight marks, but it feels smooth to the touch.

[00:01:34]Just a quick soak and a rub with 2000-grit sandpaper will do.

[00:01:39]Now let's look at the corresponding camshaft.

[00:01:43]Visually, the camshaft surface looks like it’s been scored, but you don’t really feel much when touching it.

[00:01:54]This is a lightweight alloy steel camshaft.

[00:02:01]European bikes have always used high-quality materials for their engines.

[00:02:07]The intake lobes don't have any major issues.

[00:02:11]You can see some wear marks on the camshaft seat here, but it's not a big deal.

[00:02:19]It won't affect performance.

[00:02:21]Since these camshaft rockers rely on these oil jets for spray-type lubrication, when the weather is cold, it's the same old rule: Warm up the engine.

[00:02:38]Otherwise, the camshafts and rockers will suffer from accelerated wear.

[00:02:46]Removing the cylinder head... Look at this—one valve has snapped off completely, and it's absolutely trashed the valve seat.

[00:02:58]The remaining three valves are toast as well.

[00:03:02]It’s a pretty brutal sight.

[00:03:06]Fortunately, it’s repairable.

[00:03:09]I'll get four new valves and press in a new seat.

[00:03:14]This is what it looks like after the repair.

[00:03:18]After all, a KTM cylinder head is way too expensive.

[00:03:21]I’ll lap the valves, then clean up the combustion chamber a bit to make it look decent.

[00:03:29]Look at this piston.

[00:03:31]There’s no fixing this— it has to be replaced.

[00:03:34]The cylinder is gone too.

[00:03:36]I’ll have to install a sleeve.

[00:03:38]This hydraulic tensioner... how many engines has it ruined?

[00:03:44]Once it fails intermittently, this is exactly what happens.

[00:03:51]I bet quite a few KTM 790 owners have been hit by this.

[00:03:56]Look at the magneto rotor; that’s also Japanese.

[00:04:02]So when some people complain about Chinese bikes using Japanese parts, there’s really nothing to complain about.

[00:04:12]Even European bikes use them.

[00:04:14]Why shouldn't Chinese bikes use them, right?

[00:04:18]The CFMOTO 800 engine was essentially provided by KTM.

[00:04:23]However, the core ECU tuning wasn't shared with CFMOTO.

[00:04:31]So, between the 800NK and the 790 Duke, the gap between them lies in that specific tuning.

[00:04:41]This is why CFMOTO has been emphasizing lately that their main focus going forward is "refining the tune."

[00:04:51]They’ve realized it themselves.

[00:04:54]Look at these bearings.

[00:04:57]No issues here.

[00:04:59]They’re good for continued use.

[00:05:01]Removing the balancer shaft.

[00:05:04]No wear on the balancer shaft either.

[00:05:06]No need to check the transmission shafts— these things almost never break.

[00:05:11]Check this out: it’s a 285-degree crankshaft.

[00:05:17]It’s different from a 180-degree and different from a 270-degree.

[00:05:24]Both the 790 and the BMW 850 use 285-degree cranks.

[00:05:32]This crank is a one-piece forged alloy steel crankshaft.

[00:05:38]Like I said, European bikes usually "max out" the engine specs.

[00:05:45]They give you everything you’d want.

[00:05:48]Hence the price of the spare parts, and the price of the bike... well, you get the point.

[00:05:56]Looking at the crankshaft, you can tell the owner wasn't exactly gentle with it.

[00:06:06]But then again, I shouldn't say that.

[00:06:11]This machine isn't meant to be ridden gently anyway.

[00:06:16]It’s built for aggressive riding.

[00:06:18]This looks okay.

[00:06:20]It feels smooth to the touch.

[00:06:23]Not really worn out, just normal signs of use.

[00:06:28]Same for the bearing shells.

[00:06:30]Alright, let's look at the main bearings.

[00:06:33]They all show normal wear.

[00:06:38]They can definitely be reused, no problem at all.

[00:06:43]These are copper-based bearings.

[00:06:46]As for the MT brand, I'm not sure what bearings they use.

[00:06:51]Someone told me before that they use Mahle— German Mahle bearings.

[00:06:58]Let's pull the piston out and have a look.

[00:07:02]This one is perfectly fine.

[00:07:06]This piston and the rings are still good to go.

[00:07:11]These fracture-split connecting rods are actually made in China.

[00:07:18]Even if it's not a CKD (local assembly) version, the rods on the imported versions are ours too.

[00:07:25]So don't say our components aren't up to par.

[00:07:30]And this crankshaft— BMW, KTM, and others are all using them.

[00:07:37]These are all Gangyang crankshafts from Jiangsu.

[00:07:41]Since CFMOTO released the 800, KTM 790 parts prices have become much more affordable.

[00:07:51]For this piston, we’ll just use a CFMOTO 800 replacement.

[00:07:57]The old MT ones are identical to this.

[00:08:01]You could say they’re exactly the same part.

[00:08:04]Look, this side is punctured right through.

[00:08:07]Now look at the cylinder.

[00:08:12]The assembly video will be in the next episode.

[00:08:16]If you enjoyed this, please give it a like.

[00:08:18]Thanks for watching!