Great pictures. Since you have access to your frame, from what you can tell is this the same frame as the rc390? Is there a part# that you know of for your frame I can reference for my frame? Will be also rebuilding 390 engine in the future any inside knowledge greatly appreciated!

 

The frame is a bit different. But a lot of part in the engine and around are similar between the Duke and RC. I use several parts websites to compare if parts are similar. They have good schematics which show you part numbers. Helpful if you want to buy a similar part on eBay between a Duke and RC.

 

Thank you. will be researching front fork setup. I have seen a build online converting 390 duke to spoke wheel setup. seeing if I can use entire front end from duke 390 on rc 390 frame. if not find a way to use spoke wheels on rc frame/stronger wp forks.

 

Please do post more. I'll be interested in whether folk think that one differently colored valve is normal or not.

 

EDIT: Apparently it is the Loctite that makes the screws inside the engine very hard to undo. Use heat or a really good impact wrench...

This bike has been over-torqued like crazy, it's an absolute pain! I even got an impact wrench up to 250nm and it doesn't do anything. Unfortunately, I didn't get the right clutch holder (Amazon basic one...) and I broke both my inner and outer clutch hub, trying to make an improvised clutch holder. Ordered a second-hand clutch on Ebay to replace the hubs...

The TUSK clutch holder from works like a charm. I also ordered the KTM clutch holder but it's on backorder, I will cancel that one.

It was a two-man job and a massive wrench to be hit with a brick to get the clutch off. Be we got it off finally.

Next up is the gear connected to the countershaft. Same issue. Just impossible to get off. After hours of trying, we gave up. And stripped the bolt. If anybody has suggestions on how to get this out, please let me know. Think I need to bring it somewhere to get it drilled out.

With everything remove (except the gear above) we tried to open the case. It split up to 1cm, but unable to open the case. It seems that we need to remove that gear. So, no success there. My hope was that we could split the case with the gear still attached.

Meanwhile, Santa arrived with all the replacement O-rings, some special tools and other parts that will be replaced, once I get it open.

Edit: The genuine KTM tools that you really need are the two in the middle + the engine lock screw!



Very keen to learn that too - not sure what causes that.

 

Use heat on any further bolts. A propane torch works well. It sounds like red loctite, or something similar, was used so you need heat to break down the thread lock compound.

Threadlocking solutions

Threadlockers lock and seal your threaded assemblies, protecting against vibration, corrosion, and galling. But depending on your need, you have to choose the right threadlocker and consider strength, form, and removability. Which one will you need? LOCTITE® makes your choice easy.

www.henkel-adhesives.com

 

I did try with a battery impact wrench but to no avail. Just hits the ratchet immediately.



But I think this is it ... need to heat up the bolt first. Kinda pissed I didn't know that before. Now that my bolt is practically stripped .... sigh.

Any suggestions on how to get that gear/bolt out? Drill it out or spot welt on top of the bolt and heat it up with a torch?

 

Also might be worth investing in an impact wrench. I have a cordless but if you have an air compressor I'd get one for that.

 

Agreed on the impact wrench^^

 

Might try a set of vice grip style pliers on this as a last resort.There appears to be a bit of a shoulder on that bolt, very tight grip and then smack the vice grip with a hammer. Do you know the direction of the thread? We all have tried and tried to later find out it’s a reversed thread direction.

 

Cut flats on the outside of the bolt with a dremel tool. Or a hammer and chisel used properly might work. Again, apply a lot of heat first.

 

We got him 🔥

After applying a lot of heat, a concrete chisel at a 45 degree angle and 2 hours of swearing.

Might try a set of vice grip style pliers on this as a last resort.There appears to be a bit of a shoulder on that bolt, very tight grip and then smack the vice grip with a hammer. Do you know the direction of the thread? We all have tried and tried to later find out it’s a reversed thread direction.

Tried this as well @Spartacus - but this one was too stuck

Splitting this beauty (it got quite some abuse trying to open it - so I hope I didn't do any damage)

All cleaned up

And I think I found my problem - way too much play on the crankshaft - time for a new one:

I do wonder what could have happened for this to occur at only 16k km's....

 

Wow that’s alot of play.... either starved of oil or never changed the oil. What does the valve gear look like cuz it will show wear faster from this type of abuse?

 

+2 Lots of other stuff should be visibly damaged if that's oil starvation. Piston, valve gear, little end bearing and pin. If they don't, it's a bad part. Others will know more but I wonder if you need to change just the bearing, or also the con rod or even the pin.

 

1) Congrats! 2) I've had one con rod big end bearing go in my life (49 yrs riding). On that one (1973 Bultaco 350 Sherpa T) you had to exert lateral pressure to hear the clunk; no movement visible to the naked eye. Now, is the the crank pin or bearing?

 

BTW, when you said the 'engine broke' what were the symptoms?

 

Def looks like oil related. Make sure you look at the cam journals for damage, as the head is the last bit to get oil. How does the cylinder look?

 

The new parts are on the way, to be safe I ordered a new OEM crankshaft. I don't have the proper tools/knowledge to take the current on apart. But the pieces are starting to fall together what happened to the bike. Since I got it I had a "Low Engine Oil" warning - which I ignored as there was enough oil, so I wrote it off as a sensor issue.

I also had a "Faulty Lambda Sensor" warning. Which apparently is responsible for determining the mix of fuel/oxygen. Now with the engine open, there is a tonne of carbon deposits everywhere (piston/valves/spark plug) - probably related the to the faulty lambda sensor. And probably clogged up the flow of oil and starved some parts of of oil ultimately causing the engine to jam/run dry.

I brought it to the shop to check but its hard to find a reliable shop here in Hong Kong. I took the bike back and did an oil change myself to find all these metal shards. It also became apparent that the previous owner didn't do any basic maintenance ever on the bike.

Initially it wouldn't even run idle - just a metal clink sound and died. But after the oil change it ran idle but with a rattle (sounds like the timing is off)

Video with sound here

This was the read-out the shop gave me:

@Chip So there you have it
@Spartacus What exactly are the valve gears
@OneJzsupra I will make a photo of the head later and post it here - as I don't really know how to look for damage. The cylinder/piston/rings looks fine to me. No visible scratch or wear marks

 

Since I got it I had a "Low Engine Oil" warning - which I ignored as there was enough oil, so I wrote it off as a sensor issue.

I don't think the light is a 'low engine oil' warning. It's a low oil pressure warning. And usually it's pretty much over pretty fast after that. Especially with that rodbearing being so loose.
Looking at that engine and you mentioning the poor maintenance by the previous owner, could be they didn't use the correct oil too.

Nice to see your a hands on person and just strip it all apart!

 

And just for fun - this was the quote (in HKD - so divide by 8 for USD) they gave me for look at the bike. Later I found out they didn't even look at the spark plugs or throttle body ... just were just looking to charge me through the roof. And this is the official KTM shop...

 

Valve gear refers generically to the cams, and upper end (whatever wears or rubs on them).
Looks like the first owner never changed oil or was very lax. While you have it open I would probably replace the oil pump for “piece of mind” insurance. Probably not absolutely required but I wouldn't rebuild without.

 

"Since I got it I had a "Low Engine Oil" warning - which I ignored as there was enough oil, so I wrote it off as a sensor issue."

Check the oil pump then. I seem to remember that a crankshaft bearing as bad as yours can cause low oil pressure but I bet I heard that on Car Talk and it referred to multi cylinder car engines. So make sure that oil pump functions when you get it running again.

 

The oil pump (not my photo) is mechanical - similar to the photo above. It looks fine to me - still better to replace you reckon?

 

Hard to see in the photos, is the cylinder good to go? It doesn't look too bad in the photo, the cross hatching looks pretty good as well. Honestly if you taken the engine apart that much, I would have a machine shop make sure the head is decked and that the cylinder is good. Verify all clearances for the crank, rings, and rod and put her together.

 

It's absolutely a low pressure sensor and not low level. So you need to figure out what caused that, assuming it's not a result of a really, really, really bad bearing. You should be able to plug a pressure tester in where the sensor unit goes. Alternatively, just bolt it up and start it. If the light doesn't go out in a 5-10 seconds shut it down and put in a new pump.

 

After noting the rugged build of that pump It's probably OK ... pressure loss was almost definitely out of that big end bearing.

 

If your engine died from oil starvation (regardless of the exact cause), I would replace anything that had to do with the oil system. Rod bearings don't just die without a reason, whether it is low oil volume or low oil pressure something had to START the catastrophic event.

How are the cam journals in the head?

 

Thanks for all the tips. I've attached some better photos, maybe you can help me assess any obvious problems?

The minor scratch marks here come from me sanding all the carbon away

 

Cam journals look to be in good order, there's nothing on them that catches with your nail right? The head over all looks to be pretty good, my only concern is the head seating surface for the head gasket.... What happened and why does it look so scratched up lol. I'd inspect it and make sure you don't have any gashes, if you do I'd get it decked.

 

Also I would look at replacing your valve stem seals.... You can see in the photo that one valve is actually darker than the rest, even when you look at the head one of the retainers is a bit darker. Have a look at the seating surface for that valve and make sure it looks good. Did you measure valve lash before pulling your cams?

 

That's a wrap for today gents ... 6 hours of assembling.

My new crankshaft finally arrived, so it is time to put everything back.

I will share some tips for the people attempting to do this themselves.

I ordered all the special tools the manual says you need ... you don't need that many. For instance the protection cap for installing the balancer shaft no need. Locking screw and flywheel puller you need.

Next, the counter shaft, transmission and shift levers.

Some tips:

• Do not take your transmission apart if it's not needed - its an absolute pain to puzzle it back together
• Make your life easier and buy a simple lock ring plier and the clutch holder tool.
• Do not forget to put back your bearing holders before installing your transmission
• Grease up your springs inside your shift rails generously. Notice the difference length of shift rails.

I spent hours cleaning the cases before, hence they are so clean. Works fine with a good degreaser and lots of tissue paper, paint brush and q-tips for those hard to reach corners. Got some compressed air to make sure all the debris is out of all the oil channels.

Lets make a gaskets! Needs to cure for 24h. So I didn't install the oil filter and didn't fill the engine with oil - against the manual's advice.

When putting the cases back together even the slightest off-center will make your crankshaft stuck - which is very scary. I couldn't get the cases to fall in place themselves and had to use the engine screws to tighten the engine cases together. After that all was smooth.

Unfortunately, I didn't take a photo after putting the case back together. Continued with installing the gear shifter, oil pump, primary gear and clutch basket.

After installing the shift drum you have to shift through the gears (turn transmission shaft by hand while turning the shift drum to shift up and visa versa to shift down). You need to put it in neutral before continuing! Otherwise your shift shaft isn't positioned right.

I can't reference Jeet's videos (timestamp 34m) enough - even tho I don't understand anything he says. It's fantastic visual reference.