Huge power loss and sounds different

Back again guys, happy new year first of all.

So yesterday I was out on a ride having fun as always. Coming up to a turn I down for a down shift and my throttle cable decides to stick open I pull in the clutch and of course it stays revving away. Out of habit I shut the bike off with my clutch hand. Engine shuts down and the rear wheel locks up because my of my genius self. No biggie I keep it balanced until it finally stops. I hop off and troubleshoot as best I can on the side of the road with no tools but easy diagnosis, the throttle cable won't snap shut when I let go of it. I can still manually force the throttle closed by rotating it forwards, so I hop back on and head home.

The bike had noooo power on the way back and was very easy to stall from a stop. It also sounded different. No knocking but when I would give it a little gas it would just get louder without accelerating much at all. Obviously I wasn't going to go full throttle or experiment too much with it, I just wanted to get it and me home. Well I pull into the garage and my first solution is to maybe lube up the cable? I open the throttle housing and spray a ton of WD40 into it, making sure it dripped down past the housing. Works like a charm, and the throttle snaps completely shut when I let go of it. Problem solved right? Of course not.

So this morning I go out and start it up for a ride. Back out of the garage, and as soon as I start to let out the clutch I realised nothing had changed. The throttle cable was fixed but again the bike is very easy to stall and has no power. When I set off again I pulled the clutch in to stop and the revs fell on their face, like the engine barely stayed turning over (maybe 800 RPM?). So I turn the bike around and same thing. I twist the gas and the cable works fine now but it just gets louder without much movement.

Has my clutch gone out? I just had the fluid changed a few thousand miles ago, and I do remember asking the shop if they had mineral oil and they said that's all they use for clutches. I put new oil in it and I checked the valve tolerances last month and everything checked out. Bike has 30K miles on it, never been raced or ridden super hard.

Oh and one more thing I forgot. On my ride home yesterday when I was limping it back, I noticed that if I give it gas the whole bike shuddered. Not smooth at all like it usually is.

Sounds to me like you may have more than one problem. The symptoms you describe sounds like the vacuum line is unplugged from the rear throttle body. Check to see if this line is off, loose, split etc.

When you do anything with the throttle setup of the bike, you need to re sync those throttle bodies.

I had wondered about balancing the throttle bodies. I've never done it before but I'll look up a DIY. Is it possible they got thrown out of sync when the throttle cable stuck?

I would have a look if a valve shim didn't pop out due to over revving.
Normally the rev limiter would save it but it sounds like there is more to it. The shuddering is not normal.

Update on the bike. I finally got around to taking the intake system apart. Open up the air box and both of my velocity stacks are loose. As in no longer latched onto the throttle bodies.......what? No idea how that freaking happened. But I'm going to reassemble everything and give it a shot. Butterfly valves both respond well to throttle inputs. Perhaps a velocity stack was constricting air flow since it wasn't connected anymore?

One of the metal tabs that the rear stack latches onto was broken My heart stopped for a second there. But then I realised wait...if the metal piece had fallen into the intake (worst case scenario) then my bike probably wouldn't be running right now instead of just running crappy. I peeked down into the head and only saw valves, no damage. Even took a somewhat dumb chance and started it up and the rotating assembly is fine. Like I said I'll put everything back together here soon and maybe I get lucky and the cause was just the stacks. If not due to my current work schedule I'll probably have to drop the bike off with the shop up the road to get the throttle bodies resynchronized. After that well, I'll be running out of ideas

Just got back inside. Everything was reassembled and didn't change anything. Bikes revs freely (to 3-4K RPM, didn't want to push it) when in neutral. It definitely doesn't like when a load is applied though, stalled it twice putting it back into the garage. Also it hunts for its idle RPM. Not by a lot but you can definitely notice the needle ticking up and down if you stare at it. To me this is good news, since I believe that is a tell-tale sign of throttle bodies not being synchronized. I'll call up the local dealer who is less than 2 miles away and changes my tyres and see if they'll do my throttle bodies (they normally only deal with Jap and Victory bikes).

Dealer said they'd take a look, but asked if I knew what they were supposed to set to. Having never done this before, I told them I'd find out and get back with them. I'm searching the forum and have found plenty of people who have set there's, but that's all they've said is they "set it"...no actual numbers. Managed to find pics of an SDR that set his both to 29 cmHg. Anyone know if this is correct/will work for a standard SD?

Definately dont start the bike anymore. Where did the metal tab from the intake go? There's no way it can get out of the MH airbox besides going into the motor.
I dont mean to freak you out, but a piece of metal like that going into a motor is perfect for bending a valve, damaging valve seats and punching holes in pistons.

Does the bike like to start? Does it backfire or 'chuff' back through the throttle body, particularly the one with the missing tab? Is there any ticking or tapping noise.

Get the tappet cover off and get the spark plugs out. Shine some light down in there for a look see. You can buy great little sticky beak flexible camera and screen that are perfect for inspecting inside motors. As Guy suggests, check the valve shims are in place.
It will still be OK to turn the motor over by hand. Put it up on the rear stand, put it in gear and use the rear wheel to turn the motor over. Does it turn freely? Does it get tight or catch anywhere? (shouldn't get tight anywhere if both plugs are out)

If there's no obvious damage to the piston/cylinder, shims are good and all seems to rotate freely, valves are moving up and down, put it back together and it should be safe to start.

Get a tuneECU cable and the program and check for faults.

Just to remind you what damaged valves can do to a 990. It's not worth the risk!

The reason I say the rotating assembly is fine is because after I first had the issue on the side of the road, I drove the bike home (something like 12 miles). If a metal tab was floating around inside the engine I don't see how it's mechanically possible that the bike would even be running. It starts up normally, doesn't make any destructive noises, and spins up freely. A dislodged shim I'll have to look into more, but when the throttle snagged it didn't bounce off the limiter, it just hung out around 6K RPM if I remember right.

I suspect one of the idiot shops that worked on it earlier this year might have broken the metal tab off, but thankfully removed it. Those guys really suck, but that's in the past. Again, I freaked out like probably anyone would when I noticed a metal tab missing above my throttle bodies. But I am genuinely positive there's no way it found it's way into my engine. I'd see smoke coming out of the exhaust, I'd hear valves being beaten to death, pistons getting scratched to dust, something. I imagine a valve shim that popped out would do something similar. I'm struggling to imagine any piece of metal having room inside the block to just hang out waiting to strike. Something like that would have already destroyed something. For the time being, I'm assuming its a vacuum/throttle body problem.

Both cylinders or one only running?

You guessed it No. 47. A quick water spray on the exhaust proves only the front cylinder is firing. Pretty much narrows it down to either a bad plug or bad power commander but mechanically the bike is fine.

I have a cable. I don't have a PC though, only Macs. Most of my friends are away on vacation but I might try and reach out to them. A stuck shim is still a possibility if it didn't move a whole lot. I'll take apart the rear head tonight and make sure they're all still planted flat. If they are, I'll disconnect my PCV and return the bike to it's stock computer to check against the PCV. If that still doesn't solve it then I imagine everything pointing at a spark plug failure.

Was thinking throttle cable and TB tab just coincidence - fiver says it's loose/faulty rear coil pack.

Maybe check plug first, then PCV before ripping heads off? Start at the easy ones first.

Normally, yes. But I'm about to be away from home at work for a month straight. So I'm troubleshooting with the interest in what could actually fix the bike the fastest. A stuck shim could take a little over an hour to completely repair the bike. The PCV or plug/coil requires me to order parts that might not even get here until I'm gone from home. And I've been in my bike's heads quite a lot, they don't scare me anymore

You a bike therapist? [WINKING FACE] cool hope you manage to get it solved quick mate, I also work away from home so understand your frustration

Had a similar problem on two different accasions.First one was a lose front coil pack.Second one was the fuel pump plug to the tank had a bad connection because of me removing the tank so often that the plug snap connection wore out.Cheers.Bad TPS setting can affect your stalling problem,not so much your throttle body sync but still worth checking.Cheers

This damn bike is starting to wear on me, seriously. I'm out in the garage, remove the coil pack (it felt very snug so that should eliminate a loose pack issue) and do a resistance check on it. I'm reading 13K from each prong to the output tip of the coil, seems fairly normal. Next is to check the shims. Not a big deal at all. I bust out my special tool from CJ Designs that makes it easier to rotate the crank in order to rotate the piston to TDC.

OF COURSE the tool strips! And I mean strips, after only like 2 rotations. Granted I used a 12 point socket (with a tight fit), but still. There's no way this thing should be reduced to having only 2 and 1/2 points for a 6 point to grab onto after a few turns. So I spent the next chunk of time trying everything I can to force the socket onto the tool but it's not having it. So I grabbed my stuff out of the garage and walked away, bike still on the rear stand and everything. It can fall over out there for all I care right now. It's just one of those scenarios where I'm like really? You're really going to fight me on every single step of this? That was literally the one and only thing I didn't need to fail for me to check the shims and of course it fails miserably. I pondered marking the cams in their current position and taking them out but the risk vs reward doesn't add up to me. If I put the cams back in even slightly wrong there goes the whole valve train.

I'm just tired and frustrated right now. Maybe I'll go back out and work on it later but right now I'm pretty upset with how familiar I am with taking my SD apart and putting it back together.

Had similar thing. As far as symptoms you described. Front cylinder coil was loose. Check coils/connectors/plugs. Pushed it back in and ever since works great.

Hey guys, back from my long trip away from work and decided to get busy in the garage again.

Got around to getting a replacement tool to turn the crank over. Some real heavy-duty stuff too, got the rear cylinder to TDC no problem. Pulled the cam bridge, the cams, and pulled the buckets out. Now I'm not 100% sure on what I'm supposed to be looking for in a stuck shim scenario, but 2 of my shims "fell out" of their buckets. Or at least they weren't all the way seated like they were supposed to be. But then again I have no way of knowing for sure since I pulled my buckets out with a pair of pliers. So it's possible when they popped out they became dislodged. I don't know. As far as just the shims go I don't see any definite way they could have completely stopped the whole cylinder from firing. Even if they weren't seated, the valve tolerances would just be a little off.

I'm currently waiting on new plugs and the special socket to change out the plugs while the bike is apart as well. I can't see what the current plugs look like so I can't currently check on a failure. Maybe once I put it back together and start it up it'll magically work again?

If you just lift the buckets off yeah the shims can just drop out. At least they didn't fall anywhere they'd be a bitch to get them back out from. You can pop a spot of oil on the shim to help it stick in place when you put it all back again. Did you check the clearances before you removed it all?

edit just read back through and saw you checked them a month before this happened.

Why are you stripping out cams etc before checking plugs and coils?

Only true for SDR, not SD.

The reason I checked the shims first is because I was waiting on my spark plug socket and new plugs to arrive and figured I could at least check them in the mean time. They finally arrived in the mail today

So I head out to the garage thinking I'll swap the plugs, reassemble everything, start it up and there's a solid chance the bike will be fixed. Well I bust out the CJ Design spark plug socket (like 40 freaking dollars for a 9/16th's socket and a swivel extension, but who cares I have it now). Takes some time to find a good angle due to the frame above the rear cylinder plus how I have my cable management set up. I finally get it in there at the right angle for the ratchet to clear the frame and start twisting. And twisting. And twisting some more...wtf?

There's no resistance to this thing at all. I even put a good amount of pressure on top to make sure the socket is seated properly. But nothing. I crank this this for like 2 minutes just praying the plug will come out. Nope. I even stuck my telescopic magnet and rattled it around so I could see if the plug was loose or not. The socket never moved it. I think maybe operator error? I bust out the new plugs (KR8DI's) and try a fitment test. OF COURSE the socket doesn't fit. It's ever so slight, but yeah it won't fit.

So thanks YET AGAIN CJ Designs!! You guys are 0/2 with me with a tool that stripped itself to death after 2 turns and a $40 socket that doesn't even fit what you say it will. And yes, I bought the 07+ socket and yes, my bike is a 2007 model. I hate to throw a pity party here but holy shit.

Updated, and ordered the tool you got. Thanks man.

Guess when it get's here tomorrow I'll try try again. I'm in the middle of separating from my current job, going through job offers, and packing up my place all at the same time. So while set backs like these are only minor, they're very frustrating. Throw in the fact that I have basically zero dealer support out here and I feel like every time I walk out to my garage I'm going to stroke out. Yet again this forum is pretty much the only (but still great) source of help.

Sorry dude for some reason I thought you had the SDR. I have a spare thin walled socket from when I had the SD I could have sent you. Any problems with the one you've bought let me know and I'll bung it in the post.

As for a socket for turning the crank, I bought one in Halfords. Never had a problem with it.

New tool worked like a charm. Pulled the rear plug out. Electrode was bent in and the tip of the plug was all black. Running rich and not sure how the tip was bent...possibly when I was pushing down on the old socket when the piston was at TDC? Curious. It looks like the idiots at Red Line didn't change the plugs out like they said they did. Bike is on a trickle charge right now. Once the battery is charged I'll start it with a new plug in it and see if that solved the dead cylinder issue.

Can you post a pic of the end of the plug?

Never been able to figure out how to post pics on forums lol

Tried to turn the bike over, battery wasn't having it. Hooked it to a tender for a few hours until it said it was fully charged, tried again, completely discharged again. Ugh. One thing after another. I'm feeling better about the dead cylinder though.

Looking around online, it looks like an "oil fouled" plug. Oil pressure might have pushed past the dead piston and soaked the plug? I know the bike runs rich (not terribly, but you can smell the gas when it's idling), but I doubt it's running so rich the plug is black from it.

http://rmfletcher.hubpages.com/hub/Used ... ring-guide

If you go to that website and scroll down a little where it says "spark plug fouling", my plug looks like the one on the right. The one that looks wet up to the threads. And then the tip is bent in on itself. No idea how that happened. I'm basing all my theories on the failure occurring while I was riding, and a snagged throttle cable instigating the problem to the point of the rear cylinder no longer firing. Cable snagged, engine revved, shut it off, rode it home but only on the front cylinder.

Reading more online, a piston hitting the spark plug points to a lot of mechanical errors (worn bearings, loose rings). I have major doubts this is going on with my engine. I know KTM's are well built, I stay on top of my oil changes and only put high quality fully synthetic in it. Carbon build up is another possibility but I ride my bike way to much for that to happen I think. I rarely venture into the top end but I definitely hit up my low and mid ranges every time I ride. I don't know.

Thanks again. I couldn't get my camera to focus on the plug, it kept trying to focus on my hand lol the plug is still wet though.

But if anyone could shed some insight I'd appreciate it. Right now obviously I need a new battery. I'm pondering pulling the front plug and comparing. If they're both dark/wet perhaps it's time for another new tune? The only trusted dealer by me doesn't do dyno-tuning, they tune based off of EGT's. Haven't looked into that very much. If the bike starts and runs ok I'll pull the plug again after a while and check on it.

Maybe stating the obvious and it's hard to judge from your pictures but that plug looks awfully long to me, is it the correct one?
I'll have a look tomorrow if I can find an old 990 one to compare!

after reading the first page again u need to get a strong touch and look very carefully into that cylinder at top dead centre and see if there is any marks or the broken tab not in there

Would that tab ever get past the valve though? I guess maybe it could but I would imagine it did a bit of damage on the way past. This is what a dropped valve did to my spark plug though. As you can see it's a lot lot worse.



Looks the same length to me Guy

The metal tab that's missing is too big to only dent a spark plug. This thing is like an inch wide and a quarter inch tall roughly. I wouldn't have made it home if that was the cause of my problems. I will pull the front plug at some point. I gotta look up how to do it, I already know it's going to be a tricky job just by looking at the radiator.

Biggest question right now is can I try and start the bike while it's still attached to the tender? It's not likely it'll start but I want to give it a shot just to see if my rear cylinder fires ok.

I'm with CK - reckon that plug was dropped, bent and then fitted - no reason why you can't try and start engine with battery on tender.

Just tried to start it with the tender still attached after charging it all night. Tender indicates the battery is fully charged but still not enough juice to start it. Bike popped a few times but no go. Got a Soft 31 Dat 10.1 on the dash. I know a Soft 32 is a rectifier issue so thankfully that's not showing up (again). But unfortunately it's looking like I'm going to have to get a new battery before I even find out if swapping the plug worked.

Soft 31 Dat 101 'just' means loss of/not enough power to clocks and could be due to a number of causes - in your case, probably just the battery - jump it with car battery?

[quote="Reb"]Definately dont start the bike anymore. Where did the metal tab from the intake go? There's no way it can get out of the MH airbox besides going into the motor.
I dont mean to freak you out, but a piece of metal like that going into a motor is perfect for bending a valve, damaging valve seats and punching holes in pistons.

Does the bike like to start? Does it backfire or 'chuff' back through the throttle body, particularly the one with the missing tab? Is there any ticking or tapping noise.

Get the tappet cover off and get the spark plugs out. Shine some light down in there for a look see. You can buy great little sticky beak flexible camera and screen that are perfect for inspecting inside motors. As Guy suggests, check the valve shims are in place.
It will still be OK to turn the motor over by hand. Put it up on the rear stand, put it in gear and use the rear wheel to turn the motor over. Does it turn freely? Does it get tight or catch anywhere? (shouldn't get tight anywhere if both plugs are out)

If there's no obvious damage to the piston/cylinder, shims are good and all seems to rotate freely, valves are moving up and down, put it back together and it should be safe to start.


If I were you, I would go all the way back to this post and follow it. You need to see what is going on it that cylinder before you try to start it again. Stuff like this doesn't fix itself and that plug didn't get like that on it's own. Just my nickles worth, but we race desert racing and had an errant tiny washer that had flipped inside the air filter (don't ask) and it got sucked in and the plug looked like that. Upon tear down it look more like Colonel_Klinck's pictures.

I looked down the throttle bodies when I had the air box removed. Saw all 4 valves, no debris, no damage, no scrapes, nothing. I'll look down at the piston later but I'm still positive a piece of metal that size isn't in my rotating assembly. I do appreciate the advice though. And who knows, I may be that guy that ends up completely eating his own words at the end of the day. Or maybe that piece of the air box isn't in there but there is a foreign object in the cylinder. If the engine is destroyed, well....that's going to really suck. I'm storing it for 2 months at my parents place while I'm away at work. And then as soon as I'm back I'm moving to a new state with my next job. So a blown engine is going to really put a wrench in how smooth my transition would be. I would have the money to rebuild the engine (provided there was a place that could do it).

I know I'm jumping the gun here but what is your guys experience on rebuilding the engine? Cost? Worth upgrading the internals? I know I've read people swapping in the camshafts from the RC8R provided they also upgrade the pistons. Whatever, I'm getting ahead of myself. New battery, and look at the actual rear piston for damage/FOD. Thanks again guys.

Don't disagree about looking at piston head etc but would be very surprised if TB tab got into cylinder without visible/audible damage to valves, visible from top, and seeing what happens after starting it briefly with a new plug would at least offer more clues - having said that, my view is based on running mine some twenty odd miles after losing the rear cylinder spark plug electrode into the cylinder with no apparent damage.........

These little cameras which allow you to look in to the cylinder are not that expensive anymore.
Maybe someone in your area has one, best way to have a peak inside without taking it all to bits.

Update: pulled the valve cover off the rear head and pulled the plug. I didn't want to shop around for a camera so I did the next best thing. I stuck my telescopic magnet down there to pick up any possible debris. I have 2 magnets and the one I started with was my heavy duty one, this thing will sweep up bolts/sockets off the ground without even touching them. Anything under 5 lbs and its coming up. Stuck it in there, gave it a few twists, pulled it out and nothing came with it, so that's a big relief. I figured while I had everything apart I would stick my phone in there as well just to make sure. Now I'm no expert on diagnosing mechanical failure, but I see what might be (keep in mind I'm biased, worried/expecting there to be a problem) small scratches on the piston crown. Really small, like 3 of them. Also on the side wall where the spark plug sits, the wall gradually shrinks with smaller and smaller grooves the farther it goes down. One of these grooves is missing about 1/8th of itself O_o...

I used both my big and small magnet to see if it was a metallic piece sitting on the groove or maybe it was just a collection of oil that looked like a solid. But upon using my small magnet and phone to really poke at it to see if it moved, I realised that a small piece of that groove is missing. Couldn't be very big at all though, just a small metal shaving. Might have gotten past the exhaust valve? I triple checked with both magnets, nothing magnetic is sitting on the piston at TDC.

If anyone is willing to post my pics/small video I took I'll email it to them so they can upload it here. I'm not 100% sure if I should be worried or not, this goes a little outside of my experience.

Here is the image:

and the video with link incase embedding doesn't work for whatever reason:

Sorry for the mostly useless vid. I was holding the magnet and the phone while trying to zoom/focus/not working/take gloves off/etc lol

You can see a few small scratches on top of the piston and the missing piece of the groove.

IMO it sounds like you had an over speed when your throttle stuck and the piston crown touched the plug. If it hit the plug then you may also have a bent valve and this is causing the cylinder to not fire and could account for some noise.

I seriously hope I am completely wrong but I worked on ships as a diesel fitter for many years and saw this a number of times. Hope for your sake this time it is just something simple like a coil pack that failed.

Best of luck there with this mate, keep us informed it is quite intriguing.

Hmm I'd either fit a new plug and see if she starts ok or bite the bullet and strip the rear cylinder down and check the underside of the head, bore and piston for visual damage. It's not as bad a job as it sounds but does mean either dropping the engine of pivoting it forward on the lower engine bolt. It's the only way you can get the rear cylinder off.

Ripping the head off could save additional damage that may be caused

At this point guys I'm really pressed for time on getting this at least figured out. I'm going to put in the new battery and start her up. I'm being flown out to TN on Thursday and Friday, driving to MD Saturday and Sunday, work the next week, and then that weekend I have to have all my stuff packed/stored for me being away at work for 2 months straight. A good friend of mine is holding onto my bike and car while I'm away during that time. If the rear head is toast that's 2 months straight either they or a shop could be rebuilding it for when I get back. And if the head is already damaged, I'm not going to do much worse by starting it again. A bent valve is a bent valve, whether its 1 or all 4, it still need an overhaul.

I'll lower the piston a little later today and take another look for any debris. If not, battery in, fingers crossed

Fire in the Hole..........

Good luck mate, hope it goes well.

You have my sympathy with the time constraints, I also work away and spen 3 months away from home in another country in Africa and then a month at home on break. I understand the difficulties you facing.......

So I found the damage I was looking for. Lowered the piston a little and tilted the camera and boom: hemispherical scratches below the exhaust valves. The piston itself is surely fine, these are just surface scratches. But now I can honestly say it's likely I've bent at least one valve. So the project is now probably going to leave my hands. While my bike is in storage while I'm away I'm going to see if I can't get it worked on in the mean time. Anyone know of a good shop in North Carolina? So far my rebuild is covering the following:

-Pull both heads and check for further damage, replace valves/piston as needed
-Port/polish both cylinder heads
-Retune

Not 100% sure on how much it'll cost. I know a rebuild on non-performace car engines is typically $1000-$1500. Anyone with experience with this?

Bad news

Will say if you get the heads ported they might want to add material to the intakes rather than remove it like they would on the exhausts.

Are you sure that what you're seeing is not just the valve 'shadow' profiling of the piston crown?

I can email someone to upload the newest vid I took. 90% sure these aren't piston eye brows or valve profiles.