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Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by kamanya, Jul 6, 2008.
Very good info... "All". Thanks
I have a 04 that spun a rod bearing due to water pump seal problem at 6000 miles.
The dealer rebuilt -replaced just what was wrong ( Warranty ) . When I went to pick it up the service manager started the bike up and I said to him. Hey the cam timing is off --The bike sounded different- I rode the bike and it seemed OK. I was confused. I am still riding it now 32000 miles and I still don,t think it is right. I checked the marks on the cam when I do a valve check and it looks OK. But I still think some thing is off one tooth.
Is their a chance to mess up the timing chain sync when rebuilding a 950 motor ?????
That'll teach me to listen to KTM mechanics rather than OC inmates :)
Knowing this is a 5 year old thread, I thought I'd start here with a question which may or may not be related to the balance shaft problem discussed here.
Is there a consensus that you can get slippage in the balancer shaft on a 990 from a backfire--or from rotating the motor clockwise instead of clockwise while timing cams or running/rotating with cam timing off 1 tooth.
Making a last minute valve adjustment on a new to me '07 990 with 30k miles, I believe I spaced it on cam timing and ended up a tooth off. In my haste to get ready for an Alaska trip, I may also have rotated the motor in a clockwise direction in timing the cams. I went back in and corrected the tooth off problem. Bike runs well enough but has a strange and inconsistent rattle which sounds like timing chain. Tensioners are in spec. Locking bolt used for all timing for both cylinders. Could the keyed balancer shaft gear have slipped, the spreader gear slipped or something else have happened to create a problem like this?
Thanks in advance for any help/info which can be provided.
Damn! I was really hoping some of the experts from the early days of this thread would weigh in.
My questions relate to the 990. Specifically, can a guy damage something on the balance shaft by turning the motor clockwise and/or running a tooth off on one cylinder.
And, does the 990 "spreader" eliminate this potential or create something else to slip or reset?
The quick answer to your question is 'no', the gears cannot skip or slip if the engine is turned in either direction while the cam chain tensioners are engaged or removed. They are two separate sub systems of a common drive assembly.
If the chain had skipped, then both the intake and exhaust would be off the same amount (provided that they were both installed correctly) for that cylinder.
It is technically possible that the chain can skip a tooth while the tensioner is disengaged, however I would say that the chain/guides would be at their service limit for this to happen. Aside from that, I just would not move the engine while the cams are installed AND the tensioners are removed.
Can you describe this more? When does it do it? Does engine feel as strong as before?
H2W is right, it is impossible to have slippage on the shaft unless the woodruff keys are broken. If they did, I am sure you'd have some serious noise coming from your engine and it wouldn't run. Only the timing gear and the one balancer have the keys. The spreader gear doesn't have a woodruff key but is machined so that it can only go on in one way. It too, is pretty certainly not going anywhere.
(I've added two pictures of the fabled extended tensioner bolts to the original post.)
I'm wondering if by the looks of the pictures of those balance cams there should of been a smiggen of metal flakes with each oil change somewhere , anything on the magnetic plug or in any filters?
Thanks for the responses. The motor was never turned over without the tensioners installed. The tensioners themselves are in spec by the "clearance to the cylinder" method shown in the service manual. Is there any other check as to the hydraulic aspect of the tensioners?
Sounds are always hard to describe. I haven't mastered posting pictures. So posting an audio may be beyond my limited capabilities.
It is most noticeable in the lower rpm ranges 3500-5000. And then when lightly loaded/small throttle opening. It is particularly noticeable when throttling up--say from 3500 up to 5000 where it is more of a slow roll on. Noise varies with RPM, does not change based on gear selection or clutch engagement/disengagement. Seems louder with warmer engine.
I did change the oil from unknown viscosity/brand to 5/50 Rotella full synthethic. I will be changing to a 10/50 on the outside chance that the 5/50 oil is providing less pressure to the tensioners. Possible??
Thanks again for the help--very much appreciated
Unless you put a pressure tester in the line, (special connector to the front tensioner hole), you can't know what the pressures are.
They should be; min. 0.8 bar at 1500 rpm.
min. 2.4 bar - max. 3.5 bar at 6000 rpm.
I've found that different oils do make the engine sound different, so before you tear into it, drain your oil, check to see there is nothing on the sump plugs magnets and then try going to the thicker oil and see.
But other than that, I don't have much more.
Thanks again Kamaya. I have rechecked again my cam timing, valve clearance and bridge bolt torque. Guess I'll change the oil and see what is sounds like. I haven't yet pulled the ignition cover to see that end of the balance shaft. Anything there to be checked??
The only thing on that side is the balance shaft seal in the cover. It has been found to play a crucial role in the amount of oil that makes it into the breather pipe and subsequently overboard through your front carb. This however has a marginal effect on oil pressure and I don't think has anything to do with your symptoms.
The cover can be a bit of a pain as there are big magnetic forces, tight frames space and delecate cover gasket. A trick, I learnt on here I think, is putting a few zipties through the covers' bolt holes and into the corresponding case holes to act as guides and keep the gasket in place whilst mounting.
To kamanya: very very good job! Can I ask you some questions? I think, I have a problem with cam chains elongated.
If I understood right, you don't dismounted the engine from frame and don't replaced timing gears on balancer shafts, double timing gears in cylinder heads?
No, the engine can stay in the bike.
Just the chains are replaced.
Both gears - balancer shaft and in cylinder head do not need replacing.
But you do need to pull the double timing gears in the cylinder to get the chains out and remounted in again.
Just follow in the manual and it all should be easy to do.
The bearings are pretty strong and should be fine too.
Many thanks for your answer in short time) Repair manual is my on-desk book))) and it says that all global works on engine starts from dismount engine.
So, in global I need to dismount air box, throttle bodies, cylinder heads and both side engine covers. I'm right? Next works, I hope, I understood correctly from manual.
Is the timing gear on balancer shaft can be removed? I hope I needn't to do this, but all may be to do)
Already I checked compression ratio and oil pressure value. All parameters are good, but cam mechanism very noises.
Once more thank you)
Yes, off with everything that you would normally take off to do a full service. You have to drain the radiator anyway to get to the right hand side of the engine so take that off too.
You have to pull the balancer shaft out to get the chains out. Once you've got that far, it's not difficult.
Take A LOT! of pictures on your way in so that you can be sure of stuff on the way out again.
Start your own thread if things don't go well and you need help. There's a ton of guys on here who will be able to help you.
Not the cylinder heads, just remove the cam covers, cams and cam gears. Leave the cylinder heads alone. You can't take the rear one off anyway without dropping the engine.
Be really careful when you are putting it all back together again. Follow the manual so that you get the timing right.
So awesome that a post almost 10 years ago can resurface and the OP’s still answering questions.
Long Live ADVrider.
Kamanya, thanks for lot of information. This weekend I will start to repair.