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Discussion Starter · #1 ·
Hey guys,
I am in the middle of tearing apart my 99 996 for a valve check and timing belt change. I was taking off the trumpets and airbox and one of the trumpets just wouldnt turn and I wound up breaking one of the metal tabs that holds it down. I'm not worried about what I broke but what I am worried about is I had the valve cover directly below it open. I can't find the metal tab anywhere and I have looked inside of the valve cover and turned the engine over by hand and can't find it in there either. Any ideas or thoughts?
Stupid move on my part but accidents happen :/
 

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My thoughts are that you should probably find it?

Any foreign metal objects in the engine is bad, plain and simple.
 

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Small magnet extender?
 

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You have to keep on until you find it or you are certain it is outside.
From what you say its not very clear what part you mean, can you please explain again?
You mean you opened the front cyl cover and then went to undo the stack?
Then the airbox is still in place and the piece should be in the airbox, no?
I cant make ends meet. Is it just the thin plate that holds the stack in place? Then its magnetic, if its the stack peg, then its alu.
Take a few pics, itll be much easier.
 

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You have to keep on until you find it or you are certain it is outside.
From what you say its not very clear what part you mean, can you please explain again?
You mean you opened the front cyl cover and then went to undo the stack?
Then the airbox is still in place and the piece should be in the airbox, no?
I cant make ends meet.
Spot on!:)
 

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Discussion Starter · #6 ·
You have to keep on until you find it or you are certain it is outside.
From what you say its not very clear what part you mean, can you please explain again?
You mean you opened the front cyl cover and then went to undo the stack?
Then the airbox is still in place and the piece should be in the airbox, no?
I cant make ends meet. Is it just the thin plate that holds the stack in place? Then its magnetic, if its the stack, then its alu.
the trumpets are held in by two little arms. you rotate the trumpet and these two arms lock over two bumps that stick out on the trumpet. one of these arms broke off and fell somewhere. they are under the airbox not in it. i have looked everywhere inside that valve cover but haven't taken the camshaft out or anything yet. I agree that I have to find it but I am just looking at options and trying to get opinions. I have not taken apart a desmo engine before and I don't know where that piece could make its way to. I imagine that camshaft area is pretty enclosed other than a few oil galleys maybe. I can't see it going anywhere except the bottom of that camshaft area and resting against one of the red valve seals perhaps. Any thoughts after that description anyone?
I know there are people here who have taken apart these motors and have ideas as to where this piece could travel to or where it could have fallen?
 

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Ive done it so many times Im sick of it ;)

How about it went down the intake? Use a good flashlight and see if the intake valves are closed or not.
On the front cylinder you cannot see directly so you need a mirror.
First get the magnetic pen suggested and fish for it, I would.
Doing valve lash on a 996 is interesting at best and such pen is the shit! Its 2 bucks and it can save you soooo much trouble, very small not shiny item but it delivers.
I have even fished up a shim from the bottom end once, it was the pen or split the engine :)
 

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Discussion Starter · #8 ·
Ive done it so many times Im sick of it ;)

How about it went down the intake? Use a good flashlight and see if the intake valves are closed or not.
On the front cylinder you cannot see directly so you need a mirror.
First get the magnetic pen suggested and fish for it, I would.
Doing valve lash on a 996 is interesting at best and such pen is the shit!

Anyhow get the magnetic pen, its 2 bucks and it can save you soooo much trouble.
uggggghh god you are giving me chills. I don't think it went down there. The throttle bodies were still on and closed obviously. That was one of the first things I checked. Ill check again but I know it isn't there thank god. I will make a run to the auto parts store and get one today. I am also going to scour the garage floor like a rat sniffing for even the slightest lick of cheese.

To clarify for everyone, this is the most forward trumpet directly behind the radiator. The tab that snapped is the one that is belt side of the motor. Underneath is the valve cover. The valve cover was off and open. I can't visibly see the snapped tab on my garage floor or in the valve cover as of yet.
 

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Didnt mean to scare you, now anything is better than that right :)
I started from the beginning too so I have respect for anyone in your position, no worries.

Pone the rubber seal wasnt tight, then it could have travelled down the frame and just lays there.

If that piece gets into the head valvearea it will pretty much just lay there, its too big to block an oil channel and you need two at the same time perfectly positioned, if it gets into the combustion chamber it may hurt something but likely not as its long and thin and then be spit out. I wouldnt overdo it.
 

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Relax!!!

To start off with, working on one of these early Desmo 4-valve heads isn't that difficult. Even if you wound up having to pull both cylinder heads to repair the 'trumpet' (no clue?), it's doable. Most people freak out about not wanting to deal with the timing belts. You're already in the mindset of doing that. Also, my 2-cents says that if you want to check your valve clearance correctly, the heads are off to where you can take your time. Did this for the first time with my 851 (am thinking the 996 is very similar in design)a few years ago. See if you know someone who can lend you the DesmoTimes' workshop manual. Very easy to follow. In closing, I hope I didn't take this thread 180 degrees in the wrong direction.....Again, just seemed like you were starting to freak out a bit...... Good luck and relax.
Pat
PS: have you ever inspected your rockers for chrome-flaking like one of the other posts is talking about? Pretty sure "some" batches of 996s had problems with this...
 

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By trumpet he means velocity stack.


Those metal tabs are steal best I can tell so a magnet should snag it.


Im curious though reading back through your original post and some others here, did you take the intake side valve inspection cover off with the airbox still on? I guess the forward tab is what broke and you think it may have tumbled down the leading edge of the intake manifold and into the head?

If thats right and you cant see it, best to pull the head then and dig though it till you do. Better safe then sorry.
 

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Discussion Starter · #12 ·
By trumpet he means velocity stack.


Those metal tabs are steal best I can tell so a magnet should snag it.


Im curious though reading back through your original post and some others here, did you take the intake side valve inspection cover off with the airbox still on? I guess the forward tab is what broke and you think it may have tumbled down the leading edge of the intake manifold and into the head?

If thats right and you cant see it, best to pull the head then and dig though it till you do. Better safe then sorry.

Yes,
Thank you for clarifying. I just bought a very tiny magnet pen so I will toy with that for a bit. What you said is exactly what happened pretty much. I have spent hours digging around in that valve area with my fingers and I have removed the non belt side bearing/cam cover and looked through there as well. I simply can't feel or see anything that looks remotely like it. I have turned the motor over by hand multiple times and havent heard anything out of the ordinary. I have done everything shy of taking the head off. I will try the magnet pen but I don't expect much.

My current question (to those that have taken apart a desmo motor) is how roomy is the compartment for a cam? Are there little crevices and open areas that the metal piece could sit in and hide from me?

Also, I'll be honest and say I'm not even sure I broke it. It may have always been broken and I never knew and because of that I think I broke it and lost it. I'm not the original owner and who knows if someone broke it years back you know? By the way the trumpet/v stack came off I could say it either was never there or I did break it. I have no definite answer so I have to make sure and look everywhere inside that valve cover for it. If it is lying on the engine somewhere then so be it, it will roll around and drop off in a corner or lodge itself somewhere and I'll never worry about it. But if it is in that cam area I don't want to risk that obviously...
 

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Discussion Starter · #13 ·
To start off with, working on one of these early Desmo 4-valve heads isn't that difficult. Even if you wound up having to pull both cylinder heads to repair the 'trumpet' (no clue?), it's doable. Most people freak out about not wanting to deal with the timing belts. You're already in the mindset of doing that. Also, my 2-cents says that if you want to check your valve clearance correctly, the heads are off to where you can take your time. Did this for the first time with my 851 (am thinking the 996 is very similar in design)a few years ago. See if you know someone who can lend you the DesmoTimes' workshop manual. Very easy to follow. In closing, I hope I didn't take this thread 180 degrees in the wrong direction.....Again, just seemed like you were starting to freak out a bit...... Good luck and relax.
Pat
PS: have you ever inspected your rockers for chrome-flaking like one of the other posts is talking about? Pretty sure "some" batches of 996s had problems with this...


I'm not freaked out so much. It's only November and I have til april or may before I'll ride it again. I think I have PLENTY of time to take it apart if need be. I'm actually more amazed that I can't find it. (see above reply for further info as to whether I even broke it). Anyway, its not THAT small of a piece you know? I figured if I broke it I would have at least seen it by now somewhere...
 

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Discussion Starter · #14 ·
To start off with, working on one of these early Desmo 4-valve heads isn't that difficult. Even if you wound up having to pull both cylinder heads to repair the 'trumpet' (no clue?), it's doable. Most people freak out about not wanting to deal with the timing belts. You're already in the mindset of doing that. Also, my 2-cents says that if you want to check your valve clearance correctly, the heads are off to where you can take your time. Did this for the first time with my 851 (am thinking the 996 is very similar in design)a few years ago. See if you know someone who can lend you the DesmoTimes' workshop manual. Very easy to follow. In closing, I hope I didn't take this thread 180 degrees in the wrong direction.....Again, just seemed like you were starting to freak out a bit...... Good luck and relax.
Pat
PS: have you ever inspected your rockers for chrome-flaking like one of the other posts is talking about? Pretty sure "some" batches of 996s had problems with this...

To actually answer this post...lol

I'm not afraid of the thing at all. I have been tinkering on motors for years. My dad and I built my first car together and ever since then I haven't stopped. I have always stood by the idea that its just a bunch of nuts and bolts, you can always just put it back together or replace parts. And if not, then you can pay someone to do it.

I just thought of something from one of the earlier replies as well. It can't possibly be in the combustion chamber since the airbox was still on so that rules that out.

Regarding the flaking rockers, I know the original owner very well. His name is Rex Svaboda (he works the tower at BUB speed trials in Bonneville and does a lot of work for events at the Bonneville salt flats, some of you may know him). Anyway, he is a hell of a mechanic and he does things properly and he took care of all flaking issues. I will check the oil and screen of course when I drain and change my oil but I am not too worried about those. Plus, they are easy to change anyway. I was worried about the belts but those seem easy too. The valves are new to me (desmo valvetrain, never had a motor with it).
So thats where I stand. I will search everywhere without any more dismantling and if I can't find it by tonight I will pull the cam and free up some space in that area to search more.

As stated above though, I am unfamiliar with how much free space there is in that cam area for that little tab to hide from me. It doesn't seem like much but there are people on this forum who have actually seen this area of the motor from every angle and would know more than I about that.
 

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The tab mistery

I voting for it being missing before you got to it, but better safe than sorry.

Check your clothes, especially if you wear pants with a leg cuff.

Also, check the shoes you wore to be sure the tabs not stuck around the shoes laces.

I'm in aircraft maint., and everything has to be accounted for.

So, good luck witht he adventure and recently I dropped a nut in the shop while working on one of my CBX's. I later found it 15 feet away from where it was dropped a foot to the floor.

Later, George in Delaware
 

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Discussion Starter · #16 ·
I voting for it being missing before you got to it, but better safe than sorry.

Check your clothes, especially if you wear pants with a leg cuff.

Also, check the shoes you wore to be sure the tabs not stuck around the shoes laces.

I'm in aircraft maint., and everything has to be accounted for.

So, good luck witht he adventure and recently I dropped a nut in the shop while working on one of my CBX's. I later found it 15 feet away from where it was dropped a foot to the floor.

Later, George in Delaware

hahahahahha
yeah thats not a bad idea actually
I had a bucket of coolant under the bike and i drained that figuring it was in there but nope...it wasnt.
I am leaning toward the belief that it wasnt there ever because as I remember the trumpet was pretty loose and would wiggle up and down a bit unlike the other trumpet. Most importantly, I never heard it hit the floor or even make a noise. I feel like I would have heard it if it hit the ground or landed in the motor or something like that. I am fairly certain that unless it is hiding in the area where the rocker arm pivots, it isn't even in the vicinity. I have been using a magnet pen for the last half hour or so and that was a nice way to get to areas that my fingers cant. Unfortunately, the rockers and cams are magnetic but once you are past them it is ok and I never even heard anything move. I have both plugs out and have been furiously turning the motor over by hand in an effort to get it lodged somewhere or hear it move or something like that. I can't hear anything aside from the spitting noises the spark plug holes make from compression. It spins freely and smoothly too.

I just don't know. I am doubting it is in there but I would like to pull that cam out still so that I can really dig around.

So here is my most recent question.

I still have yet to fully understand this desmo system but i am getting there. So can I take the belt off and pull the cam out with out having to remove rocker arms or shims or anything like that? Is that possible or will everything fall to pieces when I remove the cam?
 

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Discussion Starter · #17 ·
I'm afraid to say it and I'm still not sure, but I believe I have found at least one or two flaking rockers. eff my life. Not really what I was expecting...I guess this stuff happens though.


Its gonna be a long winter....especially for my wallet
 

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Well that sucks. Flaked rockers are not a fun time lol.


If you ran a magnet all around the inside of the intake cam part of the head and didn't pick anything up I'd think you're probably in the clear.

The chances of it running perfectly straight down the intake manifold into the head is slim at best. Doubt it would have made it down an oil return passage either.

Like others said, it was most likely either gone already of flew off somewhere and maybe you kicked it somewhere by accident.
 

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Discussion Starter · #19 ·
Can I unbolt a cam and just pull it out?

This is upsetting, I'm finding that every rocker I look at is a dud. Maybe I am wrong, but are they supposed to look like new or do they have some wear marks? Is there a difference between wear and flaking?
 

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I think you have to pull the closers to pull the cam out but don't quote me on that. Don't have the manual on hand at the moment.

Some dulling of the chrome is likely normal. If they are flaked you should see an edge where the chrome stops, and the actual rocker starts.


Do you have non-ferris flakes of metal in the oil? That would be a sure indicator of flaked rockers. I had that when I first got my 748 and sure enough I had a flaked rocker. Hopefully they're not all bad. If so, might be worth looking into Megacycle, or Electreon replacement as they are supposed to be beefier.
 
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