Broken rocker arm

[He Man]

depending on which motor you have, it might be cheaper to buy a new motor 900 and 695/620 motors are pretty cheap.

[suzyj]

They are better than stock, but there are better options. Theres a shop if i can find their name, that makes custom guides matched to valves so you get the best fitting possible, and if u just cut the seat good you should get a great seal and itll be better than stock for sure.

My understanding is that the proper fit between guide and valve (and between valve and seat) are accomplished by reaming and honing.

http://ladywrench.net/projects/the-top-end-reaming-and-honing-valve-guides

The idea is that you first ream the head so the hole for the guide is accurately round and 2 thou under the size of your guides. Then when you've pressed the guides in, the inside of the guides will have closed up a little making for a tight fit on the valve stem. You need to ream and hone this to size accurately, and then cut the valve seat to match.

I can't think of a way anyone could make a valve guide that's a good fit without the reaming and honing.

[He Man]

yes that is how i understand it to work as well, but i figure if you have a guide that is desinged to be honed so that it is as true as possible to the valve stem, you wont have issues with guide that necks in the middle but flares in the end.

[Howie]

Valve guides need to be reamed to proper diameter after installation.  After reaming the center will be slightly different than it was with the original guide so the seat must be cut to correct for this with proper equipment.  Usually the seat will need to be topped and throated to attain correct seat width and contact area.

[uberranger]

So, just to clarify, these procedures (reaming, honing, etc.) are all things done when one buys new valves and guides? 

It would seem intuitive that cutting/honing would be necessary if only one or the other is  replaced.  Perhaps I misjudge the precision of the pieces involved.

Also it would make sense to ask if this is something a poor DIYer could do.  From the mention of equipment it would seem not.

[Speeddog]

As Howie said, if the guide is replaced, the seat needs to be re-cut to align it with the position of the new guide.
It's marginal to then install a used valve into this new guide and seat.
Best to fit a new valve as well.
It's OK to fit a used valve that's been re-cut, as long as the shank isn't too worn.

If the guide is *not* replaced:
You can fit a new valve.
Best to get the seat re-cut to mate with that new valve.

Looking at the $/labor standpoint:
By the time you've got the head off, and all the valve gear out, and bought some new parts....
The cost of getting the machine work done (to get the most out of what you've already spent) is small.

From a DIY standpoint:
Buying all of the equipment necessary to install, ream, and hone the guides, and then properly cut the seats, is quite a bit more expensive than paying the local cylinder head shop to do it.
But that shouldn't stop you from doing it if you want to.

Check out suzyj's thread, lots of info there:
http://www.ducatimonsterforum.org/index.php?topic=56614.0

FYI, I'd consider suzyj in the top 1% of DIY'ers.

[suzyj]

yes that is how i understand it to work as well, but i figure if you have a guide that is desinged to be honed so that it is as true as possible to the valve stem, you wont have issues with guide that necks in the middle but flares in the end.

My shiny new Kibblewhite guides have an ID of 6.98mm, before being fitted. The valves won't physically fit without reaming.

[suzyj]

FYI, I'd consider suzyj in the top 1% of DIY'ers.

Crawler. 

[brad black]

Can we see the broken rocker?

[uberranger]

Per request, for your viewing pleasure at my expense:



Such a sad sight...

[suzyj]

Per request, for your viewing pleasure at my expense:



Such a sad sight...

That'll buff out! 

[uberranger]

Yeah...about that 

     So anyway, I finally got the horizontal head off (been really busy moving and such).  After closer and more thorough inspection, the rocker arm is the only thing obviously broken.  It seems silly to hope that the corresponding valve could be alright, but I believe the other valve/rocker arm set to be fine.

     With that in mind I suppose I'll order a KW valve and guide and have a friend who works in a machine shop do the work getting everything trued up.  I will then adjust the valves (something I may have to ask about in another thread) and ride off into the sunset- hopefully.

     Are there any flaws with this course of action, or any steps left out? 

     I've been riding my dad's XT350 and really really really want my bike to be running. 

     Now.

[He Man]

My shiny new Kibblewhite guides have an ID of 6.98mm, before being fitted. The valves won't physically fit without reaming.

KB states that they are all oversized to allow you to fully ream out the whole valve guide. to my understanding the stock OEM guides arent built to a tight of standard as this so you get a bottle neck effect where the tip and top of the valve guide might be looser than perfect, and the middle of the guide is perfect. This is what KB told me on a chat when i was trying to decided between foxwoodperformance and KBs.

of course all that is out the window since im not longer installing either.

The actual cost of machining both heads is roughly $300 from the calls ive made (NYC pricing). the real cost comes in reinstalling the valve components. Its really not worht it because the unique tools you need are essentially one time use since you probably wont be digging into the heads all that often.

if your going to remove one head and swap teh guides, it might just be worth while to do both heads.

[uberranger]

To clarify, I'm not just going to replace the guide and hope the valve is ok.  If the rocker arm is broken, the valve almost must be bent. 

[uberranger]

Ok, so here's my current status and revelations in case it might benefit someone:

Valves are in fact NOT damaged...I don't understand this.  The carbon deposits, upon further inspection, are not disturbed (same for the piston) and the valve slide open/springs shut with no resistance.  It also will hold water (important?) 

I now believe I bought the bike with a broken rocker arm.  I don't know how it could've happened though.  Any thoughts??  One of the guys at Ducati Indianapolis said the same kind of thing happened to him in the vertical head because he didn't let the oil circulate up there before taking off (cold start).

Anywho, I now just have to replace the rocker arm (of which I have a full set).  The problem is getting the darn shaft out.  You need a draw-bolt type thing (or the special ducati tool, or one of the cheaper knockoffs).  I'm currently waiting on a machinist buddy of mine to look it over.