Broke a valve while swapping chain tensioner *Updated 1st Post*

[Snake2715]

Ok,

**All references to "Right" and "Left" are when sitting on bike**


8/10/13:
So the cam chain tensioner had a slight drip since I bought the bike.

Today I decided to swap the camchain tensioner gasket. I did so and put the chain tensioner back in. Typically I am super cautious but not today, like an idiot, I didnt head GSJacks advice in my own thread:

http://gstwins.com/gsboard/index.php?topic=65092.msg777778#msg777778


So heres what happened. The cam chain tensioner actually locked compressed when I tightened it down. So when I installed it I thought it released and it did not (headphones while working can have a downside). Instead of pulling the valve cover to verify all was good,I cranked for a split second and it sounded weird I STOPPED immediately. This was not even a full crank.

I then pulled the valve cover and removed the right side cover to check timing. While turning it by hand to line up the timing marks I heard a pop and the chain went slack. I stopped..

I then pulled the carbs and air box and removed the tensioner in the long shot hopes that its spring had broken and caused the slack.. no it was still compressed and never released..so here I am. I never even knew they would locked compressed.


What is the next step??


I have not been into a bike motor past this point so please give me some insight while I go weep in a corner. I am really really pissed at myself.. I am wondering what damage may have been done or not done since I was cranking by hand.

Any advice you give will be great.

I am going to order the manual now from the link.


1998 GS500 just rolled 8800 miles. MINT condition in all respects until today.

**


8/11/13:
Ok valve cover off starting to remove cams:


So I pulled the carbs and see the intake valves they are there like they always were. I pulled the plugs and left side piston is down and I cant see that valve (got a light in the hole) and there is no valve laying in there. The right side plug the piston is up and I can see the valve there but not sure its broken.

Ok got the cams out and bagged. Pulled the exhaust off and both valves are there...

All buckets and shims spin freely. No valve shims are forced upward or out of their spot now that cams are out.

So the right piston is almost top dead center.. Out to check all valves.. the cams are out so the valves should all be seated correctly I figure..

Intakes look good ( a little sludged up, but thats been there when I bought it). The right valve is seated and looks good..

I check the left valve and its not seated.. its almost seated but there is a small gap..

I check again and I see the crack in the left valve guide..

THIS IS THE LEFT EXHAUST VALVE




From looking down the spark plug hole I see literally no marks on the piston at all. I cant see the whole piston but I see no marks on what I can see.

Interesting enough the left exahust valve was the only one I had to adjust when doing my valve adjustment.. :

http://gstwins.com/gsboard/index.php?topic=63467.msg752485#msg752485


So my questions to this point:

8/21/13:

Head is off. Pic heavy. The left exhaust valve (whle on bike) is not seated as you can see the light shining through in the one pic. I took a few pictures and will post them all.

Notice the guide pin if thats the name is in the right side of the head for reference








Left exhaust valve:


Right exhaust valve:


Right Piston:




Left Piston. I see no marks on this at all:


Right piston is the raised piston:





















What next?

[Blueknyt]

Your about to learn how to remove cams and cyl head.....take your time.

[Snake2715]

I will do research as much as possible timing sucks we are about to move.

will I need a shop to do any head work?

New head gasket I presume...

[Blueknyt]

If you are about to move, best wait till you can get to it. if you did break a valve, who knows what other damage is there.  untill the head is removed you dont have another direction other then swap out another running engine or scrap the bike.  worry about getting settled in a new place, setup your work area, then work on the bike.  pull the head and we can go from there.   make sure you have a decent camera for some of the step by step stuff, its good reference for reassembly and you can post the pics of your progress for those that can attempt to answer any questions that come up.

[Snake2715]

Ok well I have 30-45 days to move so I will tear into it soon.

[jacob92icu]

It does not sound to me like you broke a valve. Did you actually see a broken valve? Cause I have a hard time believing you could brake a valve turning it by hand.

So all you did was remove the valve cover and then the cam chain tensioner and put it back in?

Sounds more like the chain was not on properly on the bottom and just felt tight, then when turning over it fell off and is now slack. Thats the best case scenario though.

[gsJack]

+1

My thoughts exactly after reading Snake's post late last night and thought I'd wait till morning and I was awake before replying.    Did you actually see a broken valve Snake?  When I broke off an exhaust valve while cranking to start on a freezing cold morning the engine stopped with a big bang.  Removing the right cover and turning the crank with a wrench it would only go a bit in either direction before locking up.  Removed the plugs and peeked in and saw the broken valve in there.  If you haven't actually seen a broke valve you can investigate further before pulling the head.   

[Snake2715]

I don't see a broken valve.. how do i investigate?

so I pulled the carbs and see the valves they are there like they always were. I pulled the plugs and left side piston is down and I cant see that valve (got a light in the hole) and there is no valve laying in there. The right side plug the piston is up and I can see the valve there but not sure its broken.

How can I check this? I know the timing is off how do I get that back on? lift the chain and spin the cam?

[gsJack]

You need to get #2 to TDC to check timing.  I'd pull the camshafts without turning any further with a loose cam chain.  Hold the cam chain up while turning to #2 TDC so the chain doesn't get wedged in below the crank gear and don't drop it down the slot.  After the piston is in correct timing position reinstall the cams and make sure you have a working tensioner holding the chain tight.  Then you can turn the engine over a few turns with wrench to see if all is good to go and then cranking with starter for a compression check should confirm valve condition, thumb over the hole check  should tell you if you don't have a gage.  GS engine timing if you don't have manual yet:

[jacob92icu]

Only timing I have ever done is with a timing light on my old bike. However, I think with the GS it is most likely a governor plate with tick marks that have to match up (never been into the gs motor) T for Top dead center, and 1F for retarded firing point, stuff like that. The manual should have a good description of it. I dont have one

Hmmm that sounds backwards. But that is probably just cause the timing is off. One more definite way to tell if your exhaust valves are good is to remove the exhaust and look through the exhaust like this:



This valve is in the seated position. The other should just be sitting there as well.

[Snake2715]

Not at home now but if the tip of the valve broke would I be able to see that or would the funnel portion have broken right off and fell in?

[Bluesmudge]

If the cam chain tensioner is not in or is compressed, the chain will jump when you turn over the engine. It is very possible you did not hurt anything, you just need to remove the cams, reset the timing and install the tensioner correctly this time.

[Snake2715]

Ok got the cams out and bagged.

Pulled the exhaust off and both valves are there...


All buckets and shims spin freely. No valve shims are forced upward or out of their spot...

Now if I do as GSJack said there should be no pressure on the valve due to the cams being removed correct?

[Snake2715]

So the right piston is almost top dead center.. I made the post above and went back out to check all valves.. the cams are out so the valves should all be seated correctly I figure..

Intakes look good ( a little sludged up, but thats been there when I bought it).

The right valve is seated and looks good..

I check the left valve and its not seated.. its almost seated but there is a small gap..

I check again and I see the crack..

I am stopping here until more guidance.

I presume I need to pull the head at this point?



From looking down the spark plug hole I see literally no marks on the piston at all. I cant see the whole piston but I see no marks on what I can see.

Is it possible the valve either bent and caused this crack, that this crack was already there, or that the valve is indeed broke and I may need a new head and valves?






So pull the head at this point?

[Blueknyt]

the guide sure looks cracked to me.  only my opinion but should be serviced.  with cams removed, are all 4 valve buckets sitting same hight inside the head? meaning both exhaust valves appear to be same height and both intakes seem to be same height?   either way, i would still get that guide replaced, perhaps freshen the valves with new seals and a good lapping as long as everything is straight.

[Snake2715]

Thank you so I should remove the head?

I did a once over earlier and all shims seemed to be sitting the same, but I can go back out tomorrow after work and give it a really good look and will post my findings.

This is so crazy the piston at TDC was the other side of this valve guide.


Should I put it back together in time to make sure i have compression or at this point pull the head and see what she looks like?

[gsJack]

Mmmm, from memory without rereading, right cyl near tdc, right intake valve guide cracked but valve looks seated, no visible marks on rt piston, left intake valve looks to be not seated, but all buckets spin freely so not held open by stuck bucket.

Strange, maybe one more check before pulling head, pour some water in the valve ports to see if it leaks thru to piston to check valve seal; have not done this myself but others here have.  Think I'd test the right ones as it sits and then slowly turn engine with wrench while holding cam chain up to get left piston up so you can see thru plug hole after pouring water into left ports.

It seems strange your right intake valve guide would be cracked while the left one where you think you see the open valve is not cracked.  By the way, my exhaust guide where the valve broke had half the tip broken off and the piece was long gone thru the exhaust when I pulled the head so I never saw the piece.  What was left was solid so I left it like that, it's common practice to grind off those valve guide tips to increase flow thru the ports when making performance mods to engines so I wasn't too concerned about it, 70k trouble free miles later I'm not concerned about it at all.   

Still wondering if it's common for GS valve guides to crack like that without any valve damage causing it, has anyone else seen this happen? 

[jacob92icu]

If your going to replace the cracked valve guide you are probably going to replace the seals and lap the valves. Hell you might as well replace your piston rings. If so, no need to do the water leak test, you can wait till after you do all that work.


Besides, your main problem looks to be the cracked guide, so a valve leak test wouldnt do anything for you at this point.

[gsJack]

Wasn't thinking water test before pulling head, was thinking test instead of pulling it.  Guess I don't look at the cracked valve guide as being the main problem, whether a valve is broken/bent or not is.  Half of the tip of my guide was broken off when the valve broke and I let it go 8 years and 80k miles ago without a problem so far.

It could be a problem if the tip of the guide broke off later and caused some damage  in the cylinder, mine was an exhaust guide so the piece disappeared without going thru the combustion chamber.  That's why I asked if it's common for GS valve guides to just crack like that without any valve damage causing it, has anyone else seen this happen?

Anyone?

[Snake2715]

Mmmm, from memory without rereading, right cyl near tdc, right intake valve guide cracked but valve looks seated, no visible marks on rt piston, left intake valve looks to be not seated, but all buckets spin freely so not held open by stuck bucket.

To correct this:

The intake valves all appear seated. The right valve is seated or appears so, its guide is ok. The left valve (piston is down as of now) is actually the one with the cracked guide and does not appear seated.

I did not touch a thing after the chain went slack. There is no way that the left piston hit that valve when I turned it by hand as its in the downward position and as soon as the chain went slack I stopped. I made no more rotation... now if the left piston smacked that valve when I cranked it for a split second.. that may be possible. I am not sure if this is a newly created problem or if I stumbled on it (the cracked guide)....



Updated first post, I will continue to do this as I progress so its easy to see my current status.

I cannot say enough how appreciative I am of all who are helping here. This is new to me, and I am glad to have the forum around. I will have no problem digging in and getting the work and parts needed. Just really like the idea of the members insight as I do this.

I presume the manual will be here in a few days time, but for the time I wil continue to make progress on it.

Of interesting note.. that is the exact and only shim I replaced when I did my valve adjustment... :

http://gstwins.com/gsboard/index.php?topic=63467.msg752485#msg752485