Cam chain tensioner popped out on the highway....is my engine toast?

[Bluesmudge]

I was riding home from work yesterday, cruising around 65 mph on the interstate when I lost all power. I tried turning to reserve thinking I was out of gas but quickly realized that wasn't the issue and pulled to the shoulder of the busy highway.
I tried to start the bike but all I got was a clack clack lack. Hand over the exhaust pipe showed a little bit of compressions.

I used my AMA roadside assistance to tow the bike 50 miles home. I now don't recommend AMA's roadside assistance it since it took them 2 hours to get a tow truck to me while I sat in the dark on the side of the interstate in cold and windy 38 degree weather.

This morning I went out to the bike and noticed the cam chain tensioner was sitting on top of the starter motor cover!

So I'm assuming the tensioner came loose and then the bike instantly jumped timing and bent both valves to oblivion. Does sound seem like a relatively simple top end rebuild or could I have done more catastrophic damage?

The bike had a top end rebuild done by a shop 2 or 3 years ago. They were the last ones to install that cam chain tensioner and I feel like they didn't torque the screws down enough. Why else would the whole thing just pop out? I left a message with the shop to see if they warranty their work but I won't hold my breath.

[The Buddha]

Oh, that sucks.
OMG, yea, they'd flake out cos its 2+ yrs ago. An auto transmission shop did that same nonsense to me and he was referred by a friend. And in my case, I had that car wrecked and just needed to submit a receipt to get some more $$ from insurance. He couldn't be bothered to find the receipt from ~2 yrs ago.
But Hope we see your progress.
Cool.
Buddha.

[Bluesmudge]

I took the valve cover off. The first damage I see is the small cam chain guide that sits above the tensioner is shredded. Pieces of it all over the engine. So I'll definitely have to remove the cams to replace that piece.

What diagnosis would you run? Can I check the valve clearance to determine if the valves are bent? Or do I need to buy a compression tester?

I'll check the timing next to see if its off and how far.

[The Buddha]

I took the valve cover off. The first damage I see is the small cam chain guide that sits above the tensioner is shredded. Pieces of it all over the engine. So I'll definitely have to remove the cams to replace that piece.

What diagnosis would you run? Can I check the valve clearance to determine if the valves are bent? Or do I need to buy a compression tester?

I'll check the timing next to see if its off and how far.

Valve clearance will help. So would the shining light in the intake and exhaust port trick.
And yes check what's happened to the timing. However the shining light is far more effective as is the valve clearance. It will be very very high - unless its broken a valve. In that case that valve will be 0.
Cool.
Buddha.

[Bluesmudge]

Ok, so for "shining light in the intake and exhaust port trick" do I shine a light down the spark plug hole when the cam lobe isn't touching the shim/valve and then look in the corresponding exhaust port/intake port for light? Seeing any light would mean bent valve, right?

For checking the valve clearances, should I re-install the cam chain tensioner before checking?

[herennow]

Yeah, look at the top of the pistons through the spark plug hole, you do have one of these " cameras on a wire " endoscope things, dont you?

Sorry about the problem!!

[The Buddha]

The light trick is you make sure all the valves are closed - CCT should be re-installed and the valves timed properly if you're turning the motor over - which you may have to. Unless you removed the camshafts. So shine in intake port, look in spark plug hole and exhaust port. Shine in exhaust and look in spark plug and intake port. Shine in spark plug and look at the other 2. The brighter the light and the less ambient light the more likely it will be easier to see.
But anyway if you can - check the valve clearance of any valves that are closed right now - without touching anything. If that is huge like 10X the specs - you can guess the valves are bent. Even 1 bent valve = you are better off taking it apart not reassembling and setting timing etc etc. Then take off the cam shafts and do the light trick.
Cool.
Buddha.

[Bluesmudge]

Its too cold for me to work on the bike today, but I did quickly throw a feeler gauge on the 3 valves that are in position. Both intake valves are less than .15 mm so likely still in spec. Right exhaust valve is more than my largest feeler gauge at .50 mm so definitely bent. Maybe it's possible the timing jump ended up somewhere with interference with the exhaust valves but not the intake valves. Is that possible?

I'll keep updating as I dig into it more.

[The Buddha]

Yes, it depends on the direction and position the valve was when it was hit by the other valve. Say the exhaust was well open and the opening intake valve hits the back side of the open exhaust valve. That resulting leverage will deliver the exhaust valve a good shear and bending force while on the intake valve it may be mostly compression and a little bit of bending.
This bike is valve to valve interference not valve to piston. BTW they should have just made it non interference - like it has any performance illusions.
Cool.
Buddha.

[Bluesmudge]

This bike is valve to valve interference not valve to piston.

I did not know that! This whole time I was assuming valve to piston interference. In a way, that's a good a good thing because I know there are probably no piston/lower end repercussions of all this.

I remembered I have a full head in the attic of my garage with only 5,000 miles on it. I think I'm just going to order new cylinder and base gaskets and copper washers, maybe new rings, and swap the whole extra top end over. I think that will be much faster and cheaper in the short term than doing all new valves and cam chain guides. Then I can take my time refreshing my old head since I've never replaced valves before.

[herennow]

Does sound like the easiest way. I've also got a spare head stashed away that I refurbished (actually my original head)
Hoping to do some traveling around Switzerland next summer to use up the bike a bit. Not doing nearly enough since my daughter arrived (8 years ago now ...YIPES..)

[The Buddha]

You didn't break a valve. You should be fine. Ofcourse you're gonna remove the head - so you will see the state of the piston. You basically lose nothing if I'm wrong about the valve-valve interference (which I am not, Dgyver and Werase643 have confirmed it in ancient posts on here). Good call on the spare head swap. Enjoy swapping.
BTW I'll go over everything the shop did a few yrs ago. TBH, how do you torque down something that it lasts several 1000 miles and 2 yrs. When I leave shaZam! loose it gives up with in the first 5 miles. That took some special talent.
Cool.
Buddha.

[Bluesmudge]

I finally got around to ordering all the gaskets and other random parts, plus a cylinder hone. I'm assuming Partzilla will take a few weeks to get everything to me.

I purchased a new cam chain tensioner as well. I had been running a manual version for the last ~25,000 miles but I want to go back to the automatic adjuster. I was never 100% confident in whatever tension I would set and I figure a brand new tensioner should last a good long time.

[HPP8140]

I finally got around to ordering all the gaskets and other random parts, plus a cylinder hone. I'm assuming Partzilla will take a few weeks to get everything to me.

I purchased a new cam chain tensioner as well. I had been running a manual version for the last ~25,000 miles but I want to go back to the automatic adjuster. I was never 100% confident in whatever tension I would set and I figure a brand new tensioner should last a good long time.

Good luck with the repair. Question on replacing the tensioner....does it require more than removing and replacing? Will the timing shift?

[Bluesmudge]

Good luck with the repair. Question on replacing the tensioner....does it require more than removing and replacing? Will the timing shift?

The timing shouldn't shift, so long as you don't turn the engine over at all while the tensioner is out.

The hard part is that you have to wind it in, then while holding the tension figure out how to tighten the two mounting bolts (the bolts that backed out and caused my whole issue in the first place) and then once its mounted you can release the screw used to wind it and the tensioner will snap out and put tension on the timing chain. The whole process really requires a third hand and/or removing the carburetors. That was part of the reason I switched to the manual tensioner...with the manual APE tensioner I was able to replace a leaking tensioner gasket without removing the carbs.

[herennow]

Bluesmudge, you mentioned earlier that the sprocket on the cam had disintegrated, I wonder if all those metal shards have got all around your engine? Maybe take off the sump and try to wash down everything with kerosene and let it drain out?

[Bluesmudge]

Bluesmudge, you mentioned earlier that the sprocket on the cam had disintegrated, I wonder if all those metal shards have got all around your engine? Maybe take off the sump and try to wash down everything with kerosene and let it drain out?

I don't think I ever said that the cam sprocket disintegrated. The cam sprockets look fine.

I did say that the moment the cam chain tensioner popped out the timing probably jumped and bent the valves to oblivion. But that was before I learned from the buddha that this engine is valve/valve interference, not valve/piston. So, the forces involved would be much less than I was originally imagining. It seems like my intake valves bent my exhaust valves since the intake clearances are still in spec and the exhaust clearances are massively out of spec.

It does look like some of the cam chain guides had chunks taken out of them, so I did order a new sump gasket so I can drop it and see what's in there. The spare head I have has all the cam chain guides in place so those will all get replaced with the head.

[The Buddha]

He said the top guide in the valve cover. That's basically a rubberized plastic. Just needs to be cleaned out. A little left here and there wont matter. Its a soft material.
Cool.
Buddha.

[Bluesmudge]

I got the easy part done! It's always easier to take it apart than put it back together.

The top end is off the bike and the parts have arrived!

The hardest part of disassembly is getting the exhaust bolts out and getting all the electrical connections out of the way to give the head enough clearance to come out of the frame.

I can pretty much confirm what Buddha said: Definitely valve to valve interference and not valve to piston. The timing was probably 5 or 6 teeth off when I first got the valve cover off. One I got the head off I confirmed that there was damage to the underside of all 4 valves. The intake valves still seem to seal fine but the exhaust valves are so bent I can see a giant gap with the naked eye. The top of the pistons look fine but are covered in a compressed goop made out of all the chunks of the cam chain guides.

My original plan of swapping in the low mileage head (with fresh rings, hone, and gaskets) just to get the bike running is probably still the best plan. Hopefully the valve stem seals are still good on that head. It might just work if I can remember how to put everything back together.

[Bluesmudge]

Nevermind...there was exhaust valve to piston interference. I just removed both pistons and they each have a decent gouge from the exhaust valves. Suzuki, in their infinite wisdom, cast a relief for the intake valve into the piston head but not for the exhaust valve.  The damage looks like you sunk your fingernail into some clay. I don't want to risk running it as-is...seems like thats asking for a hot spot and more damage.

So now I'll be waiting for Partzilla again. At least my GS will have brand new pistons...that's kind of cool.  Saves me from scrubbing the carbon off the old ones.