Jumped / broken cam chain? Interference engine?

Saturday morning ride left me stranded to what I only imagine right now as a cam chain / tensioner failure.

Most of my ride was in and out of traffic and I had finally pulled off to a curvy uphill road. Rolled into the corner nice and quick, hit the throttle and before I even hit 7k, bike died. Sounded like I hit the killswitch. My first thought was that I popped the head gasket.

Pulled off the side of the road, checked my switches and key - all good. Tap the starter and it whirrs over, freewheel - no engagement, as starter was winding down, sounded like the cam chain jammed. Tapping the starter just results in a thud as the starter engages.

I guess that my preliminary question is, "does the 550 Seca have an interference engine?" That is my main worry. I'll pull the valve cover tonight to confirm.

:|

 

Yes. All XJs are "interference motors."

Keep us posted.

 

Went home for lunch and propped up the gas tank, pulled the valve cover.
Noticed immediately the slacked chain, and was able to pull the chain up from the intake side.

So the chain has definitely snapped, hit the valve cover, and ruined my day.

I guess the next step is determining whether or not I introduced the tops of my pistons to my valves.

How common is it to snap a chain? Engine has roughly 21k miles

 

Not all that common. Especially at only 21K miles, unless it had an internally-rusted spot that caused the failure.

You're sure the chain itself broke, not just a guide falling to bits?

If you had 7K on the tach, you probably have a few bent valves. Luckily 550 valves are relatively easy to find and not uber-expensive.

 

I bought an old ninja 250 that some one wrapped up to redline and the tensioner let go and belt every valve.

Now I'm not saying try this but I used a screw driver and straightened every valve and put it back together and rode it for 20k before selling it and never had another issue.

 

Chain is definitely snapped. see here - http://imgur.com/0SibpQZ

Such a bummer, I've had this bike running like a top. Even right before it let loose, no noises, vibration, leaks, etc.

edit: Seems the 550 cam chain is discontinued everywhere, if I DO happen to find one, I probably won't straighten them with a screwdriver.. haha!

 

If it were my bike I would pull the head straighten the valves if a replacement chain could not be found you could repair it with another used chain.

 

Does the other end of the chain have all the plates and pins? If not, you had better plan on fishing all those tiny metal bits out with a magnet.

 

I didn't have the time to get the rest of the chain out yet. I plan on digging further into it this evening. I'll update with pictures of the carnage later.

 

Chacal should be able to supply a cam chain.

 

The chacal forum said it was discontinued. I'll get a hold of him once I figure out what I'm going to do.

Anyway, here is the carnage - as promised!
Album: http://imgur.com/a/DIFmu

I'm only going to assume that I mashed all the valves. Some even have reverse valve casting numbers imprinted into the pistons.

 

Looks like a crack in one of the pistons.

 

yeah, number 4 intake valve relief looks like a hairline crack. I'm pulling the cylinder bank either tonight or tomorrow in conjunction with the oil pan to look for metal chunks, so I'll throw the pistons in degreaser and check the rods then.

Does the pan come off with the engine in the frame?

 

I'm more concerned about the chain and how/why it failed.

From looking at the pics, I see that the link directly connected to the failed link is obviously "re-riveted" (it's pins aren't mashed like the others) leading one to believe that might be a replacement chain to begin with.

The failure is truly odd; it looks like the link just pulled apart.

What's the history on this bike/motor; how much do you know about it?

 

I've had the bike for about 3 years, spent the first half of that summer rebuilding the brakes, forks, carbs, de-rust/crust the tank, light hone the bores, new rings - gapped and clocked, lapped valve seats, set / rechecked valve clearance, etc. I know very little about the previous maintenance (or assumed lack thereof).

Bike was originally from upstate NY, kid near me bought it and realized that his Advance Auto Parts store training was insufficient for motorcycle love and care. Picked it off craigslist for $350, I put over ~$1100 into parts, fluids, tires, and beer.

Last year, I had the head into the shop to weld a stripped exhaust stud, and also had the deck milled to rectify a within spec warpage. This was my gift of thanks for many miles of classic 80's motoring. $$$

I have put probably 10k miles since then. Oil and filter was changed 1k miles ago, mid march. Used the same old formula 4T and purolator spin-on filter that I have always used.

edit: I've gone over my head a bunch of scenarios that would influence this type of failure, and I cannot think of anything. Wish I could say I was dumping the clutch at 10k and hanging off the grab bar with one hand, but sadly that is not the case. The cam chain tensioner is set correctly, the guides do not have abnormal wear, maybe I have just gotten too fat these days.

 

So YOU didn't replace the cam chain once already? It sure looks like somebody did.

Does the cam chain have any identifying manufacturer's marks on it or anything to help identify it?

What I'm trying to figure out is if the cam chain was the initial failure; or did it break as a result of something else (like a spit shim, loose sprocket bolt, or ???) locking the top end and causing the break.

 

I did not replace it, I wish I did. I'll have to check for any identifying stamps. I do know that it has no sloppy links, tight links, or noticeable twists.

The cams rotated freely with the chain off, I feel confident ruling out any rotational problems. Did a valve 'jam' in the seated position and shock the valvetrain? Hard to tell at this point, initial inspection doesn't suggest it.

On the bright side, I did have the local cycle center locate a NOS chain from a cycle shop in Michigan while I was there on an unrelated visit (Suzuki Katana has dual disk calipers, 8 total pistons in the front brakes....those seals get pricy fast!)

 

I've put this bike off to the side for now... still making mental inventory of what / how I'm going to do.

The timing chain had some faint stamping of a manufacturer. Image here http://imgur.com/5p6CJkE maybe hashtag chacal can identify :lol:

I'm going to replace the pistons since I'm sure they're structurally stressed.
Considering buying an ebay head / valve assembly. I've gotten pretty good at checking valve clearances, it's the waiting for the right shims to arrive in the mail that I haven't improved.

I the intake cam bearing and cam seem like they might have some damage. The aluminum in the head is slightly scored, the cam has an unnatural look, however there is no noticeable grooving based on the fingernail test.

Nobody answered me before, does the oilpan clear the frame while engine is installed?

 

As a small update, I haven't bent the vales back in a vice as suggested earlier. I actually haven't spent a dime on the bike.

I may have a line on an 86 radian.. either as parts (read 600cc engine) or ANOTHER project until I can source my parts for the 550. I'm conflicted.

I have much more research to do about a potential engine swap.. However summer is running out and the 550 is inspected, registered, and insured- Sounds like the best option!?

 

The Radian motor will physically drop right in. The exhaust head pipes are the same except the Radian has a "balance tube" between #2 and #3 ahead of the collector box.

You should probably use the carbs that come with it to eliminate any headaches there; I believe the only other serious difference is the charging system and I suspect the TCI might be different.

 

Let us know how it goes with the Radian engine - that's what I've bee playing with. Got the head apart right now and managed to find some NOS rings ( from Iowa !) that are on they're way to the UK now.. I also ebayed the TCI for about 15 US but no chance to try it yet as I'm still building up the cycle parts..

Cheers

J