Rattling in cylinder

[Fullerdou]

Long time reader, first time poster.

I’m a fairly new owner of a 1985GL 1200 interstate. Have use this forum to diagnose & fix many Of the usual problems. Wiring harness was one of the main ones.

I bought the bike with 40,000 miles on it for $2500. After fixing some minor problems and getting her fixed up, I was having a ball riding her. After putting about 1000 miles on it, on the way to work one day one cylinder started rattling really badly after the engine was running super rough for a while.

At first I thought the timing belt had slipped one notch. The motor kept running but not very good. After limping at home to the storage unit and turning it off. Tried to start it again engine locked up.

I tore the bike down including taking the radiator off to get to the timing belts. It didn’t appear that they had slipped. Tried turning the motor by hand and could tell that something was ticking on the left-hand side. Took the timing belts off tried to move individually still no luck. Decided to pull the left cylinder head off. And was quite amazed.

After popping the cylinder head off. I looked inside the cylinder head and there was a 6 mm Phillips head bolt stuck in the exhaust valve. I got to looking around and after more research and tearing the air intake further apart I discovered that the screen covering the carburetor intake bolts had a rattle out. One bolts was still in the compartment with the screen the other had gone down through the carburetor, worked its way through the intake valve and the cylinder lodged it underneath the exhaust valve.

Both valves were bent.

It was in the number one cylinder. Cylinder still looks good no scratches in the sidewall just a few minor dents in the top. It looks like the valve seat was damaged. Found two used heads I’m going to order them on eBay and then resurface the valves and go from there.

Has anyone ever heard of that happening before? Seems like a fluke.

One question I have is are the Aspencade and interstate heads interchangeable, and what years. Will 1986 Aspencade fit on my 1985 interstate?

[AZgl1800]

that is not the first one by a long shot.

1976, I owned a 1972 Renault R16 hatchback, the very first of the so called SUV named vehicles.

Wonderful little car. One day, the motor got very sick, don't recall what the symptoms were now, but I do remember what I found.

One of the air filter housing bolts had backed out, and somehow, that little 6mmx20 bolt got thru the carburetor, and thru the intake valve and punched a hole in the piston.

The Renault dealer would only sell me a full set of pistons and ring set.
one of the online auto parts books would sell me a single piston and ring set.
so, that is what I did.

I don't recall if I did anything to the intake valve or not, but that car ran more than a 100,000 miles for us before we sold it w/o any negative symptoms at all.

[WingAdmin]

Ouch, that's a nasty result. I've not heard of that specific screw backing out like that, but anything is possible.

Maybe you should have just given it more throttle, you could have just blown it all the way out and ejected it from the exhaust!

[Charlie1Horse]

But, how can one of those screws get through the screen to the intake? They are above the screen and would not be able to enter the carb. I would think that someone must have worked on this and dropped the screw into the carb where it lodged for a while before falling into the cylinder.
Russell

Those who say it cannot be done should try not to interrupt those who are doing it.

[SlowTyper]

I agree it was likely some mechanic's failure putting the thing back together before you bought it. I just had the carbs off my GL1200A to work on them recently, and had a terrible time getting those screws loose. They are tight! So I doubt one came loose on its own, and if it did, as another poster indicated, the second screw on that protective screen would have had to have been very loose also, and a lot of air flow would have been required to push the screw up over the lip into the carburetor opening. Furthermore, would a screw vibrate all the way out when it is inserted downward?

[Duq_]

Similar thing happened to me on my first bike, a CX-500. The rattling noise was incredible!
I was luckier than you though, in my engine the screw was smaller and the piston had smashed it into the head right between the valves without damaging them. After removing the screw and putting the engine back together it ran fine again.
In my case the screw came from the butterfly valve in the carburettor.

[CWN]

This kit will fix most aliments :<)

[ct1500]

The screens are flame arrestors BTW. I would tend to agree with other posters about someone being in there previously as the old head gasket looks a little too pristine for my eyes. . No fluke.

[Fatboy46]

back in 1965 I saw a new Chevy engine out at a dealer.. 1 piston remained intact. the other 7 were shattered. a screw from the carb had made it's way into the engine and managed to bounce around enough to trash 7 cylinders. Car had 17 miles on it. Not yet been sold

[CrystalPistol]

Uncle Alex once saved a piston by drilling and tapping and inserting a bolt and shaving top off after a spot of weld inside piston.

It was likely a cast iron piston though, in a very old tractor engine, but it worked from then on.