How much trouble am I in?

That is a brand new gapped plug.


Put in a new plug it seems to run great. What could have caused that?

So what I hear is that you now are running ok and this is the plugged you replaced. I have never seen anything like that and the hope would be that any UFO would have been blown out the exhaust.

On the other hand, it doesn't take much of a ding to cause this. A small bump on the way to installing or something like that, but a mark like that, that's wierd.

How did you discover this? Did one cylinder just all the sudden drop out? Did you install it and it just wouldn't start and you took it out to find this?

I haven't had much success with those little scopes and it sort of begs to remove the head and if it happens again, this option becomes an absolute necessity if not already.

I have been checking the plugs alot latley. I put new amal premiers on and I have been adjusting the needles. ( btw I ended up with the clip in the middle instead of usual top slot). I check them twice a day latley. I just couldn't believe my eyes when I saw that.

I have been revving the crap out of it too. It's running so good I thought I would blow the carbon out.

Also, my old amals had a chunck of slide missing. I wish I could remember what side it was. I has been a few weeks when I changed the carbs.

I will pull the head if I have to, but I cannot see anything wrong.

Most peculiar, the only thing (however improbable) I can think of is that one of the two inside allen screws of a two-into-one carb intake manifold came loose and was sucked into the combustion chamber and got stuck between the piston and the plug before it went out via the exhaust valve.

Tape a 1/4 bore pipe to a vacuum cleaner and have a "suck" around in the cylinder...go fishing, you never now if you find some "Tiddlers" in there.

I missed your post about the Amals. Indeed a chunck of the slide could have caused it as well.

From the photo, it looks as though you have no gap between the electrodes. Perhaps the head of the inlet valve has come off. Have you still got compression on that cylinder ?

Yes, there was no gap at all. I am surprised it ran.

Compression 135 both sides.

Can a piece of the slide hang around for a month or so before it worked its way out?
I wonder what the valve looks like?


:should have said..... 74 850 Interstate stock ...twin amal premiers

I'd shine a light down the plug hole & inspect the top of piston. It doesn't look like that plug has had a big impact though.

Ian

I'd put my money on the piece of slide. It's an odd shaped thing that could lodge itself up against the valve guide for a while before coming loose again and creating havoc. If you have a balance tube exhaust I'd take that off and make sure it isn't lookin to travel into the other cylinder. It might be an idea to take the carb off and inspect it and the intake port, air cleaner, for anything unusual. I wouldn't pop the head off if it's running strong.

I had a similar experience when I was holidaying in the Kootenay Mountains one year in my F250 4x4 with big honkin camper on back. Heading out of downtown is a real steep hill and at the top my low gas tank starved the fuel pump and I stalled. It was so steep the curbs were 18" high to contain the runoff in spring. It wouldn't start with no gas in the pump so I cut it over to the curb which I couldn't see with my hood mounted hiway mirrors and I ended up at a 45' angle against the curb with my front end poking out in the main lane. I jumped out and grabbed my 5 gal jerry tank from the back and dumped some fuel in the tank thinkin if a cop comes by now I'm going to get a ticket for sure. The 5 galons didn't help on this steep hill so I popped the hood to prime the carb just when the cop came along. He stopped came over and said "outa gas huh?" Yep I said, he says " you got some gas there, you're ok huh?" I says yep and off he went. I new I was going to like the town of Kaslo after that, a helpful cop who didn't just want to write me a ticket, wow!

In the chaos I dropped 3 or 4 washers that were under the nut that was securing the air cleaner, down the carb of the big V8 but didn't know it till I discovered my plugs looked like yours and it did explain where those washers got to. I was staying in a remote area out of town with no compressor or tools other than what I had in the truck. The washers bounced around from the intake manifold to the exhaust manifolds until I had cleaned the town of Kaslo out of gasket kits for my engine as I lacked the equipment to really clear the crevices of the manifolds out properly. On the last top end gaskets I scrounged from the auto wrecker from his left overs and on the day I had to leave I fired it up. It sounded good for a few minutes then I heard a miss and my heart sank. I hit the road anyway after regapping the plugs and made it the 400 miles or so home with no other problems. The last bits must have finally blown out the exhaust and sooner than later because the big v8 purred all the way home.

flashbackk said:

Yes, there was no gap at all. I am surprised it ran.

Compression 135 both sides.

Can a piece of the slide hang around for a month or so before it worked its way out? NO CHANCE
I wonder what the valve looks like?


:should have said..... 74 850 Interstate stock ...twin amal premiers

Click to expand...

WHAT'S BEHIND THE AMAL'S?

What brand and grade of plug is that ?
Some extended nose plugs do stick into the combustion chamber a bit.

This is only on one side ?
That torch idea of looking in there seems a good idea...

ham can air filter stock.

NGK BPR7ES

Just one side. The other is fine.

I'll be pulling the head tomorrow. Gonna have a look see just to make sure.

flashbackk said:

ham can air filter stock.

NGK BPR7ES

Just one side. The other is fine.

I'll be pulling the head tomorrow. Gonna have a look see just to make sure.

Click to expand...

Before you pull the head you might want to check inside the filter, the back plate is secured by two short 1/4" bolts to the battery tray. Have a look if both are still there?

Strange.
Is this the only time the gap has been closed ?
When you removed the plug on the previous occasion was the gap OK ?
If so then you could deduce that something has entered the chamber that isn't welcome there.
Do as all other commenter's suggest.
Doesn't sound like the piston has hit the plug.
When doing the plug change might a small piece of crap have dropped in there ?

Hold off on pulling the head.

I think the torch (light) and looking into the spark plug hole for any serious carnage on the piston dome would be the first order of business.

Take a step at a time.

Good that the compression was even between cylinders. Did you take compression with the throttle wide open?

BPR7ES should not be a problem. Did you use a gasket with the plug?

My vote is with your slide, I had exactly the same problem, worn amals and a broken piece of slide squashed up the plug, of course murphs law states this will happen while passing, 400km from home and on a public holiday - still manged to hitch a ride home for me and the bike, No damage to the engine happily just the wallet for new carbs.

I think a detached valve head would give a "bit more than a love bite to the plug"..mayby Danceing with shrappnel :lol:

acotrel said:

From the photo, it looks as though you have no gap between the electrodes. Perhaps the head of the inlet valve has come off. Have you still got compression on that cylinder ?

Click to expand...

You'all do realize that Commando's were Clint Eastwood's ride of choose & we know his philosophy = How Lucky Do Ya Feel Punk! Did I use up 5 or 6 shots... A real movie start warrior cycler will remove head to be sure.

As the motor did not blow up, you can forget about it inhaling a steel fastener.
It had to of swallowed softer pot metal slide piece, so you can expect to find peckered up piston crown and chamber surfaces to collect more coke to choke on and likely the exhaust valve rim beaten to a sneering curled lip and its seat chipped or dented or loosened which could cause some stem bend to hang up or wear to leak oil to smoke in your pipe. Its also possible the extra shock load on fouled valve may of damaged its push rod, lifter face and cam lobe. So will next Pull on your trigger just a click or BANG!

Pulled the head and only found a very few light scratches on the piston directly under the plug. No debris found. Basically,
I got lucky. Whatever passed through the head ( mostly likely the peice of slide ) did no damage at all. So that's the good news.

The bad news is that we snapped the head of the center stud off and spent all afternoon prying and sawing the head off with a hacksaw blade.
While I had it apart I ended up ordering parts for a valve job and 20+ pistons. Oh and I snapped a fin off prying the head loose.

Soooooooooo that's the luck I have. The way I do everything.... :roll:

Pretty expensive for having nothing wrong.

Actually, it's a good thing. The engine hadn't been opened since the 70's.