Triumphrat

mr_hybrid · 02-11-2006

I need to know if anyone has ever had a spark plug, for no apparent reason, get spit out of the head. I've only owned by Sprint for a couple of months now (I bought it used in late October). The bike purred like a kitten until January 4th. The spark plug in #1 cylinder spit out of the head, taking all the threads with it. Luckily it was contained by the coil. Talked to the previous owner and he had the plugs replaced along with all the other stuff they do at the 24000 mile service (the bike now has 27000 on it) . Contact the dealership where the work was done and they want to see the bike. I trailer it down to Denver and they look at it. They are not sure why the plug spit out. They said it could be that carbon build up caused some sort of preignition and that caused some massive explosion that would force out the plug. It couldn't be caused by them overtightening or cross-threading the plug. Now they want to charge me two hours of diagnostic time to come up with this idea of the preignition, plus another $100 to put in a Helicoil (which they won't guarantee will work), plus the cost of new plugs and a coil. I just wonder if there is a logical explanation for the plug coming out other than cross-threading or over-tightening the plug when they did the service about 3400 miles ago. If there is I will shut up and pay my bill

John

rodneybrown · 02-11-2006

And why couldn't it have been caused by them overtighting or cross-threading the plug???? This is the first time I have ever heard of something like this. I've heard of hydrostatic lock breaking connecting rods and bending valves but blowing out a spark plug that's frickin' amazin'. I would think that if the threads were good on the plug and head something else would give before the threads stripped and spit out the plug. Something smells here when just 3k after being at the dealer. By the way, what did the gap and electrode look like when the plug came out?

mr_hybrid · 02-11-2006

I couldn't tell you what the gap looked like because a piece of the ground electrode was missing. I'll try to post some photos.

John

rodneybrown · 02-11-2006

I got the following from another Sprint list that I am on:

"Happened to my '99 at about 45,000 miles. #1 plug came out with all the threads from the head.

It started to come loose about 50 miles before it came out. Just a vague feeling in the running of the bike that something wasn't right.
The engine still ran smooth, but with occasional loss of some of the power (probably due to loss of compression as the spark plug worked it's way out). Eventually, the plug came out, the engine lost all will to run and the bike just died by the side of the road. Yes, there is room for a heli-coil in there.

I can only point to overexuberant mechanic trainee as to that point no-one but the dealer had touched the bike, though I don't have any proof of that. Steel spark plug and aluminum threads in the head. It's not hard to overtighted a spark plug, especially if you break out the torque wrench to set the plugs."

I have the plug torque somewhere but I just do what feels right. A plug doesn't have to be cranked up by King Kong.

Paul-K · 02-11-2006

It sounds like you're about to get screwed to me. Did they pull the head and look at the insides to see that the carbon build up was there or just guess? If it is a result of a carbon build up, did they clean all that up? Was there a build up in the other cylinders? If not, why? If they don't get all the offending carbon out of there what will keep you from having a repeat?

mr_hybrid · 02-11-2006

From what the service writer told me, the head is not pulled yet, they just saw the carbon build up on the valves looking down the intake bores. They said the bottom end all checked out fine. So that does make me wonder why #1 cylinder blew and not the others? The plugs are fine on the other cylinders. I am going to get some mechanical engineers at work to calculate the forces required to blow the plug out of the head. If the forces are huge, why didn't the connecting rod let loose first?

ST-ern · 02-12-2006

It's a fairly small diam plug thread; wouldn't take much for a ham fisted tech to overdo it.

dolson · 02-12-2006

Or under torque it either. If it isn't snugged up the vibrations will loosen it and start a stress fracture through the vibrations.

Don

SprintST · 02-12-2006

Was that Dan in AZ's story on triumphnet? He's the only one I can recall having a sparkplug strip out.

Quote:

On 2006-02-11 18:28, rodneybrown wrote:
I got the following from another Sprint list that I am on:

"Happened to my '99 at about 45,000 miles. #1 plug came out with all the threads from the head.

It started to come loose about 50 miles before it came out. Just a vague feeling in the running of the bike that something wasn't right.
The engine still ran smooth, but with occasional loss of some of the power (probably due to loss of compression as the spark plug worked it's way out). Eventually, the plug came out, the engine lost all will to run and the bike just died by the side of the road. Yes, there is room for a heli-coil in there.

I can only point to overexuberant mechanic trainee as to that point no-one but the dealer had touched the bike, though I don't have any proof of that. Steel spark plug and aluminum threads in the head. It's not hard to overtighted a spark plug, especially if you break out the torque wrench to set the plugs."

I have the plug torque somewhere but I just do what feels right. A plug doesn't have to be cranked up by King Kong.

rodneybrown · 02-12-2006

Yep, that was Dan.