SP with stripped spark plug

[HarveyMushman]

What's the favorite method for repairing a stripped spark plug?  I can thread it finger tight but no more, and it doesn't stay put when I hit the starter button . . . 

I assume I should pull the head before re-threading, but maybe not? 

[Frenchfrog]

I've had helicoils fitted very sucessfully.Head off and take it to the best local machinist is what I'd do.Timesert may be better.

[guzzisteve]

Pull the head, get correct length TimeSert, use red LokTite.

[HarveyMushman]

Thank you both.

[Idontwantapickle]

A skilled mechanic can Timesert it with the head on the engine. Best fix there is.

[Jurgen]

With TimeSerts you don't even need Locktite.  Use them on all the old Porsches.

Jurgen

[Idontwantapickle]

With TimeSerts you don't even need Locktite.  Use them on all the old Porsches.

Jurgen

A friend that has restored some Porsches told me that it was standard practice to timesert almost every threaded hole in the engine. Decreases the drama when servicing knowing all the threads are steel.

[HarveyMushman]

TimeSert ordered, might be here tomorrow.  Trying to decide between doing it myself and finding a mechanic/machinist to do it.  Seems simple enough . . .

[John A]

If you do it with the head installed, use sticky grease on the drill and tap, clean chips off often.

[bigbikerrick]

Its so darn easy to pull a head on a Guzzi, that to me ,its not worth the risk of doing it with the head in situ. chips down in the cylinder, will risk scratching up a perfectly good cylinder wall.
Rick.

[Moto]

I've done a TimeSert myself on a transmission drain plug, and imagine the spark plug hole would be as easy (though deeper). But I would be taking the head off -- it's dead easy to do, and there's no easy fix up if you ruin the cylinder wall with swarf.

I waffled around for a while imagining that I would have a mechanic do the drain plug, only to kick myself when I got it done and realized how simple it was.

Moto

P.S. I did the drain plug without removing and disassembling the transmission, of course, but the cost-benefit calculation is different with the cylinder head.

[John A]

My concern with doing it in place would be the errant chip sticking on an exhaust valve seat face. On the side of doing it in situ it's a good way to hold the head still. I've done it successfully both ways, each has pluses and minuses

[Zoom Zoom]

A number of years ago I had a riding mower worked on by what I thought to be a reputable shop in my area. They stripped the spark plug, which blew out shortly after starting to cut the grass. Went back and the bird brain did what has been suggested above with the head still on the motor. As I watched on, I questioned his method. He said the same thing about the metal chips getting caught by the grease and a ball of tape he put in there. The next time the engine quit, I pulled the head to see 1/3 of the circumference of the piston missing down to the inner edge of the top ring. That didn't take long and the cylinder wall was scored bad as well.

Do yourself a favor and TAKE THE HEAD OFF! It will be better in the long run.

John Henry

[Rick in WNY]

Listen to Zoom Zoom, I can't recall him ever steering anyone wrong.

Besides that, I agree with him. Guzzi heads area easy to remove, so save yourself the trouble down the road.

[John A]

If you are at all unsure defiantly pull the head. There be dragons in there. If I do it in place I'll use a bore scope to snoop around after and if I'm not satisfied all the chips are out, I'd then pull the head but by being carefully diligent I've never had to.

[HarveyMushman]

I bought a Time-Sert kit and pulled the head.  The problem then becomes holding the head still enough to use the Time-Sert.  So I put the head back on the studs to hold it still, which worked well.  After I finished with the plug business I pulled the head off again and vacuumed the debris off the top of the piston.  Glad I didn't try to do it with the head in situ . . . 

Question:  What are the piston and valves supposed to look like?  How black is too black? 



Note: This engine doesn't run.  I had to fix the plug to resume efforts to get it running after several years of storage.  It didn't run before storage either. 

[rodekyll]

That part of the valves Don't matter as much as the part that contacts the seats and the stem/end of stem.