Stripped plug

[timberwolf]

Right, did not think of the old air cooled VWs using short rech plugs, the VWs I deal with use glow plugs. :hmm3grin2orange:

Anyhow, I was never saying it can't be done/won't work, just saying with short reach plugs you don't have much thread to work with. Using an insert basically one thread is lost and when you only had 5 to start that 20% less shear strength than it was original condition which someone obviously had no trouble stripping.

 

[heimannm]

The insert of course has a larger O.D. (more contact area) and once installed and locked in place, the spark plug now threads into steel.

I am not suggesting that we all go out and install threaded inserts for the sake of it, but it the original threads get stripped, the insert can be a way to keep a saw running for a good long while yet.

Mark

 

[timberwolf]

Yes, the plug threads into steel... but what does the intsert thread into?
Granted the steel inset won't wear like aluminium threads will.

The extra mm or so of diamiter the insert catches does give about 7% more surface but that is assuming 100% thread depth. Anyway you cut it a plug hole repaird with an insert is not going to be as strong as original and I can't count the number of botched insert repairs I have seen.

On high performance stuff you can also run into issues with poor heat transfer out of the plug as well.

Even welding won't bring it back 100% as weld is often not quite as strong as the original casting.

 

[paccity]

prob, over thinking. but are the stock threads cut to have the plug indexed? and if not would the saw benifit from it? thinking? prob not with the varianse of the plugs them selves. just thinking about the old tuner trick on 4str's. and on the heat transfer , couldn't you just run a cooler plug ? stock don't know if it would make that much of a diff?

 

[roalco]

Well, it finally happened.

I screwed with a saw long enough to strip the plug threads on the cyl. Mmmm, humble pie, so tasty.

Is anybody in the Vancouver BC area set up to do a timesert? I'd rather not helicoil, and I'm not set up either way. I'll buy the timesert, but if I could skip the reamer and tap, that'd be nice.

I'm in North Van, shoot me a PM. Should be able to help.

 

[Dan_IN_MN]

What about using a sparkplug with a larger diameter thread? Just a thought.

 

[timberwolf]

There are a few 18mm plugs out there not common though. Also the chambers are tight on most saws so no room for a larger plug anyhow.

 

[heimannm]

timberwolf - Do you know of a source for Champion TJ8J plugs or equivalent? These are the odd ball short plugs with the hollow insulator and terminal down inside.

Thanks,

Mark

 

[timberwolf]

http://cgi.ebay.com/ebaymotors/NOS-8-Champion-TJ-8J-TJ8J-Spark-Plugs-/380298058228

 

[heimannm]

O.K. I just slapped myself for overlooking the obvious...

Mark

 

[ironman_gq]

I got the heli-coil plug repair kit. I uses sleeves like the timeserts that you put in and expand the top to lock it in. I paid like $45 for the kit. it uses a piloted ream/tap that uses whats left of the old threads to pull itself in straight then you put sealant on the external threads of the insert and thread it in and use the expansion tool to lock it in. Whole process took about 5 minutes and Ive never had a problem

 

[Tzed250]

I got the heli-coil plug repair kit. I uses sleeves like the timeserts that you put in and expand the top to lock it in. I paid like $45 for the kit. it uses a piloted ream/tap that uses whats left of the old threads to pull itself in straight then you put sealant on the external threads of the insert and thread it in and use the expansion tool to lock it in. Whole process took about 5 minutes and Ive never had a problem

That is the insert shown at the start of my 660 thread.

.