Spark Plug Question

[Laro3879]

I swapped out my plug yesterday and when I reinstalled I threaded it in finger tight first, then hit it with a small quarter-inch drive ratchet.

 

The manual says to go 1/2 turn past finger tight, however I got maybe 1/4 turn before it felt about as tight as I was willing to go. It ran great after install, but I’m a little worried that I missed something.

 

Has any one else experienced this?

[dad2u]

From your wording, it sounds like you put the same plug back in.  The 1/2 turn advice is for a new plug, on which the washer has not been compressed and heated.  If you are reinstalling a plug that has been used, this advice is NOT VALID as the washer is compressed and cannot be further compressed, and turning it a 1/2 turn from contact will guarantee that either you strip the threads, or put it in so tight that you will have a terrible time getting it out in the future.  The plug will not rattle loose, nor leak, if it is snug.  Do not overtighten it.  Luck!

[Laro3879]

From your wording, it sounds like you put the same plug back in.  The 1/2 turn advice is for a new plug, on which the washer has not been compressed and heated.  If you are reinstalling a plug that has been used, this advice is NOT VALID as the washer is compressed and cannot be further compressed, and turning it a 1/2 turn from contact will guarantee that either you strip the threads, or put it in so tight that you will have a terrible time getting it out in the future.  The plug will not rattle loose, nor leak, if it is snug.  Do not overtighten it.  Luck!

Thanks for the reply.

That’s the thing, the plug was new but I could only really get it to go 1/4 turn or so. And like you said, I’m not about to wrench on it (hence the small ratchet).

It picked up the threads easily and threaded in for a while before stopping at finger tight, so I’m pretty sure it’s not cross-threaded. It just seemed strange that it would get so snug so fast.

[Gary in NJ]

Here's the easy answer. 20-25 ft-lbs. New or used, always the same.

[Laro3879]

Here's the easy answer. 20-25 ft-lbs. New or used, always the same.

Pretty sure it’s more like 8 ft lbs.

[Erik Marquez]

2 hours ago, Gary in NJ said:

Here's the easy answer. 20-25 ft-lbs. New or used, always the same.

8 ft lb is all  it needs, at least on this application. 

 

NGK cites Torque Specs: Aluminum: 7.2-8.7 lb. ft.

[Erik Marquez]

53 minutes ago, Laro3879 said:

The manual says to go 1/2 turn past finger tight, however I got maybe 1/4 turn before it felt about as tight as I was willing to go. It ran great after install, but I’m a little worried that I missed something.

Yes the owners manual says something like that, but I think you missed the part about when using a used plug.  

But as you found out its so subjective and user dependant to be almost useless. 

Just snug it up (also subjective) or use a known good calibrated inlb tq wrench and tighten to 96inlb

[Laro3879]

Please throw that "manual" away...
Bother the OEM owners manual and the OEM service manual make no such recommendation. 

Message received, thanks for the help. I’d say I got about 8 ft lbs on it as it’s pretty much “wrist tight” with a 1/4” drive.

For the record, the manual I referenced was the 2006 DRZ400SM OM, although I like the looks of your service manual better.

[Erik Marquez]

5 minutes ago, Laro3879 said:

 

Message received, thanks for the help. I’d say I got about 8 ft lbs on it as it’s pretty much “wrist tight” with a 1/4” drive.

For the record, the manual I referenced was the 2006 DRZ400SM OM, although I like the looks of your service manual better.

 

Actually you quoted a post before I could edit it ... the OEM owners manual does say something like what you cited , but has info on using a used plug as well as new.
You  missed the part about used plugs I think, the owners manuals I have have the verbiage like I posted above.

 

[Laro3879]

Actually you quoted a post before I could edit it ... the OEM owners manual does say something like what you cited , but has info on using a used plug as well as new.
You  missed the part about used plugs I think, the owners manuals I have have the verbiage like I posted above.
 

Right, yeah I saw the used plug part (my plug was new though so I followed what it said for a new plug).

I just chalked it up to machining variance and went with “pretty snug” rather than trying to get the whole 1/2 turn. Glad I did as 8 ft lbs is probably about where I ended up.

Thanks again for your reply, I appreciate the quick turnaround.

[Dmouse]

 Whether it's right or wrong, but I've almost always torque a new plug down, then loosen it, then torque it again. When I was a beginner, I had a couple of my bikes new sparkplugs come loose after a few rides, and that technique has worked for me since

[shuswap1]

2 hours ago, Gary in NJ said:

Here's the easy answer. 20-25 ft-lbs. New or used, always the same.

You might want to edit this before someone torques to this level and is buying a new case

[74jimbo]

It's fine. Run it

[Gary in NJ]

On 1/22/2019 at 12:57 PM, Laro3879 said:

 

Pretty sure it’s more like 8 ft lbs.

Was thinking cars...that's why I always reference the shop manual...too many numbers in my head and most of them are wrong.

[Jonathon Coffey]

Anti-sieze on the threads help too.

[Gary in NJ]

13 hours ago, Jonathon Coffey said:

Anti-sieze on the threads help too.

Agreed. But when using anti-seize be sure to reduce the tightening torque by 15-20%

[Scottg07]

6 hours ago, Gary in NJ said:

Agreed. But when using anti-seize be sure to reduce the tightening torque by 15-20%

Why reduce with anti-seize?

[Gary in NJ]

5 hours ago, Scottg07 said:

Why reduce with anti-seize?

Because anti-seize is a lubricant and reduces friction. That is the reason torque specs sometimes provide a dry value and a wet value. If a dry/wet value is not given, use the lower number in a range, i.e. 12-15 lb-ft, or reduce the single value by 15-20%.

[Scottg07]

29 minutes ago, Gary in NJ said:

Because anti-seize is a lubricant and reduces friction. That is the reason torque specs sometimes provide a dry value and a wet value. If a dry/wet value is not given, use the lower number in a range, i.e. 12-15 lb-ft, or reduce the single value by 15-20%.

I would tend to think reduced friction would benefit from increased torque? 

[highmarker]

ngk nickle plated (silver) plugs don't really need or advise anti seize.  Lower priced champion autolite etc in black oxide or gold zinc should use it.  The little peanut plugs used in bikes like the crf don't take much of a turn to squash the gasket, best to go by feel vs stripping it to a spec.

Edited January 25, 2019 by highmarker