Spark Plug Hole Problem

[cactus]

I don't know if this ever happened to you guys. I installed some new ngk spark plugs on my cb350, installed it as the instruction says (hand tight and 1/2 turn with wrench) no problem there. I went for a ride for a couple of miles, let it cool down to check the plugs. Here comes the problem, I tried installing the spark plugs again, this time I can hand tight it in, but trying to torque it not even 1/4 turn feels like im gonna strip the threads, there is no way I can go 1/2 or even 1/4 a turn. The thread looks fine for both the plugs and the head. help?

 

[HerrDeacon]

The 1/2 turn instructions is just for the first time installing a new plug. It helps compress the split washer that is on the plug. Once this is done initially, you don't need to turn it 1/2 turn again.

 

[cactus]

Ya I thought that was the case, just wanted to make sure. So what would be the procedure then, hand tight it and 1/8 turn?? or snug turn?

 

[xb33bsa]

if you cannot do it by feel, the correct torque, use a torque wrench to proper specs
snug is not right, it needs the correct torque for heat transfer

 

[cactus]

I have the manual for the cb350 and I tried looking for it but could not find the proper torque spec number. All I can find is this

 

[xb33bsa]

14-15 lb ft should be fine thats on the low end for clean dry threads
if your threads are lubed then yeah you need to be careful and just go with good feel and the 1/2-3/4 turn is proly good sense

http://www.gobookee.org/get_book.php?u=aHR0cDovL3d3dy5hdXRvbGl0ZS5jb20vc2l0ZXMvZGVmYXVsdC9hL3VwbG9hZHMvZW4vdG9ycXVlc3BlY3MucGRmCjIyMzkgLSAyMDAzIFdlYnNpdGUgUGFnZXMgLSBBdXRvbGl0ZQ==

 

[Redliner]

1/2 turn AFTER the crush washer has sealed? Sounds optimistic...

 

[cactus]

see that's the problem, initially I didn't have a problem torquing 15 lb ft it or 1/2 a turn. Now after reinstalling the plugs not even 1/4 of a turn feels like im stripping the threads it would feel like i have to put all my body weight just to be able to torque it to come close to go 1/4 turn which I don't want to do. So what Herrdeacon is saying, the half a turn is just the first install, now basically I just want to know how tight do I turn it after reinstalling it again.

 

[Redliner]

The first install is to crush the crush gasket, so there will be more travel only that time.

 

[cactus]

Ya that much I figure. So Im guessing when re installing (gasket already crushed) after hand tight a snug tight turn with a wrench would suffice?

 

[crazypj]

Snug is probably too tight in your case
Better invest in a torque wrench ;D

 

[dualitymike]

I'd also suggest investing in a torque wrench. If you plan on doing any kind of work on your bike, it's really a basic tool and you'll use it a lot. If you want to do some exhaustive reading on NGK spark plugs, they've published a booklet on everything there is to know about their plugs. If you just want to have the proper torque settings for your application, skip to page 10. There's a chart that gives the torque spec based on diameter of the threads and whether you've got an aluminum or cast iron head. Yours is aluminum. Here's the link to download the PDF for free.

http://ngkntk.co.uk/wp-content/uploads/2011/03/Motorcycle-Cat.pdf

 

[cactus]

thanks for the suggestion guys. went ahead and torque it at 18 lb/ft