Honda Twins banner

Spark plug hole striped 1968 cl175

2K views 15 replies 8 participants last post by  Adamgs340 
#1 ·
So today I threw some new tires my 1968 cl175. I got that done and decided to take it for a ride. I a made it around the block and heard a pop and the bike stalled. I looked down and on of the plugs blew out of the cylinder. So I pushed it home and checked the hole. The threads are gone. So I am looking for ideas on how to fix it. It was originally a 12x1.25 thread. I looked a heli coil kits and various others threaded inserts. The problem is the original plug only has a 1/2 inch reach the shortest insert I have found is 15mm. So I thought what about drilling and tapping to a 14mm plug. I have found a ngk plug that looks like it will work a B8HS. Is this a good idea or should you guys use an insert. Thanks for the help. Here is a picture of it
 

Attachments

See less See more
1
#2 ·
You'll probably get opinions on both sides. For me if the 14mm threads don't interfere with valve seats I'd go for it.
But I'd probably do them both and put a note of the new plug number somewhere with a handheld engraving tool. ☆Even if you're planning to keep the bike forever.☆
 
#4 · (Edited)
When I got my Sloper I found one spark plug hole had been enlarged to accept the larger plug *without using an insert* with the same heat range. The PO did a decent job and the threads were in good shape and I would have been okay running it that way, but I needed to tear into the motor anyway, so when I pulled the head I had it the plug hole welded, drilled and tapped to fit the original plug size. It's a more expensive option for sure...
 
#6 · (Edited)
I would pull the head and use a helicoil insert, trimmed to size. I might even install an insert into the good plug hole while the head was out, just to keep things the same.
You _can_ install the helicoil with the head in place. The thought of all those metal shavings inside my motor would keep me up at night.
I would not enlarge the hole unless I was desperate. Some day, someone will curse you for your actions. :)
 
#9 ·
The helicoil is just a coil of wire. Measure the depth of the hole accurately and trim the top side of the helicoil (the part without the installation tang) to end just below the top surface when it is installed. It is stainless steel, so it may be hard to cut with clippers. After you cut it and before you install it, dress the cut end with a file so it is smooth and without any burrs where you separated it.

Good luck
Mike M>
 
#15 ·
Hi Adam.

I had the same situation with my 1968 CL175. I purchased a Time-sert thread insert kit. It comes with all the special necessary tools and 6 inserts of different lengths.
It worked really well, and I did not need to remove the head. High quality tool, but expensive at $155 USD.

Michael
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top