Honda Twins banner

1 - 16 of 16 Posts

·
Registered
Joined
·
48 Posts
Discussion Starter #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

·
Registered
Joined
·
2,928 Posts
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.☆
 

·
Registered
Joined
·
163 Posts
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...
 

·
Registered
Joined
·
69 Posts
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. :)
 

·
Registered
Joined
·
48 Posts
Discussion Starter #7
What's the best way to reduce the helicoil? Just grind the top since the bottom has the tang to thread it in. The run a tap through it and a die over it?
 

·
Registered
Joined
·
69 Posts
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>
 

·
Registered
Joined
·
6 Posts
Also, by using this type, no need to worry about a tang dropping inside the cylinder. Just use plenty of grease on the tap to catch the swarf.
 

·
Registered
Joined
·
51 Posts
Also, by using this type, no need to worry about a tang dropping inside the cylinder. Just use plenty of grease on the tap to catch the swarf.
And there is no chance of the insert working its way down through the head and dropping into the combustion space
 

·
Registered
Joined
·
48 Posts
Discussion Starter #14
You guys are the best thanks a bunch got the inserts today gonna fix it over the weekend. After looking the plug I was gonna use did not have a projected electrode. The originals did plus this way it's all back to the way it was. Thanks again
 

·
Registered
Joined
·
51 Posts
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
 
1 - 16 of 16 Posts
Top