• Don't overlook our Welcome Package, it contains many links to important and helpful information about functions at VHT like posting pictures and sending PMs (private messages), as well as finding the parts you need.

    AD

"loose" spark plug, fix or leave alone?

toomanybikes

Member
Joined
Aug 11, 2020
Total Posts
31
Total likes
0
Location
Medfield, MA, USA
Last summer I picked up a '73 CB350G semi-basket case with 20k miles. It's now all put together, tuned up, starts easily, updated, runs fine, i.e. ... 100% roadworthy.

The only weird thing I noticed is that the threads for the right spark plug seems to be very loose the first few turns in and then tighten up at the very end. Is this normal or at least OK? Or is it enough of an issue to warrant pulling the cyl head and using inserts for "new" threads? As mentioned, bike starts, idles, and runs fine, so compression is not an issue.

Pic of almost final bike for reference, if anyone is curious. The original cables have now been replaced.
PXL_20201117_170443328.jpg
 
Moved to 350 Engine and Transmission section.

It's not normal but at this age and all the plugs and "plug removers" the bike has had in its life it's probably to be expected. When I bought my CL450 it had a slightly "difficult" plug hole and when I had the head done, the machinist chased the threads for me. It's a little sloppy for about the first half of the threads but feels normal toward the end and it tightens up fine. I'm running 11.6:1 pistons in it and I've had no issues with mine so I think you'll be fine, just use caution when you change plugs and don't overtighten, especially with a used plug that the gasket has already been crushed.

Bike looks good, did you replace the cables with gray or go with modern black? Also, how are those aftermarket mufflers? Were they on the bike or did you buy them?
 
ancientdad said:
Moved to 350 Engine and Transmission section.

Bike looks good, did you replace the cables with gray or go with modern black? Also, how are those aftermarket mufflers? Were they on the bike or did you buy them?
Click to expand...

I replaced the cables with modern black. I still have the originals in case I sell the bike, but can't imagine anyone would want to put them back on.

The mufflers are emgo dunstall replicas that came with a different bike I bought. They fit perfectly on the OEM headers, sound decent (but not obnoxious), look similar, no popping, and didn't require rejetting. Overall a great swap. I still have the original exhaust, but one of the ends has some rot.
 
Eventually those remaining threads will give up and then it'll be Time Sert installation. Heli Coil would be a temporary fix when that happens, those will fail.
 
You must log in or register to reply here.
Back
Top Bottom