Honda Twins banner
1 - 9 of 9 Posts

·
Registered
Joined
·
222 Posts
Discussion Starter · #1 ·
Strange but true I just got back from a ride and I felt a compression leak against my leg. Thought it was a loose spark plug. Nope! The head nut (one of four - two on each side) just above the spark plug is missing! I just have the threaded bolt showing. What size are they? Where can I buy one? Does it take a washer? Torque?

What would cause this to happen? Engine has not been apart in three years. It just completely unscrews itself and falls off in a few miles?

450 CL
 

·
Registered
Joined
·
13,085 Posts
There are 8 total, not 4, and the only way I can think of that one would come loose is if they weren't evenly torqued to specs originally and re-checked before the first run as well. I'd say it's highly possible that you'll have a damaged head gasket, but you could replace the 10mm acorn nut (or blind nut, as Honda refers to it) and washer and re-torque the entire top end to 21.7 foot pounds as per the FSM (rounded up to 22 is fine). The washer is copper if the missing nut is from one of the two right-hand outside studs, where oil flow goes up the studs to the top end of the engine. The nut is #15 at the link below, washer would be either #10 or #11 depending on if steel or copper

https://www.cmsnl.com/honda-cl450k3-usa_model50473/partslist/0018.html#results
 

·
Registered
Joined
·
222 Posts
Discussion Starter · #3 ·
What rotten luck!

I found these acorn nuts on Ebay that list as fitting a Honda 450. I thought they'd save me money. But don't want to buy twice.

https://www.ebay.com/itm/392003528196

The uncovered stud is on LH side of the engine, to the right of the spark plug, and the closest stud to it. Looks like # 11 in the diagram but you're description sounds different. Assuming I lost head gasket, would I buy six of the #10's and two of the copper #11's?

Your help is very much appreciated. I can't believe this happened. Even the washer was gone.
 

·
Registered
Joined
·
6,495 Posts
Those nuts are not the more common thread pitch, so watch it........
Two copper washers are needed, both on the rider's far right - I always replace them when doing a rebuild.
 

·
Registered
Joined
·
13,085 Posts
I found these acorn nuts on Ebay that list as fitting a Honda 450. I thought they'd save me money. But don't want to buy twice.
https://www.ebay.com/itm/392003528196
I doubt they're the same - note that the socket size to fit the nut is 14mm. The OEM nuts for the head are 17mm. Probably not rotten luck, but rather the result of not properly and evenly torquing the head during the rebuild. You should always follow up with a re-torque on the head after the engine sits for a while, say overnight, before the first startup. Gaskets crush and to a degree, torque on engine top ends is somewhat relieved after sitting and should be re-checked.

Looks like # 11 in the diagram but you're description sounds different. Assuming I lost head gasket, would I buy six of the #10's and two of the copper #11's?
I was trying to describe the two possible washers used across all 8 studs depending on which stud was where the nut came off. Again, only the 2 right-hand studs (right side of the bike while sitting on it) use copper washers, the rest of them use the steel washers. Steel washers usually do not need replacement, and I've never found the need to replace the copper washers either myself but because they are of softer material to seal the oil passages, replacing them certainly can't hurt. Many people here have parted out 450 and 500T engines over the years, so it's possible someone will have extra nuts for the top end studs and be willing to sell you what you need

Product Auto part Engine
 

·
Registered
Joined
·
6,495 Posts
I replace the copper washers because they're pretty ugly after 45 years.
I put a lot of work into beautifying these motors, don't want it spoiled by funky looking washers in plain sight.
Like I said, you won't find those head nuts at the hardware store, as they're not the commonly available pitch.
 

·
Registered
Joined
·
222 Posts
Discussion Starter · #8 ·
I wanted to thank Ancientdad for his help. I am still crying in my beer that this could possibly happen but I have pulled my head out long enough to remember those I am indebted to. I wish him a great day and think its wonderful that people like him are around to help out.
 

·
Registered
Joined
·
13,085 Posts
I wanted to thank Ancientdad for his help. I am still crying in my beer that this could possibly happen but I have pulled my head out long enough to remember those I am indebted to. I wish him a great day and think its wonderful that people like him are around to help out.
Happy to help. There are lots of people here who enjoy sharing their knowledge and experience, and I enjoy being part of it. We all have a common interest in our vintage Hondas, and everyone here has learned something along the way that can be of value to someone else.
 
1 - 9 of 9 Posts
Top