Lost valve nut

Gregthebunny

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hello,

I am looking for some guidance. The nut on the rocker valve adjusting screw for my 1975 has backed itself off and is somewhere in the top half of the engine. I know it is not in the bottom half because I have started the engine to make sure it still ran correctly (I know, super risky). I was wondering how the best way to retrieve the nut from the engine would be, and how far it could have made it into the engine. Should I check the oil sump first or start at the top end? I have never pulled an engine off a bike before and was also wondering how much time it typically takes. Any help would be much appreciated and helpful.
 
Many, many years ago I lost a circlip in the engine of my BSA Bantam. What could go wrong I thought. I soon found out when it came up the transfer port and said 'hello' to the piston.

My advice is that you need to find it before running the engine even if it means you need to dismantle it.
As Mr Bosco suggests try using a magnet but if that fails it will be time to get the spanners out.
 
Get a torch and have a good look, take the other valve cover off and shine the light across inside as well. A bent bit of wire or welding rod can also work wonders.
I have found two on separate occasions in the number 1 inlet , the nut was by the spring both times. Both times the motor was being taken past red line.
What cylinder and valve lost its nut on yours? Just curious.
 
Hi, Greg and welcome to the forum. I agree with the above comments that you need to find the errant nut before running the engine. Unfortunately, the cam box cover won't lift off with engine in frame - unless your frame is some kind of high-neck chopper?

The suggestions of taking off the valve covers, having a good look with a torch, maybe a small dental mirror, fishing about with a flexible magnetic probe is about as good as it gets. If you don't find the nut that way, might be worth dropping the sump and oil filter and taking a look to see if has dropped down the camchain tunnel? But otherwise, you are looking at taking the engine out for a strip search.

How long does that take? The answer depends on how much experience you have. From you post, that might not be a lot. Also, what tools you have, how much experience with tools, and other facilities you have. For example, it is easier to pull the engine if you have a garage or workshop than if you need to work in the street. It is a heavy engine and to lift it out you will need to be strong, or have somebody to help with the heavy lifting, or a block & tackle mounted to an overhead beam.

Many years ago, I pulled the engine out of a Yamaha SR500, stripped it, replaced a gearbox shim, re-assembled the engine and had it back in the bike and running in one day, but that was an engine which I was unlucky enough to be familiar with working on. You would need to factor a couple of days, with the timescale going up for any lack of tools, facilities, experience, people to help with lifting and so forth.

But, if you need to get in there, there is a lot of help and experience available from the good people hereabouts.

Hope this helps, Good Luck, Raymond
 
Open intake valve cover on that side check behind the cam, where that nut tends to end up.
Also a cam lobe tends to smash it into an oil fence behind the cam breaking off the fence.
or if you are unlucky it punches a hole thrrough the floor under the cam letting the oil free from the motor.
 
"having a good look with a torch"

Be aware that in some parts of the world a "torch" is what they call a flashlight! Don't want you to burn your bike down trying to find the nut!
Years ago I worked for an Aussie company based out of Griffith NSW. A couple of the boys from the mothership were over here in the states at an outfit in Cali with me doing a large rebuild. One of the maintenance guys told us he had been hearing a noise in the bottom of one of the vessels. One of the Aussies told him "no worries we'll get a torch and have a look after lunch". We came back from lunch to find the maintenance guy firing up an oxy/acetylene rig about to cut a hole in the bottom of a .5 million dollar SS extraction vessel. :lmao: We had to explain to him that "torch" was a flashlight in Aussie speak...
 
All the suggestions above are good ones. Let me also suggest using a borescope to snoop around in the head and sump. You may be able to rent or borrow one from a local auto parts store.
 
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