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PT: Exhaust Vincent Head Exhaust Threads

Roslyn

Well Known and Active Website User
Non-VOC Member
I am soon to move my bike into the shed ready to try and fix it and one of the things that need doing is the threads on both heads and any advice as to where to to get them repaired as it will the first time i will have stripped a Vincent engine down by my self without any sort of support.
 

Monkeypants

Well Known and Active Website User
VOC Member
I repaired minor damage to one of these by scraping the threads with an appropriate tpi threading tap. This enlarged things slightly so larger exhaust roses were required. As Bill mentions, there are many variations in size for these.

That repair has been ok for about 60,000 miles or so including a couple of careful exhaust off and on agains.

Glen
 

Bill Thomas

Well Known and Active Website User
VOC Member
I saw the other day, Albervin, Say use 2 washers, I would not,
It leaves less thread to grip, We need all the thread we can get !.
I think I used a thread chaser, To clean the threads, They are cheap to buy,
Also make sure the pipe flange is square to the inside hole, To give max' thread contact,
Never use a spanner till you are sure it's in square.
 

vibrac

Well Known and Active Website User
VOC Member
I put this job with the positioning of push rod ends in rockers as the job I least like doing on a Vin. I find turning backwards helps get the nut square (and some coppa slip). The time to tighten fully is after the first run when engine is hot
Its a job not to do in a hurry which is why on the racer we have stub pipes and springs
 

Robert Watson

Well Known and Active Website User
VOC Member
I have repaired exhaust port threads a couple of ways.

as above I made a tapered mandrel and pushed it through older nuts to tighten up the fits into the ports, these for ones that feel just a bit loose.

next - a local who shall remain unnamed, made a three part tap - the first part is a standard 1 7/8 X 20 TPI tap that is just a few threads long, you can screw this into the existing port, right to the bottom where it picks up well on what is usually the last few remaining good threads in the bottom of the port. It has a timed 20 TPI stem. Down this timed stem goes part number two which is a starting tap at .050 oversize and also timed 20 tpi inside and out. when it has done its job and is removed next goes down a finishing tap made the same way. finally the pilot is removed and the finishing tap taken right to the bottom of the port. Now you have a virtually brand new thread but + .050

here come the fun.

I have made new nuts from scratch that are .050 oversize as one solution for the nuts.
the other one is to make a straight stub that is .050 oversize. Having done this you can now take an old worn out nut and bore it to suit the stub with a couple of thou interference fit, I think I may have stepped the stub at the appropriate length as well, in any case this can then be pressed onto the stub and there you have a new nut, and a little easier that making a new one from scratch. I had worried a little that the flange part of the nut may come loose from the stub and was prepared to make a couple of little lock screws to hold it in place but in many years and many thousands of miles this has not been required.

this can quite easily be done on the bike with only removing the exhaust pipes.
 

Sakura

Well Known and Active Website User
VOC Member
I have repaired exhaust port threads a couple of ways.

as above I made a tapered mandrel and pushed it through older nuts to tighten up the fits into the ports, these for ones that feel just a bit loose.

next - a local who shall remain unnamed, made a three part tap - the first part is a standard 1 7/8 X 20 TPI tap that is just a few threads long, you can screw this into the existing port, right to the bottom where it picks up well on what is usually the last few remaining good threads in the bottom of the port. It has a timed 20 TPI stem. Down this timed stem goes part number two which is a starting tap at .050 oversize and also timed 20 tpi inside and out. when it has done its job and is removed next goes down a finishing tap made the same way. finally the pilot is removed and the finishing tap taken right to the bottom of the port. Now you have a virtually brand new thread but + .050

here come the fun.

I have made new nuts from scratch that are .050 oversize as one solution for the nuts.
the other one is to make a straight stub that is .050 oversize. Having done this you can now take an old worn out nut and bore it to suit the stub with a couple of thou interference fit, I think I may have stepped the stub at the appropriate length as well, in any case this can then be pressed onto the stub and there you have a new nut, and a little easier that making a new one from scratch. I had worried a little that the flange part of the nut may come loose from the stub and was prepared to make a couple of little lock screws to hold it in place but in many years and many thousands of miles this has not been required.

this can quite easily be done on the bike with only removing the exhaust pipes.
My kind of repair!
 

Roslyn

Well Known and Active Website User
Non-VOC Member
How bad is the thread ?, Only the nuts vary a lot in size, Maybe a slightly bigger nut would get you out of trouble ?. Cheers Bill.
I damaged the threads while taking the armour exhaust system on and off crossed threaded one and it did not do up right after and the front one was not the best and managed to messed that one up as the exhaust nut went loose then tight so might have stripped that one put some sealer on them after to just to get them tight and to stay put and not leak when the engine is running.
 

Roslyn

Well Known and Active Website User
Non-VOC Member
I have repaired exhaust port threads a couple of ways.

as above I made a tapered mandrel and pushed it through older nuts to tighten up the fits into the ports, these for ones that feel just a bit loose.

next - a local who shall remain unnamed, made a three part tap - the first part is a standard 1 7/8 X 20 TPI tap that is just a few threads long, you can screw this into the existing port, right to the bottom where it picks up well on what is usually the last few remaining good threads in the bottom of the port. It has a timed 20 TPI stem. Down this timed stem goes part number two which is a starting tap at .050 oversize and also timed 20 tpi inside and out. when it has done its job and is removed next goes down a finishing tap made the same way. finally the pilot is removed and the finishing tap taken right to the bottom of the port. Now you have a virtually brand new thread but + .050

here come the fun.

I have made new nuts from scratch that are .050 oversize as one solution for the nuts.
the other one is to make a straight stub that is .050 oversize. Having done this you can now take an old worn out nut and bore it to suit the stub with a couple of thou interference fit, I think I may have stepped the stub at the appropriate length as well, in any case this can then be pressed onto the stub and there you have a new nut, and a little easier that making a new one from scratch. I had worried a little that the flange part of the nut may come loose from the stub and was prepared to make a couple of little lock screws to hold it in place but in many years and many thousands of miles this has not been required.

this can quite easily be done on the bike with only removing the exhaust pipes.
I do not have a lathe or milling machine just basic hand tools and lots of hammers etc
 

Roslyn

Well Known and Active Website User
Non-VOC Member
I thought the idea was to see how far can you get way with using a bigger hammer and chisel you should have seen how i removed a jammed up ESA on the shadow and used a hacksaw in the process and the mentioned tools.
The original esa cam was so worn out and the sprocket was missing a couple of teeth that is why i bought and fitted a new series D esa and sprocket springs nut etc
 

Sakura

Well Known and Active Website User
VOC Member
I thought the idea was to see how far can you get way with using a bigger hammer and chisel you should have seen how i removed a jammed up ESA on the shadow and used a hacksaw in the process and the mentioned tools.
Well, it's your bike and you're free to try anything you want. I do, however, feel it only it's right to offer a few words of caution and say I think your chances of success are minimal! Please do let us know how you get on, preferably with pictures!
 

Roslyn

Well Known and Active Website User
Non-VOC Member
Well, it's your bike and you're free to try anything you want. I do, however, feel it only it's right to offer a few words of caution and say I think your chances of success are minimal! Please do let us know how you get on, preferably with pictures!
Do not worry the Shadow is in good hands as I know more or less every thing about Vincents read every thing about them even helped my late father working on the bike some times by my self as well I understand the part number system and the difference between models. rode my first Vincent before I passed my test at the age of 16.
 

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