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This thread started on 11th July when I discovered that my ’47 UL wasn’t running right. Poor performance and spark plugs that were a different colour were the symptoms.
Folks on this site suggested I had a manifold air leak
It took me while to build a manifold leak test tool but the diagnosis of manifold air leak proved spot on. Unfortunately when I came to remove the manifold nut to the rear cylinder (where the leak was) it became clear that the intake nipple was also loose and would need replacing. See follow up post of 14th September.
Having asked about the task on the forum it was clear that this was not going to be a simple job and I viewed the prospect with some trepidation. In fact my first thought was to get some professional help. In the end I went ahead myself reasoning that so long as I did nothing that would damage the cylinder any mistake could be rectified.
With acknowledgement to those on this forum (especially Cotton and Big Lake Bob) for their tips and advice this is how I got on. I hope it assist others in the same position:
The problem I had was that the old nipple had not been set properly. The locating rivet hole had obviously worn oversize and a non standard brass rivet inserted from the outside of the cylinder and just peened over to seal the hole. Looked at from the inside of the intake the rivet was clearly loose and hence the nipple was free to move if any pressure was exerted on it such as when loosening the manifold nut. Once I had ground off the peened end I was able to knock out the old rivet without difficulty.
I did not try and unscrew the nipple from the cylinder. It felt as though it would have come right out but followed the advice that this might damage the internal threads. Instead I (very) carefully ground through the old nipple with a Dremel and diamond tipped bit. It was tedious but worth the effort. The old nipple eventually fell out and the intake internal threads remained undamaged and actually seemed in good shape.
I had secured a new Colony nipple and a packet of locating rivets
I used JB weld High Steel to build up the internal diameter of the rivet locating hole in the side of the cylinder. I just worked it in a little at a time until I could just about push the new pin through and it was a good tight fit at both ends. This was especially tricky on the inside diameter of the intake as I didn’t want to get the JB weld on the threads. I kept screwing the new nipple in and out as I worked to ensure that the threads were kept clear.
I had a number of options for sealant. JB weld epoxy, Permatex and Gasoil were all recommended as provided the necessary seal but being resistant to gas. I felt the epoxy would create a permanent join and didn’t really want that. In the end I opted for the Permatex. The sealant was applied and the new nipple located onto the cylinder threads and tightened down.
I used a drill press to insert a bit through the hole on the side of the cylinder and drill through the new nipple. I used a slightly smaller bit than the diameter of the rivet and then gently reamed it out until the rivet could just be inserted but remained a good tight fit. I then smothered the hole and new rivet with more Permatex and finally located it in position.
In order to lock the rivet in place to enable the top to be peened I used a length of 1 ¼ inch round steel bar. The internal diameter of the nipple is a little larger but when you account for the rivet head as well I just needed to grind a flat spot to the end of the bar before it would slide in and lock the bottom of the rivet in place.
While this was being done I had sent my manifold to Mullie Motors in Amsterdam to have new peek seals fitted. They did a great job.
When back together I pressure tested the manifold again. All seemed air tight.
I got the bike back on the road last weekend and just had a shake down ride of maybe 5 or 6 miles to make sure everything was ok.
When the engine had cooled I pulled the plugs again. See the photos attached to this thread. The carb had not been adjusted at all since the shots posted in July although next time I take the bike out I will lean it out one notch.
It has taken me while to get this job done but I only get a few hours each weekend to work on the bike. On this occasion I think it was a good thing. This is not a job that can be hurried (not for me at least) and the delays enabled me to think through and plan each step and what I would need by way of tools, parts etc.
Martin
This thread started on 11th July when I discovered that my ’47 UL wasn’t running right. Poor performance and spark plugs that were a different colour were the symptoms.
Folks on this site suggested I had a manifold air leak
It took me while to build a manifold leak test tool but the diagnosis of manifold air leak proved spot on. Unfortunately when I came to remove the manifold nut to the rear cylinder (where the leak was) it became clear that the intake nipple was also loose and would need replacing. See follow up post of 14th September.
Having asked about the task on the forum it was clear that this was not going to be a simple job and I viewed the prospect with some trepidation. In fact my first thought was to get some professional help. In the end I went ahead myself reasoning that so long as I did nothing that would damage the cylinder any mistake could be rectified.
With acknowledgement to those on this forum (especially Cotton and Big Lake Bob) for their tips and advice this is how I got on. I hope it assist others in the same position:
The problem I had was that the old nipple had not been set properly. The locating rivet hole had obviously worn oversize and a non standard brass rivet inserted from the outside of the cylinder and just peened over to seal the hole. Looked at from the inside of the intake the rivet was clearly loose and hence the nipple was free to move if any pressure was exerted on it such as when loosening the manifold nut. Once I had ground off the peened end I was able to knock out the old rivet without difficulty.
I did not try and unscrew the nipple from the cylinder. It felt as though it would have come right out but followed the advice that this might damage the internal threads. Instead I (very) carefully ground through the old nipple with a Dremel and diamond tipped bit. It was tedious but worth the effort. The old nipple eventually fell out and the intake internal threads remained undamaged and actually seemed in good shape.
I had secured a new Colony nipple and a packet of locating rivets
I used JB weld High Steel to build up the internal diameter of the rivet locating hole in the side of the cylinder. I just worked it in a little at a time until I could just about push the new pin through and it was a good tight fit at both ends. This was especially tricky on the inside diameter of the intake as I didn’t want to get the JB weld on the threads. I kept screwing the new nipple in and out as I worked to ensure that the threads were kept clear.
I had a number of options for sealant. JB weld epoxy, Permatex and Gasoil were all recommended as provided the necessary seal but being resistant to gas. I felt the epoxy would create a permanent join and didn’t really want that. In the end I opted for the Permatex. The sealant was applied and the new nipple located onto the cylinder threads and tightened down.
I used a drill press to insert a bit through the hole on the side of the cylinder and drill through the new nipple. I used a slightly smaller bit than the diameter of the rivet and then gently reamed it out until the rivet could just be inserted but remained a good tight fit. I then smothered the hole and new rivet with more Permatex and finally located it in position.
In order to lock the rivet in place to enable the top to be peened I used a length of 1 ¼ inch round steel bar. The internal diameter of the nipple is a little larger but when you account for the rivet head as well I just needed to grind a flat spot to the end of the bar before it would slide in and lock the bottom of the rivet in place.
While this was being done I had sent my manifold to Mullie Motors in Amsterdam to have new peek seals fitted. They did a great job.
When back together I pressure tested the manifold again. All seemed air tight.
I got the bike back on the road last weekend and just had a shake down ride of maybe 5 or 6 miles to make sure everything was ok.
When the engine had cooled I pulled the plugs again. See the photos attached to this thread. The carb had not been adjusted at all since the shots posted in July although next time I take the bike out I will lean it out one notch.
It has taken me while to get this job done but I only get a few hours each weekend to work on the bike. On this occasion I think it was a good thing. This is not a job that can be hurried (not for me at least) and the delays enabled me to think through and plan each step and what I would need by way of tools, parts etc.
Martin
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