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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Godet Modified Steering Stem
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<blockquote data-quote="davidd" data-source="post: 104908" data-attributes="member: 1177"><p>I thought that it was best to make some comments on Godet's modified steering stem in a separate post because there is a slightly complicated history.</p><p></p><p>Back in 2014 I was often in contact with Patrick regarding certain aspects of the design of the new Grey Flash. In one email he said that he had given up on trying to get an 1-7/16" original carb because he could not find one, even to borrow. I told him that he needed to find one because it was critical to the project. I explained it was critical because from a competitive point of view it was a mistake to give up the extra 4 mm of choke size on a converted street bike that is competing against bikes that were specifically designed for racing. The big carb that was ordered from Amal by Phil Vincent specifically for the Grey Flash was one of the few advantages that made a Grey Flash faster than a Comet. To that end, I asked Carleton Palmer to provide Patrick with one of the original big carbs, which he did.</p><p></p><p>As an aside to one of our emails about the carb, Patrick said that Bruno Leroy had a horrible first running of the new Flash at Cadwell. Bruno reported to Patrick that the bike was wobbling and jumping into the air every time he entered a corner. Patrick stated that he had to solve this handling problem, but he did not know exactly what the cause was. Of course, I knew exactly what the cause was and told him that I could solve the problem: he was using a very powerful front brake, which caused the front end to seize under braking. This could only be cured with a modified steering stem.</p><p></p><p>I contacted Norman to see if he had a spare steering stem and he did not. He had kept one for his own machine, but at that time I think that he was not certain that there would be any more batches. It was only three weeks before the IOM TT and time was of the essence. I knew that Pat Manning had purchased two of these stems from Norman, so I told Norman not to worry, I would send one from the US. In fact, I had Patrick's UPS account number to ship the carb. I packed up one of Pat Manning's stems and sent it to Patrick. </p><p></p><p>It turned out that the stem calmed down the wild nature of the handling under braking and performed very well at the TT. This was reported on this forum and I was very happy for all concerned with the modified steering stem project. At the time, Greg Brillus had proved the concept on his twin racer, but Patrick, who was experiencing the problem, confirmed that this as a true cure. Because the stem given to Patrick was a loaner, I asked to get it back. Patrick took it off and sent it. However, I had given Patrick a mechanical drawing of my modified steering stem right from the start. My steering stem cures the braking problem like the JE stem, but the geometry is slightly different and the Girdraulic performs differently. Both geometries get rid of the braking problem.</p><p></p><p>Jumping to 2018 and I was helping David Tompkins with his racing efforts. David was not using a modified steering stem and had a crash that I thought might be caused by the geometry problem. When that happened, I sent him one of my steering stems. David was hesitant to try it and quizzed me hard about it. He wrote Patrick asking about the steering stem Patrick makes. Patrick replied:</p><p></p><p>"I have manufactured a batch of aluminum revised stems exact to David's drawing." August 8, 2018. This is Patrick's photo:</p><p>[ATTACH=full]26116[/ATTACH]</p><p>Thus, the stem looks like the JE stem, but has my geometry. I was a little surprised by this, but pleased that the geometry had worked so well for Patrick. This stem was the same that was used on the Gallur Grey Flash ridden by Cam Donald. I posted that article on the forum here in the first post:</p><p></p><p>[URL unfurl="true"]https://www.vincentownersclub.co.uk/threads/cam-donalds-review-of-the-new-grey-flash-2018.10342/[/URL]</p><p></p><p>Because Patrick made my stem geometry look like the JE stem, you can't always judge this book by its cover. If you see what looks like a JE stem It could be a DD stem if it came from Patrick. I have given the mechanical drawing of my stem to many folks. To date, Patrick was the only manufacturer to make it. I made a small batch for my use. I spent a lot of time making the stem work the way I wanted it to work decades ago. However, both stem designs fix the problem and Norman has been very generous with his efforts producing the JE stem. </p><p></p><p>This was a slightly complicated bit of history, but it is a slightly complicated problem with the Girdraulic.</p><p></p><p>David</p></blockquote><p></p>
[QUOTE="davidd, post: 104908, member: 1177"] I thought that it was best to make some comments on Godet's modified steering stem in a separate post because there is a slightly complicated history. Back in 2014 I was often in contact with Patrick regarding certain aspects of the design of the new Grey Flash. In one email he said that he had given up on trying to get an 1-7/16" original carb because he could not find one, even to borrow. I told him that he needed to find one because it was critical to the project. I explained it was critical because from a competitive point of view it was a mistake to give up the extra 4 mm of choke size on a converted street bike that is competing against bikes that were specifically designed for racing. The big carb that was ordered from Amal by Phil Vincent specifically for the Grey Flash was one of the few advantages that made a Grey Flash faster than a Comet. To that end, I asked Carleton Palmer to provide Patrick with one of the original big carbs, which he did. As an aside to one of our emails about the carb, Patrick said that Bruno Leroy had a horrible first running of the new Flash at Cadwell. Bruno reported to Patrick that the bike was wobbling and jumping into the air every time he entered a corner. Patrick stated that he had to solve this handling problem, but he did not know exactly what the cause was. Of course, I knew exactly what the cause was and told him that I could solve the problem: he was using a very powerful front brake, which caused the front end to seize under braking. This could only be cured with a modified steering stem. I contacted Norman to see if he had a spare steering stem and he did not. He had kept one for his own machine, but at that time I think that he was not certain that there would be any more batches. It was only three weeks before the IOM TT and time was of the essence. I knew that Pat Manning had purchased two of these stems from Norman, so I told Norman not to worry, I would send one from the US. In fact, I had Patrick's UPS account number to ship the carb. I packed up one of Pat Manning's stems and sent it to Patrick. It turned out that the stem calmed down the wild nature of the handling under braking and performed very well at the TT. This was reported on this forum and I was very happy for all concerned with the modified steering stem project. At the time, Greg Brillus had proved the concept on his twin racer, but Patrick, who was experiencing the problem, confirmed that this as a true cure. Because the stem given to Patrick was a loaner, I asked to get it back. Patrick took it off and sent it. However, I had given Patrick a mechanical drawing of my modified steering stem right from the start. My steering stem cures the braking problem like the JE stem, but the geometry is slightly different and the Girdraulic performs differently. Both geometries get rid of the braking problem. Jumping to 2018 and I was helping David Tompkins with his racing efforts. David was not using a modified steering stem and had a crash that I thought might be caused by the geometry problem. When that happened, I sent him one of my steering stems. David was hesitant to try it and quizzed me hard about it. He wrote Patrick asking about the steering stem Patrick makes. Patrick replied: "I have manufactured a batch of aluminum revised stems exact to David's drawing." August 8, 2018. This is Patrick's photo: [ATTACH type="full" alt="26116"]26116[/ATTACH] Thus, the stem looks like the JE stem, but has my geometry. I was a little surprised by this, but pleased that the geometry had worked so well for Patrick. This stem was the same that was used on the Gallur Grey Flash ridden by Cam Donald. I posted that article on the forum here in the first post: [URL unfurl="true"]https://www.vincentownersclub.co.uk/threads/cam-donalds-review-of-the-new-grey-flash-2018.10342/[/URL] Because Patrick made my stem geometry look like the JE stem, you can't always judge this book by its cover. If you see what looks like a JE stem It could be a DD stem if it came from Patrick. I have given the mechanical drawing of my stem to many folks. To date, Patrick was the only manufacturer to make it. I made a small batch for my use. I spent a lot of time making the stem work the way I wanted it to work decades ago. However, both stem designs fix the problem and Norman has been very generous with his efforts producing the JE stem. This was a slightly complicated bit of history, but it is a slightly complicated problem with the Girdraulic. David [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Godet Modified Steering Stem
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