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FJR Motorcycle Forums
Technical & Mechanical Problems
The Really, Definitely Completely Un-Authorized TBS
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<blockquote data-quote="3dogs" data-source="post: 722518" data-attributes="member: 424"><p>The <a href="https://www.fjrforum.com/forum//index.php?showtopic=23101&hl=" target="_blank">TB Sync</a> procedure (fifth post down) that I wrote calls for gently accelerating the engine up to 4k (not revving the piss out of the poor engine that was mentioned) to balance the throttle plates. There are several problems with syncing the throttle blades at idle as outlined in this thread.</p><p></p><p>When you ride down the Interstate at 70mph the throttle plates are not closed but open part way. Getting them in sync at idle doesn't mean that they are synced/balanced at part throttle (the vast majority of engine operation takes place at part throttle). Accelerating the engine to balance the individual cylinder air flow will be a closer simulation to actual riding conditions than operating the engine at idle with minimum air flow. In fact if you sync the cylinders at idle and then rev the engine you'll find that they are not in balance. I've tried this at idle and the "revving the piss out of the engine" produces a better sync or balance.</p><p></p><p>Also, when holding the throttle open with a Vista Cruise, or by hand, the cylinders will never seem in balance because there is no load on the engine. Ideally the best sync method would be to use a dyno. With the engine loaded and maintaining real road speed the throttle can be synced accurately under real riding conditions--If you don't have a dyno use the acceleration method and you can get close to the same results. Revving the engine to sync fuel delivery is a method that has been used for years (before EFI) on carburetors both on cars and motorcycles and still is practiced today on carbed and EFI fuel systems.</p></blockquote><p></p>
[QUOTE="3dogs, post: 722518, member: 424"] The [URL="https://www.fjrforum.com/forum//index.php?showtopic=23101&hl="]TB Sync[/URL] procedure (fifth post down) that I wrote calls for gently accelerating the engine up to 4k (not revving the piss out of the poor engine that was mentioned) to balance the throttle plates. There are several problems with syncing the throttle blades at idle as outlined in this thread. When you ride down the Interstate at 70mph the throttle plates are not closed but open part way. Getting them in sync at idle doesn't mean that they are synced/balanced at part throttle (the vast majority of engine operation takes place at part throttle). Accelerating the engine to balance the individual cylinder air flow will be a closer simulation to actual riding conditions than operating the engine at idle with minimum air flow. In fact if you sync the cylinders at idle and then rev the engine you'll find that they are not in balance. I've tried this at idle and the "revving the piss out of the engine" produces a better sync or balance. Also, when holding the throttle open with a Vista Cruise, or by hand, the cylinders will never seem in balance because there is no load on the engine. Ideally the best sync method would be to use a dyno. With the engine loaded and maintaining real road speed the throttle can be synced accurately under real riding conditions--If you don't have a dyno use the acceleration method and you can get close to the same results. Revving the engine to sync fuel delivery is a method that has been used for years (before EFI) on carburetors both on cars and motorcycles and still is practiced today on carbed and EFI fuel systems. [/QUOTE]
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FJR Motorcycle Forums
Technical & Mechanical Problems
The Really, Definitely Completely Un-Authorized TBS
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