Join Date: May 2003
Location: Fairfax Station, VA
Motorcycle: 2007 GSX-R 750, 1989 GSX-R 1100, 2002 Yamaha V-Star 1100 Custom
Re: 1991 GSXR 750 issue
As I read your post and when you began by saying "the whole bike shakes" on WOT regardless of gear, at first I thought you might be dealing with a fuel delivery issue through the mains, but then later when you mention "clank", I became concerned that it is either something other than your chain and more serious or a combination of more than one thing going on.
Is it possible that at WOT the bike is shuddering because the fuel delivery circuit through one or more of the carbs is dirty and the bike is shaking/sputtering because of that and therefore the loose chain is clanking around in response to a very disruptive fuel flow? In the past, I have had such an issue with the bike shaking under WOT in any gear and it was indeed a carb issue that was resolved with a cleaning/rebuild. Since your bike is new to you and the condition and history of the carb maintenance may not be known, I bring this possibility up as a potential issue contributing to your situation because the shuddering sounds very similar to what I experienced, although I did not have any clanking. Therefore you may have two things going on here.
As mentioned already, check and/or adjust your chain to specs including inspecting the condition of both sprockets. If there is no adjustment or replacements necessary, it is likely not the chain clanking around. If the chain was very loose or the sprockets needed replacement, test ride the bike again and see what is happening. If the shuddering still causes a clank, then it is likely inside the cases. However, the shuddering cause still needs to to be resolved and ensuring that the fuel delivery system is not being restricted at WOT is your next thing to look into and correct if necessary. Once that is established, test ride the bike again. If you are still getting a shuddering and/or clank or just now the clank, then I'm afraid you have a serious issue within the cases that likely warrants the bike inoperable until the issue is resolved by splitting the cases and inspecting everything.
During these test rides, a clank that is coming from within the cases is serious and may be dangerous and catastrophic. Please be careful and once you hear that noise, immediately slow down and nurse the bike back home.
"The price of freedom is eternal vigilance." Thomas Jefferson