Thanks OGR. This morning the engine bar was also taken out. Didn't see any cracks etc. Rode with 1/3 tank and the bike was definitely smoother, even in the mysterious range of 3.5-4.5k rpm.

Come to think of it, I think I should use the word "shaking" as opposed to "vibrations" to describe this rpm range. I know single cylinder vibrates more, and I know it vibrates even more when reaching top of its power/torque rpm, but that range mentioned above I would call "shaking". Yes, I am going to be relentless with this issue here.

So being cautiously optimistic, I tanked it up, and that "shaking" returns at that mysterious rpm range. Mind you this shaking is slightly better than when the broken bashplate was there. I cannot help to think that the extra weight must be sitting on somewhere along the frame that causes the shaking, but below that maximum weight the tank no longer touches that spot, which explains why only when full tank the shaking occurs. At least that's my theory. The immediate guess is may be some gummie somewhere between the frame and the tank would help. But then it may have to do with the "acoustic" effect of all the vibrations and screws combined, which would be a pain to figure out if it's even possible to figure out. The shortcut solution may be bar-end weights, but I've read those who have them still experience the same problem, though they get used to it or ignore it.

As far as I understand from the service manual, the tank connects to the frame at two points: two screws to a mount under the seat, and two long screws at the front behind the upper tank protectors. The frame connects to the steering only at one point, the set of steering nuts and bolts and washers. I am thinking right now putting some gummie between the lower clamp of the handlebar and where it sits on the fork mount frame. What do you guys think? Dangerous mod, useless, etc.? Has anyone taken the tank off to identify where the tank is touching the frame, and where the weight from a full tank might weigh it down to the point of touching the frame?

Well after reading this thread about cracks and breaks in engine bars and bash plates I thought I better check mine .......... all Ok!
But I did find this stuck in the downtube part of the frame (just behind where the oil drain plug is situated) ............

http://i144.photobucket.com/albums/r...Star/021-1.jpg

http://i144.photobucket.com/albums/r...geStar/022.jpg

I'm pretty certain I know what it is but who else wants to tell me?

Barry.

Is it a C*ck ring?

Well that was my first thought but after trying it out I found it was too small! :HappyRoll_ANPIUI:

So what is it?

Your C*ck was?

looks like an exhaust gasket to me :p

Yes, I reckon that's what it is!
I think when the bike was assembled at the dealers (or would it be at the factory?) someone must have dropped one of the gaskets off the header pipes when fitting it and obviously couldn't find it so they put another one on.
They must have put another one on because the exhaust doesn't leak!

Barry.

still no news from my dealer about the cracked/broken bashplate mount, that's seriously taking the piss.

I discovered 2 days ago that the front right engine gard mount (behind the R/R) was cracked (as I half expected unfortunately)

I know it's a known problem...

looks like another reason to complain to them.... anyone knows who to contact in Yamaha UK ??