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It's not. I checked my screws today to make sure they weren't set to too few turns after playing with the 45's a few weeks ago and they're where i usually have them. So again i say, the bike is exactly as it was before the tire swap and it didn't do that then. Why would the fuel change w/o changing anything?

In short, bike was riding perfect and never did this before. Then i get a new tire of the same brand and model put on and then it does this. Gotta be something with the wheel/tire/chain. I see no reason why the alignment should be the problem since it's set exactly as it was before. But i'll take Pat's advice anyway and check the alignment with his method. I can't think of anything else. By the way, it's not a surge that causes you to feel the bike surging in forward motion as you decel. You just feel the vibration that comes and goes in a cycle.But the bike decels as smoothly as ever.

are you sure this isn't a cush drive issue?

Probably not Jeff. The cush drive rubber only lessens the shock in the drive train when accelerating/decelerating.

Donnie, please post if the 45s cure your problem?

The cush rubber suprised me actually. With all the things i've read i expected it to be a bit rotted and beaten. But it was like new.

I think i was wrong about one thing.......it's hard to detect, but i believe it DOES do it with the clutch pulled in. So if i'm right about this it much be the Wheel/tire/chain. But it's faint by comparison, so i suppose the engine putting a load on it makes it much more obvious. Tonite i'll finally have time to try Pat's alignment method. Even tho the notches are where they were before the tire swap i'm wondering if the adjusters somewho got elongated where the axl goes thru. I noticed they looked out of round so i'm thinking they get that way normally and is probably what causes the notches to be off. Anyways, i'll check it tonite. If that doesn't work i believe i'm going to buy a chain because i don't know what else i can do.

Pat, you were right about the alignment notches. i used the frame to measure to the center of the axl ends and it was off by almost a 1/4". Unfortunatly that didn't fix the problem. It's got to be a stretched chain. theres just nothing else i think it could be. I don't know why i didn't notice it before the tire swap, but somehow i must have simply not felt it. I'm about to go out and lift the bike so i can turn the wheel and check for tight spots in the chain. Are the stock chains very cheap? At 8.5k it just doesn't seem like it should already be shot, especially since i don't ride hard most of the time.

Well, i may be talking to myself here, but i just checked and the chain is definatly stretched. So it looks like after spending $260 for tires i'm not about to spend another 3 bills for chain, chain breaker and sprockets. Arg ! Wonder if i can keep my 17 front thats only about 3k old. Anyone have a recomendation for the best chain and sprockets without spending top dollar?

Since you're about to spend the three big ones, spend four more and get the belt drive from Brent and fuggetabutit. The ratio is the same as a 17½ tooth front sprocket.

So, did you ever find the cause of the vibration? I have the exact same vibration and, unfortunately, I have learned to live with it.
I put air in the tires one day and it started happening right then and hasn't left. I adjusted the chain, the tire alignment all to no avail. Would love to get it to go away.
frank

This vibration thing seems to be ketchy. I have noticed a vibration on de-cel at slow speeds also. I can't figure it out either.
Scott

I'll be purchasing a 2006 SM very soon, and have been doing a lot of research at all the Triumph forums, etc...I'm certainly no expert, but I'll throw in a thought or two, maybe it'll help. This premature chain wear is a concern...perhaps dazco's experience is somewhat isolated as I've read of some riders that are getting 30-40,000 kms on their bikes without chain stretching, but maybe THEY are the exception. Anyway, proper regular lubrication of the chain aside, I wonder if anyone posting that they are getting this vibration had also earler switched their front sprockets to a higher tooth-count, and if so, was the rear wheel aligned using the notches (inaccurate), or by measurement from the swingarm center bolt (accurate)? This vibration may not be noticable until after a few thousand kms, which would allow the wear of the chain and sprockets. If I am not mistaken, Triumph uses X-ring chains as stock equipment. There are obvious benefits, however, X-ring chains have flat-sided seals, as explained at http://www.quality-cycle.com/truth_about_motorcycle_chains.htm . I quote,

"Is a X-Ring Type chain better than a “standard type” O-ring chain??? Much, much better because it’s seals are flat sided, which means the seals have a much greater “contact patch” with the Side Plates. Since the seals are flat, it allows for multiple “sealing lips”......each one acting like a separate seal. As one “Lip” starts to leak the lubrication the 2nd lip seals it in....& because X-Rings are flat shaped on the top & bottom too " .

I would reason that because the flat-sided seals provide greater contact area, these X-ring chains would be more prone to failure from a rear wheel mis-alignment. In other words, the chain will wear/stretch along one edge quicker than the other, and the chain could seize, break, and cause extensive damage to the bike, if not the rider. An O-ring chain might be more forgiving, but there are inherent problems with their design, too. I used to ride a lot of bikes with O-ring chains in the past, and never had a stretching issue.
And, since I mentioned lubrication above, what chain lube do you prefer? Is a chain wax better than than a chain oil?
Your experience and advice is appreciatted.
thanks

OOPS...previous post, above, was meant for "cyclic vibration" subject matter. You can disregard here.
Sorry, folks

S'all cool.. I just decided to split the thread at the point where the header was changed.