vibration in 5th when giving it some beans

hi all,

sorry about all the questions and concerns, but the bike is new to me so just want to make sure its not going to go pop on me...

so if I'm riding along the motorway in 5th everything is fine. if I drop down to 4th to pick up a bit of speed and then into 5th to hold the newly gained speed everything is fine. but if I stay in 5th and accelerate from say 90mph to 110mph there seems to be a bit of vibration. if I stop accelerating and drop down to 90 or 100 its fine, and smooth.

is this normal or is there something I should check pretty sharpish?


also, what should the top speed be of an 02 plate st1300a2 (bluey green in colour as I notice that seems to have some unofficial bearing on speed )

thanks in advance,

Could be a tire issue.. some of those only show up at low, med or high speeds. I had a bad brand new Dunlop RoadStupid tire that would bounce between 75 and 90 but seemed okay at lower or higher speeds.

I've just had new tyres fitted and the wheels balanced, checked and replaced bearings as needed too - did the same before and after changes

seems more engine or drive to me, if I open the throttle in 5th it vibrates let off back to where it was stops again :S

tb, try it with different rear shock damping and/or preload settings. That may change the amount of vibrations, but doesn't find the source. I too think it is likely tires because they flex under acceleration differntly than when running at constant speed or during deceleration. You can test that with changing tire pressures. If none of that changes the behavior, do a driveline u-joint sound check.

What grade fuel do you use?

I don't think it's the tyres if it only does it in top gear, although I would never have thought you would be "lugging" the engine at those speeds.... depends on amount of throttle applied I guess......

From the OP's original discription of it only occurring when gassing it in 5th and not when dropping to 4th and changing to 5th to maintain the same speed it sounds like he's lugging the engine.

I agree with First that lugging wouldn't/shouldn't be a problem at those speeds. And I thought that was more of a problem with carbureted bikes than FI bikes.

We don't know much about the bike but could it be in need of a tune-up as in plugs and air cleaner? I don't recall for sure but roll-on throttle in that range never gave me any signs of lugging.

And are you running Premium gas? Could that be pre-ignition?

This does sound like a gas and or lugging problem to me, the ST likes the RPM's above 4000.

Lugging at 90 to 110 mph? Seems not...Thats 5100 to 6300 rpm, if memory serves.

BakerBoy said:

Lugging at 90 to 110 mph? Seems not...Thats 5100 to 6300 rpm, if memory serves.

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Hey I like to lug my bike at that speed all the time!!

Lugging isn't strictly a function of RPM. It's power vs load vs throttle opening. I'm not saying it has to be lugging. But if the bike had some problem producing normal HP at a higher RPM the symptom would be the same as it is at a lower RPM.

That's why I asked about engine state of tune. Are the plugs and air cleaner in good shape? What's the mileage on the bike and when what the last service done and what did that entail?

The other thing is pre-ignition or engine knock. Was the bike filled with Regular? It's also most noticeable when the engine under load with a lot of throttle. In both cases the onset of the problem and the way the OP remedies it would be the same.

tbullivant said:

but if I stay in 5th and accelerate from say 90mph to 110mph there seems to be a bit of vibration.

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Where do you feel this vibration?

I had a vibration problem occur a couple of years ago with similar symptoms which seemed to come from the engine. It only occurred once under hard acceleration but a month later, on one short trip, the problem reappeared but the vibration had morphed into random misfiring on hard acceleration. Then it was fine for another month. When it reappeared, it was worse. Suggested causes were similar to some that I see here. The problem eventually revealed itself to be due to fuel delivery issues.

Here is a string of threads that document my effort to track down what begin as a vibration problem. I seriously doubt what's going on with your bike is as serious as it was with mine but your vibration could be as simple as the opening salvo of a fuel pump going bonkers. A bad fuel pump or clogged fuel filter is something to consider along with all the other suggestions. :

This is the thread where I describe the vibration that began my ordeal:
https://www.st-owners.com/forums/showthread.php?120563-ST13-Engine-Vibration

Here is where it clearly began to misfire, rather than just vibrating:
https://www.st-owners.com/forums/showthread.php?122391-Sudden-Engine-problem!

And here is how I discovered the root of the problem:
https://www.st-owners.com/forums/showthread.php?123140-It-Just-Keeps-Getting-Better!!!!!!

Lastly, here is how I fixed the problem:
https://www.st-owners.com/forums/showthread.php?124281-ST1300-Lower-Fuel-Tank-Replacement-quot-How-To-quot-Guide

Thanks Mick, coincidentally I was reading about your troubles yesterday when searching the forums for similar issues. I get the vibration under acceleration in 5th felt up through the bars and the whole front end. Im going to inspect the tanks, pumps and filter and do the clutch completely. Just having the time. Cheers for your help

tbullivant said:

I get the vibration under acceleration in 5th felt up through the bars and the whole front end.

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If that's where you are feeling it, then it's different from what I felt and probably not related to the engine. My vibrations were felt through the seat and I think(?) foot pegs.

I once had an Avon front tire on an ST1100 that was so unbalanced from the factory that the installers had to use a ton of weights to dial it in. While on a trip, one of the weight went flying off and from that point on, the front end would vibrate and dance a little as I got over 80 mph. Having the balance checked on your front tire would be an easy & cheap thing to do to check it off as a possible cause.

good call, will get them to re-balance it.

If it was the tyre it wouldn't matter where the throttle was or which gear it was in....

Best pull the final drive and make sure your not making metal. Could be a lack of grease on the final drive splines? Guessing here but I've notice a bit of vibration there in the past. I've removed and greased my final drive at 50,000 miles.
I know there's no maintenance interval check on the final drive but I'm gonna pull it again at 85K in concert with a rear tire change for another check and re-grease.

freetime2247 said:

Best pull the final drive and make sure your not making metal. Could be a lack of grease on the final drive splines? Guessing here but I've notice a bit of vibration there in the past. I've removed and greased my final drive at 50,000 miles.
I know there's no maintenance interval check on the final drive but I'm gonna pull it again at 85K in concert with a rear tire change for another check and re-grease.

Click to expand...

Just pulled the final gear drive from the drive shaft and it was really dry. Had some remnants of grease lying below in the swingarm. I'm suspecting it's dry at the yoke (u-joint) end too. I can't pull the driveshaft off the front splines. Maybe the yoke is okay after all? We'll see once it's pulled out.

STurgisSTeele said:

Just pulled the final gear drive from the drive shaft and it was really dry. Had some remnants of grease lying below in the swingarm.

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Did you have the same symptoms as the OP?

ST Gui said:

Did you have the same symptoms as the OP?

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Not exactly. I'm having vibration all the time. Especially bad when on the throttle.
I just pulled the driveshaft off and found the yoke cup very dry and discoloration on the yoke itself, as if it got too hot.

Also found the driveshaft joint with a little wear and the o-ring must have allowed moisture inside.