1150 motor and a lot of vibration 5,000+ RPM

[CivilRock]

I searched "1150 Vibration" and found a ton of threads. Here are some of the titles:
"GS 1150 - Prone to vibration?"
"1150 vibrations, holy crap."
"Hand falling asleep at throttle"
"buzzzzzzzzzzz"
"1984 GS1150ES Vibrates a lot on highway..."
"Design change GS1150 to improve vibrations?"
"Dynojet Kits for 1150's and Buzzing Handle Bar"

And they go on and on...

I'm going to go out on a limb and guess that it's a common problem. And it seems that most of the solutions end up with carb sync suggestions. The resounding advice is that the 1150 is very sensitive to carb sync, and sync them at 4500 RPM (with a fan on the bike) to help with high RPM vibes.

So here's my problem: My RS38 carbs can't be synced while the bike is running. When I first got the carbs I sat down to sync them and couldn't find the adjustments. Then I read the manual and found out that they're adjusted under the top caps, which prevent you from adjusting them while the bike is running. Mikuni recommends to mechanically sync all smoothbore carbs and adjusting them for idle.

I first need to confirm that the sync is the problem. I'm going to assume that with the throttle wide open, that high RPM vibrations should disappear, right? In my head, if the sync is the problem, it would show it's head the most at high RPM and with little throttle openings. It's just hard to find a place to do that without going 3x over the speed limit.

Is there an easier way to get rid of this high RPM vibration? It's not just uncomfortable, it's worrisome. The mirrors don't just vibrate, but the whole instrument cluster vibrates. I can hear something resonating in the headlight when it's really bad. I feel like it's going to crack parts and shake bolts loose. It's so weird, because from idle to 5,000 RPM it's like butter smooth.

-Kevin

 

[Rob S.]

That is weird. I just got back from a short spin, probably never got much over 6k rpm, and the thing that kept occurring to me was, "smooth."

 

[CivilRock]

Yea. That's what I always said with my 1100 motor and stock carbs.

 

[UncleMike]

No way around it - the carbs on the 1150 need to be dialed in. I like to be quite precise with my valves as well.

 

[blowerbike]

some cranks was closer than others when they left the factory.
my 1150 was buzzy pretty bad.
my brothers 1150 was very smooth with little buzz.

added:
if your RS carbs are out of sinc the bike will run BAD till the throttle is wide open.
no if ands or butts about that.
i do a lot of RS sinc for people..drop off and pick up the next day.
the complaint is the bike is missing or running uneven till opened up.

 

[Rob S.]

Can't the cranks be balanced? I'm assuming they're (1150s) already welded.

I remember decades ago, one of the big mods was getting your crank welded and balanced (900 Kaws).

 

[rapidray]

I sync EVERY set of RSs I put on a bike, WITH THEM RUNNING!!! Someone gave you some bad info!
Ray.

 

[blowerbike]

I sync EVERY set of RSs I put on a bike, WITH THEM RUNNING!!! Someone gave you some bad info!
Ray.

i bench sync and call it good...
are you actually using vacuum gauges?

 

[blowerbike]

Can't the cranks be balanced? I'm assuming they're (1150s) already welded.

I remember decades ago, one of the big mods was getting your crank welded and balanced (900 Kaws).

press pin cranks can be trued but not balanced...think about it.
the rods going everywhere when you try to spin it...lol

 

[Guest]

i bench sync and call it good...
are you actually using vacuum gauges?

Me to bench sink. Really the only reason the slides would not need to be even is if your compression was a lot different in each cylinder

 

[dorkburger]

Yea. That's what I always said with my 1100 motor and stock carbs.

When I sold my 1100 in favor of the 1150e, I noticed much more vibration with the 1150. The 1150 es I currently ride is buzzy also. I did a vacuum synch (stock carbs) last year and it did help, but not fix it entirely.

 

[Guest]

Geez after 10 pages of posts on "Good Bang for the Buck" performance upgrades to an 82 GS1100, I thought the 1150 replacement engine was the leading contender.

Posters even said they ride hopped up 1150s to Bike Week with the wife on the back, I guess they should have also told us the wife was so over stimulated when they got there that they had to sleep with the "stranger". Where's the bang in that?

http://www.urbandictionary.com/define.php?term=stranger

 

[CivilRock]

I sync EVERY set of RSs I put on a bike, WITH THEM RUNNING!!! Someone gave you some bad info!
Ray.

Shoot, I resorted to the Sudco Mikuni Tuning manual. Maybe their advice is too general of advice and doesn't apply to the 1150 motor?

So do you sync them with the tops off? Is there some secret?

I had my gauges out, fuel IV source set up, tools ready, and assumed I'd just find the adjustments when I got there. Turns out the adjustment is made under the top covers.

Do you make an adjustment and then put the cap back on and take a reading?

This is my source of info on the RS carbs. Maybe it's old? (see scan below)

I understand if tuning these RS carbs to perfection is a trade secret, but I'm super curious now, and I might just do some experimentation. I'm going to ride the bike to work today, and I'll see if I can differentiate WFO 5k+ and 1/8th open 5k+.

I also might just hook up my sync gauges and see if they're off at idle and/or off at high rev. Then I can work from there.

The main point of this thread was to identify if there was a serious problem, or if this is characteristic of the 1150 engine.

Isleoman,
Knowing the slight fundamental differences between the 1100 and the 1150, I have to hope that this is just a tuning glitch. Around town and 95% of my seat time so far has been huge grins with the 1150. But I'm very sensitive to the motor while I'm still sorting it out.
This weekend I raised the needles one more clip and it is now buttery smooth off idle. I was testing it out, up and down my driveway (200ft) and clicking into 2nd with moderate throttle was lifting the front wheel. I could never get my 1100 to wheelie. The first time (after 9 years) I ever got the front off the ground was at the track on the super sticky launch pad. Now, with the 1150 it's just a matter of rolling on the throttle. Not that wheelies are a distinct measure of power, but it's an indication that there's definitely more.

-Kevin

 

[blowerbike]

Me to bench sink. Really the only reason the slides would not need to be even is if your compression was a lot different in each cylinder

some 1150 engine's has more buzz than other's like i mentioned earlier.
bench sync and tune from there.
your buzz is here to stay...just the way it is.
and yes roll on wheelies is an indication of more power..
in your case you have at least 20hp more than your other engine/combo.

 

[rapidray]

See my post in the Carburetion section on this.
Ray.

 

[CivilRock]

Ray, you are right. Thanks.

The adjustment is so so slight, like 1/32nd of a turn on the adjuster. I think if I took them off the bike and rechecked the mechanical spec, it would still be perfect. Taking off the caps while it was running seemed to make no difference in the reading at all. Just to make sure, I would make an adjustment and then put the cap back on. Only removing one cap at a time to make adjustments. But again, it seemed to make no difference. I even just used my palm to cover the top and watch the gauge and no difference.

I can see how these might fall out of adjustment over time. The way the set screws and lock nuts work are just like adjusting valves, and I can see how they'd get out of whack being slammed closed hundreds of times.

I only adjusted 1 and 4, and by then 2 had dropped in line. I quit when they were all within 1 cm on my gauges. Idle was cleaner and there's noticeably less vibration at idle and just wicking the throttle. It's raining today, so a road test will have to wait.

Experience trumps the written manual.

-Kevin

This pic is my initial readings. I got them all within 1 cm and called it good.

 

[UncleMike]

Ray, you are right. Thanks.

The adjustment is so so slight, like 1/32nd of a turn on the adjuster. I think if I took them off the bike and rechecked the mechanical spec, it would still be perfect. Taking off the caps while it was running seemed to make no difference in the reading at all. Just to make sure, I would make an adjustment and then put the cap back on. Only removing one cap at a time to make adjustments. But again, it seemed to make no difference. I even just used my palm to cover the top and watch the gauge and no difference.

I only adjusted 1 and 4, and by then 2 had dropped in line. I quit when they were all within 1 cm on my gauges. Idle was cleaner and there's noticeably less vibration at idle and just wicking the throttle. It's raining today, so a road test will have to wait.

Experience trumps the written manual.

-Kevin

This pic is my initial readings. I got them all within 1 cm and called it good.

If that was your initial, you'll definitely notice a difference. What RPM did you sync at?

 

[CivilRock]

If that was your initial, you'll definitely notice a difference. What RPM did you sync at?

I'm not sure. That pic was at idle. I don't think my Bandit 400 tach that is driven off the Dyna 2000 lead is very accurate. It indicates about 800-900 at idle. I turned it up just a little to maybe 1500 just so the mercury didn't bounce around so much.

Half way through I had to re-fill my temporary fuel source and I got out my fan because the motor was getting hot.

It will be easy to tell if there's an improvement. I don't expect all the vibration to go away, just hoping for less.

 

[UncleMike]

I'm not sure. That pic was at idle. I don't think my Bandit 400 tach that is driven off the Dyna 2000 lead is very accurate. It indicates about 800-900 at idle. I turned it up just a little to maybe 1500 just so the mercury didn't bounce around so much.

Half way through I had to re-fill my temp fuel source and I got out my fan because the motor was getting hot.

It will be easy to tell if there's an improvement. I don't expect all the vibration to go away, just hoping for less.

Try syncing where the vibration is worst.

 

[CivilRock]

Try syncing where the vibration is worst.

I'll do that next time, but I was kind of nervous about holding my bike at 7,000 RPM and trying to adjust it. I'm going to go out and test it this way first.

I didn't know if this setup would suck the mercury into the engine. I don't think my little box fan is strong enough to keep the engine cool. I didn't want to draw (more) attention to myself in the neighborhood.