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83 gs750es 'tank slap'

  • Thread starter Thread starter Anonymous
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Anonymous

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I am confused... Under decelleration I get massive tank slap. I checked the boards, and found a few other people with the same problem. Is it just the nature of the bike to do that, or is there something that can be done to fix it?
 
Re: 83 gs750es 'tank slap'

83gs750es said:
I am confused... Under decelleration I get massive tank slap. I checked the boards, and found a few other people with the same problem. Is it just the nature of the bike to do that, or is there something that can be done to fix it?
Click to expand...

How massive? I get a shimmy at lower speeds on decelleration, but most of it has gone away with the addition of a fork brace (redundant, I guess, since there is already one under the fender).

I tend to take my hands off the bars to stretch a lot on decelleration - when it starts to shimmy, I grab 'em pretty quick.
 
well, it starts out as a minor shimmy... then within a few seconds, if I dont put my hands back on the bars, I have a feeling she might buck me off. I had an 02 R6, and I could ride for miles without any kind of shimmy.. So, there my questions comes in.. is it just the nature of these bike to do that? These bikes being any older bike..
 
83gs750es said:
.. So, there my questions comes in.. is it just the nature of these bike to do that? These bikes being any older bike..
Click to expand...
Absolutely not! My 1983 GS750ES has not the slightest hint of a "shimmy" on deceleration. I am sure the experts will suggest possible causes.....I would wonder about front tire condition and stearing head races/bearings.
 
It's not in their nature, as long as you don't push them further than they were intended to be pushed they are stable if everything is right with them. Check the steering heads bearings. Clean them up and reinstall them. If you don't know the procedure for tightening the steering stem I can post it later. It's in the manual if you have one. Could also be a wheel out of balance or flatspotted.
 
I suspect my occasional little shimmy is more a road condition factor than anything else - Wisconsin is the heart of the "buckle-belt."
 
A quick way to find out is adjust the steering head brgs, just tighten it up 1/8-1/4 turn doesnt take much That is what was causing the problem on my GS850. It wouldn't hurt to take it apart and lube the bearings. With the bike on the center stand it should turn lock to lock nice and smooth. If it catches in any spot you will have to replace the bearings. IT"S not that hard to do.
 
"Absolutely not! My 1983 GS750ES has not the slightest hint of a "shimmy" on deceleration. I am sure the experts will suggest possible causes.....I would wonder about front tire condition and stearing head races/bearings."

Well, Finally someone who doesnt have that problem.. Well, I guess that makes me feel both better and worse about it... Better.. I know it can be fixed, worse, I dont know where to start... lol

"It's not in their nature, as long as you don't push them further than they were intended to be pushed they are stable if everything is right with them. "

This usually happens at about 50 over that and I havent taken my hands off the bars...



"A quick way to find out is adjust the steering head brgs, just tighten it up 1/8-1/4 turn doesnt take much That is what was causing the problem on my GS850. It wouldn't hurt to take it apart and lube the bearings. With the bike on the center stand it should turn lock to lock nice and smooth. If it catches in any spot you will have to replace the bearings. IT"S not that hard to do."

Could you explain how to do that please?
 
Response from your PM....

Response from your PM....

83gs750es wrote:
I was wondering if you ever found out the problem for the tank slap on you 83 gs750. I recently purchased one and its doing the same thing. Looks like this is a common problem with this bike. Is it really a problem, or just a design flaw? I guess its always safer to keep both hand on the bars... Thanks.

=====
I found that the correct size tire(100/90,80/16) in good condition properly inflated(35-40psi) took care of it. If my tire gets down in the 30psi range it will still shake some. Hope this helps.
 
Re: Response from your PM....

Re: Response from your PM....

moto_dan said:
I found that the correct size tire(100/90,80/16) in good condition properly inflated(35-40psi) took care of it. If my tire gets down in the 30psi range it will still shake some. Hope this helps.
Click to expand...

I checked the tire and air pressure, tire size is stock, and air pressure was at around 22psi, I inflated it to 40, but it still has that problem.
 
If nothing else is obviously wrong, it is probably a loose steering head-you do need a special socket tool to tighten this up. The part number is in the Suzuki service manual. There is no design flaw- I have 45,000+ miles in the saddle of one of these and can attest that these 58in. wheelbase bikes are very stable on and off the throttle. If something is not loose then something is bent. Ride On, Ed.
 
Re: Response from your PM....

Re: Response from your PM....

moto_dan said:
I found that the correct size tire(100/90,80/16) in good condition properly inflated(35-40psi) took care of it. If my tire gets down in the 30psi range it will still shake some. Hope this helps.
Click to expand...
I am running a Metzeler ME33 Laser in one oversize (110/90-16) at the owner's manual recommended 32 psi for 2-up riding (solo is 28 psi but I'm too lazy to switch pressures depending on whether my wife is with me :oops: ). I think that this pressure is fine for the Metzeler, as well as the OE Bridgestone. Incidentally, I think the ME33 is a fine front tire for the GS750ES. On back, I now use a Metzeler ME550 in a one oversize (130/90-17) at an owner's manual recommended 2-up pressure of 40 psi (solo is 36 psi). Interestingly, the ME550 is about 6 to 8 mm narrower than the ME55A Metronic of nominally the same size......chain guard & brake torque arm clearances that were minimal with the ME55A are now generous.
 
My 81 750L doesn't have any shimmy on deceleration other than what I get from road conditions - grooved pavement, etc.

I was just thinking that I only know a couple of people who have experienced a tank slapper.

One was on a modified Z1 that was set up for drag racing back in the 70s. The front end had just been modified and at about the end of the quarter at about 155 mph from what I can remember he went into a tank slapper and ran off the end of the strip before getting it back under control. The front end was changed back to stock before the bike was raced again.

Another was on a MotoGuzzi California II. It happened while riding on a two-lane highway that was pretty rough. He was riding at about 80 and a tank slapper started that he couldn't get back under control and ended up dumping the bike at about 60 resulting in serious injuries. Later the cause was determined to be a combination of road conditions, worn steering head bearings, and worn wheel bearings.

Head Shake

Similar to a tank slapper only a little less violent. Usually a quick shaking of the handlebars is all that results.
* EXUP Brotherhood's glossary of terms

Tankslapper

A violent repetitive swinging of the handle bars from left full lock to right full lock. Very scary to new riders, or anybody of any riding level. Some result in crashing but you can ride them out. Firstly, one of the best ways to avoid having one is to not strangle the bars when you ride. Don't grip them like you're trying to strangle your mother-in-law. A nice relaxed grip prevents many a tank slapper. If you happen to have a violent tank slapper, the best advice is to ride it out - DON'T ROLL OFF THE GAS!. If you are able to ride it out, immediately check your front brakes (pull the lever and pump them up). Violent slappers can spread the pads in the calipers, and you may need one or two pulls on the lever to bring the brakes back to full power.
* EXUP Brotherhood's glossary of terms

This is really a quite different thing than a shimmy or a headshake.


I have only witnessed the one that happened at the strip. I have experienced head shake when test riding a bike that needed a lot of work and experienced various forms of shimmies on many bikes but I personally hope that I never experience a tank slapper.

I have heard discussions about tank slappers and been to AMA safety clinics where they were discussed but they do not seem to really be that common on the street. However, it is probably a good thing for people to know something about as a little knowledge may help in the event we ever experience one. Most of the discussions of tank slappers were concerned with bikes either pushed way beyond their limits or with modifications that altered the steering geometry.

I had an H2 Kawasaki that I used to run at the strip in the seventies and a sever headshake was enough to keep me from messing around with the bikes rake and trail.

Mike
 
First step cover the tank with a towl. Remove the large bolt for the handlebars and remove them. Loosen the large jam nut. Use a chisel/ lg screwdriver and a hammer and tighten the adjustment nut 1/8-1/4 Turn Then reassemble VERY SIMPLE
 
Jeez, I thought I had seen it all. I would not beat on the steering head with any device much less a chisel! Folks, if you are gonna perform your own maintence, you are gonna need proper tools and a little common sense. That includes a service manual, torque wrench and in this case Suzuki part #09940-14911 otherwise known as a Steering nut socket wrench. Proper torque is 29-36lb-ft. Otherwise just pay up and leave the wrench turning to the pro's for you and your bike's sake. Ride On, Ed.
 
Hi Ed,
Using Lynn's method (and mine too) isn't a big deal as long as the bearings aren't tight to begin with. I don't think she led anybody who could think things through astray.

Cheers, Steve
 
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