81 GS750EX -- twitchy front-end

[Anonymous]

I recently purchased an 81 GS750EX mainly for commuting reasons. My commute is about 45 minutes on four lane divided rural highway (~65 -to- 70 mph) and about 15 minutes small city traffic.

I finally have the bike running pretty reliably, so I'm starting to get used to how it handles. I want to say that the front-end seems a bit twitchy, but I also want to clarify that... the bike gives a nice smooth response to my stearing (and counter stearing) inputs. It is not twitchy stearing. The issue seems to be more about how the front-end responds to changes in the road surface. Fairly small "edge-traps" seem to get more of a response from the front end than I prefer.

This may or may not be related, but the front end also seems to hammer (pound up and down) a bit on the small freeway concrete seems when "cornering" at freeway speeds... these are freeway curves, so its not exactly high-performance cornering, but you know what I mean. It does not seem to hammer (or at least not nearly as much) on the straight aways.

I installed new fork seals, but the old springs seemed fine. The front tire seems to be in decent shape. I've been running it a 40psi, which is what the tire calls for. Its slightly wider than stock, but I can't remember its exact size at the moment (I'm at work on a lunch break, and it was raining buckets this morning, so I rode inside the four wheeled steal box). If the front tire might be part of the issue, let me know, and I'll send more details.

Any insight appreciated!

Thanks!

 

[HiSPL]

40 psi seems slightly high for a front tire. Are you using a tube inside? My front pressure is good between 35-38 psi with a metzeler me33 and 37 psi with a Battleaxe.

1) When you did the fork seals did you clean the internals real good and put it new fork oil?

2) Springs that "look" good can still be worn out. I would suggest either replacements from race tech or progressive, or adding preload spacers if your on a budget. Any thing that can raise the spring rate on that bike will make the ride comfort and the handling much better.

3) Are you using any air in the forks?

4)When you do anything to the front end it is recommended that you loosen all the bolts in the triples, stem, fender brace, and axle. Then follow this sequence in reassembly....


-Put bike on the centerstand and pile some weight on the back seat or slide a jack under the engine to lift the front wheel off the ground.

-make sure both fork legs are inserted into the triple clamps an equal amount. If you are lowering the front end this is the chance to slide the legs up in the clamps, measure both sides twice to be sure they are equal heights.

- with all bolts still loose, start with the axle and torque to the proper value. Then torque the fender brace, then lower triple, then upper tripple, and finally the steering stem. You basically want to move from bottom to top. This sequence will pull everthing into alignment as you go. This makes sure that your front end has no stresses that it shouldn't be dealing with, such as misaligned forks...

HTH,
-=Tim=-

 

[Anonymous]

front end

front end

I have an 1981 750 EX I replaced the oil, seals and put in spacers (about one inch). I also added a forkbrace and steering damper. A great improvement it really tightened things up. Andy

 

[Anonymous]

Tim,

Thanks for the details on the re-assembly process to ensure that everything is lined-up correctly. I will go back through that.

Andy,

Care to share any specifics on the fork brace you went with?

Thanks!

 

[Anonymous]

That hammering may be exaggerated by a too-firm tire. I run 32psi in my front tire - probably a bit lower than ideal. As to the squirming, my '81 1100EX does the same thing. Moving up to 32psi front helped a lot when compared to the too-low pressures Suzuki recommended for the old tires back then. I do run a vintage fork brace. I'll be very careful with tire choice when I have to replace the tires that came on my used bike (Pirelli Sport Touring).

 

[Anonymous]

I purchased it off ebay from Legends Motorcycles Denver, Colorado. It is a Daytona and new it only cost me $26.95 plus shipping. They are called "legendsmc" on ebay. Great to deal with fast shipping. It fits over the the stock rubbers and looks great. Not sure if it improves handling much but it does add the bling value and for the price you can't go wrong.

 

[IanFrancisco]

You have to be careful with fork braces to be sure that they don't cause the forks to bind. 40psi seems high to me too. I read that the best tire pressure is whatever it takes to keep the pressure change after warmup no more than 2 or 3 psi over the cold pressure, about 33psi for my bike. Varies with hot or cold weather.
A lot of the wandering and following rain grooves is up to the tires you run. I had the old Continental ribbed front and that was way scary on the freeway. Front end hopped all over the place. New AM20/21 Roadrunners solved that. Expensive at $90-100 each but they should last a while.
I just put Progressive springs on my bike with new H-D Type E oil (for Showa forks) and what a difference! Got rid of the fork "patter", what you call hammering up and down at speed and the whole front end seems both plusher and firmer at the same time and the tire feels much more glued to the road than before. Even with the old stock rear shocks which are in decent shape (only 10K miles) the bike handles great, even leaned over in a sweeper at 65-75 mph, hold its line and gives me a great feeling of stability and confidence. It'll be interesting to see what good rear shocks will do for the handling.