GR650 Fork Spring and Oil Replacement

[EMFL]

This is my first post on this wonderful forum. Love the community spirit and sharing of information.

Anyway, I have been wanting to rebuild a motorcycle for a very long time and finally pulled the trigger on a '83 GR650 Tempter. I have striped the motorcycle down to the frame and now building her back together.

I finally figured out how to remove the fork cap and sharing this information, since I didnt find it all that intuitive. Not my first time working on forks.

The fork caps on the GR650 do not have a nut, but a cap that is secured by a circlip. Sharing some information about the forks and how to replace the springs.

Since the bike is almost 40 years old, using a mallet and screwdriver handle, I gave the cap several wacks to loosen the crust built up around edges. Otherwise it was very difficult to get the cap to budge.

Now the trick is to find a way to depress the cap, and then coordinate removing the circlip. I used a phillip screwdriver, and a regular pick to remove the circlip. It took about 4 tries to be able to depress the cap while attempting to remove the circlip. It is possible, just need patience. Beer would probably help too.

I will post more information when finally complete. Currently researching springs and fork oil.

[EMFL]

Here's some additional photos

20190824_135728.jpg

[EMFL]

From another angle

[Steve]

For springs, check out Sonic Springs.

For oil, probably 10w of your favorite brand.

Beer seldom helps any difficult project.

.

[EMFL]

Thanks for the info about Sonic Springs, have read about them on other posts here. Other brand was checking out was SVRacing Parts, previous experience from my v-strom.

I am glad you mentioned the 10wt oil, since that is what I was leaning towards as well.

I will follow-up on the final outcome, and post the results. Cheers.

[Brendan W]

Nice bike. Taking all the weight off the front wheel helps a little bit with the spring tension.
Two things. Measure the old springs to see if they are still within service limits for length and check which way up they go.
A bike that age depending on service history may have a layer of sludge at the bottom of the forks. Unless you want to strip the forks completely, a few oil changes in the first year helps flush it out. I am one of the crazies that blend 10W40 motor oil and ATF approximately 2:1 with a target of 15W fork oil.
Lots of info on the web at places like snakeoil.com and grammasrecipes.com Seriously it was a thing back in the day and I can't believe these bikes need the claimed antifoam etc properties of modern fork oils given their modest performance.
With the right amount of the right oil I would try it out before pulling the trigger on new springs even if just to complete a flush programme..

[RichDesmond]

Congrats on the bike, I’ve always had a soft spot for those ever since they came out.
Sonic Springs are good. (I’m the former owner of the company)
If you need advice on what rate to choose let me know.

I would not do business with Blair under any circumstances.

[EMFL]

Thanks for the information. I did measure the stock springs and they are out of spec. I will make sure to clean out the forks to remove any sludge since the forks havent been touched in about 10 years, that's good advice. Thanks for the additional resources too.

I did order from Sonic Springs and went with the recommended 0.8 spring weight, I am a scrawny 165lbs. Will use the 15wt oil, and see how the setup feels. Getting excited to put the forks together. I have been prepping the frame and swing arm for paint, which will be my next task. Look forward to posting my progress.

Cheers!

[Steve]

At a "scrawny 165 lbs.", I would heartily recommend that you get 10w oil, instead.

The only thing that 15w oil will do for you is feel like it is locking up the fork movement.
10w oil will let the forks move, but will keep them from moving too fast.

.

[RichDesmond]

At a "scrawny 165 lbs.", I would heartily recommend that you get 10w oil, instead.

The only thing that 15w oil will do for you is feel like it is locking up the fork movement.
10w oil will let the forks move, but will keep them from moving too fast.

.

Seconded.

[Brendan W]

Thirded.
Next time out I'm going for 10W target.
Been hearing Steve going on about it and reckon he knows a thing or three and I'm more of a 200# type.

[Steve]

Not sure I know all that much, but I do have some experience I'm willing to share.

I've got you beat by a couple of stone, and my bike has another 5 stone on top of that.

10w feels GREAT with my 1.1 springs.

.

[salty_monk]

Are they 35mm forks like the GS650G? If so a MikesXS emulator will drop straight in whilst you're there... I weigh about the same as you & give another vote for the 10w. I like the Amsoil Synthetic stuff (there is no independent testing so manufacturers 10w may differ from each other...)

We did a brake upgrade on a Tempter a while back, can't remember the member now but I can try to look it up if you want to pick their brains. From memory it was more like the GS450 single brake setup than the GS550 / GS750

[exzachtly1]

I just went through replacing my front springs on my GS650L. I used the progressive springs.

For the compress + remove circlip dance, I found something that worked very well for me. If you have any wood clamps handy, the long ratcheting kind like these https://www.amazon.com/IRWIN-QUICK-G...gateway&sr=8-3, with the forks still on the bike you can put one end over the top of the fork with a socket underneath it (small enough to go over the air valve but narrow enough to leave room to get to the clip) and wedge the other end down below somewhere on your triple tree. Took a little fiddling to find the perfect spot but once things lined up, I just compressed the clamp and voila, the spring seat was depressed and I could fish the clip out.

Your mileage may vary... but it worked really well for me. I'm going to be getting back in there soon to replace the seat springs and o-rings and air valves (all the new parts were about 60 bucks, not bad) because mine were rusted to hell like yours and one of them is leaking from the air valve. If I remember I will take a picture of how I did it.

[EMFL]

Hmmm, I am rethinking the 15wt now. Hard to argue with experience, and the members on this forum have been very helpful with insight. Yeah, I will return the 15wt for the 10wt. Thanks for the info!

A helpful tip on removing the circlip, I may have to leverage this method on reinstallation. My method was a more brute force.

Yes, these are 35mm forks. Another great recommendation on the emulators. I will research this.

I am planning on upgrading the front brakes. I have the blackbird rotor and the modified front bracket, when it is time to instal this I will make sure to reach out.

Thanks!

20190902_094806.jpg

While I had the forks off the bike, i did shine the forks up. Started with 300, then 400, then 600, and finished with 1200 grit sandpaper. The results are very nice, attached a side-by-side picture below. Took about 3hrs for both forks, very zen like work. Next will polish them up with mother's aluminum polish.