Let's talk about forks, man

[Guest]

OK? My old 82 GS650G is starting to come together nicely thanks to info I've gotten here. This is my first bike, so I'm a bit inexperienced as to how things come apart and work.

I got the rear suspension sorted and working on the front. I got progressive fork springs and new fork seals. The seals aren't leaking far as I can tell, but figured might as well change em if I'm taking this apart.

I have the forks out, but my bike doesn't have a screw on cap on the top like I'm seeing in all the writeups. (my air valve is on the side, not the top) All I can see is a little plug that plunges slightly when depressed. I see a small clip in there, but no eyelets or anything for snap ring pliers. I can't manage to depress the... plunger (?) and get at the clip at the same time. Any tips for taking the top apart to get at the springs? I have the manual downloaded from Basscliff's site and even that is showing me a threaded cap on the top of the forks which I don't have.

I'm still not understanding the reasoning behind the PVC spacer. When I put springs on a car, I get springs specific to that model and throw em in. Is it because they make one part number to fit an extremely varied number of bikes? And they're really not that model specific?

[Billy Ricks]

OK? My old 82 GS650G is starting to come together nicely thanks to info I've gotten here. This is my first bike, so I'm a bit inexperienced as to how things come apart and work.

I got the rear suspension sorted and working on the front. I got progressive fork springs and new fork seals. The seals aren't leaking far as I can tell, but figured might as well change em if I'm taking this apart.

I have the forks out, but my bike doesn't have a screw on cap on the top like I'm seeing in all the writeups. (my air valve is on the side, not the top) All I can see is a little plug that plunges slightly when depressed. I see a small clip in there, but no eyelets or anything for snap ring pliers. I can't manage to depress the... plunger (?) and get at the clip at the same time. Any tips for taking the top apart to get at the springs? I have the manual downloaded from Basscliff's site and even that is showing me a threaded cap on the top of the forks which I don't have.

I'm still not understanding the reasoning behind the PVC spacer. When I put springs on a car, I get springs specific to that model and throw em in. Is it because they make one part number to fit an extremely varied number of bikes? And they're really not that model specific?

On the fork "plugs" you just have to get up over them with a big screwdriver or something and maybe put your hands against your chest and push hard. You will probably find yours are seized in place, it's pretty common. Take a hammer and a piece of pipe or a drift and see if you can knock them down any. They'll pop back up but this is just to see if they are frozen. If they are try some penetrating fluid for an evening or two then attack them again. I had to cut one out of one of my forks because it was so rusted in place.

Use the recommended length of PVC. The springs do fit several models so the spacers make up for that. You can use a longer or shorter spacer once you see how it rides to adjust the sag.

[Truth]

On the fork "plugs" you just have to get up over them with a big screwdriver or something and maybe put your hands against your chest and push hard. You will probably find yours are seized in place, it's pretty common. Take a hammer and a piece of pipe or a drift and see if you can knock them down any. They'll pop back up but this is just to see if they are frozen. If they are try some penetrating fluid for an evening or two then attack them again. I had to cut one out of one of my forks because it was so rusted in place.

Use the recommended length of PVC. The springs do fit several models so the spacers make up for that. You can use a longer or shorter spacer once you see how it rides to adjust the sag.

I can get the little plug to move a little. Maybe 1/8th of an inch or so downwards. Is this as far as they go? I guess I'm just having a hard time pushing this down and getting at the clip at the same time.

[Billy Ricks]

Is the front wheel off the ground and the forks fully extended? If you can move them 1/8th that's enough to get a small screwdriver under the clip and pry it out. It's a little tough without three hands but it can be done.

[Truth]

Oh yeah wheel is off the ground. Forks are laying on the bench. I'll keep fiddlin with it until it comes out. Thank you! At least I know I was on the right track.

[Calvin Blackmore]

they dont go down very far
and dont hit it with anything it may get cocked sideways and be a permanent part fo the tube

I hav eone like that now

mine was rusted a bit and I got over zealous

threaded a grade 8 bolt and tried a dent puller
it still stuck

as long as the spring is pushing iit up agaisnt the circlip then its a matter of a nice friend pushing while you uses some dental pick or whatever to fish the circlip out

they are a bugger they just want to turn

I did mine alone
it was very very soul destroying but i got one at least

[Truth]

I had to walk away from this thing for a while. Came back to it, clamped the forks in a black and decker workmate, and they came right out! Success at last.

Now... Does anyone use a fork oil level gauge? I need 210 ML's of oil and a depth of 165 mm's. I bought a tool that I thought I needed, but now that I have it I see it's only a volume measurement. CC's and inches. And there's no instructions with this thing.

[koolaid_kid]

I use a wooden dowel rod from my local hardware store. Works fine for measuring depth.
BTW, 1 cc = 1 ml, so you could also measure volume. I prefer depth, but that's just me.

[twr1776]

I use one of these with a tube on the end for level. I overfill the forks slightly and draw out the excess.

http://www.hopkinsmfg.com/10111.html

[Larry D]

Heck...I used a sprayer from old spray bottle...cut it to the proper length, overfilled the forks a little and then sprayed the excess into my hazardous waste bucket.

[Steve]

Can't help you much with your disassembly, I have not done any 650 forks.


However, I might be able to shed a bit of light on this:

I'm still not understanding the reasoning behind the PVC spacer. When I put springs on a car, I get springs specific to that model and throw em in. Is it because they make one part number to fit an extremely varied number of bikes? And they're really not that model specific?

Lets start with some numbers:
Car weight: 2500-3500, depending on the car
Bike weight: your 650 is about 475 pounds
Your weight: 150-250, never met you, don't know.

Even if you are on the lighter end of the scale, 150 pounds, let's scale that up to the car. Since we added 1/3 of the weight of the bike, let's add 1/3 of the weight of the car, or 800-1200 pounds. See what it does to the ride height? If that is what you were going to do all the time, you would want stronger springs or a way to simply raise the height of the car.

The rate of the spring will control how much it compresses for a given force that is applied. There are different springs available, if you know where to look (check with any local racer, he will tell you that there are many different springs available for their cars), but any given spring will still compress a certain amount when you are on the bike. The PVC spacer will simply adjust the ride height without changing the rate of the spring.

For good ride and control, you want your bike to "sag" no more than 20-25% of its available travel when you sit on the bike. The ideal spring will keep it from bottoming out when hitting a large bump. The ideal fork fluid will be light enough to allow the suspension to follow small irregularities, but heavy enough to keep it damped on large movements.

Yep, there are compromises EVERYWHERE, good luck on finding the one that works for you.

.

[Truth]

Thanks! I still need to run to the hardware store for PVC, make my spacers, and then put it back together. Can't wait to ride this thing after I'm done.

[Truth]

After making a call to progressive to make sure I was on the right track as far as spacers go (I was), I finally have this back together and back on the road. Quick test ride down the street, and this thing is much firmer than before. Engine braking in a low gear made the front wheel hop violently sometimes, which almost left a load in my pants first time it happened. Suspension is now nice and tight, but not hard.

I made the front spacer a little on the long side to hopefully match up with the stiffer MDI's in the rear. So far seems to have worked perfectly. I wanted about a half inch of spacer protruding from the forks with everything fully extended, so the entire spacer length wound up at around 1.75 inches. I haven't measured sag yet, but I doubt there's all that much. (I only weigh 170 pounds)

So far with rear MDI's, front progressive springs, 10 weight fork oil, and superbike bars this thing rides and handles like a completely different bike than from what I've started with. Thanks guys. This site has been a HUGE help. Next up.... Carb rebuild.