Have an 89 fj1200, the front suspension is bottoming out and even small bumps. Can anyone recommend an econmical (re: cheap) spring? Other than fork seals and oil, what else will I need? Thanks for the help!
Quote from: chefmatt on May 06, 2014, 08:23:14 PM
Have an 89 fj1200, the front suspension is bottoming out and even small bumps. Can anyone recommend an econmical (re: cheap) spring? Other than fork seals and oil, what else will I need? Thanks for the help!
Not knowing what you currently have, you might be low on fork oil. Some history would go a long way if you want help...
Don't know the history of the bike...bought it recently. No help, sorry
Should I have my mechanic check/top off the oil before spring replacement?
Sonicsprings.com have some fairly economical single rate springs available. Or, you could try Ebay if you know what you're looking for. If your current springs aren't too soft (probable), you could add a longer preload tube which might be enough - for a while.
As FJMonkey says, check the oil level if its way low that would allow the fork to bottom hard.
Quote from: chefmatt on May 06, 2014, 08:29:31 PM
Don't know the history of the bike...bought it recently. No help, sorry
Time to crack it open then... I love the RPM solution, the RPM fork valves and new straight springs are awesome... Not a budget item but I see it as a safety item. Prop the front end up and pull off your fork caps. How much oil is in there?
How many ounces of fork oil do they need?
Quote from: chefmatt on May 06, 2014, 08:40:09 PM
How many ounces of fork oil do they need?
More of a measurement from the top with the forks compressed and springs removed. Try the search function....
got it thanks. thank you google, its 395cc or13.36oz.....
Matt,
You're much better off measuring the distance from the top of the fork tube to the oil level.
If you try to fill by volume, you'll have to remove the forks and completely drain them of all old fork oil, this means rinsing with kero and leaving them upside down for a day.
Good height for fork oil starting point would be 150mm of air space with the springs removed and the forks fully compressed.
When I got my FJ the front forks were dry. It was freaking scary on the test ride when the bike bottomed out the suspension on the compression and the rebound stroke. Like Mark says, it's a safety issue to have a properly functioning suspension. You don't have to upgrade it to get a LOT out of the bike. But there are a LOT of potential improvements to be made. (Interestingly enough, Randy's front end solution isn't much more expensive than the Racetech solution when comparing retail prices. And the performance is much greater.) But either way you go, both are far better than the stock solution. (I'm running the Racetech's and after months of building my skills and riding as much as I can, I can say that I'm ready to upgrade to the RPM solution.)
Cheap, first thing is clean the forks, install new oil and see what you have. IMO the first good improvement is getting the correct spring rate. Beyond that the emulators come into play but now we are increasing the cost.
As far as cheap springs they are all priced about the same. You can go here and plug in your weight to get a spring rate. Scroll down to the yellow highlighted area and click it on. http://racetech.com/ProductSearch/2/Yamaha/FJ1200/1986-89 (http://racetech.com/ProductSearch/2/Yamaha/FJ1200/1986-89).
I think Randy at RPM also carries them. http://www.rpmracingca.com/products.asp?cat=39 (http://www.rpmracingca.com/products.asp?cat=39) Occasionally you run across a used set from someone wanting to go up or down with there spring rates. You need to figure out what spring rate you want first.
George
I took route 70 in northern California down out of the mountains. It is a scenic highway with many curves and three tunnels running beside the Feather river. I was unhappy with the mushy front forks on all the curves. The PO had installed some kind of progressive springs that still did not do the job. Randy did his fork and shock mod and I couldn't be happier with the ride and handling now. I hope to someday make the same ride with the handling I have now. Dave
Quote from: chefmatt on May 06, 2014, 08:23:14 PM
Have an 89 fj1200, the front suspension is bottoming out and even small bumps. Can anyone recommend an econmical (re: cheap) spring? Other than fork seals and oil, what else will I need? Thanks for the help!
What ya got here is a "pig in a poke." You don't know what's in the sack till you open it up, pardner.
Are the tubes bent or scored? Are Jimmy Hoffa's ashes in your sliders?
You gotta take the forks apart and look.
What you do know is that you have substantial wear on some 25 year old suspension units. If you are bottoming-out you are probably beyond the spacer-and-add-oil "patch" and need to get things ship-shape.
You almost certainly need a basic rebuild.
First thing: get a manual and the tools that you'll need to remove and disassemble your forks.
When you get the tubes out of the sliders roll the tubes on a flat surface (pane of glass e.g.) to check them for "true". If they are bent you need new ones.
You'll need to replace the seals, springs and oil.
Budget-out the best solution that you can afford (stock to RPM)and get your parts.
It is not hard to do.
If you get stumped someone here will surely unstump ya.
2 points to add. Bent tubes can be straightend, they do not always need to be replaced.
Any true fork rebuild should also replace the bushings. They wear out and will allow the forks to bind and become non-responsive to small bumps. Who wants suspension that doesn't act on the small stuff?
No one has recommended Progressive Suspension fork springs. They made a big improvement in my 1983 Venture. How would they compare against the Race Tech straight rate springs if that was all a guy changed? Has anyone tried both? I'm not using my FJ for track days or even hard riding, mostly just touring.
Thanks,
Anson
The front end path I've traveled in my years with my FJ was:
1) Bought my '84 new...played around with heavier fork oils, different anti dive settings.
Result: Marginal improvement
2) Installed progressive springs in 1986. Result: A little better, but initial fork dive was still there.
3) In '89 I removed the progressive springs and installed straight rate springs and Race Tech cartridge emulators. Result: Much better than the progressive springs. Fork dive was almost eliminated with the 1.0kg straight rate springs and the emulators softened things up to be acceptable.
Fast forward 14 years...
4) In 2004 I removed the Race Tech emulators and installed Honda CBR600 F3 cartridges. The real stuff, Race Tech gold valve compression cartridges and rebound cartridges. Jon Cain made special adaptor hats to fit the Honda cartridges in the FJ lower slider.
Result: Holy Shit....cartridge forks ROCK...I am sold on cartridge forks. A different Galaxy than damper rod forks, even with emulators. Firm, yet soft. It took a couple of try's with the shim stacks but once dialed in cartridge forks were a huge improvement....huge.
5) in 2007 I installed some 1992 FZR1000 up side down (cartridge) forks....and, yea baby, the chicks are back.
That's where I stand today...
My point is....if you want to go backwards in time, fine, install progressive springs or emulators. However we are in the 21st century and you have much, much better options available to you...
If the RPM IAT fork valves had been available in 2004 when I converted to cartridge forks, things would have been different.
Hope this helps... :drinks:
I went with .95 straight rate springs and they work good. I wouldn't go back to progressives.
George
RPM fork valves, .85 straight rate springs, and I am very happy with the front end.... :good2:
So today I did the fork overhaul....Loosened the bolts holding the clutch and brake cylinders to get access to the top caps of the forks. lifted the front end using a hoist. The caps came off quite easily using a large bolt as an allen wrench. Drained the fork oil - it was as black as crude oil. Left fork drained 10.2 oz, right almost 12 oz. Probably this had alot to do with problems in the first place. After letting oil drain, used 15w fork oil - 12.2 oz per fork......also instead of replacing springs, we put in Harley Davidson spacer springs. they fit perfectly . The Harley springs are approx 1.5 inch stacks, and the same diameter as my fj springs. We were originally were going to use pvc pipe as spacer, but the pipe diameter was about .25 to large. Didnt replace seals or wipers, this was supposed to be a quickie job. Ha! Nothing goes as planned. The damper rod was hell getting back in all the way - it would slide in to within an inch or so, but we couldnt get it down close enough to screw the fork caps back in. after about two hours or trying to figure it out, lots of turning the fork cap trying to align the damper rod, I finally used a large screwdriver inserted into the preload adjustment slot, and gently tapped the damper rod down. Worked fine. Screwed the the caps back on, re-assembeled everything, and took it for a ride. The ride is much stiffer than before, I can really feel the road though the bars. small bumps no longer bottom it front end out, feels much more stable. Job would have taken an hour max if we didnt get stuck with the damper rods.....thanks for the help fellas!
Quote from: chefmatt on May 20, 2014, 11:08:39 PM
The damper rod was hell getting back in all the way - it would slide in to within an inch or so, but we couldnt get it down close enough to screw the fork caps back in. after about two hours or trying to figure it out, lots of turning the fork cap trying to align the damper rod, I finally used a large screwdriver inserted into the preload adjustment slot, and gently tapped the damper rod down. Worked fine. Screwed the the caps back on, re-assembeled everything, and took it for a ride. The ride is much stiffer than before, I can really feel the road though the bars. small bumps no longer bottom it front end out, feels much more stable. Job would have taken an hour max if we didnt get stuck with the damper rods.....thanks for the help fellas!
Bad news. You have a problem. You still missed the damper rod hole. The reason it's no longer bottoming out is that it's now binding on the damper adjuster rod. Once you get the rod properly aligned, it will drop into place (or at least drop on top of the spring/spacer).
Another thing to consider is spring mathematics. I'm not sure what Harley "spacer springs" are, but if they are springs then you may need to reconsider and get the proper diameter PVC and use it for an actual solid spacer.
When you stack 2 springs together like you did, the combined spring rate is less than the rate of the weaker spring. So, "in theory" you may have actually reduced the effective spring rate and once you get the damper adjuster rod properly installed the bike may actually be less sprung than before. The new oil will definitely help, but the spring rate may not be what you really want/need.
Thanks for the info..I hope you are wrong tho..yikes. No
Matter how I tried to guide the damper rod that last inch to meet up with the threads in the fork cap, couldn't get it. Until I tapped it down...very gently mind you, didn't take much at all. Any tips on alignment of the rod? Thanks
Quote from: chefmatt on May 22, 2014, 11:49:02 AM
Thanks for the info..I hope you are wrong tho..yikes. No
Matter how I tried to guide the damper rod that last inch to meet up with the threads in the fork cap, couldn't get it. Until I tapped it down...very gently mind you, didn't take much at all. Any tips on alignment of the rod? Thanks
He's not...
You have gotten the adjusting "D" shaped rod wedged into one of the outer oil flow holes.
(http://i1215.photobucket.com/albums/cc517/racerrad8/006_zpsf5f7ae63.jpg~original) (http://s1215.photobucket.com/user/racerrad8/media/006_zpsf5f7ae63.jpg.html)
You have to center the rod when inserting and make sure it is clocked with the "D" shaped hole in the center and it will slide right in.
Randy - RPM
Quote from: FJ_Hooligan on May 21, 2014, 11:57:12 AM
Another thing to consider is spring mathematics. I'm not sure what Harley "spacer springs" are, but if they are springs then you may need to reconsider and get the proper diameter PVC and use it for an actual solid spacer.
When you stack 2 springs together like you did, the combined spring rate is less than the rate of the weaker spring. So, "in theory" you may have actually reduced the effective spring rate and once you get the damper adjuster rod properly installed the bike may actually be less sprung than before. The new oil will definitely help, but the spring rate may not be what you really want/need.
OK - I am having a problem getting my head around this one. Can you explain it further?
Is the effective spring rate lower, but you've effectively added preload? I thought this was how they originally did "progressive" springs -- two different springs stacked on top of each other?
Thanks!
Springs in series act like resistors in parallel. If you put 2 springs in series (stacked together) with each spring having a 2 pound/inch rate, the effective rate of the combination will be 1 pound/inch.
I'll bet the Harley spring spacer is a short spring with a fairly low spring rate. Adding this would give a nice cushy initial rate. After a bit of movement, the spacer spring will coil bind (and start acting like a solid spacer) and the rate would then go back to the main spring rate.
It adds preload, but then you would have done that anyway with a solid spacer. The FJR used this stacked spring trick on it's rear shock. In comfort mode, two springs were stacked up to give a softer ride. In sport mode, the two springs were isolated from each other and the shock only used the stiff spring.
A progressive spring is essentially a bunch of different rate springs stacked up on each other. Initially the spring is nice and soft. As the spring compresses, the lower rate coils bind up and the higher rate coils begin to stiffen up the ride.
Clear as mud?
Are there more than one of those slots for the damper rod? I felt that it went through that slot easily...
Quote from: chefmatt on May 22, 2014, 01:18:58 PM
Are there more than one of those slots for the damper rod? I felt that it went through that slot easily...
Yes, look at the picture I posted earlier.
The issue with this statement;
Quote from: chefmatt on May 22, 2014, 01:18:58 PM
I felt that it went through that slot easily...
is this statement...
Quote from: chefmatt on May 20, 2014, 11:08:39 PM
The damper rod was hell getting back in all the way - it would slide in to within an inch or so, but we couldnt get it down close enough to screw the fork caps back in. after about two hours or trying to figure it out, lots of turning the fork cap trying to align the damper rod, I finally used a large screwdriver inserted into the preload adjustment slot, and gently tapped the damper rod down.
That last inch is the range the "D" shaped rod contacts the damper rod at the bottom and you used a hammer to install it.
It will slide right in without any force when properly installed.
Randy - RPM
Let's confuse things further! Swap to a set of forks with topout springs (or whatever the hell they're called) from something newish! First used I think on the YZF-R1, screwed with people setting traditional sag until they were more widely understood.... :)