To make front fork stiffer

[jyrki]

Hi, what would you recommendate to make front suspension stiffer? 1988 fj1200, original springs, 483mm. Stiffer springs from some dealer?

[FJmonkey]

Stiffer or perform better? Straight rate springs have been the budget choice for stiffer springs. Installing the RPM valves and straight rate springs are a major improvement. I have the valves and noticed a huge improvement when I installed them. The reflective dots glued to the freeway between lanes now feel like they are just paint and not a bump.

[Pat Conlon]

After experimenting with different oil levels in your forks, the next step is to consider the fork springs.
For a 550 lb street bike the oem Yamaha springs were light @ .644 kg/mm so I would start there.

1) Progressive springs are the easiest plug and play option: https://www.progressivesuspension.com/product/1465/fork-spring-kit
They offer a mild upgrade over the stock springs.



Any heavier springs will turn your front forks into pogo sticks. They will over whelm the oem damper rod valving and the spring rebound will become annoying. Plan on upgrading the fork valves to match the heavier spring rates.

2) RPM fork valves and .80 kg/mm matched straight rate springs give you a very nice ride.
http://www.rpmracingca.com/proddetail.asp?prod=M/C:RPMForkValve&cat=33



Additional discussion: http://www.fjowners.com/index.php?topic=7486.0

If money is a concern, try the straight rate .80 kg/mm springs now and save your money and add the RPM valves in the future.

3) Race tech makes valves for our FJ they call "cartridge emulators"  
They can handle much heavier fork springs than the RPM valves, up to 1.0 kg/mm
http://racetech.com/ProductSearch/12/Yamaha/FJ1200/1986-89

Over the years I've had all three of the above options ^^ on my FJs.... I like the RPM set up the best for street duty.

Hope this helps.

Pat
.

[Motofun]

Me personally? I'm not a fan of progressive springs.  They're a compromise.  If you have buy new springs buy the proper straight rate set up for your weight and riding style.  If you have no money, you can decrease the sag by the use of shims above the spring stack.  This is an old school technique and not the best solution but better than nothing.

I should add you lose travel with this technique so you will bottom out earlier....do not over do it.  quarter inch perhaps?

You know, after reading this a third time...If you have maxed the stock preload and it's still too "soft" I wouldn't go any further.  I was flashing back to my old CBX days.....

[FJ_Hooligan]

A cheap trick to stiffen up the stock spring is to cut the closely wound section of coils off (see Pat's picture of springs above).  Use a longer spacer to make up for the loss of length.  The resulting spring will have a higher rate without wasting fork travel to collapse the close coil section. 

Hoffman did this and it works well as a poor man's solution to initial fork performance improvement.  You would definitely want to move onto better (more expensive) solutions as money allows.

[andyoutandabout]

It's Christmas, treat yourself to the RPM valves. They are kinda other worldly when set up with the right weight springs and fork oil volume/grade.

[ZOA NOM]

Don't forget the fork brace to keep the springs in line...

[andyoutandabout]

Rick is right. The brace is another essential. The front end will thank you. These additions are money well spent. Don't forget engine bars if you haven't got a pair yet.

[ZOA NOM]

Rick is right. The brace is another essential. The front end will thank you. These additions are money well spent. Don't forget engine bars if you haven't got a pair yet.

It's a little early to question the guy's bravery Andy... 

[axiom-r]

Or - just stiffer front forks.....

[aviationfred]

Or - just stiffer front forks.....

I waiting for someone to bring up USD 50mm forks 


Fred

[Mike Ramos]

Or - just stiffer front forks.....

I waiting for someone to bring up USD 50mm forks 


Fred

Gentlemen,

True works of art, no doubt about it! 

One can easily & with certainty understand the enjoyment and novelty of modifications.

Improved master brake cylinders, calipers & discs; modern suspension components such as a rear shock, fork springs & brace as well as Fork Valves (or emulators).

Individual air filters, timing advance, carburetor re-jetting and improved exhaust system to allow for a free breathing engine without a doubt add to an exceptionally improved riding experience.

No question it is a pleasure to individualize to one's own personal preference and enhance the performance of a basically sound motorcycle platform. 
   
However, and with no intention of being trenchant, when does the FJ begin to lose its' unique character?

It seems as if once a modification is accomplished that is not actually needed for "top shelf" STREET BASED performance, the uniqueness & appeal of the old FJ is perhaps compromised.

Just to make clear, the effort and the ability to install the USD's is admirable!   

Ride safe,

Midget

[Tuned forks]

Mike, I've wondered that too.  As wheels get replaced, suspensions get replaced, brakes get replaced, when is it no longer a FJ?  When the engine is replaced, the frame, the bodywork?  Not sure as I'm still new here.  I suppose it's still a FJ because in the hot rod world you can replace the entire drivetrain, brakes, suspension, change the bodywork, interior, etc and it's still called a '32 Ford or '69 Camaro or whatever.  I'd be curious to read others' comments on this subject.

Joe

[Millietant]

An interesting conundrum Midget, but in my mind you're actually missing the point of the "uniqueness and appeal" of the FJ.

As a long term FJ owner, the appeal of the FJ is that at over 30 years old, with a small number of cost-effective modifications, it can perform in a way that can match what's available on the market new today (within the confines of average owner/rider ability) and is a totally relevant vehicle (and mode of transport) on today's roads.

I believe the uniqueness of the FJ is the way it handles its duties in such an unruffled and matter of fact way, across a whole spectrum of situations, primarily due to its simple but hugely effective engine and capable chassis.

All of the mods we do seem to be about enhancing its inherent strengths - rather than eliminating weaknesses - that's the magic of the FJ today - a stock one is still an awesome road bike today, but a modified one can be Mega !!

[Millietant]

Joe. - I think the biggest difference between the hot rods and the FJ in the terms you refer to, is that the rods alter the intent and purpose of the base vehicle (ie they take a cheap family runabout and change its whole character), totally redesigning it to perform different duties to the original, whereas we generally try to just improve the way the FJ carries out it's intended duties.

I know that there are some exceptions and I applaud these bikes, but the majority of us are still captivated by the original and are just trying to optimise them to perform to modern standards for those duties (without splashing out substantial cash on a new bike).

Although personally, I still get a buzz when a modern "superbike" owner/rider realises just how good a well
set up 30 year d FJ is on the road.