Suspension Upgraded, what now?

[krusty]

This post is primarily directed to Randy but others may chime in if they have similar experience. Any info posted may benefit others in a similar situation.
I have finally installed Randy's suspension upgrade, front & rear, to my 91 1200. I ordered the complete heavy duty set-up as most riding is done with wife on board with combined weight,  in full riding gear, of about 170kg.
So far we've done about 400klm since installation. My initial observations are that there is a lot less dive under braking and handling feels much improved. What I am concerned with is that the ride feels a bit harsh particularly of small irregularities in the road surface. It is not jarring but i was expecting that it would be a lot smoother. We did hit one large pothole and the front soaked it up quite well.
It set-up most likely needs fine tuning. The tyre pressures were set as per instructions. The front forks have 250ml of Motul in each fork and after doing the measurements described in the instructions  I calculated that I needed exactly half of the supplied pvc tube in each fork. I can't remember what the actual length was as I have lost the instruction sheet on which I had written my calculations. The rear has yet to  be adjusted for sag but I'm not clear on how this is done.
What I am aiming for is a smoother ride. Where do I go from here?

[Country Joe]

Here is an article that describes setting suspension sag.
https://www.motorcyclistonline.com/motorcycle-suspension-tech-tips-how-to-set-rider-sag-mc-garage
I, too have the RPM fork valves, springs and shock. David R. had already installed the fork springs, the preload spacers suit me just fine. I installed the rear shock and have been all over the place as far as spring preload settings go, but have ended up almost exactly where it was as delivered. I have the light spring, due to never carrying a passenger. If you perceive the ride to be too harsh, just start reducing your spring preload a quarter turn at a time until you think it is too low then bump it back up a quarter turn and ride it for a while. I found that going stiffer on the preload did in fact make it ride harsher.
Joe

[Bozo]

I have the full front and rear RPM setup, the front has 0.85kg/mm springs with 100mm spacers and RPM emulators. The front was great from the word Go. The rear with a one person spring was too soft (standard spring was 700lb) I had to go to 750lb for my wife to ride once in a while. Eventually I found the 750 was also better for a single rider as well, together we would weight around 190kg (around 380lb i think) and luggage (if I do have it attached) is around 45kg (90lb).
The bike rides well over our harsh roads and never seems harsh unless you hit a Sharp bump i.e the pot hole or a lift in the concrete etc but that can't be avoided on most suspensions.

[Bones]

I did the same as you Krusty and after measuring everything just cut the spacer in half. First ride after fitting I thought I did something wrong as it seemed to ride like a German wagon compared to the magic carpet ride people were saying about them. The instructions state the preload should be on the second notch when assembling so I just turned the preload back to zero and the ride was a lot better. I think I was just too used to it being soggy and it took a while to convert.

I ran it at that setting for a while before realising after putting a zip tie on the fork leg that it was too soft and the forks were fully compressing on a ride so I bumped them up to the first setting and have left it there since. The ride is firm but compliant and handles the bumps well, especially speed bumps at speed which you don't feel.

I rode an FJ recently with stock suspension and although it was rode smooth I didn't feel confident on it in the corners where the back would skip around and the front was too soft and had no feel at all, I was glad to get back on mine. I've got the .85 kg springs with a Hagon on the back and it rides well.

[Sparky84]

I calculated that I needed exactly half of the supplied pvc tube in each fork. I can't remember what the actual length was as I have lost the instruction sheet on which I had written my calculations.

I did the same as you Krusty and after measuring everything just cut the spacer in half.

Is the supplied PVC tube that close to being right(or at least half right)

So no need to measure,
Just cut it in half and she'll be right mate,
won't this upset any settings or as you've done Bones use a cable tie marker to check how far down they go on a ride?
I suppose you could always trim the tube if required.

How far done from the top did you fill with oil?

Will the Anti Dive units still operate with Fork Valves in?, I'm sure mine are still operating as I have changed the AD units before and still have 1 new unit left over.

Cheers Alan

[racerrad8]

I need to make sure we separate the two issues Krusty had referenced: Spring pre-load (spacer length) and oil level (air gap).

Both will cause you not to have the ride you should be getting or expecting from the RPM fork valves. One or the other, or the combination of the two being incorrect will not allow the fork valves to function properly.

Krusty, I don't know what year you have, but I believe something is definitely incorrect in your measurements. Both for the spacers and oil levels.

The spacer supplied is always longer than 12" and cannot just be cut in half and installed. I pulled three from the box this morning they were between 12 1/8 and 12 3/8". The spacer lengths vary from year to year from. The average shortest spacer for the early model years is 4" and the longer spacer is for the ABS bikes as they have the longest for tube is just under 6". The non abs 91-95 falls somewhere in the middle.

So, even if you have a 95 ABS bike the spacer is going to be too long if it is just cut in half.

If they were all the same, I would have spacer lengths pre-cut for the model year you own. But with manufacture variances from internal fork components that is not the best way to set up your forks. The spacers are just not one size fits all. A thickness difference of one of the washers supplied can be felt in the fork valve action and is commonly used as a tuning tool. The washer thickness is half the distance of the pre-load adjustment notches.

The proper measurement is critical. If you have too much spring pre-load the RPM fork valve cannot travel fast enough on high speed travel to allow the bypass valve to function properly. If that occurs, then the ride is harsh and the magic carpet ride cannot be obtained.

Krusty, I think we need to start over on your spacer lengths. I can email you the instructions again and we can get it figured out.

Now, onto oil levels/amounts. For the same reason mentioned above you should not use the fork fill by volume method. That might okay for "general" maintenance, but for optimum performance from the RPM fork valves we need to have established fork oil levels.

Krusty what was the "air gap" after filling the forks with the 250ml. The reason I ask is we use 85-90% of the liter bottle between the two fork tubes. I have never measured the volume added, but that shoud probably be in the range of closer to Yamaha "volume fill" recommendation. Yamaha has a fill rate of 424ml for the early AD forks. So, as 250ml your fork are way too low on oil.

I usually add about half of the bottle to the forks with the fork valves and springs removed. I cycle the forks several times to push out the air bubbles. Then I let them sit for at least a half hour to allow the small air bubbles to rise to the surface. I cycle them again and if anymore air comes out I repeat until there is no more air. I then drop in the fork valve and push it down through the oil to seat it.

From there I use the the Fork Level Gauge to draw the oil down to the level of 6" from the top of the fork tube fully compressed. I have been told a turkey baster marked at 6" works and some people use a tape measure to obtain the 6" air gap.

Once the air gap is properly set, then I extend the fork and drop in the springs, upper washer against the spring, the spacer followed by the fork cap. When installing the fork cap there should be a minimal amount of force, if any is required to push compress the spring and start the threads of the fork cap. If you have to put a lot of weight onto the cap to start the threads, then your spacer height is too long.

One other very important component of the proper function of the RPM fork valves is the setting of the internal damper rod to the medium setting for the 84-90. Unfortunately, they cannot be set externally because all of the forks have been apart and not reassembled properly.

In all of my years, I have only had one set of forks correct when they came apart. That was the virgin forks from Texas Dave's 84 when he stopped off here several years ago. Heck, even Flynt's 84 Stormy bike had the forks rebuilt incorrectly and the previous owner was a licensed, old school motorcycle mechanic.

So, with that said, the disassembly the forks is really required to properly set them up for the RPM fork valves. Between the damper rod not being indexed correctly and the taper spindle being installed upside down, all early forks should be disassembled.


Now onto sag adjustment, please do not refer to that article, that is not applicable for the RPM products.

There is NO, ZERO, NADA sag adjustment on the front of the bike with the RPM fork valves. The pre-load adjustment can be changed for personal preference.

In reference to the rear sag, the measurement should be taken from the rear edge of the tail section to the ground. One measurement for no rider and one for rider or riders. The measurement difference (SAG) for the RPM rear shock is 1.5-2" (40-50mm)

Bozo, you bought the single rider spring of 800, hopefully you went up to the 850 which is the spring I install on the higher or dual rider shocks. I never have had any springs softer than 800

Randy - RPM

[krusty]

Randy, accept my apology for having a seniors moment re the fork oil (I'm almost on the wrong side of 70). I had a litre bottle of oil and used approximately half in each fork (I was thinking I had a half litre). Also I had totally forgotten that I did measure the air gap and had to extract a few ccs of oil from each leg. As I have lost my notes I don't recall the actual amount. As mentioned in my OP it is a 91 model (without the rod or ABS). I will open the forks and remeasure every thing and get back to you.

[racerrad8]

As mentioned in my OP it is a 91 model (without the rod or ABS)

See, I'm almost on the wrong side of 50 and had the same moment as I missed the mention of the year model...



That means if you just cut the spacer tube in half they are too long for sure.

Also, one more thing...which fork oil did you use because that matters a lot too...

Keep me posted.

Randy - RPM

[krusty]

This one.

[Sparky84]

One other very important component of the proper function of the RPM fork valves is the setting of the internal damper rod to the medium setting for the 84-90. Unfortunately, they cannot be set externally because all of the forks have been apart and not reassembled properly.

In all of my years, I have only had one set of forks correct when they came apart. That was the virgin forks from Texas Dave's 84 when he stopped off here several years ago. Heck, even Flynt's 84 Stormy bike had the forks rebuilt incorrectly and the previous owner was a licensed, old school motorcycle mechanic.

So, with that said, the disassembly the forks is really required to properly set them up for the RPM fork valves. Between the damper rod not being indexed correctly and the taper spindle being installed upside down, all early forks should be disassembled

I think mine at present are not indexed correctly after rechroming, (then they were leaking from damper rod stopper screw) so how do you index correctly?

So I need to pull them apart and check the taper spindle and reassemble indexing damper rod correctly.

Cheers Alan

[rlucas]

See, I'm almost on the wrong side of 50...

And just which side of 50 is the so-called "wrong" side? Hmmmm?

[krusty]

Randy, could you please email me instructions for calculating spacer length.
Thanks

[Sparky84]

Randy, could you please email me instructions for calculating spacer length.
Thanks

This may assist Krusty with measurements also hopefully you received instructions in email I sent

http://www.fjowners.com/index.php?topic=16738.msg169103#msg169103

Cheers
Alan

[fj1289]

See, I'm almost on the wrong side of 50...

And just which side of 50 is the so-called "wrong" side? Hmmmm?

The inexperienced side ?!

[Bozo]

I need to make sure we separate the two issues Krusty had referenced: Spring pre-load (spacer length) and oil level (air gap).

Both will cause you not to have the ride you should be getting or expecting from the RPM fork valves. One or the other, or the combination of the two being incorrect will not allow the fork valves to function properly.

Krusty, I don't know what year you have, but I believe something is definitely incorrect in your measurements. Both for the spacers and oil levels.

The spacer supplied is always longer than 12" and cannot just be cut in half and installed. I pulled three from the box this morning they were between 12 1/8 and 12 3/8". The spacer lengths vary from year to year from. The average shortest spacer for the early model years is 4" and the longer spacer is for the ABS bikes as they have the longest for tube is just under 6". The non abs 91-95 falls somewhere in the middle.

So, even if you have a 95 ABS bike the spacer is going to be too long if it is just cut in half.

If they were all the same, I would have spacer lengths pre-cut for the model year you own. But with manufacture variances from internal fork components that is not the best way to set up your forks. The spacers are just not one size fits all. A thickness difference of one of the washers supplied can be felt in the fork valve action and is commonly used as a tuning tool. The washer thickness is half the distance of the pre-load adjustment notches.

The proper measurement is critical. If you have too much spring pre-load the RPM fork valve cannot travel fast enough on high speed travel to allow the bypass valve to function properly. If that occurs, then the ride is harsh and the magic carpet ride cannot be obtained.

Krusty, I think we need to start over on your spacer lengths. I can email you the instructions again and we can get it figured out.

Now, onto oil levels/amounts. For the same reason mentioned above you should not use the fork fill by volume method. That might okay for "general" maintenance, but for optimum performance from the RPM fork valves we need to have established fork oil levels.

Krusty what was the "air gap" after filling the forks with the 250ml. The reason I ask is we use 85-90% of the liter bottle between the two fork tubes. I have never measured the volume added, but that shoud probably be in the range of closer to Yamaha "volume fill" recommendation. Yamaha has a fill rate of 424ml for the early AD forks. So, as 250ml your fork are way too low on oil.

I usually add about half of the bottle to the forks with the fork valves and springs removed. I cycle the forks several times to push out the air bubbles. Then I let them sit for at least a half hour to allow the small air bubbles to rise to the surface. I cycle them again and if anymore air comes out I repeat until there is no more air. I then drop in the fork valve and push it down through the oil to seat it.

From there I use the the Fork Level Gauge to draw the oil down to the level of 6" from the top of the fork tube fully compressed. I have been told a turkey baster marked at 6" works and some people use a tape measure to obtain the 6" air gap.

Once the air gap is properly set, then I extend the fork and drop in the springs, upper washer against the spring, the spacer followed by the fork cap. When installing the fork cap there should be a minimal amount of force, if any is required to push compress the spring and start the threads of the fork cap. If you have to put a lot of weight onto the cap to start the threads, then your spacer height is too long.

One other very important component of the proper function of the RPM fork valves is the setting of the internal damper rod to the medium setting for the 84-90. Unfortunately, they cannot be set externally because all of the forks have been apart and not reassembled properly.

In all of my years, I have only had one set of forks correct when they came apart. That was the virgin forks from Texas Dave's 84 when he stopped off here several years ago. Heck, even Flynt's 84 Stormy bike had the forks rebuilt incorrectly and the previous owner was a licensed, old school motorcycle mechanic.

So, with that said, the disassembly the forks is really required to properly set them up for the RPM fork valves. Between the damper rod not being indexed correctly and the taper spindle being installed upside down, all early forks should be disassembled.


Now onto sag adjustment, please do not refer to that article, that is not applicable for the RPM products.

There is NO, ZERO, NADA sag adjustment on the front of the bike with the RPM fork valves. The pre-load adjustment can be changed for personal preference.

In reference to the rear sag, the measurement should be taken from the rear edge of the tail section to the ground. One measurement for no rider and one for rider or riders. The measurement difference (SAG) for the RPM rear shock is 1.5-2" (40-50mm)

Bozo, you bought the single rider spring of 800, hopefully you went up to the 850 which is the spring I install on the higher or dual rider shocks. I never have had any springs softer than 800

Randy - RPM

Randy, I had a brain fart, yes that was 850, I remember asking you before I bought the spring.