Rear shock too stiff.... 210lb rider!

[Dean J]

Ok so first off, when my bike was stock the rear suspension was fine set at 4 clicks from bottom. Buuuuuuuut.......... since i changed my rear for a monster seat unit on custom subframe, and binned off the stock exhaust etc it is super harsh even set to minimum preload! feels like i have a rigid bar where the shock should be! Low speed and high, small or large bumps, they all hurt!
Also Headshakes are every full throttle upshift, hitting a rut on full throttle, and presumably cresting hills etc ( im taking it easy at minute until i get to bottom of this!)

Only thing i can think of that could possibly have killed the shock is welding the new subframe rails on, but they were a good 1 and 1/2 inches away from the top shock mount so id be surprised if it had cooked the shock!

the shock still compresses with me sat on/pushing down on it, and appears to have some rebound so im really rather confused!

Seating position isnt drastically different, weight slightly farther forward perhaps, but wouldnt have thought enough to make a major difference!?

Any ideas?

 

[Motogiro]

If the shock seems like it's operating normally I would think the valving may have changed. Since you've change the angle of the subframe it's probable you may be experiencing the rebound at a different angle on your back. Same thing with the angle change regarding the font going light under hard acceleration. As soon as your front wheel starts to go light you'll get a shimmy which is pretty normal when the the front wheel lifts or returns to and from the ground. The increased angle of the seat with your weight pressing against it may be increasing the lift in the front.

How much have you changed the angle? How much do you weigh? Could it be you need a higher setting on the spring and your already compressing the shock near it's limit? Did the spring become annealed and lost some tempering so that there is more compression than original?
How about some pictures.

 

[Dean J]

There is a slight increase in seat angle, but not massive amounts, and im sitting fairly well the same as i did before, just maybe a touch further forward. think when i get chance ( next weekend probably) ill take the bike out and try putting my weight/ass further back in the seat see if that helps any.

Have tried different preload settings all way up to fully hard, which is completely untolerable.

Will swing a pic up shortly.

 

[Dean J]

about the best pic i have showing the seat angle... Im still sitting pretty much in line with the shock, so id have thought it wouldnt have changed much if any at all! Do you think the welding could have cooked it?

 

[Motogiro]

Your bike looks like the 05-06 S1 version with an S2 swingarm. I don't know if that subframe angle change would effect it that much but obviously you're experiencing more than just a hard tail and have head shake under throttle. Maybe check your bike against a stock FZ6 because the suspension has been modified from stock. You could have a bad shock. Thing is you're having other problems that additionally point to geometry so you may also have to do measurements.

 

[Dean J]

Its an 04 with 07 swinger.

Was riding it before i started modifying her, Everything was absolutely fine before the subframe mods....

 

[Motogiro]

Its an 04 with 07 swinger.

Was riding it before i started modifying her, Everything was absolutely fine before the subframe mods....

Yes, I meant 04-05 S1.
If it was fine before the mod, that may be the problem. If you think about how your body works, the rebound is going to be at a different angle. The force moving more forward and less upward during compression. Still I don't think it would make you feel like the shock has much harder compression.
Then there's the front under acceleration. Have you checked tire pressures?

 

[PhotoAl]

Have an 07 swingarm on my 04, actually swapped out the swingarm, shock and spring. No significant change from the swingarm, the ride was a little better but figured it was the old shock has almost 30,000 miles on it and the 07 shock had 7,000 on it. Are your bearings in good shape? If the heat did anything it may have overheated the bearing. Have you checked to see if the alignment is off? I had that issue and it made for some strange handling, particularly under hard braking.

 

[Dean J]

Alignment hasnt been changed, tyre pressures perfect etc.

I havent checked swingarm bearings yet but it is on my list as soon as i get the chance! although I cant see how the bike was sat for 2years, i get her on road for two months, then she sits for a week and the bearings die!

Ill be checking bearings and bushes etc first chance i get, if its not that i may have to get another stock shock just to see if that is the problem! Otherwise its going to be an expensive job having a rear shock built,valved and sprung specifically for the bike!

 

[FinalImpact]

Did you move the top of the shock or is it still in the same OEM location? Also, any chance the energy from welding found a path through the shock vs ground to electrode? i.e. Ground on S/A and welding on sub-frame?

 

[FinalImpact]

Also there is a couple of us on here who have useless R1 springs which are lower rate and installed height (10 mm). You would likely need to shim them but I have no use for it so its yours if wish to try it.

 

[Dean J]

Shock is in its factory location, not moved at all.

I suppose it is possible that the welder grounded through the shock, and also my friend who did the welding ran the welder inverted at one point, ie bike becomes live, welder becomes earth, could that have damaged it?

 

[FinalImpact]

It all about potential; so I ask again, was the swing arm ever used as ground and the sub frame welded on? I'd guess no but I have to ask. The shock has a metal bearing in one end and it could transfer energy. What it would do to the shock, I suppose it could hurt the valving, but I find it unlikely you used the S/A for a ground. but please recite what you remember. Beyond that, I guess its all about loading and you changed the load. Sit back further and see what it does.

You might also check the sag. That will give the rest of a clue as to what is going on. I've posted on it and done. Its good info to have. Would have been great to have before the mod. Your bike is much lighter you may have it under the 400lb barrier with the fairing, tail and exhaust gone.

 

[Dean J]

Ah ok, to the best of my knowledge the swingarm was never used as the ground.

Also missed your offer on the R1 spring - that would be super cool to give me something else to try before buying a whole shock! id need to find a decent courier price though as i am in the uk! If you want to message me your address i can get a price?