ExpertX shock recalibrating (DIY)

[LazyBastard]

Anyone who has actually worked on the insides of shocks.... I've been reading the expertx suspension manual, and they have a minimal writeup about recalibrating the shocks.

What I've been able to determine is that to increase compression damping, add shims above the piston, and to increase rebound damping, add shims below the piston.

My questions are these;
1) How do you determine how much shim to add or remove?
2) Where do you get these shims?
3) Where do you get the nozzle to refill the n2?


Now my two observations regarding the performance of the suspension are these; a) It bottoms out more easily than I'd like, b) It bounces back up real hard (a$$ kicker). I think I should increase both compression and rebound damping, right?

 

[sledheadgeorge]

Thats what I had done to mine. Increased compression and rebound. Works even better now. I will try and find out what my shock guy did and let you know.

 

[LazyBastard]

Thanks.

 

[Auskins]

Wow, I'm marking today down somewhere...Its the first time I seen LB ask a question!
LOL
Just yanking ya!
Hope you gets it to work out.

 

[LazyBastard]

New trick to learn. When I get it all figured out, I'll start dispensing advise.

 

[Jack_Shaft]

LB, Boivin has a real nice damping set-up that they should be able to give you, it was developed by one of their dealers, Aaron Excell of Excell Motorsports. The shocks are Ski-doo based parts, so the KYB shims from the Ski-doo racing catalogue are the ones you want, all of the individual shim P/N's are listed in these manuals.

As for the nozzle, have a look around at MotionPro.com, they have some great MX tools and they sell a needle/ regulator/ adaptor kit that works with the KYB shocks.

IF Boivin won't give you the damping layout (which does exactly what your asking for) I may be able to haul out one of my old bins and find it for you.

 

[vcrash]

LB, Any chance that your shocks are calibrated for the 121 setup instead of the 144 rails, That would deffinatly be your problem if that were the case, I havnt experianced any loss of performance in mine yet(4 years old) approximatly 15000kms.

 

[LazyBastard]

Mine definitely haven't CHANGED performance, and the whole unit was ordered from ad-boivin with 144" rails, so I'm sure that they would have put the right shocks on it. Regardless, I can't imagine that they would require different calibration from 121" since the skid is identical save for the added rail length. Every part of the skid is positioned identically with respect to the tunnel.

Jack_Shaft:
Have you EVER been able to get through to someone with a BRAIN at adboivin? They make a good skid, but their customer service blows. I'll try to talk to them, but I already know... the person who answers the phone will say she doesn't know, and will transfer me to a tech, who will also say he doesn't know - and will also say he'll find out and call back, and he will NEVER call back.
... know where online I can find a skidoo racing catalog?

 

[4Fighter]

Mine definitely haven't CHANGED performance, and the whole unit was ordered from ad-boivin with 144" rails, so I'm sure that they would have put the right shocks on it. Regardless, I can't imagine that they would require different calibration from 121" since the skid is identical save for the added rail length. Every part of the skid is positioned identically with respect to the tunnel.

Jack_Shaft:
Have you EVER been able to get through to someone with a BRAIN at adboivin? They make a good skid, but their customer service blows. I'll try to talk to them, but I already know... the person who answers the phone will say she doesn't know, and will transfer me to a tech, who will also say he doesn't know - and will also say he'll find out and call back, and he will NEVER call back.
... know where online I can find a skidoo racing catalog?

Have you tried email? They were pretty good at getting my questions answered. As for the shocks...well I'm sending them to Excell when I have some free-time to wrench again.

 

[vcrash]

cmon Lazy, ya have 11.5 more inches of leverage with the longer skid, the dampening has to be increased to deal with that, Im sure that boiven would have valved it appropriatly since purchased as 144 though.I thought for some reason that you started with the 136.

 

[LazyBastard]

There's no more leverage. The force comes from the weight of the sled via the same two points on the tunnel. In both cases, the rails are planted on the ground. In fact, the extra length of the rails will cause the skid to bridge some holes, which effectively reduces the distance the sled has to accelerate into the hole and should REDUCE the need for damping.

 

[vcrash]

your right about the bridging, however when all of the force is transmitted from the rear of the skid which it is at times the there is a big differance in applied force as well as the extra mass being that much farther from the pivot point, either way, your problem is not enough rebound dampning.There are some really good shock guys right here in ontario that im sure can help ya out, if you post your problem on doo talk they will be able to send ya in the right direction. good luck.

 

[LazyBastard]

there is a big differance in applied force

Last I checked, force = mass * acceleration. Since mass (of the sled) and acceleration (force of the shocks/springs working against the inertia of the sled) are the SAME, so is the FORCE.

I think you're being confused between pressure and force. It is true that the pressure at any point along the rail is lower with the longer skid, but the force being applied to the shocks is the same.

as well as the extra mass being that much farther from the pivot point

What extra mass? You can bolt on either 121 or 144" skid and they have no affect on the mass of the sled. The only mass we are concerned about is that which is being supported by the springs/shocks. The rails are, for all intents and purposes, the ground. There is no extra mass, and the pivot point is the same.

 

[Jack_Shaft]

The 144" shocks are valved identically to those of the 121" skid. Period. Boivin is only ordering 6-800 of these shocks from KYB per year and cannot afford to change anything in their specs at those volumes.

LB, I am going to look through my books to try and find the damping set up that Aaron Excell developed over the first season or two that he sold Expert X's. If you were to send your shocks to him, he would re-valve them aa such and I gaurantee you would prefer them that way.

I know all about the customer service at Boivin. I worked with them on certain projects for 4 years. Without investing in competent English speaking staff, they will never fulfill their potential.

 

[LazyBastard]

If you can look that up, I would greatly appreciate it. Two reasons I'm not going to be sending my shocks to him, and neither has anything to do with price or competency. 1) any time you cross the border, bad things can happen. 2) i *like* doing things myself.