1983-85 200X: Rear Spring Rate?

[christph]

I'm thinking about installing a stiffer rear spring on my 83 200X but can't find the stock spring rate. I need it as a baseline. Does anyone know what the stock rate is? Also, is it a linear or progressive spring? Since it has no raising rate linkage I'm thinking it must be a progressive spring. I looked in the service manual and online but I'm finding nothing.

[wonderboy]

I can't help with the actual rate measurement, but I can address the progressive question. The spring is a straight rate spring, not progressive.

To understand how a progressive spring works, first a bit of background info. The rate of a spring is dependent on a few parameters including how many coils of the spring are active. This means how many loops of wire in the spring are free to flex. The more coils of the spring are active (all else being equal), the lower the rate (the softer the spring).

The way a progressive spring is made to be progressive is by closely spacing some of the spring coils. So as the spring compresses, the close together coils come into contact with each other. This takes some of the coils of the spring out of the equation. The spring now acts as if it were a spring of fewer turns, which means higher rate (stiffer).

The springs on the 200X, 350X, and 250R are single rate since the coils are spaced such that even at full compression, none of the coils contact each other.

[christph]

Thanks for the explanation. I read an 1983 Dirt Wheels article on a tricked out 200x and they used an aftermarket progressive spring, and the suspension doesn't have a raising rate link so I thought it might need one. Now that I know it is linear I have a much wider selection of springs to choose from because progressive springs are few and far between. Now if I could only find out the rate.

[onformula1]

Here's my 3 cents-

The first gen. 200X and 350X uses a single spring, dual rate. It is not progressive.

The 85-86 250R uses a straight rate spring.

No spring is truly linear, but we call them linear (I could go on forever on this topic, but it won't help)

Here is a picture of a 200X, 250X, 85-86 250R. (Left to right)

214903

The stock 200X spring is very stiff, due to the design the time you set the preload, trike weight & and rider weight the dual rate part is coil bound. So the spring is now a straight rate. That rate is 18.0 Kg/Mm or 1005 lbs./inch.

The reason a 200X shock feels so soft to many is-

1-Its blown or flat worn out. (Showa used a poor quality shock fluid back then)

2- Poor, old school piston design from the mid 70's, too many bleeds and very soft valving.

Feel free to PM me if you have any questions.

[christph]

1005 lbs./inch! Damn, that's high. I guess that's why the progressive rate spring I read about in the 83 Dirt Wheels article was 1000-1300 lbs./inch.

[onformula1]

Yeah, they have a HUGE wire diameter and are too short to mod. stiffer with out a lot of work.

What is your issues with the shock? just too soft?

Make sure the shock bottoming bumper is still there, most are trashed or long gone.

Funny thing is- I have never built a 200X shock that had more than half the shock fluid in it or over 50 PSI of nitrogen, I have only seen two that had a bottoming bumper that was there or good.

[onformula1]

I forgot I have also seen stock 200X springs up to 19.1 Kg/mm or 1067 lbs./inch. (Not many)

Quality control was not great spring wise in the 70's and 80's.

Kayaba set the standard starting in 1990 now most are very good/close.

Can you scan that article for us?