250sx fork spring question

[250 Drex]

I have a 1985 250SX. The front end needs to be rebuilt, I have neck bearings, wheel bearings, fork seals and boots. Sitting still, there is very little compression left, and the bike leans to the left in the front end. The tubes look straight but I’ll know for sure when I get it apart.

With the amount of sag and the left lean, I suspecting that the springs are shot. Does anyone make after market springs? I saw old posts about Progressive and Dennis Kirk having them but I don’t see anything listed on the websites. Are there springs that are compatible? 200x tubes are 33mm and the right length, does anyone know if they will work?

Thanks,
Drex

[ATC King]

If it's leaning and the fork tubes are the same height in the trees, it's not the fork springs.

Rear tires, even from the same batch, aren't always the same diameter at the same pressure. When that's the case, measure the height of each tire with a tape and bubble level and inflate until they're the same.


There's plenty of dirt bikes and bicycles out there that only use a spring in one side of the fork, air or coil. A weak spring shouldn't make it lean. In the extreme, Cannondale has the Lefty fork, which only has one leg. They've been building the Lefty fork for probably decades now.

As far as the actual spring, a spring is a spring. All you need are the dimensions and to choose the proper strength. You'll likely save money by doing the research for a generic spring and not buying a machine specific one where someone else already done the research, and marketing.

There's several motorcycle fork diameter charts out there. If you look at those you may be able to get an idea of the spring diameter you need. Besides that, buy an inexpensive caliper an measure them.

The repair manual for your trike will have free length tolerances. If they're below that they're needing replaced anyway.

I'd suggest forgetting about progressive rate springs if your trike didn't come with them. It just introduces tuning problems on damper rod forks. Stick with straight weight springs.

[Footy]

My 350X leaned to one side the same way. It turned out to be worn out steering stem bearings.
Worn out rear axle bearing could do the same thing.
When you get the forks off roll the fork tubes on a flat surface to make sure they are straight.
Also put the triple clamps on a flat surface and check to see if they wobble on the flat surface. If so one off those could be bent.
These fork springs are so soft there is just no way they would cause the atc to lean to one side.

[ATC King]

I feel like this is stating the obvious, but I didn't mention it.

Bent parts are pretty much common on trikes anymore. Most have been run into the ground and crashed, some may have struck an immovable object (tree) just hard enough to bend parts on the front but not wipe out anything enough to make it jump out without a closer look.

Bent axles, front and rear, are a major thing to look for. Sometimes wheels are bent, sometimes the frame, sometimes the axles, and for the unlucky, all of the above.

The front axle is what imparts rigidity to the forks. If it's run loose it's easier to bend, besides all the extra abnormal wear a loose axle can cause if rode for a length of time. A bent axle will have the forks looking cattywampus.

Axles can be straightened. There's a bit of help there because finding a used and straight axle at this point is becoming more difficult and prices people want are insane for some old rusted and worn part that really needs more work put in than it's worth. Finding anything without pipe wrench marks on it is pretty tough too.


There's a whole lot of 'em out there where it doesn't take any measuring to see things are bent. Others are plain worn out and everything is wiggling, which makes it harder to tell is a part is bent or everything it's attached to is just loose.

[250 Drex]

Thanks for all the responses. I’ve got parts lined up to completely rebuild the front end, I’ll deal with bent stuff if I need to. I checked and leveled the rear first, didn’t help. I am replacing all wheels and tires, skinny up front but keeping the drum brake. I want to keep some unsprung weight up front for hill climbing ability. If a bunch of things are bent, I may go in a different direction and put modern and more readily available parts on it.

Drex