Total Motorcycle Community Forums

Just got a 84 yamaha xt-250 But no owners manual It has a tire type air valve on top of the front forks Air? What about the oil inside how to depressure safely? Should I change the oil inside? what kind of oil how much oil sorry for the newbie questions but I gotta learn some were Thanks

ask your friendly neighbor hood yammy shop...im clueless when it comes to dirt.

Sounds like it might have an "air gap" in there too. The basic idea is that the air compresses really quickly and easily to take up small irregularities in the roads.

You need to get the shop manual for your bike, we can't tell you how much oil you need, or how to change it. Short of measuring how much you take out and replacing the same amount.

Many bikes from the 70's-80's had those air valves on them. The theory was that you could adjust the pressure in the fork to act as a sort of secondary spring. The reality was, the air pressure would blow out the fork seals very quickly.

We used to use them to bleed off the air that would build-up in the forks after a hard ride caused by heat build-up. If your fork started to feel harsh halfway into your ride, you stopped and bled the air off, and the fork worked normally again.

Notice I did not say 'worked well again'. Those damper rod forks can only do so much with what they have to work with, hence the universal usage of shim-type pistons in all modern (since the mid 80's) dirt bike forks. And all performance streetbikes as well. Damper rods are only found on bikes built to a lower price point these days. Not that you should worry about them on your bike, they will provide adequate service on your XT. If the fork feels too soft, don't add air, add about 5cc of fork oil to each leg until it feels how you want it.

And you should track down a service manual for the bike. It will give all the info you need to service the forks..... and everything else.

Check out the Garage forums too:

index.php?c=3

If you check on the oil type at the Yamaha shop, be a bit wary when they say 10W-40... that is what they always say when they don't want to look it up for you my '86 Kawa 454 took 5W-30. 10W-40 won't hurt anything, but the wrong oil can change how nicely the bike shifts.

Check eBay for a Clymer's guide. I find them to be quite helpful, particularly for older bikes.

--Dave

safety-boy wrote:...my '86 Kawa 454 took 5W-30. 10W-40 won't hurt anything, but the wrong oil can change how nicely the bike shifts.

Considering we're talking about fork oil, I don't think it'll affect shifting.

I think ATF fluid was listed as an alternative for fork oil back in the day. It's still common in some newer bikes as well .