ATC 350X fork air pressure

[Fixer_Upper]

I am a 13 year old kid reviving my dads old 350x. I’ve been riding it for a while and was wondering what kind of air pressure was supposed to be in the front forks. No, I am not hitting large jumps but my forks feel like they kind of sag down about 1/3 way when just sitting on it, then it feels almost like it is relying 100% on the oil that’s in there meaning that it gets semi stiff. The point is that it feels like there is no pressure in the forks and that they do not feel like forks at all. Based on research I have done with other bikes it is because there is no air pressure in the forks. If anyone would help me out and tell me the amount of air pressure that should be in these forks that would be a great help!

[Aulbaugh]

They don’t require any air pressure.

[BOB MARLIN]

For the most part the air valves are for letting air out due to elevation changes and such. But I do seem to remember the owners manual saying you can put max. air pressure of 3 lbs. (or maybe it was 6 lbs.) if you want. It sounds to me that you have a fork oil problem, either not enough, too much, not equal amounts in each leg or the wrong type or weight.

[atctim]

Please do not put air in the forks unless you want to blow the seals out and have a leaky mess. Your forks most likely just need rebuilt, meaning fresh fluid and new seals. Most any motorcycle shop can do this for under $200. I would guess and say the front fork oil has never been changed. This is something you could do for yourself. I am certain there are videos on youtube, or we could walk you thru changing it yourself. You will need to buy fork oil firstly.

[oldskool83]

i only ever added about 2-3PSI after forks were fully rebuilt. If not your just wasting your time and going to ruin a relic even more

[floydechoes2000]

Too bad you don't live closer, I'd help you rebuild them. I don't run any air pressure in mine at all, I'm a tad over 200 pounds and mine doesn't sag more than an inch. I am running progressive springs though which I highly recommend if you're riding in rough terrain, they work amazing in tight, rocky and rooted New England.

I'd check Youtube for videos, slowly and carefully disassemble yours one at a time and compare what you remove to the parts illustration on Partzilla to make sure you're not missing anything. Fork seals and oil are cheap and it's not hard to do if you're mechanically inclined or have someone who is helping you.

Good luck!

[Supraman0614]

The fittings are strictly there to equalize the air pressure. Raise the frame to get the front wheel off the ground, and push down on the valve on each fork a few times to let the pressure equalize. If they still feel bad, drain the oil in both and refill with the proper amount (should be in your service manual). There are different weight oils you can use to make them stiffer as you like. If the seals aren't leaking, you shouldn't have to rebuild them.

[Fixer_Upper]

Thanks everyone! Could it also be possible that my forks are empty?

[atctim]

There is a drain bolt at the bottom. There is a fill cap on top. Get the front end off the ground, open up drain plug and top cap. Drain and refill with FORK OIL. Each fork should hold 9 ounces. This way you can not only check the fork oil, but you are replacing it with new oil.

[ps2fixer]

I like to check specs in the Honda Spec manual. Here's what Honda says. Note, I'm pretty sure the shock pressure rating would be for the rear shock? I don't know much about suspension and rebuilding them, seems simple enough but that spec is a lot of pressure lol.

The final drive case is an interesting thing on that page. Wonder if that's a mistake or what. Numbers match the ATC250SX exactly, years and all, the ATC250ES the spec is completely missing from it. This is a book by Honda btw, there's similar types of mistakes in the service manuals.




Just to double check numbers, here's the specs from the Honda 350x service manual.

Front:


Rear:

[Fixer_Upper]

Thanks for the help everyone! I took your advice in changing the fork oil, but while doing so I discovered that the left fork was not full of oil, but clay like dirt. so does anyone know what I should do from here? I will soon tear the left fork apart (the right one will probably be dealt with after I know what I’m doing with the left one) to see what damage has been done. I have also heard of 250r fork conversions, and by looking at eBay I’ve noticed that 250r forks are a lot cheaper than X forks. I am open to any advice as I am trying to avoid 700$ fork replacements/repairs.

[BOB MARLIN]

In my opinion, and it's just an opinion and I'm sure others will disagree , converting over to 250r forks is NOT what you want to do. They are a different size as well as being a trailing axle set up. Your 350x is a leading axle set up. It may not seem like a big deal, but it will screw up your steering geometry and the trike wont turn for crap. Not such a big thing on a motorcycle because you more or less lean the bike one way or the other to change direction. On a 3 wheeler its all in the steering geometry because you can't lean a trike. If your fork had actual dirt inside they are probably toast. If it was just a goo with no grit you could probably save them. Conventional forks like the 350x are very simple but I don't now what parts are still available. People on this board usually have a hoard
of parts laying around, so your best bet might be posting in the classified section to see if some one has a set they would sell.

Edit: I assumed you were talking about 3rd gen 250r forks. I do believe there are some parts from the 2nd gen 250r forks that can be used in the 350x.

[ironchop]

In my opinion, and it's just an opinion and I'm sure others will disagree , converting over to 250r forks is NOT what you want to do. They are a different size as well as being a trailing axle set up. Your 350x is a leading axle set up. It may not seem like a big deal, but it will screw up your steering geometry and the trike wont turn for crap. Not such a big thing on a motorcycle because you more or less lean the bike one way or the other to change direction. On a 3 wheeler its all in the steering geometry because you can't lean a trike. If your fork had actual dirt inside they are probably toast. If it was just a goo with no grit you could probably save them. Conventional forks like the 350x are very simple but I don't now what parts are still available. People on this board usually have a hoard
of parts laying around, so your best bet might be posting in the classified section to see if some one has a set they would sell.

Edit: I assumed you were talking about 3rd gen 250r forks. I do believe there are some parts from the 2nd gen 250r forks that can be used in the 350x.

I agree with this if you're wanting to do a simple swap over.

The only way to do it correctly is to figure the rake and trail of the OEM 350X setup and machine custom trees to use with the R forks to get the factory 350X rake and trail geometry... At that point, if machined triple trees are required, you might as well use newer and better designed forks with the custom trees

Also, finding truly straight R forks or lowers that aren't bent or dented is a crap shoot. Alot of them got ed over the years

Sent from my Z958 using Tapatalk

[TSpencer]

The forks are fairly simple to rebuild. As long as your springs are in spec, the only other real wear parts are the inner and outer fork bushings. Just take the forks apart following the manual, clean it all up and replace the bushings if they are copper colored and the Teflon coating is worn off. Tells you right in the service manual what to look for. Put in new oil seals and dust seals and fill with new oil and youre good to go. Race tech has the bushings if they need to be replaced. Just did this myself last month and I'm by no means a mechanic. It's a fairly easy job. The only thing I did different from the manual is I used 10wt fork oil instead of the recommended ATF.

[Dirtcrasher]

Biggest things are snap ring pliers for the clip, a bushing driver and a seal driver, which can both be made fairly simply.

Blue loctite the oil lock piece bolt - Make sure the tubes are straight or send them to me...