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Thread: Best MX Suspension Mods for an 85 250R??????????????

  1. #1
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    Best MX Suspension Mods for an 85 250R??????????????

    I have a box stock 85 250R and I want know what company does the best suspension mods? and what settings work best for MX? What can be done to the forks? ReValve? Springs? Oil level? Air?......... Can the rear shock be worked or should it me replaced? If so, what shock is being used? Aftermarket linkage? I'm 180 lbs.
    VIRUSDOG
    85 250R
    82 250R
    84 200x
    85 185s
    84 185s
    85 Big Red
    85 225 shaft
    Coming soon: ATC 650R!

  2. #2
    Billy Golightly's Avatar
    Billy Golightly is offline Always finding new and exciting ways to not give a hoot in hell Catch me if you can
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    I've played with the stock suspension on my 86 250R A LOT and have sort of made it a personal mission to get inverted fork like performance out of the original OEM ones and to get a stock shock performing as good as an aftermarket one.

    One the front suspension you have a few different options. The best thing to do is get a Race Tech "Gold Valve Emulator". I've had a set of these in my R for close 3 years now and have after a long time dialing in and changing things finally gotten them down pat where I am pretty happy with the performance of them. The emulators more or less are a spring loaded check valve that slips down inside the fork tube and rests on the top of the dampening rod, and the fork spring goes on top of it. The check valve has a bolt with a small diameter high tension spring on it. Modifications are done to the bottom of the dampening rod to allow the oil to enter it much faster at the bottom. When the forks compress the oil works its way to the top of the dampening rod where it meets the emulator valve and depending on the spring tension and the velocity of the fork compression determines how far the valve opens and how much compression dampening you get. You can of course adjust the tightness of the valve opening with the spring ratio, but you can also adjust the preload of the spring just like on a rear shock so that you can dial in exactly how much tension it takes before it opens (Pre-loading a spring has almost zero effect on the overall tension of the spring once its moving, but instead changes how much tension it takes to make it BEGIN moving). That allows you to adjust out and keep the front forks from "diving" and feeling mushy if you grab the front brakes.

    A lot of guys run the progressive fork springs (Me included). The problem is that they are a very tightly wound spring, meaning they have a lot of coils. A higher quality spring will be able to achieve the same compression tension with the fewest amount of coils as necessary. Extra coils is extra weight, and its also extra area that you don't have for oil. The OEM springs are pretty openly wound. So if you install progressive springs and use the same amount of oil as the service manual states for the OEM ones that are wound much more openly, then your oil level is going to be off. Race tech and other manufactures offer high quality "loosely wound" springs that can be whatever spring rate you desire. Performance wise your much better off wit that style vs tightly would ones.

    And speaking of oil levels...the *main* function of oil levels (Once theres enough to cover the dampening rod holes and keep it from running out) is to meter the size of the air chamber in the forks. What happens when air compresses? It builds up pressure. That will effect compression dampening as the forks compress and it will ALSO effect rebound dampening speed/force when the forks return to their native positioning The bigger the air chamber, the more pressure it builds up as it compresses. The smaller, the less. So now lets go back to the fork spring issue for a minute. Lets say the tightly wound progressive springs displace 20% more area (This is just a figure for talkin) in the forks than the loosely wound OEM ones. If you used the same oil volume as what the service manual calls for OEM springs, thats 20% less air chamber area, which is going to greatly effect the level of compression dampening force and the speed of your rebound dampening! Measuring by oil level is the best way.

    I've ridden a LOT of machines and I would say probably better than half of them, I can feel that they are over sprung and under dampened. Your machine should have some sag in its suspension travel (That might be another post soon, how to set sag for those that dont know) and the first couple inches of wheel travel should NOT be jarring the crap out of you. It should be smooth and easy. The dampening of the oil flow being metered and the air chambers compressing should allow you to have enough room for small bumps to not make you feel like your riding a rigid, but provide slow enough dampening on big travel movements that you dont run through the whole travel and make the skid plate bury itself in the dirt.

    I also see a lot of people changing oil seals and never the Teflon coated bushings in the forks. Thats just as important, as is the little white plastic ring that goes around the top of the dampening rod (What goods the check valve sitting on top gonna do if it just passes around it?)


    On the rear end, You can get same type of performance out of a revlaved and possibly resprung (If your a heavier rider and need it) stock rear shock for about $350 than a $1,000 after market one. Baldwin Motor sports and other shops that handle PEP suspension parts can do a "Guts kit" for a stock 250R shock and make it perform awesomely. You will totally feel the changes in the compression and rebound clickers when they are done. The 250R rear linkage is also very good, much better than most people think, and its better than the OEM honda 450R linkage by far. Some of the aftermarket linkages like Walsh's Savior setup and other help correct that, but the stock 450R linkage is pretty inferior in my opinion. If you get a well tuned shock on both, you'll be able to tell the difference. I'm personally a big fan of the CR500 linkage setup. My Laeger TRX250R quad has it and I *will* be adapting that to an ATC frame in the near future.

    I am be NO MEANS trying to claim to be an expert. I decided a while back to quit playing with motors so much and focus more on suspension and ergonomics on my projects. I learned a lot of this stuff by trial and error, but never really understood exactly what made it work, just that "it did". But, I got a book a few months ago written by Paul Thede of Race Tech, its called the Suspension tuning bible: http://www.amazon.com/Techs-Motorcyc.../dp/0760331405 and it has *really* helped me to understand how things work and articulate the ideas much better than I ever could have before. It has a lot of great illustrations and charts that help make understanding some of the things I've wrote about here a lot easier.

  3. #3
    Billy Golightly's Avatar
    Billy Golightly is offline Always finding new and exciting ways to not give a hoot in hell Catch me if you can
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    Another real quick and then I'll promise not to write anymore books for a while is suspension "stickage". I learned about this by watching Wayne Mooridian (PEP) at national working on a 450 pro class quad. Ever notice how when you first get on your trike how the front forks move sort of "notchy" feeling? Like, they go down in steps sort of and not in a full fluid movement? That is the level of stiction, or friction in the moving parts. Its the sum of the tension from the bushings inside, the fork seals, and anything that contributes to the movement of the forks telescoping. Its *very* important to make sure you have good slick oil, and fork seals and internal bushings that do not drag too much. This sounds like some stupid petty little thing but its a big deal. It can have a big effect on that first few inches of "nice and easy" travel I was talking about earlier. Forks are very hard to work out the stiction level with. Shocks are easier.

    To get a good idea of how the stiction level should be, go around to friends machines, a brand new one at a dealer, where ever. Put two fingers on the rear grab bar and compress the suspension about 1/4inch. You should see it return right back up. You will have to watch closely and carefully. Try it out on brand new machines or something that has been well setup to get a baseline so you know what to look for. As a general idea, take your shock off, the axle/carrier and all the parts off of the swingarm EXCEPT for the linkage, and with it still bolted to the frame cycle it up and down. It should be free, but not flopping around as that would indicate something worn out somewhere. If it ever gets hard through any part of the travel or feels like its dragging, then you've got friction somewhere that needs to be take care of. Stiction in the rear end can be caused by:

    Too tight of swingarm pivot bushings/bearings (Lack of lubrication, or if they are solid bushings made with too tight of tolerances)
    Powdercoated frames that have made the distance where the swingarm bolts in too tight, adding side-load friction to the swingarm pivoting.
    Powdercoated frames that have made the distance where the bottom shock linkage attaches to the frame too tight, adding side-load friction to the linkage pivoting.
    Poorly lubricated or maintained movement points (front pivot, linkage movement points, etc)
    Something bent, or twisted, making alignment of the movement off.
    Removed and re-welded suspenion points (Top shock mount, linkage mount on the frame, linkage mount on the swingarm) that did not allow enough tolerance and side play so that when the bolt is clamping it actually pulls the mounting ears into the moving part.


    Just something else to think about

  4. #4
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    AMEN!!!

    Most people does not know how much a well tunned suspension can give them.
    Simply put. A stock engine with a well tuned suspension will make you faster. The fastest engine will not go anywhere if the suspension is not up to it.

    Thanks Billy

    TORKER.
    THOSE WHO SAY IT CANNOT BE DONE, SHOULD NOT GET IN THE WAY OF THOSE BUSY DOING IT...

  5. #5
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    Oh wow, that was a plethora of information. Makes me want to fine tune my X and T3's suspension to me :
    LED obsessed
    2015 Yamaha FJ-09

  6. #6
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    You got some links to find these parts since you have got all this stuff.?
    ]1986 ATC 330R
    1985 ATC 250R vintage PSI racing ported motor
    Get your replacement ATC 250R decals and custom Big Bore #'s here http://shop.3wheelerworld.com/catego...=2&pagegroup=1

  7. #7
    Billy Golightly's Avatar
    Billy Golightly is offline Always finding new and exciting ways to not give a hoot in hell Catch me if you can
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    I had a part # for the ones I ordered, I doubt I still have it. This page can help you determine what one you do need: http://www.racetech.com/HTML_FILES/E...R_FITTING.html Race Tech has kind of rebuilt their site and a lot of stuff has changed so I'm not real familiar with it now. I'll see if I still have it around by some change.

  8. #8
    Join Date
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    Thanks, I'll check out the race tech site
    VIRUSDOG
    85 250R
    82 250R
    84 200x
    85 185s
    84 185s
    85 Big Red
    85 225 shaft
    Coming soon: ATC 650R!

  9. #9
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    Old post but very well reading......
    All our government does is distract us while they steal from us, misspend our tax $ and ruin our country

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