YZ80 Fork discussion revisited
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  1. #1
    Senior Member abyssdncr's Avatar
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    Ok, don't stone me for reviving what appears to be a dead horse, but I figure that if I still don't get it, then there might still be some hope left.



    __________________________________________________ ___





    I've been re-reading all the fork swap threads I can find, dubiously studying the AllBallsRacing fork conversion options, comparing steering bearings, wheel bearings, brake disc diameters, and fork widths, and the best alternative I can find for a raised front end to match a longer rear shock are the late 80s to '92 YZ80 forks that will bolt in to our existing triple tree.



    Pretty much every other option requires swapping to a skinny front, which may certainly have some advantages that I don't yet fully appreciate, but I'm not keen on the idea of ditching the iconic TW image by adding a skinny front end.



    I particularly liked the pics posted some time ago by JohnnyBlaze. The stance looked good, not quite "balanced" per se, but certainly better that just adding a tall rear shock. I appreciate the dilemma that was communicated on the 12mm vs. 15mm axle bolt...kinda hard to argue with physics, and when you do, you don't win.



    On some other thread someone asked the $25,000 question, and in my opinion, it didn't get the attention that it deserved. So I'm going to stop typing shortly and get to the point:



    TW200 & early YZ80 forks are the same diameter, share fork seals, and have the exact same part number for the little bolt that connects the internals to the lower fork tube. So why can't a hybrid fork be constructed from the TW outer tube and the YZ inner tube to get a taller front fork and balance a raised rear end?



    I've noticed that the YZ has what is purported to be a 10" travel, which I find just delicious to think of, but I've also noted that the YZ outer tube extends about 3" below the axle to make up for this additional travel. But travel and whatever spacers inside the fork tube aside...



    Why couldn't this hybrid work?



    __________________________________________________ ______________





    Alright, I'm sufficiently prepared now...and a "newbie"...stone away...



    2006 TW200, LED tail & turn signals, Clarke XT350 tank, hybrid YZ80 forks, CycleRacks rear rack, Ricochet bash plate, TTR225 header, eBay pegs, MSR high ATV bars, Tusk bar risers, Tusk handguards & deflectors, Tusk KX250 stainless brake line, XT225 speedo cable, 14/47 sprockets, Mule-pin seat latches, 130 main, 0.035" shimmed needle, TW34/M6006 meats.

  2. #2
    Senior Member lizrdbrth's Avatar
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    It would work to balance out the "look", but would only have the travel of a standard TW front end.



    I wouldn't bother with getting a complete YZ front end, either. Just get the tubes, transfer your TW stuff onto them and cut a spacer to compensate for the spring height.



    No stoning, nor criticism. Sounds like you already know this is a pretty much a useless swap.



    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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  3. #3
    Senior Member pgilles's Avatar
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    Quote Originally Posted by abyssdncr View Post
    Ok, don't stone me for reviving what appears to be a dead horse, but I figure that if I still don't get it, then there might still be some hope left.



    __________________________________________________ ___





    I've been re-reading all the fork swap threads I can find, dubiously studying the AllBallsRacing fork conversion options, comparing steering bearings, wheel bearings, brake disc diameters, and fork widths, and the best alternative I can find for a raised front end to match a longer rear shock are the late 80s to '92 YZ80 forks that will bolt in to our existing triple tree.



    Pretty much every other option requires swapping to a skinny front, which may certainly have some advantages that I don't yet fully appreciate, but I'm not keen on the idea of ditching the iconic TW image by adding a skinny front end.



    I particularly liked the pics posted some time ago by JohnnyBlaze. The stance looked good, not quite "balanced" per se, but certainly better that just adding a tall rear shock. I appreciate the dilemma that was communicated on the 12mm vs. 15mm axle bolt...kinda hard to argue with physics, and when you do, you don't win.



    On some other thread someone asked the $25,000 question, and in my opinion, it didn't get the attention that it deserved. So I'm going to stop typing shortly and get to the point:



    TW200 & early YZ80 forks are the same diameter, share fork seals, and have the exact same part number for the little bolt that connects the internals to the lower fork tube. So why can't a hybrid fork be constructed from the TW outer tube and the YZ inner tube to get a taller front fork and balance a raised rear end?



    I've noticed that the YZ has what is purported to be a 10" travel, which I find just delicious to think of, but I've also noted that the YZ outer tube extends about 3" below the axle to make up for this additional travel. But travel and whatever spacers inside the fork tube aside...



    Why couldn't this hybrid work?



    __________________________________________________ ______________





    Alright, I'm sufficiently prepared now...and a "newbie"...stone away...





    I was the one who brought up the hybrid idea. I did purchase a set of YZ forks a month or so ago but am waiting for winter to start with the project.
    Sold bike.



    Youtube vids of old TW's acceleration:

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  5. #4
    Senior Member TWrider's Avatar
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    Why not just run some late RT180 forks? If you don't have a late TW wheel you could just purchase the hub/spokes/disk from yamaha and lace your drum rim to it...then have a machine shop bore the four triple bores and extra mm...now you'd have 35mm fork and an extra inch or two of height to play with...If the stock tw caliper doesn't fit the mount ears, then just run the RT caliper (which I believe is identical to the XT/TTr single piston caliper [late rt180 94-97 only, early ones used a 240mm disk and a 4 hole disk mount pattern, and a rare and strange caliper that won't easily work for a TW hub and disk], I believe you could probably even bolt the stock RT disk to the TW hub)

  6. #5
    Senior Member Gerry's Avatar
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    In my opinion, the TW suspension is pretty much 'stone-age'. I have done a range of suspension mods. I am now very happy with my front/rear suspension as it seems to now compliment the kind of riding I do.



    Not sure what kind of improvement most of you are looking for. I made a sub-tank for extra air volume and forktube pressure regulation. For me (170lb) this allowed me to have a comfortable offroad ride at 13/22mph. I then added progressive springs. I will say that air pressure and progressive springs will give you the best 'bang for the buck'.



    Since it seems I carry (always) lots of stuff, I decided to go one step further in order to improve my front suspension. I had my triple-tree bored to 35mm by a machinist and installed a TRI-Z fork set.



    Now all of this stuff is "seat of your pants" modding, but as for the above, I have done 'IT' and still ride the bike,,,, and the suspension is much, much nicer.



    The early YZ forks hold lots of potential (I think). Don't be adversed to having your triple tree over-bored (slightly) as it seems to afford you a few more options.



    Our Big-Wheel member indicated that the 'larger' Tri-Z triple-trees will fit the TW and will allow you to install a few (likely better) fork systems from Yamaha or Honda. These kind of mods present risks that generally seem to involve mostly time and money, but safety is as well a consideration.



    Again, for a straight forward inprovement, consider more air (subtank) with regulation (schrader valves) and progressive springs..... A noticeable improvement. Gerry





    Take care my Friend.........

  7. #6
    Senior Member TWrider's Avatar
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    Quote Originally Posted by mrgizmow View Post
    In my opinion, the TW suspension is pretty much 'stone-age'. I have done a range of suspension mods. I am now very happy with my front/rear suspension as it seems to now compliment the kind of riding I do.



    Not sure what kind of improvement most of you are looking for. I made a sub-tank for extra air volume and forktube pressure regulation. For me (170lb) this allowed me to have a comfortable offroad ride at 13/22mph. I then added progressive springs. I will say that air pressure and progressive springs will give you the best 'bang for the buck'.



    Since it seems I carry (always) lots of stuff, I decided to go one step further in order to improve my front suspension. I had my triple-tree bored to 35mm by a machinist and installed a TRI-Z fork set.



    Now all of this stuff is "seat of your pants" modding, but as for the above, I have done 'IT' and still ride the bike,,,, and the suspension is much, much nicer.



    The early YZ forks hold lots of potential (I think). Don't be adversed to having your triple tree over-bored (slightly) as it seems to afford you a few more options.



    Our Big-Wheel member indicated that the 'larger' Tri-Z triple-trees will fit the TW and will allow you to install a few (likely better) fork systems from Yamaha or Honda. These kind of mods present risks that generally seem to involve mostly time and money, but safety is as well a consideration.



    Again, for a straight forward inprovement, consider more air (subtank) with regulation (schrader valves) and progressive springs..... A noticeable improvement. Gerry







    1997 rt180 on the left, tw200 on the right



    the 180 shock is about 2" longer, has 3.5" more travel, has an xt350 caliper pattern(cheap calipers), is leading axle, and has the right Axle bore. It is a 35mm fork so it will fit modified bore TW triples.



    Tw forks = 30" eye to top, Rt180 forks = 31 and 5/8" eye to top, Tri z forks look to be 37" - 4", for 33 inches eye to top














  8. #7
    Senior Member abyssdncr's Avatar
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    Quote Originally Posted by mrgizmow View Post




    The early YZ forks hold lots of potential (I think). Don't be adversed to having your triple tree over-bored (slightly) as it seems to afford you a few more options.



    Again, for a straight forward inprovement, consider more air (subtank) with regulation (schrader valves) and progressive springs..... A noticeable improvement. Gerry



    Timely response Gerry, and how ironic... My YZ forks should arrive Wed. and hope to have hands on a spare TW parts bike this weekend to do side by side comparisons of the YZ & TW internals. Using the hybrid fork approach, I hope to keep the TW outer tubes, get a taller front end that has the schrader valve fork caps, and swap to progressive springs to help take up some of the spare space in the longer inner tubes and smooth out the ride. My old KZ1100 was set up this way and rode wonderfully.



    Only SNAFU I haven't worked out yet is which springs to opt for. The calculator at Race Tech recommends a spring rate of .46 kg/mm for a 185 lb rider. Most of Progressive's soft springs are in the larger diameters, but I was thinking that the 11-1114 (.45-.64 kg/mm, 19.75", & 27mm OD) would likely work, and perhaps the 11-1136 (.29-.52 kg/mm, 22.5", & 29mm OD) if the 29mm OD springs will fit in the 33mm tubes.



    I'm going to start small, simple, & reversible for the time being, but if the extra bike comes through, I'll have a spare set of triples to play with as well.
    2006 TW200, LED tail & turn signals, Clarke XT350 tank, hybrid YZ80 forks, CycleRacks rear rack, Ricochet bash plate, TTR225 header, eBay pegs, MSR high ATV bars, Tusk bar risers, Tusk handguards & deflectors, Tusk KX250 stainless brake line, XT225 speedo cable, 14/47 sprockets, Mule-pin seat latches, 130 main, 0.035" shimmed needle, TW34/M6006 meats.

  9. #8
    Banned qwerty's Avatar
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    Frank's Maintenance and Engineering, Inc., used to make just about any fork tube in just about any length you could want. No increase in travel, just a changed ride height. Could be a good option for lowering for vetically challenged riders.




  10. #9
    Senior Member Mr. BigWheel's Avatar
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    An issue that the Tri-Z triple clamp introduces is increased rake. It doesn't truly seem to affect the handling on my BigWheel, but it is ridden 98% of the time offroad. Mr. Gizmow's solution, boring out the TW's triple clamp to accept the Tri-Z fork, does preserve the original geometry. The Tri-Z front end can be run with a leading or trailing axle, allowing some manipulation of the geometry with that setup.



    The best aspect of the stock fork of the TW BW is that is has zero underhang of the fork tube below the axle. Other than that, I feel that it has few redeeming values. The Tri-Z has significant underhang and can be quite a handful in deep ruts or in rocky situations.



    However, the improvement in the front end performance far outweighs all of the drawbacks.



    Regards,



    Mr. BigWheel



    P.S. Mr. Gizmow: did you have to use spacers when you installed the progressive springs?

  11. #10
    Senior Member Gerry's Avatar
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    I made new (shorter) spacers out of PVC pipe. The springs were longer than stock but not by much. Gerry



    Take care my Friend.........

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