YZ125 vs YZ250 for trail bike?

Discussion in 'Thumpers' started by Awasome, Dec 19, 2014.

  1. Dao1

    Dao1 Long timer

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    Are you doing the revalve yourself or is this being done by a tuner?
    #21
  2. Auto-X Fil

    Auto-X Fil Been here awhile

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    I'm doing everything myself.
    #22
  3. Auto-X Fil

    Auto-X Fil Been here awhile

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    If people are interested, I'll post shim stacks when I'm done. They would apply to all 1996-2004 YZ250 and 125, I belive.
    #23
  4. NDMX743

    NDMX743 Been here awhile

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    I vote for the yz250. The 125 would be good too. Kdx's and xr's feel like marshmallows compared to them. Just my opinion.
    #24
  5. Luke

    Luke GPoET&P

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    Very interested. I have turned my 125 into a woods bike and had a third rate pro job done to it. I'm doing my own work now and think I'm most of the way there. I'm all in on this generation of yz suspension, as I'm working on a YZ250 project now too. I'm happy to share what I've got so far.

    The midvalve issue on these forks is the huge cartridge. In order to get enough flow to keep them plush you need a lot of float or shim flex. Keeping the midvalve as a check valve and doing all the work in the base valve seems to be the way to go.


    I'd also recommend messing with the rebound on both ends. Makes a huge difference in traction.
    #25
  6. Auto-X Fil

    Auto-X Fil Been here awhile

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    Whatcha got so far?

    I keep hearing about the mid being way too stiff. I saw someone on thumpertalk who went to a simple check valve and hated it, and ended up with a much softer stack with extra float. I believe they removed a face shim, a HS shim, and didn't add any shims to make up for it, thus increasing the float. I was planning to start there... at least 0.5mm float, and get there by just removing face shims. If there are more than 3-4x 25.15 face shims left at that point, I'll pull more, and put extras after the clamp to keep the float reasonable. The base will get an extra stage and fewer shims in the LS stack.

    I have the shock apart right now. I'm working with a local guy who does his own suspension. He used to MX race (A/Expert), and now he rides the same trails I do. His input was the basis for this stack. I have NOT put this back together yet, so I have no idea how it'll ride. any suggestions would be good.

    I'm 155lb + gear, 6' tall, 30. Newer rider, C-level. I ride nothing but gnar. I'm often messing around finding big logs, drops, and step-ups, and rarely get out of 2nd gear in the woods.

    Changes are:

    1) swapped 0.15 shim from the base of the HS stack to the face
    2) moved crossovers apart to add a stage
    3) Swapped smaller crossover for the 28mm in the rebound stack
    4) Removed two shims from the LS stack and stuck them after the clamp
    5) Swapped the rebound face shim for a HS shim on the compression side, further increasing LS rebound, and also decreasing HS compression. This is probably a tiny change, but while I'm tweaking, I might as well play around.

    Note that I bought no shims. I want to nail this with stock shims only, partly so I can post it up and anyone with a stock YZ can do it. These pre-SSS bikes are so cheap right now that it makes sense to convert them to woods use.

    I assume I'll be able to crank my LS compression bleeder back in, so I'm adding a little LS rebound in the shim stack. That way I can keep the rebound adjuster mid-way out or even more, and keep some free bleed around the piston.

    It all makes a lot of sense on paper (to me, anyway), but the proof will be when I put tires back on dirt.

    Code:
    STOCK				MODIFIED			
    Compression	Float:	Clamped		Compression	Float:	Clamped	
    Dia	Thick	Note		Dia	Thick	Note	
    40	0.2	x11		40	0.15		
    34	0.1	xover		40	0.2	x3	
    30	0.1	xover		34	0.1	crossover	
    40	0.15			40	0.2	x5	
    38	0.25			28	0.1	crossover	from rebound
    36	0.25			40	0.2	x1	
    34	0.25			38	0.25		
    32	0.25			36	0.2		from rebound
    30	0.25			34	0.25		
    28	0.25			32	0.25		
    24	0.25			30	0.25		
    22	0.2			28	0.25		
    40	4.5	washer		24	0.25		
    				22	0.2		
    				40	0.2	x2	
    				40	4.5	washer	
    							
    Rebound	Float:	Clamped		Rebound	Float:	Clamped	
    Dia	Thick	Note		Dia	Thick	Note	
    36	0.2	x6		36	0.25		from compression
    28	0.1	xover		36	0.2	x5	
    36	0.3			30	0.1	crossover	from compression
    34	0.3			36	0.3		
    32	0.3			34	0.3		
    30	0.3			32	0.3		
    28	0.3			30	0.3		
    26	0.3			28	0.3		
    24	0.3			26	0.3		
    23	0.2			24	0.3		
    23	0.2			23	0.2		
    26	3.1			23	0.2		
    19	0.7	shim		26	3.1	washer	
    				19	0.7	shim	
    
    
    
    
    #26
  7. Dao1

    Dao1 Long timer

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    What rate springs are you using in the forks and shock?
    What's your sag numbers?
    #27
  8. Auto-X Fil

    Auto-X Fil Been here awhile

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    Here are some sources I've been using:

    http://www.thumpertalk.com/topic/554219-yz250-shock-revalve/

    http://www.thumpertalk.com/topic/994553-show-us-ya-shim-stacks/

    http://www.thumpertalk.com/topic/899861-kyb-46mm-fork-differences-and-stock-stack-specs-99-01-yz/

    The last link shows this mid-valve stack for the 125:

    Mid Valve
    27 x .10 (4)
    20 x .10
    16 x .10
    14 x .25 (2)
    25 x .40
    11 x .30 Below spring collar.

    If that's what I have, I was considering something like this:

    Mid Valve
    27 x .10 (2)
    20 x .10
    16 x .10
    14 x .25 (2)
    25 x .40
    11 x .30 Below spring collar.
    #28
  9. Auto-X Fil

    Auto-X Fil Been here awhile

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    Stock springs: 0.43 front, 4.8 rear.

    Race Tech's calculator says I should go to 0.41 and 5.0, but that's close enough that I don't want to spend time/money on it. I'll probably run low preload and fork oil to shift things a little softer.

    Sag is at 102mm.
    #29
  10. Luke

    Luke GPoET&P

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    I've got a very plush setup right now.

    Rear Rebound:
    <style type="text/css"><!-- body,div,table,thead,tbody,tfoot,tr,th,td,p { font-family:"Arial"; font-size:x-small } --> </style> <table border="0" cellspacing="0"> <colgroup span="2" width="86"></colgroup> <tbody><tr> <td align="right" height="17">36</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">36</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">36</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">36</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">28</td> <td align="right">0.1</td> </tr> <tr> <td align="right" height="17">36</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">36</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">36</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">36</td> <td align="right">0.25</td> </tr> <tr> <td align="right" height="17">34</td> <td align="right">0.25</td> </tr> <tr> <td align="right" height="17">34</td> <td align="right">0.25</td> </tr> <tr> <td align="right" height="17">32</td> <td align="right">0.3</td> </tr> <tr> <td align="right" height="17">30</td> <td align="right">0.3</td> </tr> <tr> <td align="right" height="17">28</td> <td align="right">0.3</td> </tr> <tr> <td align="right" height="17">26</td> <td align="right">0.3</td> </tr> <tr> <td align="right" height="17">26</td> <td align="right">4</td> </tr> </tbody></table>
    This has a lot looser low speed rebound (4 instead of 6 shims) and a lot tighter high speed rebound (26mm pivot instead of 23). I'm 220#, and have a 5.4 spring on the back. Originally, the tuner installed the stiffer spring and softened up the high speed rebound. That was a terrible combination. There was too much low speed damping so the rear end would lose traction on any bumps, but there was not enough high speed damping so the bike would kick badly over bumps. I don't think the change to rebound that you want to make will work very well. With even more LS damping I wouldn't expect the wheel to track well at all.

    Rear compression:
    <style type="text/css"><!-- body,div,table,thead,tbody,tfoot,tr,th,td,p { font-family:"Arial"; font-size:x-small } --> </style> <table border="0" cellspacing="0"> <colgroup span="2" width="86"></colgroup> <tbody><tr> <td align="right" height="17">40</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">40</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">40</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">40</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">26</td> <td align="right">0.15</td> </tr> <tr> <td align="right" height="17">40</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">40</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">40</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">40</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">40</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">40</td> <td align="right">0.15</td> </tr> <tr> <td align="right" height="17">38</td> <td align="right">0.2</td> </tr> <tr> <td align="right" height="17">34</td> <td align="right">0.15</td> </tr> <tr> <td align="right" height="17">32</td> <td align="right">0.25</td> </tr> <tr> <td align="right" height="17">30</td> <td align="right">0.25</td> </tr> <tr> <td align="right" height="17">28</td> <td align="right">0.25</td> </tr> <tr> <td align="right" height="17">26</td> <td align="right">0.25</td> </tr> <tr> <td align="right" height="17">30</td> <td align="right">4</td> </tr> </tbody></table>
    I think we're headed in similar directions on this. I think yours has more low speed damping that mine, which is probably better. Mine is too mushy unless I turn the comp adjuster in quite a bit.


    I need to dig out my fork notes, but I recall that 0.5mm of float is not much at all. Stock is over 1.5mm, practically a check valve.
    #30
  11. Auto-X Fil

    Auto-X Fil Been here awhile

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    Awesome, thanks for the feedback. I'll shift things around and give it a whirl. I was stiffening the rebound stack to prevent getting kicked in the ass over logs and up ledges, but you're right, that's really a high-speed rebound movement.

    On the compression side, it seems that yours is extremely soft initially, due to that small crossover, and then stiffens quickly in mid-speed stuff. I'm able to get truly low-speed stuff almost there by opening the clicker, but that mid/low is what bucks me. Things like riding a rock garden at 10mph, or popping over a log. Hopefully my second LS stage with the 30 crossover will be operating in that sort of speed range, but without buying Shim Restacker there's no way to tell for sure. In either case, with a 70lb difference in rider weight, we'll probably end up with different setups. I'd expect mine to need to be quite a bit softer, so I might slide another shim out.

    I just tore the whole linkage apart - all the bearings are toast. Between that and the weather it might be spring before I can ride this and check it out properly.
    #31
  12. Auto-X Fil

    Auto-X Fil Been here awhile

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    Here's what I'll put back in the shock this week:

    Code:
    Compression	Float:	Clamped
    Dia	Thick	Note
    40	0.15	
    40	0.2	x3
    34	0.1	xover
    40	0.2	x5
    30	0.1	xover
    40	0.2	x1
    38	0.25	
    36	0.25	
    34	0.25	
    32	0.25	
    30	0.25	
    28	0.25	
    24	0.25	
    22	0.2	
    40	0.2	x2
    40	4.5	washer
    		
    Rebound	Float:	Clamped
    Dia	Thick	Note
    36	0.2	x4
    28	0.1	xover
    36	0.2	x2
    36	0.3	
    34	0.3	
    32	0.3	
    30	0.3	
    28	0.3	
    26	0.3	
    24	0.3	
    23	0.2	
    23	0.2	
    26	3.1	washer
    19	0.7	shim
    
    #32
  13. Luke

    Luke GPoET&P

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    I have the restackor program, I'll run those stacks for you this afternoon and see what it says.
    #33
  14. BikePilot

    BikePilot Long timer

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    11,720
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    Golden CO
    I've run both off road. For everything but high altitude and dunes I prefer the 125. For heavy dune work you really need the extra power of the 250. Also if you have trails in the 8k+ altitude range the 250 really helps because up there it runs about like a 125 at sea level.

    The 125 will teach you to be a better rider than anything else. A 250 will let you be sloppy and lazy and you might never develop. Then again if you want to just putter around and aren't interested in really honing skills a 125 might be frustrating. The husqvarna WR125 has a wider power curve than a MX 125 and might be just the ticket. I'd also recommend a look at a KDX200 if you have no MX aspirations. Much easier to ride than a 125 as well.

    The 2008+ models has fairly substantial suspension improvements. Pre-2008 I'd personally go with a different brand to get better suspension. The 47mm Showas that were on lots of things (almost all hondas from 1997-on) are fantastic and with just basic setup work are some of the best off road suspenders I've been on.
    #34
  15. Yard Sale

    Yard Sale let's be bad guys

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    Location:
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    Converting a Japanese MX bike gets you a better trail bike with better suspension, more reliable, and cheaper.

    I rode my MX bike unmodded from the showroom floor the day after purchase on gnarly singletrack.

    Most mods are optional. You can ride 60 miles on a stock 2 gallon tank. Don't slam into rock faces with your 19" wheel. Flywheel weights are unneccessary.

    Set your sag, soften the compression, jet the carb, set the timing, correct the squish clearance... these are all free to cheap mods.

    All you really have to spend money on are heavy tubes.
    #35
    shrubitup likes this.
  16. Bucho

    Bucho DAMNrider

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    Ha ha, everyone has their opinion.
    #36
  17. Auto-X Fil

    Auto-X Fil Been here awhile

    Joined:
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    889
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    Montrose, PA.
    Here's my fork stacks, and a first swing at valving.

    The idea is to greatly soften the low-speed compression. Given the big float on the stock midvalve, most of the low-speed probably comes from the base valve. Should I bother messing with the mid as much as I have below?

    I really softened the base up, but I'm not sure it's enough. Should I add another crossover (14?) between the last 24 and the 22?

    I don't think I need to mess with rebound, but I wanted a crossover in the base, so I stole a shim.


    Code:
    STOCK				MODIFIED		
    Base Valve	Float	Clamped		Base Valve	Float	Clamped
    Dia	Thick	Note		Dia	Thick	Note
    24	0.1	x10		24	0.1	x3
    22	0.15			16	0.1	from rebound
    20	0.15			24	0.1	x4
    18	0.15			22	0.15	
    16	0.15			20	0.15	
    14	0.15			18	0.15	
    13	0.15			16	0.15	
    12	0.15			14	0.15	
    18	0.5	x3		13	0.15	
    11	0.3			12	0.15	
    24	0.1			18	0.5	x3
    				11	0.3	
    				24	0.1	x
    						
    						
    						
    						
    Mid Reb	Float	Clamped		Mid Reb	Float	Clamped
    Dia	Thick	Note		Dia	Thick	Note
    27	0.1	x4		27	0.1	x4
    12	0.1	xover		12	0.1	xover
    20	0.1			20	0.1	
    18	0.1			18	0.1	
    16	0.1			14	0.1	
    14	0.1			11	0.25	x3
    11	0.25	x3				
    						
    						
    						
    Mid Comp	Float	1.15mm		Mid Comp	Float	1.45
    Dia	Thick	Note		Dia	Thick	Note
    27	0.1	x7		27	0.1	x4
    25	0.1			25	0.1	
    20	0.1			20	0.1	
    16	0.1			16	0.1	
    14	0.3			14	0.3	
    14	0.3			14	0.3	
    25	0.4			25	0.4	
    #37
  18. Luke

    Luke GPoET&P

    Joined:
    Aug 25, 2004
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    5,073
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    Auto-X Fil,

    So I ran the stacks. The last rebound stack you posted looks pretty good. It's a bit loose, but getting rid of the kick is still within the range of the adjuster. My preference would be to remove the 23mm pivot shims entirely which will make the high speed stack stiffer and allow you to run the adjuster looser. That should give more traction and the bike will probably pitch more when braking into corners and whatnot. I think this is totally a rider preference thing, and probably more subtle than I'd actually notice when riding it.

    The compression stack looks pretty good too. The HS is similar to mine, but the LS is quite a bit stiffer. Mine's a little too soft for me, next time I revalve I'll go in your direction, if not try your exact stack. I'd guess it will work well for you.

    If you want the actual details with numbers I can post those up.
    #38
  19. Auto-X Fil

    Auto-X Fil Been here awhile

    Joined:
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    Oddometer:
    889
    Location:
    Montrose, PA.
    Thanks a lot! I'll put it back together as-listed.

    Any thoughts on the forks? It was suggested to leave the mid and rebound alone, and try something like this on the base:

    Code:
    	
    Base Valve	Float	Clamped
    Dia	Thick	Note
    24	0.1	x3
    20	0.1	
    24	0.1	x4
    22	0.15	
    20	0.15	
    18	0.15	
    16	0.15	
    14	0.15	
    12	0.15	
    13	0.15	removed the 13 and moved it to the bottom as a spacer
    24	0.1	x2 - again, reuse the unused shims as spacers if needed - you could probably leave these out 
    18	0.5	x3
    11	0.3	
    24	0.1	x
    I'm not sure if that'll be soft enough.
    #39
  20. Auto-X Fil

    Auto-X Fil Been here awhile

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    Feb 17, 2013
    Oddometer:
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    It took me a bit, but I'm with you now.

    The stock float is huge, the stack is pretty soft, and the backer is close. So, it'll flow big at first (as you said, a check valve), and then add a little progression as the shims flex to the backer, but then it's done.

    The question is: what sort of piston speeds are we talking about? I'm not sure at what point the midvalve transitions will happen. Is the BV low-speed stack dominating at the piston speeds that are giving me trouble? Or is the midvalve limiting things?

    It probably is what it is. Adding a couple tenths of float would also make the stack softer. It'll delay the transition to higher speed, but also make it potentially harsher when it does happen. To keep it progressive, I guess I should leave it alone. Increasing the length of the center bushing would let me run a softer, taller stack with more room to deflect before it hits the backer, but I wouldn't know where to source one, and then I'd need a bunch of new shims... so I'll mess with the BV first. Plus, then I don't need to hack the second fork leg cartridge open.
    #40