OzVMX Forum
Marque Remarks => Yamaha => Topic started by: TonyB on July 14, 2010, 10:41:21 am
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has anyone fitted gold valves to a monoshock? and possibly compound springs. I am bent on fixing the handling of my 465. The other day i went riding with my son and took the 465 down a dirt road which had some bumps in it, i could manage possibly 70 kph before hospital loomed into mind , then i took my sons kx250F down the same road and was flat out in 5th in full control, so with all the ponies i got in the 465 i can only use half of them due to the handling and brick type rear suspension. I would really like to hear if anyone has "fixed" the dreaded rear monoshock and I am keen to see if there are dual springs (soft + harder) that i could fit to soak the square lips but still take the bigger jumps???
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Had a Racetech valve fitted to my YZ250F but as there was no "Available data" on that model it took ages to sort. Still not right because the bloke doing it no longer does it & modern shocks only run at about 175lb where the old girl runs 225lbs+ so he could never charge it fully as his regulator never went that high.
That being said though, yours will have the modern type fitting & run less pressue where mine has the one where you need to adapt a hypo needle. So you should be right.
I also run emulators in the forks, a DYI job.
Viper666
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IT175 (circa F models) came with dual springs - at the very least, that's a source of the seperator and a guide for the spring rates.
Working out the actual spring rates and lengths for a dual set up is actually FAR more complicated than you probably think, particularly when you add pre-load into the equation. I'm not saying that it is impossible, just don't go thinking that its simple and you're 100% sure of getting it right straight away.
Late model valve pistons have to be a good thing, but will take some work in getting the valving right (or take it to someone who knows what they're doing).
The other thing to watch for is a worn shock body. The valve piston wears the inside of the body around ride height, and then the oil can get past the valving and screw up the dampening.
Having said all of that, 70kph on a dirt road shouldn't be stretching the limits of the stock set-up - it suggests that you've got something wrong.
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Sounds like something wrong alright..... :o
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We have used a late model Ohlins piston with a modern type shim stack and CRF450 shock spring with a lot of success. Forget about using the standard progressive spring.
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JohnnyO tell me more... does the crf450 spring fit and wouldnt it be too stiff?? I would have thought with all the leverage on the new setups the spring would be short and stiff compared to the almost 2 to 1 ratio of the old monoshock.
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hi tony, i haven't ridden mine yet since i put the new spring in, so can't really comment on the ride. but my shock was rebuilt/serviced by RAD down at sherwood here in brissy and it's pretty good but then i found that my springs were still too soft for my 115kg lard @rse. from my searching at the time no-one had replacement shock springs for a 465 ............... until i got onto walter at yss and he got a batch of stiffer springs made up only a few weeks ago. i'd be getting on the phone to him if that's what you're after. i've still gotta sort out the forks yet but i'm hoping a combo of a little air pressure and a high oil level will help resist bottoming.
some guys are machining a new circlip groove down the shock body to move the collar down and installing a later model (shorter) spring, but i'm suss on this as it's not just 10 or 20mm shorter, it's more like 100mm. those monoshock springs are about 360 long and i didn't like what this would do to the total travel.
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The CRF 5.6 spring is in the ball park for most 90 odd kg vintage riders. It is slightly larger I.D than the standard spring but does work or you can buy a smaller ID spring from Race Tech. You'll have to get a couple of extra spring retainer circlip grooves machined in the shock body to suit the shorter showa spring or run an additional short spring as well to make it a dual rate setup.
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i could manage possibly 70 kph before hospital loomed into mind ,
Something definitely ain't right in monoshockland. Two weeks ago I went fire trailing on my mates IT465 which is a one owner bike that
to my knowledge has never had any shock maintenance other than the occasional service during its competitive days. At one stage, on a long gradual uphill straight dirt road with the occasional erosion stutters I had the old thing tapped in top and it seemed to enjoy the experience. I was probably doing 90-100kph and the bike felt fine. The only complaint I had was with the rock hard 17" Metzler occasionally forgetting what it had to do.
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what about ditching the standard shock and going for a works performance? Comes set up with springs to suit your weight/style?
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JohnnyO how much shorter than the std monoshock spring is the CRF unit? would it get coil bound before max travel is reached? And how does the bike feel now with this setup? I have got a 08 yz450F piston in there and we played many times to get the right shim stack but it is still bloody woefull. I have even toyed with the stupid idea ofconverting the whole shebang into a twin shock setup.... ::)
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Tony - if I remember rightly my mate has just fitted a Works performance shock to a YZ B - came with triple rate springs etc. Just a thought if you were thinking of going twin shock?
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Tony the shorter CRF spring won't coil bind, it has bigger spaces between the coils and less coils than the YZ spring. It is 270mm long compared to the YZ spring which is 370mm long. The good thing is that you can buy any spring rate you want through Shock Treatment.
I rode my mates YZ465 with this setup and it feels every bit as good as my 490 Maico with it's ohlins shocks.
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i think i gotta get me a yammy my 480 rears running a 9.8 kg spring and i recon that may be a lil soft
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with my yz125x i got my local spring maker to make me a stronger spring to take my 115kg it works real good on the bench set sag just right.got to ride it yet
cost 100.00
jim
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i think i gotta get me a yammy my 480 rears running a 9.8 kg spring and i recon that may be a lil soft
I just thought you’d had it lowered
(http://i15.photobucket.com/albums/a393/gmcloa/Broadford%20Nats%20%202010/VMX-Nats-2010-Sun--560B.jpg)
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[quote author=Nathan S link=topic=14053.msg140470#msg140470 date=127906957
Late model valve pistons have to be a good thing, but will take some work in getting the valving right (or take it to someone who knows what they're doing).
The other thing to watch for is a worn shock body. The valve piston wears the inside of the body around ride height, and then the oil can get past the valving and screw up the dampening.
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Nathan s point about the shock body is the first thing to check.They are untreated shit alum. and if its worn like Nathan said then you'll be wasting your time. Firkos ride on the low hour bike would suggest that the shock on that bike isn't worn out yet.
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I am running a late model Yamaha piston, with modern valving. I run two springs a Racetech 4.2 and a cut down spring which started life as a 250J spring. Had to machine extra grooves in body of shock. I had trouble getting the right race and static sag combo. But after much trial and error this is what worked for me. I am 70kg thought. It is hard to fit a decent valving stack as there is not enough length on shaft to fit. Standard valving is very primitive with not many shims. All the effort is worth it though, the rear end on my bike works very well. The bike is a YZ250H. Have a look at the racetech website in the vintage section, under the YZ465 project. Similar to my setup.
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Hi Rosvickicambel can you get more details on the workd performance shock? i went on the website but could not find monoshocks for the vintage bikes they had other vintsage but not a big monoshock. Now if i use my setup and the body is worn slightly ( from memory it isnt) but could I get it anodised or something to bring it back to spec? or what?
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Tony..Give Nick or Brad a call at Teknik Racing 02 47322626
They did my 465,,,new spring, Ohlins piston etc....Very happy
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I'm erring towards renovating the original shock body possibly hard anodising it, fitting a G3 gold valve , and triple rate springs from works performance, i recon that should be the best i can do. It might however be more expensive this way than buying a whole new shock By the way how do Ohlins pistons and Gold valvs pistons differ? do they work differently. I like the look of the gold valve as it has nice large ports and looks like the oil will flow easilly on sharp quick square edges.
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Just spoke to Nick...ohlins piston, hard anodised, new progressive spring etc....all in stock $ 850...3 week turnaround ( due to anodising ) with 12 month warranty
My 2 yz`s have these mods and not a problem
Your call