Fork choice?

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Rockt
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Fork choice?

#1 Post by Rockt » Sat Apr 30, 2016 10:47 am

Purchased a nice '88 RZ350 that I'd like to modernize suspension-wise.

I have an RGV swingarm and I've read lots about adapting it to the RZ. Seems relatively straightforward, though we'll see when I get around to installing it.

What I'm wondering about right now is front suspension. I know that USD forks are probably a bit of overkill, but... I think they look really good on the RZ so for that reason alone that's what I want to put on. I've read a lot of the posts here and it seems do-able. Double up the steering bearings on the bottom and have a spacer machined.

BUT... which forks are best for this bike? So far I've seen GSXR and YZF forks used, but is there one that fits better and/or is easier/better to install on the RZ? Or do I just find the best front end for the money I can afford and make it work?
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JonW
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Re: Fork choice?

#2 Post by JonW » Sat Apr 30, 2016 8:47 pm

you need a bike with similar weight and riding position really, adjustable is nicer too, but you can fit anything you like, some work and are easier than others, suspenion houses can adjust the innards later for you if you have it badly out. Eg. its said R1 is too hard, R6 is ok etc. you will need to read around the subject really and know more about suspension if you go off piste with something no one has done. Eg. I have KTM forks in my XT500, I had to shorten them, but the spring rate is fine and theyre adjustable like no XT fork ever was. I have RGV on my LC and RZ, one has the Andreani kit, one not... sit up riding position on a bike with rgv forks and its ok as standard, lean further forward over the bars and you might go Andreani etc....
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
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Rockt
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Re: Fork choice?

#3 Post by Rockt » Sun May 01, 2016 2:38 pm

Thanks Jon.

Not going to step outside the box any further than I have to, so no KTM forks, etc.

I found a front end off a '02 GSXR1000 but I think the price is a little high. From what I've read they shouldn't be too much trouble to mount. The only thing I don't understand is the double bearing on the bottom. I understand the spacer, but this doesn't make sense to me?
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RZed
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Re: Fork choice?

#4 Post by RZed » Sun May 01, 2016 7:05 pm

Rockt,
I have a 99' R1 front end on mine and it works great for me. No double bearing on the bottom, just the 5mm spacer. It might be that both top and bottom bearings are the same, hence double bearing??

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Charlie
1985 RZ 421 Hybrid viewtopic.php?t=9655
99 R1 USD front end
Tarrozi Hi-rise clipons
TrailTech Endurance II Speedo/Odometer
VJ23 swingarm
CBR F4i rear shock/custom dogbones
JL GP stainless pipes
2018 XSR 900

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JonW
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Re: Fork choice?

#5 Post by JonW » Sun May 01, 2016 9:03 pm

you can actually use the old lower bearing cups as a spacer, but a nice simple alloy one is easy. no idea what double bearing comment means.
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid

Like Watches? www.PloProf.com & www.DeskDivers.com

Rockt
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Re: Fork choice?

#6 Post by Rockt » Mon May 02, 2016 9:23 am

RZed wrote:Rockt,
I have a 99' R1 front end on mine and it works great for me. No double bearing on the bottom, just the 5mm spacer. It might be that both top and bottom bearings are the same, hence double bearing??

Image

Charlie
Charlie, your bike is fantastic! I'd seen it before when I was getting interested in RZ's and it's one of the bikes that motivated me to do this hybrid suspension thing. Nice job.

I actually would have preferred a 1st gen like yours - I like the tail section better, I like the red frame and since I want to go without a fairing, the lack of mounting tabs on the frame would be cleaner, (I don't want to grind mine off since I want to be able to return it to stock someday if I want). But I found this nice '88 and couldn't let it pass, so I'll work with it.

I've got the same RGV swingarm, so I may need a bit of advice down the road when I start on mounting it. Gotta work on the front first.
RD400F RD400G RD350LC RZ350

Rockt
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Re: Fork choice?

#7 Post by Rockt » Mon May 02, 2016 9:26 am

JonW wrote:you can actually use the old lower bearing cups as a spacer, but a nice simple alloy one is easy. no idea what double bearing comment means.
Well, I read a lot in a short time, so there's a good chance I misunderstood that. So now it sounds simpler, though I'm sure it won't be without its challenges.

I found a front end from a Kawasaki ZX9 that looks decent. Not sure the year. Any reason it won't work?
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JonW
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Re: Fork choice?

#8 Post by JonW » Mon May 02, 2016 9:31 am

Ive no experience of the ZX9 sorry. Almost anything can be made to work, but if its very wide you wont get much turning of the bars before you hit the tank, but that depends on the forks and the tank etc...
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid

Like Watches? www.PloProf.com & www.DeskDivers.com

Rockt
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Location: Ontario, Canada

Re: Fork choice?

#9 Post by Rockt » Mon May 02, 2016 9:37 am

I actually didn't think of the turn-to-turn issue. Charlie, is that a problem for you with the R1 USD forks?
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JonW
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Re: Fork choice?

#10 Post by JonW » Mon May 02, 2016 9:40 am

I should qualify that width statement... I mean the size of the fork legs and where they fit in the triples, ie if they are thin and forward you have lots of turning, if they are thick and right level with the stem, you have reduced steering etc.
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid

Like Watches? www.PloProf.com & www.DeskDivers.com

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Re: Fork choice?

#11 Post by RuZty » Mon May 02, 2016 10:13 am

The later (05+) R6 forks are slightly smaller diameter and presumably sprung a bit lighter than the R1, I've got some installed but not ridden it yet. I had it off the lift last week to turn it around and my first thought was 'wow, I hope that's enough steering lock'. I haven't measured the difference yet but it seems a lot, exactly for the reason Jon described.
The main trick in choosing components is finding something that fits and allows you to match front and rear wheels. I've used Suzuki Katana 750 rear and 1200 Bandit front that look like Charlie's. If you use the R6 front end you could look at an FZ600R (twin cyl) rear wheel to match. It ran a 160/17 tire and will be plenty for the RZ.

Rockt
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Re: Fork choice?

#12 Post by Rockt » Mon May 02, 2016 10:42 am

Thanks RuZty. Hopefully Charlie, (and anyone else with USD forks), can let us know how they work out on the road.

The main trick in choosing components is... BUDGET!! Just kiddin'... sort of. After buying the bike, I don't have a ton left over, so I have to be pretty careful. Don't worry, not going to cheap out and put something on that might be dangerous. Just have to be patient and try to find stuff that's a good deal. Otherwise, I'd just go to a bike breaker and get all the best stuff.

GS500 rear wheel and cush-drive seem to get a lot of mention, as does SV650 rear wheel. Those should be easy enough to come by.
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RZed
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Re: Fork choice?

#13 Post by RZed » Mon May 02, 2016 1:20 pm

Rockt wrote:I actually didn't think of the turn-to-turn issue. Charlie, is that a problem for you with the R1 USD forks?
The turn to turn is less than stock for sure, but it doesn't seem to hinder rideability.

I think the forks work well for me. I'm about 195lbs, so maybe the stiffer springs help offset my sturdy build. :smt043 The bike has a firm ride, soaks up the bumps, but isn't harsh. :smt023
As far as wheels, I run a SV 650 rear with the GS 500 cush drive. It matches the R1 front wheel perfectly!! And I run a 150 tire in the rear. Leaves about 1/8" chain clearance. Feel free to ask any questions, we're all here to help. :smt039

Charlie
1985 RZ 421 Hybrid viewtopic.php?t=9655
99 R1 USD front end
Tarrozi Hi-rise clipons
TrailTech Endurance II Speedo/Odometer
VJ23 swingarm
CBR F4i rear shock/custom dogbones
JL GP stainless pipes
2018 XSR 900

Rockt
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Joined: Fri Mar 25, 2016 3:29 pm
Location: Ontario, Canada

Re: Fork choice?

#14 Post by Rockt » Mon May 02, 2016 2:50 pm

Thanks for the info. on turn-to-turn Charlie. That's what I was hoping, not TOO much effect. I'm sure there are lots of good standard forks that would be just fine for the RZ (CBR600F3' are excellent) but the USD ones just look RIGHT.

I'm 135 lbs. so I'll probably have to go with softer springs in whatever fork I put on.

Just read through your whole build. Awesome job, man. Can't believe you were able to do it so fast. But that must have been a hair-pulling experience trouble shooting the fuel flow issue. Glad you were able to sort it out before giving up - a lesser man would have.

So you have a Yamaha R1 front wheel and a Suzuki SV650 rear? From the pictures, they look like a perfect match.

I won't ask you specifically about the engine here since this is supposed to be about chassis stuff, but that must be one exciting ride. To be honest, I haven't ridden my RZ yet, so I don't know how the power valves feel. But I like the way the power of the RD350LC, without PV's, comes on, so the Athena might be similar... only A LOT more!
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Re: Fork choice?

#15 Post by RuZty » Mon May 02, 2016 11:16 pm

If you just bought the bike and have a tight budget why not fix what it needs and get riding, instead of taking it apart in the spring. Spend the summer collecting parts when the good deals come up and save it as a winter project. That way you will also be familiar enough with the bike to assess the actual impact of your modifications.

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