RZ/RD 350 & Misc. 2-Stroke Tech BBS

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PostPosted: Mon Jan 14, 2013 9:06 pm 
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Location: Sydney
Pez, great to hear the F4i worked for you, I thought from what others said that it was problematical as it is longer than standard, so good to know you tamed it.

Good point on racing, as ever there are plenty of modern bikes with better suspension that would be a better fit for club racing where you dont have unlimited funds or time (and a team) to tinker. Ive spent the past few years watching a friend pour cash into old 2 stroke racers and struggle with reliability and power, let alone get to where he was worrying properly about handling other than to make large changes. Its been a sobering experience.

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PostPosted: Sat Sep 16, 2017 5:28 am 
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This old RZ wrote:
RuZty wrote:
This old RZ wrote:
Id recommend not wasting any more time $ and effort with the R-6 or F4 CBR etc..There all wrong..completley.


How do you figure this? I agree if he has a Fox it is option #1, and the CBR spring rate is double the stock RZ, just because it fits doesn't make it right, but the R6 shock is a huge bang for the buck improvement.



Its just a multitude of issues,ride height issues is too severe,the internal valving is wrong,the spring rates are probably wrong unless you fit that range of weight,rebound dampaning,compression,frame modifications,and the fact that these shocks are already probably 10 years old and in need of a rebuild themselves. Why bother?
Just becuase its a " bang for the buck"..doesnt make it a proper option. Its the exact same thing he is facing with the front end conversion..its a cheap total conversion "bang for the buck" ..BUT now it has to be totally re-valved at a large expense to correct the issues, let alone the rake /trail /offset issues that are involved.
People will state.. that "oh its not for the track" its for the street" well IMO thats even more of a incentive to do a proper shock,its safer it handles better and you dont have to modify the frame like on some of the conversions, no geometry/chassis issues ..crash hard on the track,generally your okay...crash hard on the street its often 50/50. whether you ever see your bike again let alone anything else.
Here is a short reply from another site regarding the conversions ,Its from RZsUnlimited and documents many of the issues I see ..its not that Im saying go out and buy a $400-00-$1000.00 shock..but I guess I am :smt002 even a cheapo $400.00 will perform in the long run...far better and last longer and be correct and safe!,near the limit in a moment of throttle induced forgetfullness :smt003 ..one may not have a chassis binding/incorrect valving ,compression/rebound issue quickly followed by a ....OH Fu#k!! moment.... right before it all goes really bad :smt002 Some may have no issuess with this..I do,and dont want to see some one spend $ unnecessarilly or even worse get hurt. I wont promote the practice,I just cant. If one decides to,then so be It :smt001
But outside of the fact that it costs 20 bucks on the Internet plus bearings...Thats where it ends for me.


OUOTE: RZsUnlimited."The CBR600 F4i rear shock does not have the proper valving for the RZ350. The handling characteristics change for the worse with this shock rather than for the better. It completely changes the bikes geometry as is evident by the raised ride height sitting on the side stand. The rear wheel touches the ground when on the center stand and sits too far upright on the side stand requiring a shorter side stand to prevent the bike from falling over.

I have a customer who installed one and had nothing but problems. The chain would tighten up when he tried to push the bike around but would loosen up if he would sit on the bike. This is because it raises the ride height by an inch or more. This is why the stock side stand will not work with this shock. He brought the bike by for me to look at it and you could see when you would load the rear suspension by sitting on the bike the chain would slacken to stock specification but when you would unload the rear the chain would tighten to the point that it was unsafe. When riding the bike the chain would slacken and tighten as you would ride over bumps and in the normal way the rear suspension loads and unloads. Not a good thing at all and not a shock I would ever recommend using on the RZ350 nor would any professional suspension tuner.

I once asked Yamaha factory trained suspension tuner what he thought of putting the F4 or R6 shock on the RZ350. He said it was a very bad idea for so many reasons and advised against it. That's coming from someone who knows suspension better than most.

The bottom line is that the whole CRR600 F4i rear shock craze for the RZ350 and the R6 rear shock for that matter started with a guy on Ebay who discovered that if the bushings were changed and spacers made or what have you he could get the shock to fit the RZ350. He figured it was a good way to replace the stock shock which had failed and at the same time make some money since you can buy the shocks all day long on Ebay for under $25 and then re-sell them for $140 or more. Cheap is not always better. Unfortunately because it's so inexpensive there have been a lot of these shocks that have been sold and put on RZ350's creating a false sense of improvement.

I have a customer who was building a RZ350 for track days and did not want to spend a lot of money on a rear shock. I warned him about the cheap options out there but he decided to try a F4i shock anyway. He took the bike to the track and was very dissatisfied with the response of the rear suspension. He was determined not to spend big bucks on a shock though.

He then decided to try the R6 shock which required cutting the frame to make room for the top mount. Initially he was telling me how proud he was that he got it to fit and again it was so cheap on Ebay. Well that was short lived. He got it on the track and again was very disappointed with the rear suspension. Back to the drawing board.

This time he was determined to prove that he did not need to spend the big bucks for a quality shock so he bought a used Works shock (made for the bike) off Ebay for $300 and again took it out on the track. This time although it was a lot better than both the CBR and R6 shock he still was not thrilled with the way the bike handled.

He pretty much gave up on the RZ350 and just put it in the back of the garage and bought a new CBR1000. He was thrilled with his new bike and obvious advantages it had over his RZ350 on the track. Months later he called to say he was going to put his RZ350 back on the street.

He had no plans to ever ride it on the track again. He changed out the race bodywork etc for the stock yellow and black bodywork. He told me he still wouldn't mind changing out the Works shock for an Ohlins, Fox or Penske if he could find a used one for a good price. I told him that I did have a Fox that we just rebuilt for sale. We made a deal and I sent it to him.

He called me back after installing it to tell me that I was right all along. He could not believe how much of a difference and improvement the shock made. He said he could have saved a ton of time and aggravation by just listening to me in the first place. So there you have it. This is my experience with shocks that were never intended for the RZ350 and my advise is to steer clear of them altogether.

Ohlins, Fox or Penske are the best. Works and Hagon would be a less expensive alternative and fine for the street. All of these shocks
are made for the bike which is what you want."


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