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

Hello everyone! I have been reading these forums for us 2-stroke fans for a few months and I am stunned by the incredible mods that have been done to these bikes!! It has helped motivate me to restore my 1984 RZ350 that I have stored since 1997. I have owned this and loved this bike since 1989.

When I attended the Laguna Seca Superbike race last year, I saw a beautiful RZ350 parked there and it brought back great memories of riding wide open and being chased by CBR900's and 600's in the early 1990's. It was more like terrorizing those innocent 4-strokes!! So many crushed egos!! So sad.

So now I have started to restore the RZ and for now it will be kept mostly stock with a few much needed upgrades like I see here. A new rear shock is among the upgrades and also new Battlax tires, 110/80-18 and 120/80-18 for now and installed already. Blue Dot calipers with Galfer brake lines too but I need adapters from Tony.

With all this going on I am going to be asking lots of questions with the the master builders for help, here.
I have seen the R1, R6 and F4 shock modes. They are old battered but rebuildable shocks. And a great place to start modding. I found a new 2015 R1 shock that I have installed with some mods so I want to share this and see if anyone has tried this.

This 2015-16 R1 shock has ride height adjustment(4mm) with a removable eyelet and is more compact and lighter than the previous shocks. The removable eyelet was the key for me trying this.

I have installed it without any frame mods. This shock was 12.5"(318mm) long, stock. I shortened it to 11.8"(300mm) with some cutting of the eyelet and the shock bottom itself. It can go shorter too. The eyelet hole was 27mm deep but was only threaded 17mm with the bottom not threaded like the eyelet's last 10mm.

I had my super machine shop cut off the bottom 10mm or so of the eyelet and about 4mm of the shock itself. I think more can be removed to make this shock 290mm like the stock De Carbon clunker but we stopped here at 300mm. The eyelet was then heli-arced to the shock body. I used Economy Cycles bronze bushing pressed in the bottom. The top eyelet was left in and he used my new 12mm drill bit in a lathe to drill out the top bushings.

When I installed the shock last night, it would not move enough on the top to connect the bottom mount. After looking at pictures of the shock top, I noticed a flat top above the eyelet. I removed the shock and removed this material with a sander and file to match the curved contour of the shock top. After reassembly, everything bolts up perfect.

After I have cleaned up the linkage tomorrow, I will reinstall the tire and seat and check out how soft or firm feels. The linkage needs bushings though and now on order. The shock adjusters are easy to access too.

This shock has a 9 kg/mm spring on it. The RZ shock has a 10.5 kg/mm spring. The 2014 R1 shock has a 10 kg/mm spring on it and I will try this later. I want to see if the stock damping can firm up the shock enough first.

Hopefully it will be only a couple of weeks or less before I can road test this. I am waiting on my cylinders and other parts. The machine shop is boring to first over. The RZ has 18350mi on it and I put on 16350 fantastic miles. The only reason I disassembled the top end was to check to make sure the rod bearings were not gummed up. They were clean. I used only Bel-Ray Si-7 oil. Bel-Ray was not sure if they would be gummed or not. I have seen ruined rod bearings from this.

I am sorry my pictures are way to big to post. If anyone has an idea on how to reduce the pix size, let me know. I have them on Photo bucket. And if anyone has any questions on this, do not hesitate to ask.

sounds interesting indeed. what platform computer are you using? if its a mac you can download Fast Image Resizer, and there is probably something similar for Windows, its been a long time since i used one of those in anger. pics size of 1280x800 is what i use before uploading to Pb.

It took me a while to find pictures of one but that looks like a nice upgrade. I did the R6 swap at least 12 years ago and it has held up well. I'm curious how much clearance you have under your rear tire on the centerstand with the new shock. Mine is almost touching on a flat surface but I like the quicker steering the higher rear provides. Unless you are a big guy I think you will find the spring rate fine, especially with decent damping. I'm a 'bit' over 200lbs and have never had any trouble, and the R6 spring rate is very similar.

I found I could resize my pix to barely Hd but you can see what the shock looks like. I will be checking the clearance tomorrow. It was 1.25" clearance with the stock shock and new tires. I am hoping that I will not have to re-spring or have RaceTech revalve it. I am only 160 lbs and was less that 145 when I was riding the RZ way back in the last century.

There is no reason to check the sag and such before the linkage has new bushings. One side dragged. I had RaceTech revalve and re-spring my 1998 YZ250 shock when it was new. They went for a lighter spring than stock. They said the revalving it could easily make it very firm if needed instead of the stiffer spring. They were right too. The right guy could have jumped over a house with it.

You can find these shocks on ebay as I did. $130

How much clearance is there between the shock and the wheel, Does the wheel get close to the damping cylinder that sticks out the back.

Hey guys, I forgot to talk about another option to shorten this shock even further. I also have a 2014 R1 shock. I think the lower mount can be removed and installed on the 2015 shock. This will make the total length 290mm or very close. Both shock shafts are 14.45mm and removable. I have yet to hear back from Racetech on the cost involved. This probably has given the guys at Racetech a bad headache right now.

It's money well spend on these legendary fun machines, right?

I will let you know on the clearances with some pix later just for reference and thanks for asking these question. I needed the help on this. I can tell you the ground clearance is about 1/2 inch but the linkage is not tight. The stock shock has 30mm of shaft travel before it hits the rubber bumper. These shocks have 45mm of travel before hitting the bumper.
For reference: Stock chain and sprockets and new BT45H 120/80H-18.

How does this compare to the R6 shock travel? Any issues?

Today I assembled and tightened the suspension and ended up with 15mm tire clearance and the ground. The shock top needed a little more cleaning up to clear the top mount without binding at all. Smooth. You can see from the pic the flat top that has to get a shave. I also used 2, 3mm hardened washers glued to the top bushings to make it 39mm total. The stock RZ shock bushing was 40mm. The inner fender got trimmed also like the R6.

I checked the wheel to shock clearance at 4.5" travel and 6.5" travel with no contact but close at 6.5". I then tightened the chain at the tightest point. So far with the RZ off the stand it feels firm but has a little static sag like it should and feels nice seated on the RZ.

I think eventually putting on a BT45 110/80-18 with help too with clearance if needed. The 110 is 19mm smaller in dia and will gain 9mm wheel to ground clearance on the stand if needed. If there were only 17" wheels for radial tires that would fit the stock suspension. So many wheel dreams...17 inch radials....

Now it is time to disassemble the swing-arm and suspension to clean them up and install bushings when they arrive.

I honestly wouldn't worry about shortening it more, get it together and go for a ride and see what you think. Thanks for putting ideas in my head too.

Rutzy,
You are welcome. I am waiting on the machine shop to bore cylinders, brake adapters and linkage bushings. The suspension felt good last night when I had time to inspect it. Even the stock preload is good so far. The best part like the other R6 shock mod is the adjustable damping that was not available in the last century on the RZ's. I hope it is together soon. It is still a little wintry at times here and lots of sand on the roads can that make for interesting sliding/riding. After a few good rains and it is gone usually.

The shock can be shortened internally by adding a space to reduce free length. If youre interested in shortening it more. Very easy job for any suspension shop.

Hi Jord,

Now that is good news! The stock shock travel is 30mm+- before the crumbling rubber bumper departed. This shock has 45mm. Hmmm. That would be nice to have the stock length at 290mm or close.

Is that what you did to your R6 shock? What trickery did your R6 shock get? Re-valving, new spring or anything?

Thank you much!

Good post there twowheeldrift.
I'm now in the market for the said shock.
I like the fact that it is near the same spring rate and it can be made to the exact length.
Good information you have provided.
Thank you again.

Seahorse,

You are welcome. I only wish I could go for a test ride and try some tuning on it but I have a ways to go on this restoration. The clutch, gear box and crank/rods inspection is next. The crank will get at least seals. If everything is acceptable, it is going right back together and get this show on the road.

I hope you can find a good, new shock for your project. That was part of the idea here too. The R1 guys are installing Ohlins for the track mostly and selling this one. It is a very nice, light shock. RaceTech has nothing for it right now so be aware of this. I am going to pick their brains about it this week.

I seem to be stalled out right now waiting on parts and lousy mountain weather. I pulled the engine to do a crank and trans inspection. Now it has become a full blown restoration with some modern upgrades that the RZ needs.

It is a good time while I am waiting to clean and upgrade. I had a feeling when I started with this project it would lead to going through every square inch.

I am adding a KYB bumper cut to size to keep shock travel to near stock. Has anyone had issues on the R6 shock mod with too much wheel travel?

I should have stayed off the Banshee websites. So many trick parts for the RZ that seem to be arriving in the mail.

While I am waiting on a few other bike parts, I decided to modify my second R1 shock and cut it as close to 290mm as I could. And it is very close if not 290mm.

We made five quick beads around the eyelet. A wet shop towel was used each time to dissipate the heat like the last shock. The shock shaft itself never got hot. I could not get a diagram of the shock to see if the rebound adjuster could be damaged by the heat such as o-rings. But it works very smooth as before.

This should solve and tire ground problems and slack chain issues of a longer shock as well as handling issues than may come from a jacked up rear wheel. Again, no frame cutting with this shock.