kobra's 1985 RZ350NC2 basket case restoration

[kobra]

She's a beaut!

Always loved the sound of my RZ with DG's.
Have no memory of what JL's sound like and I've ran 2 sets.

It's very throaty sounding, less high pitched compared to some others I've heard. It's like ring ding bwahhh with more bwahhh and less ring ding.

[kobra]

I made some recent jetting changes. Since the rebuild, I was having a pretty bad stumble when accelerating from a stop or riding with cracked throttle position. It would also bog while rolling off the throttle. I had a 22.5 pilot in there with 1.75 turns on the air screw. I originally had 1.25 turns then went to 1.5 and then to 1.75, and it improved each time but still wasn't right.

So I just went back to the stock 20 pilot with 1.5 turns on the air screw and it's perfect. From idle to redline, at any throttle opening, it's great! The top end feels a little 'thick', but there is no sputtering or bogging, so I will leave it. I bet a 280 main is "perfect" but 300 is safe without having rideability issues.

So, for reference:
Roughly 400ft elevation, 70 degrees F
Stock head
BR9ES plugs
Stock airbox with baffle and snorkel removed and UNI foam air filter
Stock VM26 california carbs
300 main
20 pilot
1.5 turns out on the air screw
DG pipes
TDR reeds
Maxima Formula K2 injector oil
91AKI fuel

Hope this helps someone out there.

[Redline Junkie]

I have dropped my mains from 300 to 280, seems to be perfect for me. I had 270’s first and it work really good, maybe too good, so I jump up to 300 but too rich. If I gave it a hand full it would not take it willingly. With the 280 it will scream to redline no problem.

My specs are as follows:
Slinger Head
Fresh bores with wiseco’s
V-Force 4 reeds
8mm Reed blocks
Canadian 31K 26mm carbs
22.5 pilots
Needle in third position (middle)
Spec 2 pipes
Uni Filter pods
Stock ports
I’m at sea level
Synced the carbs at idle and at 3000 RPM, they we out a fair bit on the sync.

[TwoStrokeNut]

Timely discussion on the main jets. I recently jumped from 240 to 260 with my stock carbs and airbox and aftermarket chambers. Not because it was running badly, however, but to ensure it didn't run too lean and burn something up. 260s are running great too in this bike. I am considering making the jump to 280's the next time i have things apart in an effort to find that point where performance drops off from being too rich and then jump back down one size. Its good to hear the 280s might be the end of my hunt because taking off the stock carbs is a PITA.

The bike is looking fantastic Kobra. And I'm glad she is back on the road again for you, putting smiles on your face.

[Redline Junkie]

Its good to hear the 280s might be the end of my hunt because taking off the stock carbs is a PITA.

I can't imagine what the US Carbs are like, I know the Canadian ones are super easy to remove and fool with when you have the stock airbox removed. I know that it would perform better with the stock gutted airbox, but the Pods make it so easy to work on the carbs!

[TwoStrokeNut]

Its good to hear the 280s might be the end of my hunt because taking off the stock carbs is a PITA.

I can't imagine what the US Carbs are like, I know the Canadian ones are super easy to remove and fool with when you have the stock airbox removed. I know that it would perform better with the stock gutted airbox, but the Pods make it so easy to work on the carbs!

If the stock airbox wasn't there, it would be fairly easy. Its mostly the boots from the air box to the carbs that I don't like wrestling with. One of these days, I'm going to devise a "boot-horn" (like a shoe horn) to slide those pesky things in and out easily. A modified airbox allowing it to slide back some would also do the trick, it seems, but I don't really want to modify mine.

[silverstrom]

A little silicone spray makes fitting the carbs into the manifolds and boots much easier. Then a thin piece of metal rod bent 90 degrees is helpful. Run it around the inside of the rubber and it slips right over the carb.

[OldTZracer]

I fold / roll the fat end inside-out over the carb end, place it on the carb then roll it back in place. As Silverstrom says, a little silicone spray goes a long way & makes the rubber look good too.

[kobra]

I also roll them and pull the boots out. There is only about 1/2 a millimeter to spare between the carb and airbox so I just carefully wiggle them out.

Took it out for a spin today, rode beautifully well. I am really impressed by the power this thing has, and it handles so well!

[TwoStrokeNut]

Thanks for the tips on the carb boots guys! I have not tried to roll the boots, but it looks like a great idea to try next time. As Kobra says, its really tight between the airbox and the US carb bank after the carb set is popped out of the reed cage manifolds (I actually have about -3 millimeters and it seems the carb venturis tubes are inside the airbox manifolds at times during the removal)... I suspect the hose clamps holding the boots on the carbs needs to be loosened up to allow the boot to roll forward as much as possible, so they are not protruding past the back of the carbs at all. Looking forward to trying it!

I don't use much silicone spray anymore... just got sick of dealing with the fish-eyes during the painting process if I don't get it ALL off (maybe my paint prep is lacking, LOL). For preserving rubber and plastic, I started using 303 Aerospace Protectant when I brought my first Avalanche in 2003, and the Avy forum members swore by it for keeping over-abundant amount the external plastic cladding on those first-gen Avy's looking good. It works great and seems to wash off easier during paint prep. For installation of tight rubber parts, I use a thin coat of good ole petroleum jelly. It doesn't seem to dry out as quickly as silicone spray does, so disassembly is easier down the road. And it washes away when needed with Dawn dish soap. Does great on carb rubber manifolds, radiator hoses, etc. YMMV, of course, and I'm sure everyone has their favorites.

[kobra]

Well my plugs have officially fouled, the bike starts up but as soon as I give it gas it majorly bogs and makes no power. I used to encounter this all the time riding 2 strokes as a kid. Time to get some more. I can see why BR8's are suggested as the standard plug, since for 90% of riding they work perfectly fine. It's that 10% of hard, high speed riding that it transitions into a danger zone that can cause engine failure.
It probably doesn't help my engine is running pretty rich. I plan to keep running 9's anyway just to reduce the chance of another meltdown event. I've definitely been riding it much more gently though.

[kobra]

After putting the new shock and brakes on my RZ, the fork really stood out as a weak point. It is pretty comfortable in stock form, but took about 13psi just to hold itself up in the corners and the spring was too soft. I could bottom it out with 1 finger braking and it was quite sketchy on corner entry when hoonin'.

Stock springs are around .41-.45kg/mm. I went with Sonic Springs .80kg/mm which are a fair bit shorter so they also include some PVC spacer material. I installed them with 15mm of preload and 120mm oil height with a 50/50 mixture of 10wt and 15wt.

Also installed some of the gold valve knockoffs from MikesXS because they were so much cheaper than Race Tech. This was a bit of a bitch of a job having to braze the damper rods, drill holes, and then finding out it doesn't fit quite right. I followed their instructions, here: https://racetech.com/page/title/DRod%201-2%20RZ350




If you just put the valve in as they come, they don't center over the top of the damper rod and could slide off to the side, letting oil bypass the valve. I had to make some little adapters to make it fit right.



The damper spring these valves came with is really stiff. In comparison to the springs the race tech valves come with, it is equivalent to their red spring (very stiff). I swapped it out for a blue spring with 2 turns of preload. We'll see how it rides.

[kpke]

Nice kobra. I'm anxiously awaiting your ride evaluation.

I recently went to MikesXS to look for those emulators and couldn't find them. In the past there was talk of trouble from copying the race tech ones so I thought maybe they were gone for good.

Can you provide a link for them?

Thank you.

[kobra]

Nice kobra. I'm anxiously awaiting your ride evaluation.

I recently went to MikesXS to look for those emulators and couldn't find them. In the past there was talk of trouble from copying the race tech ones so I thought maybe they were gone for good.

Can you provide a link for them?

Thank you.

I will let you know how it is soon.

Here they are: https://www.mikesxs.net/yamaha-xs650-da ... 00-00.html

Quality is great. Made in Taiwan.

[kpke]

Oh nice. Thanks.

And dumb ? of the day. Do you need oxy acetylene for the brazing or can it be done with mapp gas?

You're smart and will know the answer