kobra's 1985 RZ350NC2 basket case restoration

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ZedSledder
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Re: kobra's 1985 RZ350NC2 basket case restoration

#181 Post by ZedSledder » Sun Jan 06, 2019 4:36 pm

http://www.klemmvintage.com/mikuni-tuning.htm

This page explains alot on how you can get it tuned with are screw adjustment and needle clip#.
1985 Canadian Rz350. Restored with collector plates. Stock VM26, Triumph Calipers, Galfer brake lines. Brand new DG’s, 260 main, 22.5 pilot jet. Economy pre-load adjusters. Ohlins shock. Oem Banshee crank.

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kobra
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Re: kobra's 1985 RZ350NC2 basket case restoration

#182 Post by kobra » Sun Jan 06, 2019 4:39 pm

ZedSledder wrote: Sun Jan 06, 2019 4:28 pm The higher 420+ jets are for if you remove the airbox and use pods.
Interesting - makes that much of a difference huh? Google tells me that Mikuni jets are rated based on flow rate (not diameter like I originally thought). That tells me that the stock airbox is rather restrictive compared to pods if you need that much more fuel. And many complain of a dead spot when running pods unless they go to a Dynojet needle. Okay it's all making sense now...

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Re: kobra's 1985 RZ350NC2 basket case restoration

#183 Post by ZedSledder » Sun Jan 06, 2019 4:46 pm

I’d just keep the box. With pods your fuel consumption will go way up with little if any streetable performance improvements. You can modify your box by removing the snorkle inside and trying different filters. Some even drill the lid which I don’t think is needed on this set up.

The biggest restriction I’ve seen on these bikes were the US market cat converters.
1985 Canadian Rz350. Restored with collector plates. Stock VM26, Triumph Calipers, Galfer brake lines. Brand new DG’s, 260 main, 22.5 pilot jet. Economy pre-load adjusters. Ohlins shock. Oem Banshee crank.

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kobra
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Re: kobra's 1985 RZ350NC2 basket case restoration

#184 Post by kobra » Sun Jan 06, 2019 5:18 pm

ZedSledder wrote: Sun Jan 06, 2019 4:46 pm I’d just keep the box. With pods your fuel consumption will go way up with little if any streetable performance improvements. You can modify your box by removing the snorkle inside and trying different filters. Some even drill the lid which I don’t think is needed on this set up.

The biggest restriction I’ve seen on these bikes were the US market cat converters.
Yeah, that's the plan.

So it's looking like initial setup should be:
20 pilot (original)
240 or 250 main (genuine Mikuni)
Stock needle
Stock air screw @ stock turns out
New float bowl gasket, float needle/seat, top gasket, slide actuator seals, choke plunger seal, and fuel lines (Yamaha genuine parts)

I am going to disassemble the carbs fully to make sure they are cleaned out. It's possible one of them was plugged which led to the right side piston failure.

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Re: kobra's 1985 RZ350NC2 basket case restoration

#185 Post by brrrappp » Sun Jan 06, 2019 6:03 pm

Regarding the K&L petcock diaphragm kit: Yes the number I posted is correct. I have bought two of the kits and they are the correct one. The picture is wrong on Amazon as it is just a stock-photo.
The diaphragm is a perfect match.
The kit doesn't include the petcock bowl gasket and I also buy the Yamaha OEM o-ring for the on-off valve even though the kit includes it.
There is a wave washer that adds tension to the valve that is not included so don't lose your original one.
The round rubber spacer with holes that sits directly behind the valve in the petcock had shrunk on mine and was causing a leak. The K&L kit includes this part that is not available from Yamaha.

FYI: Dynojet numbers are based on hole size. I am not positive the Dyno-Jet mains are numbered the same as Mikuni. The current Dyno-Jet kit comes with #340 and #420 mains. (no pipes / pipes)

Mikuni main jet size numbers are directly proportional to flow rate. double size = double rate according to the Mikuni book.
I have Toomey Y-Pipe air cleaner with the Dyno-Jet kit DJ-420 main, 20 pilot, Dyno-Needle and 1.5 turns on A/S. Yes, the mileage drops but the bike runs smooth bottom to top and the plugs are normal.
One would think if the jetting was excessively rich that the bike would blubber- it does not.

That leaves me wondering about two things- 1) are the Dynojet numbers directly comparable to mikuni numbers OR 2) is the airbox a major restriction since the crowd sourced intelligence here claims that a 35% smaller main jet works fine with the stock airbox.
Conventional wisdom is that more in = more out. While I have no doubt that the stock airbox is quieter and may actually make the bike quicker at low rpm, I do wonder about some claims of similar top end HP output with the airbox as opposed to without.

This argument can be found on multiple threads here on this site. There are a ton of well informed contributors that back the claims. However, to date I have not seen Dyno charts posted to support it.

Bottom line is do your own testing and start rich.

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kobra
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Re: kobra's 1985 RZ350NC2 basket case restoration

#186 Post by kobra » Sun Jan 06, 2019 11:24 pm

During disassembly I found one of the needle jets had this little round washer/cap on it whereas the other 3 did not. Can't find anything about it on google, maybe not searching the right words.

Edit: NVM - Main Jet Washer it's called. Maybe looks like it spaces out the Main Jet a little bit. I wonder how much difference it really makes.

Image

I also have 2 sets of carbs. Both are labeled 1EL 00, but one set is labeled "05 22" and the other is labeled "04 Y3". Maybe production codes, shouldn't matter for me?

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Re: kobra's 1985 RZ350NC2 basket case restoration

#187 Post by tacky1 » Mon Jan 07, 2019 12:40 am

The washer actually keeps the nozzle in as well. The washer tightens in with the main jet into the lip to stop the nozzle following the needle up.
1985 RZv500
1984 RZ500 Hybrid
1986 RG500 Walter Wolf
1986 RG500 Skoal Bandit
1984 RZ350
1984 RZ350 Hybrid
1981 RD350LC
1981 RD350LC Hybrid
2009 CR500AF Supermoto 250X
2007 CR500AF 250X
1988 YSR50 (2)
1984 GPZ750 Turbo
1989 VFR750R RC30

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Re: kobra's 1985 RZ350NC2 basket case restoration

#188 Post by brrrappp » Mon Jan 07, 2019 12:53 am

tacky1 wrote: Mon Jan 07, 2019 12:40 am The washer actually keeps the nozzle in as well. The washer tightens in with the main jet into the lip to stop the nozzle following the needle up.
Yes- the washer keeps the needle jet aka: emulsion tube from going up and into the carb throat. P/N 137-14153-00-00
While you have the carbs apart (slides are OUT) push/tap on that brass from the bottom driving it up toward the top of the carb. It will come completely out. Its about 3 inches long and has a bunch of really small holes drilled in it to allow fuel into where the needle would be. without the washer in place, you can thread the main jet back in to give yourself something to push on or gently tap on. That way you won't bugger up the threads on the brass needle-jet tube.
Don't mess it up, I don't think that you will find any replacement needle jet....
It will pop out and you should clean it really good. Soak it in carb cleaner or acetone and then run small wire strands through the holes.


That tube has an alignment slot so you can't improperly reinstall it.

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kobra
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Re: kobra's 1985 RZ350NC2 basket case restoration

#189 Post by kobra » Mon Jan 07, 2019 1:18 am

Thanks guys! I was able to get it out by threading in one of the carb body screws (M5 fine thread) and giving it a slight tap - then using a plastic rod to tap it out the rest of the way! To my disbelief, these carbs actually look pretty good. The brass parts are a little dull, but not green or rough in any way. I don't see any fuel residue or dirt either. Guess they can be reused.

A couple interesting observations though...
-When removing the fuel lines, the brass fuel supply fittings both pulled out of the carb body. Barely took any force. They both had a very tiny amount of some clear sealant almost like super glue. I guess these are just pressed in? I have some Loctite retaining compound I can use during reassembly.
-The round slides did not want to come out of 2 of the carbs. They would get about 3/4 of the way up and jam. I soaked it in cleaner, heated up the carb body with a heat gun... nothing. Eventually I just lubed it up and pulled hard and they popped out the top. On the other two carbs, the slides came right out effortlessly. Strange...
-The choke plunger seals are totally cracked and hard. I would like to replace the rubber parts - I am guessing the plastic choke handles unthread from the rod?
-The air screws have little brass caps with a tiny hole on top. I would like to remove them simply to clean that passageway. Apparently that means drilling it out.

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Re: kobra's 1985 RZ350NC2 basket case restoration

#190 Post by brrrappp » Mon Jan 07, 2019 1:32 am

The recommended procedure is to drill a small hole in the cap covering the air screw being careful to just penetrate the cap- don't drive the drill into the screw below the cap. Thread a wood screw slightly larger than the hole you made, about 3/4 turn onto the cap. Grip the screw with pliers and pull the screw straight out with the cap stuck to the threads of the wood screw.

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Re: kobra's 1985 RZ350NC2 basket case restoration

#191 Post by tacky1 » Mon Jan 07, 2019 2:21 am

Just drill into the brass half way and use either a stud extractor or a wood screw, You can re-use the brass ball by tapping it back in or just buy a 10 pack on ebay, These are the common size used on most carbs either way..
You need 4.5mm brass balls.. :P

https://www.ebay.com/itm/OD-4-10mm-Prec ... 2749.l2649


Image
1985 RZv500
1984 RZ500 Hybrid
1986 RG500 Walter Wolf
1986 RG500 Skoal Bandit
1984 RZ350
1984 RZ350 Hybrid
1981 RD350LC
1981 RD350LC Hybrid
2009 CR500AF Supermoto 250X
2007 CR500AF 250X
1988 YSR50 (2)
1984 GPZ750 Turbo
1989 VFR750R RC30

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kobra
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Location: Bay Area CA

Re: kobra's 1985 RZ350NC2 basket case restoration

#192 Post by kobra » Mon Jan 07, 2019 4:57 am

Now where the heck do I get Mikuni genuine jets? I want to get a 240 or 250 Main. Economy cycle sells them but it doesn't say Mikuni Genuine. You guys got me all paranoid about only using genuine jets lol...

This place called Niche Cycle says they're genuine, but haven't heard of the name before.
https://www.ebay.com/itm/Genuine-Mikuni ... :rk:1:pf:0

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Re: kobra's 1985 RZ350NC2 basket case restoration

#193 Post by JonW » Mon Jan 07, 2019 9:04 am

Partzilla. Check the yam parts book and you can work out the jet sizes vs the part numbers easily, then by from Yam :)
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: kobra's 1985 RZ350NC2 basket case restoration

#194 Post by tacky1 » Mon Jan 07, 2019 11:40 am

Jetsrus.com is where I get a lot of my jets
1985 RZv500
1984 RZ500 Hybrid
1986 RG500 Walter Wolf
1986 RG500 Skoal Bandit
1984 RZ350
1984 RZ350 Hybrid
1981 RD350LC
1981 RD350LC Hybrid
2009 CR500AF Supermoto 250X
2007 CR500AF 250X
1988 YSR50 (2)
1984 GPZ750 Turbo
1989 VFR750R RC30

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Re: kobra's 1985 RZ350NC2 basket case restoration

#195 Post by kpke » Mon Jan 07, 2019 11:58 am

I have purchased jets from economy, many jets/many times. They are genuine parts. But it's been a while.

They always seem to have the best price, ship quickly, and don't forget your 10% discount code (RDTECH is it?) when ordering.

If you are concerned with their parts being genuine call John there.

Great job on the rebuild/restoration. :smt023

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