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The Young StaLLioN
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37 Posts
Discussion Starter #1
hey all! well, still working hard at my 1985 Kawasaki ZN1100B2 LTD. It has been a blast thusfar doing my custom rebuild and creating my own touch on the bike. So, my last piece of fun work was starting the carb work. As they have sat for a very long time on a shelf, I was actually expecting them to be in decent shape. BAD assumption... oxidation plus rust lines yielded a scary thought for me... "New carbs"? dooh.. Out comes my polishing compound, carb cleaners, and bunches of time.

Now, they are ready to rock... so I thought... I pulled all the parts and detailed what I now had and what I wanted. After doing research and research, I contacted Mikesxs.net. They specialize in XS650's and he sells BS34 parts and all the needed things I need. After an email, he came back saying sorry, he only supplies XS's... pfft.. whatever... thanks for the help.. Just trying to give him business. So, last night, I put my hands on my carbs and tried pulled the choke... ummm... stuck? but I just cleaned 'em and made them all pretty and nice... Conclusion of this left me grasping the head of the choke plunger of two of the carbs--- vice grips, tried to twist and slightly break free the plunger, and.. SNAP! one head broken off. This left me taking the 4 carb assembly apart. It took me longer than expected to figure out how to take the choke off. Worst of the worst happened.. I ended up having to drill the plunger out since it broke off a second time inside at the larger cylinder plunger portion. I drilled, tapped, and finally pulled the plunger cylinder out. I then had to fine sand the internal casting and polish it to the stock luster... wheww... scary indeed..

Conclusion: I am ready for parts and have yet to find them.


What I have found installed:

Main jets-- 122.5 AND 127.5 (2 of each-- never seen this before, is that right?)
Jet Needle- 5C50 (have yet to find many needle specs that include this 5 series Mikuni needle--started using it 1981 if i remember correctly)
Needle Jet-- 476-Y5 (havent found too much on this Y5 either)
Pilot jet-- 37.5
Float valve-- 2.5

Now onto jetting. I would like to buy a few sizes of the main jets so I can go through my troubleshooting and tuning for this engine with K&N individual pods and aftermarket 4 into 1 exhasut. I would also like to get the Canadian spec adjustable Jet Needles for finer tuning of my midrange since I will be buying the larger Mains. I wouldnt mind getting new needle jets as well--are there size differences i need to be aware of? I will want to potentially buy a few different sizes pilot jets as well, but I will definitely need replacements on my current 37.5's (whether with those or different sizes) since at least one of the heads is gouged and potentially irreplaceable. With the float valves, I will just buy rebuild kits which will include the gasket, rubber plug, and float valve assembly... And as of today, i will need at least 2 choke plungers.



SUMMARY:
Needed parts:
2-3 sizes main jets.. 135-150 range (thinking 145, 147.5, 150, 155, 160 x 4 each) -- Dynojet is showing a 155 and 160
Jet needle x4 (adjustable)
Needle Jet x4 (do I need differing sizes? increase size of main jet, decrease size of needle jet)
Pilot jet x 4 (size question as well)
float valve with gasket and bottom rebuild x 4 ( gasket , rubber plug, screen, etc)
alos need at least 2 choke plungers-- bad happening yesterday left me drilling one out and getting one out leaving bad marring on the head)

Thanks all for the read! I did search and found little as far as carb resourcing goes... CHeers!!

Michael H
Mobile, AL
 

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Obfuscation Engineer
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6,686 Posts
(snip)

Main jets-- 122.5 AND 127.5 (2 of each-- never seen this before, is that right?)no
Jet Needle- 5C50 (have yet to find many needle specs that include this 5 series Mikuni needle--started using it 1981 if i remember correctly)starting with the "J" engines
Needle Jet-- 476-Y5 (havent found too much on this Y5 either)Sudco International - Modern and Vintage Replacment and Performance parts for Street Bikes, Dirt Bikes, ATVs and Personal Watercraft
Pilot jet-- 37.5 correct
Float valve-- 2.5

Now onto jetting. I would like to buy a few sizes of the main jets so I can go through my troubleshooting and tuning for this engine with K&N individual podsBad idea unless you have a chassis dyno handy or are a card carrying masochist and aftermarket 4 into 1 exhasut. I would also like to get the Canadian spec adjustable Jet Needles for finer tuning of my midrange since I will be buying the larger Mains. I wouldnt mind getting new needle jets as well--are there size differences i need to be aware of? I will want to potentially buy a few different sizes pilot jets as well, but I will definitely need replacements on my current 37.5's (whether with those or different sizes) #40's are rarely neededsince at least one of the heads is gouged and potentially irreplaceable. With the float valves, I will just buy rebuild kits which will include the gasket, rubber plug, and float valve assembly... And as of today, i will need at least 2 choke plungers.Z1 Enterprises, Inc. - Specializing in Vintage Japanese Motorcycle PartsI don't know about the choke plungers but Jeff can provide the rest



SUMMARY:
Needed parts:
2-3 sizes main jets.. 135-150 range (thinking 145, 147.5, 150, 155, 160 x 4 each) -- Dynojet is showing a 155 and 160
Even at altitude I find 127.5 as lean as a stock engine will tolerate . Anything over a 140 on a stock engine even with free flowing exhaust is questionable . Even fully modified engines with added compression , bore, cam , and exhaust don't need anything over a 155 and if it is a real fire breather what ar the stock CV's still doing on the bike ?
Jet needle x4 (adjustable)Beware of aluminum reproduction needles they will wear fast and are essentially junk
Needle Jet x4 (do I need differing sizes? increase size of main jet, decrease size of needle jet)not usually
Pilot jet x 4 (size question as well)37.5 or 40
float valve with gasket and bottom rebuild x 4 ( gasket , rubber plug, screen, etc) again talk to Jeff
alos need at least 2 choke plungers-- bad happening yesterday left me drilling one out and getting one out leaving bad marring on the head)no idea

Thanks all for the read! I did search and found little as far as carb resourcing goes... CHeers!!

Michael H
Mobile, AL
and the short answer
Sea level 132.5 mains and 37.5 pilot main needles lifted by a .025" washer with stock airbox .
Valves no closer than .005" , .006" nominal no more than .008 (bit loud )
Jerker (with complete baffle ) and pods 145 mains , 40 pilots , idle mixture screws around 3 turns and needles in the stock position (no washer) Idle quality suffers below 1,200 rpm and starts pulling from the main needle jet no later than 1,400 .
Main air bleed (the brass insert into the air horn of the carb above center and around 3/16 in dia )may need to be opened slightly likewise the hole in the bottom of the slide , slightly (this allows the slide to see vacuum a bit quicker and raise faster in response to rapid throttle opening )

That will get you started or confuse the hell out of you

~kop
 

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The Young StaLLioN
Joined
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37 Posts
Discussion Starter #4
Awesome! Thanks guys... I will entertain all of these ideas and hopefully find all the parts I need in the next few days. If so, I will get them on the way and have some carbs being rebuilt asap. Some new Cam bearings should be in by the 2nd week of September. i need to header paint my 4 into 1 headers, and the polished exhaust is ready to rock. The tank, side covers, and rear fender all need to be sanded and run through a preliminary paint job as I make sure all the parts of the bike and engine are ready to rock... Fire it up, check all functionality and tune accordingly.. Then onto some new tires with my tire changer, polish the wheels up a bit (may do that in the next few weeks), and have contemplated break'n it completely down for a frame powder coating and various other beautification steps.. woohoo!! She will be roaring in no time at all...

But, Tuning and Carb building here I come!!

Quick question.. Throttle butterflies staked? Anyone know?
 

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Obfuscation Engineer
Joined
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6,686 Posts
(snip)

Quick question.. Throttle butterflies staked? Anyone know?
staked ~ DO NOT REMOVE THE BUTTERFLIES FROM THE SHAFT OR GAWD ALMIGHTY WILL KILL A KITTEN .

Unless you have no other option do not remove the individual bodies from the "rails" .
If it cant be avoided index and witness mark them to death . I insert a short roll pin through the rail and into the carb body on my own carbs to help relocate for reassembly . The thing is the throttle shaft connects through the sync adjustment hardware that has over the years taken a "set" and will maintain adjustment only in that "set" . Even if all due care is taken and you get the reassembly as good as you possibly can usually what happens is sync will drift for a good few miles until it finally takes a new set .

~kop
 

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The Young StaLLioN
Joined
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37 Posts
Discussion Starter #9
bs 34 was also used on xs650 yamaha,(mikesxs) can help.
I actually sent him a long description of what I had and what I wanted.. Surprisingly, he pretty much said he ONLY deals with XS's... Being the same BS34, I was surprised he wasnt open to helping a fellow vintage owner out with a similar/same Mikuni carb body style...
 
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