'80 G Carbs...

[Crazcnuk]

Ok, have all the parts coming to get the top end back together, now looking at ordering some kits to redo the carbs, while I have it all apart.

Just a little discrepancy.

According to the model years, the 1980 G should have:

BS34-III (3H5-00) w/ 115 mains 1&4 and 120 on 2&3

What I actually have appear to be the:

BS34-III (3j6-00) w/ 110 mains on all 4.

Is this unusual for a Canadian model? Or has someone just changed them?

According to my manual, the carbs I have are off an '80 SG.

Any tips or tricks for these, and where is the best place to find kits?

As for jetting. I am putting in a 1208cc big-bore kit, have stock airbox and a set of 4-2 with S&S slip ons with no xover.

Will I need to change the jetting?

[JWSanders]

My 80SG had 110's on all 4 as well. So did the spare set I bought. (was from another 80SG)

I've heard both. I'm guessing they did that to meet the emissions standards at the time.

I would think the big bore would require at least one step up, but better to get an answer for that from someone who has done it.

[Crazcnuk]

Problem is mine isn't an SG.

That's why I was asking, just to make sure I know what I am talking about before I start ordering parts!

I got the 3J6-00 right off the carb body itself, although I thought it was 3U6-00 at first, as it's hard to read.

[John]

You could try 120 mains on all four cylinders and go from there. Back the pilot screws out at least 1.5 turns to start with. I have a 1179 big bore, stock aibox w/ Uni foam filter, and Jardine 4-2 Spaghitti pipes with a cross over. I am using 78E carbs, with 140 mains (one step up from stock), 42.5 pilot jets, with the pilot screws around 2.5-3 turns. I am happy with the performance with this setup.

[TopCatGr58]

Cnuk,

We've found all sorts of combinations contrary to the "books"!

The variable sizes for the inner cylinders was an attempt to help them run richer/cooler since they don't air cool as effectively as the outer cylinders, but later on, they seemed to put the same size all the way across!

My SH came with 110's. I have the little big bore, but the bore won't be as much of a concern as the other breathing mods, intake and pipes. I have Indy filters, 4-1 pipes, went up 3 sizes from my original stock to 117.5, stock 42.5 pilots, about 2.5 turns out, decent color on plugs, great performance all around.

So... the 120's probably won't be too rich, especially if you have any of the intake/exhaust mods!
T.C.

[Crazcnuk]

heh I can imagine. I just thought that maybe the 'late' 80 year may have had the SG carb set, or maybe our Canuck machines were different.


Anyways, according to the Jetting 'chart'... for aftermarket 4 into 2 pipes I should go up 1 jet size. Just nopt sure if the stock headpipes with S&S slip-ons qualifies as 'aftermarket?

Also, I plan on putting a K&N single filter on in the stock airbox, possible drilling it out at a later date for 2 more jet sizes.

So i am looking at starting with +3 (-1) for 2 jet size increase and tuning from there? Sound about right?

Also 1 pilot jet increase, or not needed yet?

[Brian_D]

I agree with T.C. Start with the 'stock' jet sizes for the model of carb (not bike), then work up from there.

I found the following info in the spec sheets on yamaha's web site., unfortunately, they do not have any spec sheet listed for the H

Carb / Main / Pilot
2H7-00 / 137.5 / 45.0 E
2H7-10 / 137.5 / 42.5 F
3H3-00 / 137.5 / 42.5 SF
3H5-00 / 115(1&4),120(2&3) / 42.5 G
3J6-00 / 110 / 42.5 SG,LG,SH,LH

[Crazcnuk]

Ok, silly question, at this stage...

Exactly WHERE are the numbers on the carbs?

Was taking another look at the carbs and also found 3U7-00 on them, which corresponds with the VIN number on the bike.

Unfotunately, this number doesn't appear anywhere else in the carb number listings.

I thought the numbers looked like 3U6, which I assumed was actually 3J6, as that is a listed number, but after cleaning all the carbs, I rechecked and found they are all marked 3U7-00 near the top.

[Brian_D]

On my LH, the number is stamped on all 4 carb bodies. I haven't gotten to the point of disassembling the carbs on my project F to look at them.

Yep, noticed that too. For the E, F, SF, and G, the carb number matches the serial number of the bike. But for the SG, LG, SH, and LH, the carb number is the same - the serial number of the SG.

Note that this service data only covers the US models, so I'd suspect that the 3U7-00 carb number corresponds to the 1980 XS 1100 G 3U7 3U7 - 00010 -010000 Diamond Silver Canada model, which, by uneducated guess, would use the same jetting as the 80G US model - 3H5-00 115(1&4),120(2&3) / 42.5

I hope this helps - or at least gets the attention of some more educated people, so they can confirm/dismiss this info.

[Crazcnuk]

Except that mine has 110's on all 4, which is why I jumped to the conclusion that they were the 3J6-00...

[TopCatGr58]

Well Cnuk,

Just go with what you are starting with which is 110's! I would consider the S&S slipons and no crossover as aftermarket pipes, and with the proposed K&N and drilled box, you will probably be safe with the 117.5's, but if you can only find the 120's, then go with them. You may not need to change the pilot, possibly just turn the screws out an extra turn or so.

Just need to prepare yourself for possible changes down the road, after you get it running and broken in and can then check the plug condition with a few hundred miles on it! Each bike is different, each location also different, so expecting to hit it on the head first time out may be expecting too much!?
T.C.

[Crazcnuk]

Sounds good. Like I said I may drill out the airbox, in the future, and I do plan to get a K&N filter for it, so I will jet with that in mind.

Now, where is the best place to get some rebuild kits and additional jets? Do I need to know more about what series I have befire I order these parts?

[TopCatGr58]

You asked for it!

IF you want to replace the float needle seat, O-ring, viton tipped needles, and mainjets, you can get complete kits from 2 sources, MikesXS or Partsnmore. The jets can come from Mikes if you don't mind getting either 115's or 120's, but they don't carry the 117.5 size Partsnmore doesn't carry jets! You can get the 117.5's from Dennis Kirk.

MIKE'S XS Parts: Free Shipping over $35.00 order

Gasket - Float Bowl
Gasket - Float Bowl - Fits: 1980-84 XS650 Stock 34mm. Mikuni CV Carbs.
Oem Ref.# 3F7-14984-00


Part #20-5020 $4.00 USD EA.



Carb Float Valve (Needle & Seat)
Carb Float Valve (Needle & Seat) - Push in type with O-Ring seal, needle & clip.
Fits: XS650G/H/SH/SJ/SK/SL (1980-84) stock Mikuni BS34 CV carbs.


Part #48-1445 $10.00 USD EA.

Float Needle with clip
Float Needle with clip - Fits: XS650G-K 1980-84 Stock 34mm. Mikuni CV Carbs
- Viton tipped Needle & clip Only!


Part #48-5014 $4.00 USD EA.


Carb Rebuild Kit
Carb Rebuild Kit - Fits: XS650SG-SL (1980-84) stock Mikuni 34mm. CV carbs
Kit Contains : Push-in Float Valve assembly with O-Ring, Carb rubber passage
Plug & Float bowl Gasket 3F7. Made in Japan - 1 kit required per carb.


Part #48-1408 $12.00 USD /Kit

--------------------------------------
Main Jet - Large Round Type - N100/604 Mikuni - Series OEM Ref.# 620-14231-
Fits: Most 1980-84 Stock XS650 Mikuni BS34 CV carbs - Note: Average
Standard original size for XS650 G/SG/H/SH/SJ/SK/SL (1980-84) is #132.5 Sold in 2's

Main Jet - Large Round Type
#115 Main Jet - Large Round Type - N100/604 Mikuni type - Fits:1980-84 Stock
XS650 Mikuni 34mm. CV carbs and aftermarket Mikuni TM 36-68 Flatslide carbs.
Sold in 2's.


Part #48-0111 $6.00 USD /Pk./2



Main Jet - Large Round Type
#120 Main Jet - Large Round Type - N100/604 Mikuni type - Fits:1980-84 Stock
XS650 Mikuni 34mm. CV carbs and aftermarket Mikuni TM 36-68 Flatslide carbs.
Sold in 2's.


Part #48-0113 $6.00 USD /Pk./2


************************************************** ********
Partsnmore parts Free Shipping over $35.00 order
BUT THEY DON'T SELL JETS!

CARB REBUILD KIT
Fits XS1100SG/LG/SH/LH (80-81), Made in Japan


$12.00US /Kit

Part#48-1408

FLOAT VALVE
Fits: XS1100 (80-81), XS1100S Special (80-81), XS1100L (80-81).
OEM # 25G-14107-20


$10.00US EA.

Part#48-1445


CARB FLOAT NEEDLE (Needle only)
Fits: XS1100 (80-81), XS1100S (80-81), XS1100L (80-81).
For Mikuni Carbs


$4.00US EA.

Part#48-5014
************************************************** ************
Dennis Kirk: IF YOU WANT TO GET EXACTLY 117.5 sized jets!

Mikuni Genuine Mikuni 100/604 Main Jet Price Range: Loading...
Common Features -
Type: Jet Units: 2 pack
Order InfoGenuine Mikuni 100/604 Main Jet - Size 117.5
Dennis Kirk Part #: 17251175
Manufacturer Part #: KN1006041175
Genuine Mikuni 100/604 Main Jet

Part Number - (Price)17251175 - ($5.99)
Quantity:
7 on Hand



Your Price: $5.99

T.C.

[Crazcnuk]

So I need:

4ea 48-1408 rebuild kit
2ea 48-0113 #120 main jet (2pk)

and optionally

2ea 17251175 #117.5 main Jet (2pk)

[Crazcnuk]

Does the fact that I live over 3000ft above sea level make much difference to the equation?

And to be safe should i order a set of #45 Pilot jets?