Need help 85 xj700 carbs

I had my carbs rebuilt but only dropped the carbs off not the bike, now I’m trying to put them back on and I’m having trouble. I would greatly appreciate some advice,tips/diagrams/pictures.. having trouble remembering where all the hoses go and having trouble connecting the choke cable. Thanks in advance for any help!

 

Getting them on for me is much easier if I push the air intake boots back into the air box. Also loosening the air box screw will allow it to slip back a little. I haven't done it, but removing the battery and battery box may let the air box go back further. I put some silicone grease on the intakes and then start with one side and try to work them on from side to side. A wooden board or hammer handle also helps force them on. If someone doesn't post a picture of the choke cable I can probably send a copy of the tech manual I have on my work computer. As far as all those hoses, mine mine are routed down the brake side of the engine.

 

Here is a picture of what I believe to be correct routing of the vent hoses. The #1 hose is a little bit longer. They all end up going down between the air box boots. This bike is currently disassembled, but once I get it back together I could take more photos if needed:

 

Also check out:
https://www.xjbikes.com/forums/threads/thoughts-on-what-to-do.111133/page-4#post-570438

 

Route them below the bracket so they don't initially point up hill. It will look better too.

 

@Huntchuks - the #1 vent hose has its own special little clip. After it goes through the clip, should it go up and over the #1 air box boot, like I have it in above photo, or underneath?

 

What bike? My XJ700 carbs have two drain hoses, one between carbs 1 & 2 and one between 3 & 4.

 

1985 XJ700N. I think these might have more vent hoses than the XJ700S.

On the XJ700N, there are the two fuel overflow drain hoses, one between #1 and #2, and one between #3 and #4, just like the XJ700S.

In addition there is a vent hose that comes off near the top of each carb on the XJ700N which I don't think exist on the XJ700S. So the XJ700N has a total of 6 "hoses to nowhere" hanging off the back of the rack.

What you see in my photo above is the vent hoses that are routed over the rail for #2, #3, and #4, along with the #1 vent hose in the clip on the outside of #1. The fuel overflow drain hoses are below the rail.

I'm still not 100% sure what the correct routing for the XJ700N's rats' nest of vent hoses, but I think I'm close.

 

A little further investigation. From http://xj4ever.com/catalog/c-fuel.html:
All 1985 XJ700 non-X (air-cooled models) and all XJ750RL models with the original HSC33-series Hitachi carbs also use four sections of 6.35mm fuel line, on the short brass vacuum port coming off (horizontal and angled towards the rear) of the front left of each carb body. Be aware that these hoses run from those brass ports to "nowhere"; that is, their other ends are merely open-vented to the atmosphere. These hose run from the vac ports, and are routed "upwards" and rear of the carb rack, and their open end rests below on the airbox. The #1 and #4 carb hoses are captured by a small bright plated clip, attached to the upper rack bracket outer screws, kind of "hidden" behind the bright carb end covers. On the #1 carb, this hose is approximately 9-1/2” long, while on carbs #2, 3, and 4 the hoses are only 7-1/2” long. All 1986 XJ700 non-X (air-cooled models) do not have these brass vacuum ports, and thus do not use these hoses.

 

Huntchuks—yours is an ‘86, so you do not have the 4 upper individual ones

 

Well...that explains it.

 

Here is an example that I found on an XJ700N for sale on cycle trader.

On this one, you can see the #1 vent hose coming out from behind the chrome side cover on the carb, and then going up and over the #1 airbox boot.

 

All of the above research is correct. Additionally, California models (both 1985 and 1986 models....and this applies to both the Hitachi carbs for the air-cooled models and the Mikuni carbs for the water-cooled models) has an additional vac port on the #2 carb body, it's a much larger (fatter) port, and which points straight "up" (towards the sky) and is located just to the left of the pilot mixture screw.......this vac port is for the emissions control vapor cannister, located behind the right side plastic frame cover.

Thus on 1985 air-cooled Cali models, you actually have a total of 7 (seven!) vac hoses ---- not counting the petcock vac hose --- the two bowl overflows, the 4 carb ports discussed above (whatever their purpose is; I don't think anyone is sure), and that emission cannister hose. Whew! Vacuum hose must have been cheap back then.

Thank goodness that non-Cali air-cooled models only had 6 hoses..............

ALSO----and I can't remember, my memory is hazy and my notes are fuzzy---I think (but ain't shure....) that when vac-synching these 1985 XJ700 airhead carbs, those 4 vac ports (not the bowl overflow, and not the Cali-only emission cannister hose) should be capped off (much like the intake manifolds are capped off) in order to get proper readings.

In fact, I think you can run with these ports capped off all the time, but again----not sure. I think user @tabaka45 had some experience with this subject, and it may be his experience that resulted in my recollections above (but, maybe not)......

 

I'm going to need to do a sync on my XJ700N soon. It would be good to know if those ports need to be capped.

In addition, would they also need to be capped to do a colortune?

 

Dan, you don’t need to cap those. I have never needed to cap those when syncing or colortuning
ADDITIONALLY, the line that goes into the canister is not the end of that line...... there is a line OUT of the canister that goes to a fitting on the underside of the CALIF tank. THAT fitting connect to a tube inside the tank where the vapors are released. Those vapors stay in the tank because the cap is a NON-vented cap.
Whew——
If you want to see the canister and/or the fitting on a tank, let me know..... I can show both.

 

OK, thanks for the clarification @hogfiddles

 

I'm not sure that is how the system works while the engine is running, although when the engine is off that may be the operation.........I may be wrong, and I don't have a Cali tank here to experiment with, but...........the hose the runs from the carb to the emissions cannister (which is filled with charcoal) is providing suction (not pressure) to the cannister, and this suction also manifests itself inside the tank (via another hose from the tank to the emissions cannister). In other words, (vacuum) suction from the carb is being passed from the carb into the fuel tank, where gas vapors are evacuated. The emissions canister is also ported to atmosphere, and thus sucks in clean air, too. The fuel tank also has an "anti-rollover" valve (basically a one-way valve) that prevents fuel from exiting the tank should the bike fall over.

This is my understanding of how it works, and I may be wrong. Note that there is no explanation(s) that I have ever found within the Yamaha service or owner's manuals in regard to this system (at least in the XJ700 manuals), but the same system was used on FJ600 Cali and YX600 Cali (and perhasp FZ600 Cali models) models --- so if anyone has one of those factory manuals, perhaps they are more explanatory. The Clymer FJ/YX/FZ600 manual has a slightly more coherent illustration than the XJ700 manuals do, as they provide "flow arrows" that illustrate the movement of fluids/vapors within the system, and it shows that vapors are being evacuated OUT of the tank, into the cannister, and then back out of the cannister into the carbs (again, via the suction provided by the #2 carb).

The only problem that I have with my theory is that the suction of outside air into the #2 carb would seem to make that cylinder run very lean; but maybe it is somehow regulated inside the cannister, either by physical means (a jet of some sort) or that the fuel/air mixture coming into the #2 carb via this system is "close enough" to neutral as far as fuel mixtures are concerned, and any small difference is "adjusted out" during the synch process.

BTW, I also don't understand why the 1985 air-cooled carbs had those 4 vac ports (Cali and 49-state carbs; i.e. "all of them") and what their purpose is. The bowls are vented via the t-fittings between each set of carbs (if those are overflow ports, then they are also an atmospheric port for bowl venting), so I'm not sure why they appeared in 1985 and then disappeared in 1986. If anyone can shed light on this mystery, please do!

 

Interesting to consider the flow going the other way— that makes sense, too. I though the flow was to vent fines to the tank, not the atmosphere. Opposite flow would ‘vent the fumes to the carb to burn though, however, fuel would flow that direction in the even of a roll over then...... I think.
Maybe I’ll see if the valve can come off so I can investigate flow direction more

 

I'm pretty sure the "anti-rollover" valve is a simple one-direction check valve, and it prevents fuel (but not vapors) from exiting the tank when the tube (inside the tank) is immersed in liquid fuel....which of course can only happen when the tank is on it side, or greater. I think that it will pass vapors in either direction (which keeps the tank from vapor locking), or, the Cali fuel cap allows air IN but prevents it from escaping.

 

Hi Guys,

I just bought a 1986 XJ700 and bike was leaking gas, ran for a second then died and lots of gas leaked out of the Air filter box. Bought it as I thought easy fix???

Anyway took it home pulled the carbs and they were so gummed up and believe the guys never had them cleaned 11 k on bike.

Anyway I cleaned them put them back on and for the life of me do not know where the vacuum hoses go. I know on goes from carb to to vacuum on petcock but the other two larger one no clue. I don think they were hooked up or parts missing. The bike runs really rough and barely stays running. So I hoping when I get vacuum lines resolved I can get it to idle etc.

Does anyone have a vacuum hose routing. I see two larger ones, I know small #2 vac goes to the petcock but dont get where the other two go? Im I missing a tee connection as well?

Any help for this old Namera vet would be appreciated

Kind regards,

Dutch

 

@VanDutch - there are a total of 7 hoses attached to the XJ700N carbs:
4 vent hoses that come off near the enrichment plunger. Hoses are 8-9 inches long and just hang down behind the carbs.
2 fuel overflow drain hoses. One is attached to a T between carbs 1 and 2, and one is attached to a T between carbs 3 and 4. They are a little longer and hang down behind the engine under the airbox.
And of course, the fuel supply hose from the petcock.

I don't have my 700 out yet for the year, but maybe I can get some more photos soon.

 

Thank you for your quick response
Wow it didn’t show them in the manual and wonder why mine only had two hoses? I guess they messed with it and lost the hoses

Mine is a 86 year xj700 and maybe my txt is in error. I’m going to see wear these 4 hoses are hooked into the carb?

I saw your pic and actually thought i had a different carb set up. it’s a mindblowet and i’ll look for it in the morning

thanks Big Dan!

 

Dan and Van Dutch, ‘86 wont have the four coming from the tops— only the two from the overflow ’T’s.

dave fox

 

Thank you and think your right sir.

So i’ll leave the two hoses open unplugged. I’m trying to set up carbs and using a lil gas test tank hanging from handlebar using gravity for flow. Should I just plug the vacuum line normally plugged into petcock. Or by not using vacuum to petcock does that provide enough constant gas flow? As it seems it’s starts when carbs fill but seems to run out? The only other thought is the float bowls not set right?

any thoughts on how best to set up running without gas tank on? thanks

 

To run without the gas tank you need to plug the vacuum line that connects to the petcock and hook up an external supply of gas to the carbs gas line. You can use an old lawnmower or snowblower gas tank or buy something on ebay.

 

Thank you

plugged vacuum and used lil tank and left vacuum lines (2) hanging in runs terrible so i’m going to go through another carb overhaul. thanks

 

Did you disassemble the carbs fully, break the rack? Did you replace the throttle shaft seals when you reassembled the rack? Did you remove the pilot mixture screws, etc. to clean? Did you set all the screws at the same turns from light bottom as a starting point? Your bike may run bad with perfectly clean carbs until the pilot idle circuit is set correctly (colortune) and the carbs are vacuum balanced. If you already did those steps and it runs bad, then re-clean carbs.

 

If you use your tank from a distance, you just plug the vacuum port on the bike, and turn the petcock to PRI. Install a cheap lawn mower/snowblower/etc.... shutoff valve in the fuel line so you can stop it.

 

Van Dutch.... when you take your rack apart to clean, you need to go at least this far.......

 

man you are setting me straight and on the right path as i did not breakdown rack and did not replace the orings. and clean pilots

So i will take your advice and do that first

I did notice running the bike at 2000-3000 rpm for 3 mins after i stopped the no 3 exhaust pipe was not as hot as 1,2 and 4. I checked all cylinders got spark
plugs all looked super rich.

could it be 3 is not getting enough fuel or weak coil? I’m going to buy some nee coils - Does anyone have a source where i can buy some new ones?

Thank you for the help I owe

 

i printed your pic in color and i will use it as a baseline i’m going to get some trays …That’s some organization

 

Row 1 to the left is all carb 1. Row 4 to the right.

each row is carb 1, 2, 3, 4

each part goes in a specific compartment, all four are organized the same. I like to stay in sequence, too.
Screws/hats/brackets carb 1,2,3,4
Springs/Slides carb1,2,3,4
Etc.......

Not doing all Carb 1 then all carb 2.... etc-

I do it that way out of habit now, but I’ve done them so long, I know where they go. BUT— I still organize it because like-parts can get mixed up. Any slide can go in any bore, etc..... I keep parts from one carb with the same carb after cleaning and rebuild, unless they were obviously wrong....like brackets or bowls mixed up, etc......

ymmv

dfox

 

Always worked on single harley s/s carbs and doing carb overhauls seemed easier, despite each carb are same it’s the rails is new. Today I’m going to completely dissemble. I’ll try and get a coil pack meanwhile. Don’t give up on this old vet yet, appreciate your Valuable input

 

Read:
IN THE CHURCH OF CLEAN
THE SECRET LIFE OF CARBURETORS
https://xjbikes.com/forums/threads/how-to-clean-the-enrichment-circuit-well.8918/

Did you check your coils with an ohm meter yet? How would you know if they need replacing?

 

Did you check your coils with an ohm meter yet? How would you know if they need replacing?
https://www.xjbikes.com/forums/thre...spark-plug-cap-resistance.127651/#post-665945

 

Thanks for all the help
I was able to talk with Dave Fox whom walked me through and now bike runs now going through fine tune sync etc

it’s a lovely day in the neighborhood