vac hose diagram?

Does anyone have a picture or diagram of where the vacuum hoses are supposed to be connected on an xj700? They are loose and I have no idea where they go. Thanks!

 

Is yours a standard XJ700 or an XJ700 X model?

Or, put another way, does it have Hitachi or Mikuni carbs? Hitachi carbs (non-X models) have a carb "hat" that is slanted downwards towards the back of the bike, Mikuni carbs (700X models) have a hat that is full rounded.

 

It's a standard xj700. I used to have a xj700x, which was liquid cooled--this one is air cooled.

 

Well, that is a REALLY good question....as you're about to see. The factory manuals---owners, service, and parts manuals---are all sort of cryptic on this issue.

The 700 Hitachi HSC33 carbs differ from the 650/750 HSC32 carbs in that there are two types of vents built into the carbs:

a) one type, which I believe are the bowl vents, are located towards the rear of the carbs, in-between each set of carbs. These vents have a pivoting "T" connector......similar to the main fuel supply inlet located between carbs 2 & 3........and there are two of these T's, one each between carbs 1 & 2, and the other between carbs 3 & 4. These "bowl vent" T's are much laarger in OD (5/16") than the fuel supply T-connector (1/4") and are thus easy to distinguish.

b) there are also 4 brass pipes, 1 on each carb body, pressed into the carb body just below and to the left of the idle mixture screw casting/passage. These brass nipples accept a 1/4" hose.


Let me state right now that I do not know whether the above features are common to both XJ700N/S 49-state models AND XJ700NC/SC california-only models, but I believe they are.

Anyway, continuing: California models use an emissions/fuel vapor recovery cannister, which is probably just filled with charcol powder or some other such substance, and this cannister has two intake ports (nipples) on top, and one outler port at the bottom.

The owner's manual shows that one of the side covers (I think) has a small Emissions House Routing decal that shows a crude representation of the hose routing. One of the cannister intake port nipples has a hose that comes from "the fuel tank"....but don't ask me where. The other intake port nipple on the cannister shows a hose that goes to the "carb"....but doesn't show where on the carb it goes to. I would assume that this decal is applied (wherever it lives) ONLY to California model bikes, since it illustrates and mentions the vapor cannister, but who knows?

The outlet port on the cannister goes to "atmosphere".

The service manual is a little better, as it has not one but two cryptic diagrams concerning Emissions Hose Routing.....both a top and side view. The top view shows, again, the intake ports of the vapor cannister having one line going to the fuel tank, and the other line going to the front of one carb (???), which seems to indicate that it goes to the 1/4" brass nipple on the front of the carb, by the idle mixture screw. However, it only shows one hose going from the vapor cannister to one carb (even though two---no not 4, but 2---carbs are pictured in this illustration.

There is also, in the service manual, a side view diagram that shows one of the vapor cannister hoses going to the front of the carb(s).

HOWEVER, the parts manuals do not show any type of T- or Quad-connectors that would tie all four of the carb idle mixture port nipples (the brass ones, one on each carb body) together. Nor does it show any type of T-fitting that would tie those two bowl vent lines together.....the 5/16" lines that come off the two T-connector on the rear of the carb bodies 1/2 and 3/4.

The parts manual also shows a fuel line "anti rollover valve" that fits into one of the hoses that comes off of the vapor cannister....but again, no illustration of where the one outlet of this valve leads to (one side goes to the vapor cannister via a hose).

In all of the diagrams/illustrations, the fuel hose from the petcock outlet goes directly to the carb fuel supply inlet T-connector (between carbs 2 & 3), and the vacuum hose runs from the petcock to the #3 cylinder intake manifold, so at least the petcock is out of the loop for the emissions cannister.

Assuming that we could figure all of the above out for the California model carbs, then the next big question would be: what did Yamaha do with all those hoses coming off the bowl vents and the four brass nipples on NON-california carbs, since there obviously wasn't a vapor cannister/anti-rollover valve to contend with on the 49-state models.

By the way, the vapor cannister/anti-rollover valve issue appears on all XJ700 models, X and non-X, California versions. The only set of 700X carbs that I have...and I don't know whether they are the California or non-California model carbs....also have the bowl vent t-connectors (between carbs 1/2 and 3/4), but have no brass vents on each carb body up by the idle mixture screws passage (although there appears to be an undrilled port that could have been drilled and fitted with brass nipples on California models). The California and non-California X-model individual carb bodies and complete carb rack assemblies carry different factory part numbers between California and non-California models (true for both Hitachi and Mikuni carbs), but the diagrams in the parts books are identical, and show no nipples up there on either model for the X (Mikuni) carbs.....AND, besides the individual carb bodies and complete carb rack assembly part number differences between CA and non-CA carbs, ALL THE OTHER INTERNAL AND EXTERNAL PARTS ARE IDENTICAL---in other words, no jetting changes. Hmmmm......

Also, Yamaha sometimes spells the word "carburetor" incorrectly in some versions of their manuals..........

CONCLUSION: all a big, confusing mystery. You'd have to find an original bike that still has some of these lines intact. I'm thinking the diagrams in the manuals and parts catalogs are somewhat "generic", rushed illustrations necessary to comply with Federal laws, and the factory didn't have the time, ability, or desire to provide adequate, model-by-model drawings or photographs.

But if you or anyone else really does know, please do share!

 

Chacal
Yikes! I took some pictures and they are in my Gallery, though I don't know if even that will help. On the 'unusual pictures' section are some of the carb on my wrecked Maxim X (which I'm having brought back to me, but the relevent pics are under the Maxim700 file, just so it doesn't cause confusion. I'll work on it and do the best I can. I don't know if the pics will help, but in any case it's much appreciated!
Migs

 

The reason I'm interested in those vacuum lines, etc., is that when I first start it up, the choke must be on,, but it runs 'choppy' and continues to do so even after I let it warm up. I live in a relatively warm state, and there is some 'hesitance' to move/run smoothly in first. This happens even if it's been not running for only a few hours. After it's warm, it runs with good powew, but not as good a my previous 86 Maxim X, and still some 'lag' in 1st gear. Also, I was wondering about the difference between this and my previous Maxim X which had 5 valves. It seemed to make a difference in speed and I'm wondering specifically why. Please bear with me, as in thise matters I'm a novice and though attempting to learn by doing, understand very little. It's not so much of a complaint (the Maxim 700 still has nice power and speed--just not as good as the 700 X with five valves. When I remove any plug wire, it doesn't just run 'choppy', it turns off. Does this sound like a fuel/carb problem, or a motor (seems like a strong motor), the adjustments on and/or electrical problem? Everything on this bike seems to be very clean as if it had been detailed perfectly. 7000 miles on the odometer seems to be low expecially due to the fact that it's 23 years old. I already located a bike that's a nearly perfect replacement for my beautiful deceased xj Maxim X. and this one may be sold (as much as I love these bikes, I doubt it).