82 XJ Maxim Vacuum Hose

Good morning everyone,

I recently purchased a 82 Yamaha XJ650. This is my first bike I’ve owned with a vacuum petcock. When I purchased the bike, it was missing the vacuum hose that connects to the petcock.

I’ve read a few threads already relating to the vacuum hose, but none of them answered my question... where does the other end connect? I’ve got the hose fitted to the petcock, but I have no clue where the other end should be.

I figure maybe it goes on one of the carb intake manifolds, but not sure which carb is best to put it on.

P.S. yes, I have a manual coming in the mail

Cheers,

Nick

 

It connects to the 3rd carb boot on the bike (when sitting on it, left to right. 1, 2, 3, 4). Most likely you have a cap on the 3rd carb boot like the other ones.

Does your fuel petcock look to be replaced? the stock one used the vacuum to operate. or do you have to turn your petcock to "prime" to run the bike?

 

Thanks Taylo. The third carb boot does have a cap like the other 3.

I believe the petcock is original. The bike turns over fine but won’t start, which is probably due to the vacuum leak. I get the same result on when petcock is switched to prime. Turns, but won’t start.

 

Oh the joys of troubleshooting the no start scenario. There are some detailed threads on here for going through that. Verifying compression, fuel, and spark to determine what's going on.

Best of luck

 

bike history please. have you had bike running or heard it run?
how long has bike sat not running?

CHECK oil level before going any further in trying to start bike.

4mm vacuum hose is the size. it can go on any port on the carb boots.

fuel line is 6mm id.

this would be a good time to test the petcock.

disconnect the fuel line. install a line to drain off into a can.

with drain line in container suck on the vacuum hose or use a pump if you have one. see if fuel flows in run or reserve position.
also test prime for flow in does not need vacuum.

if no flow check to see how much fuel is in the tank.


you will want to read information over load

The Information Overload Hour

read this for specs on ignition and charging system
The Ultimate Relay, Switch, Sensor, and Diodes Guide

carbs
IN THE CHURCH OF CLEAN

 

Bike wont start issue.
electrical. If battery is to low on charge bike will not start. ignition components ot of spec or failed. bad fuse or holder

fuel issue.
no fuel flow, will fuel flow on prime? No gas in tank? petcock, vacuum line not installed
clogged carbs

 

If the petcock is switched to prime fuel should flow to the carbs even without a vacuuum line being hooked up.
Pull the fuel line from the petcock, and turn it to prime to confirm that the petcock is allowing fuel to flow when set to prime.
If it is, then you have a problem further downstream, or an issue that is unrelated to fuel.
You cancheck for fuel fow to the carbs by using a longish straight blade screwdriver to open the drain screws that are on the bottom/rear of each float bowl.
If there is fuel in the bowls, then move to double check that you have spark.
If you have spark, then you probably have clogged jets in the carbs.

Read the first link in my signature. It will lead you down the path to having a safe and reliable motorcycle.

 

Bike has not ran since June 2018.

I have spark on all 4 plugs
Fuel came out of carbs when I loosened drain plug
The bike has oil at appropriate level

Sounds like I may be taking the carbs apart boys

 

give it a shot of starter fluid into the air box see if it fires up.
and even if it does you will want to clean the carbs

if it has pods DO NOT spray them with starter fluid a back fire will light the on fire.

buy your self a fire extinguisher for when ever you are working on gas issues

 

Tried some starter and no dice. Just now ripped the carbs off and the first thing I notice is that when I pull the throttle lever, the valves/headers on the carb don’t open. I believe on my XS 650 they do. So that could be a problem.

I’ll clean the carb up and see if anything seems off on the inside. Hopefully they’re gunky as hell so that I know that’s the problem.

 

the slides you see from the back side of the carbs do not lift by throttle cable. the butterfly plates you see on the throttle shafts move with the throttle cable you can see them from the front of the carbs.

the slides can be lifted with your finger. The slides lift with vacuum when motor is running.

 

Carb #1, where the fuel line connects, had some crap in it. Cleaned all 4 then I put a little starter in the carbs and it came to life for a half second, but every time after that it only turned over like earlier

 

charge your battery. if it drops below 10 volts when cranking bike will not start.

 

Despite your success, it is worthwhile to disassemble the carbs and go through them fully.
There's nothing more frustrating than chasing problems and taking carbs off multple times.

IN THE CHURCH OF CLEAN
Inside your Carbs
Replacing your Hitachi throttle shaft seals
Setting the fuel levels

Going through everything (not just the carbs) is particularly important since we already know that the previous owner didn't know what he was dong (re: the missing vacuum line to the petcock and the extra vacuum cap).

I bought my Seca as a runner/rider (test rode it before buying) and it still took me a summer and most of that winter getting it back into proper shape (then other things happened, but that's another story).

 

I’ll throw the battery back on the charger tonight.

As for all the carbs, I did go through all 4 of them completely. Sorry I don’t think I made that clear originally. Only carb #1 had some junk in it.

I put new plugs in as well. At this point I’m assuming it’s having trouble starting because it’s been sitting for 10 months.

 

You broke the rack apart, pulled all of the jets (including the air jets), removed the idle mixture screws and replaced the o-rings with new, removed the throttle shaft seals and replaced them with new after soaking the carb bodies to clean out all of the residue from all of the passages (including the enrichment jets in the float bowls, replaced the float needles and wet-set the fuel height, and bench synched the carbs?

If not, then you didn't go through the carbs completely.
Skimping on refurbishing the carbs is the single most common carb problem we run into on this forum.
Hitachis are finicky buggers that work extremely well when cared for, but you can't treat them like Keihins.

 

I need to order new seals, rings, and float needles.
I think my next move will be doing my reading in the church and then setting the fuel height. My best guess at this point is that the floats aren't set right and its causing them to flood.

 

Make sure you get the carb kit with new needle/seat pairs. The seats are not pressed in, they are held in by an o-ring so replace both. New ones come with a plastic bowl screen on the bottom. Sometimes the seat screen will get clogged and it's just better to swap it all.

 

Well guys, I f*cked up.

While going through the carbs again I was trying to loosen the 10mm needle bolt on the third carb and broke off this fin here. :/

Any recommendations? I figure this carb is done and I’ll need a whole new replacement

 

It’s the fin that the float pin goes through

 

jb weld, drill and pin it. there is no tension on it. let it cure a few days before you put gas in it.

 

Ryengoth thank you for the suggestion. I’ve got jb weld but I think I may be better off taking it to a machine shop to have it drill and pinned... maybe

 

Forget about fixing it.......buy a used carb body......someone from this forum will have an extra one.

Trust me.......trying to fix it is a temp band aid if it works....

 

Hopefully the 650 is more prevelent because I am still looking for a carb body for my 550, with no luck. Post back if you find something.

 

Using JB weld is temporary.
Having it fixed properly by a machinist or someone who is good with a TIG is permanant.
But then, that can cost as much as buying a spare rack to rebuild unless you have a freind that works for cheap.

 

That thin old casting would be very difficult to TIG weld, thus why I suggested pin and solvent resistant epoxy. Apart from that you find a replacement.

 

Heck, send it my way and I will try to TIG tack it back together for the video footage if you plan on tossing it. No promises as it could just go poof into a blob. I can return it, success or not. lol

 

There is at lest one fella who does that work. He does such work as a hobby though, so we don't try to send him any business.
Polock cut a dovetail and pinned his.
I've left the rough break for fit, and toe-pinned one with press-fit pins (tedious but effective).
Cutting the break flush and drilling for a small stud, and making a replacement out of round stock is also an option.
Many, many ways to fix that sort of thing if you have the time and patience, but if you have to pay someone it's usually not worth the cost.

 

Thank you everyone for the recommendations and input. It’s very helpful

I’ll call around town and see if anyone could cut in and pin it for me for a decent price. I’ll probably search for an individual carb body as well.

 

Can anyone tell me whether or not carburetor #2 and carburetor #3 are the same?

This break happened on the inside right carb (#3), but I am seeing some inside left ones (#2) on eBay. Not sure if I can buy that and make it work as a replacement.

 

IMHO it's best to leave the rough break and center pin it since machining out material, without replacing it, will cause the float to sit uneven. Try setting a float level with it crooked. You could also use a small metric press-fit nutsert (m3 or m4) in the body and thread a stud into the broken off piece as a quick-fix as long as the break is fairly level. For stuff like this, like you said, there's a ton of ways to fix it if you know how to.

 

YES-- body 2 and body 3 are the same. T-shaft assemblies are different. The same body is used on the 81-83 xj750's body #2/#3, as well.

Dave F

 

Little update for y’all. Bought a new carb body off of eBay. I am currently waiting on new throttle shaft seals and fuel tube o-rings from a Chacal

I think I had said earlier that one of the previous owners had put some sort of sealant outside the fuel tubes between carb 2 and 3. I got the carbs apart and there was some sealant gunk inside the carb housing and the fuel tube itself. No bueno.

Some of the o rings on the brass fuel tubes are pretty flat and roached out. They definitely were never replaced (At least recently) which explains why someone had tried to seal up the tubes with that stuff.

Does anyone have any recommendations on what to soak the brass fuel tubes in to help get that sealant gunk off? I worry that soaking in carb cleaner may be bad for the brass. Thanks!

 

Break the whole rack down, and do a complete rebuild. The cleaning fluid will help soften any thing. You can also use heat the soften stuff. If you don't do a thorough cleaning and rebuild, you're gonna go in circles

 

Rack is all apart. Carb cleaner won’t hurt those brass fuel tubes, will it?

 

Berryman wont.

 

It can make it darken in color if you leave it in too long,but the darker color mostly rubs off

 

Btw.... All apart means ALL APART.......like this-

 

Yep, like that. Taking them to church.

 

Good

 

Need some help.
With the vacuum hose hooked from the petcock to carb #3 port, I didn’t get anything with the petcock on “on” or “prime” position. It would sputter and try to start and backfire when the vacuum line was pulled from the petcock and my thumb covered one end. Also wasn’t getting any fuel with the petcock set to “on” but was when the petcock was on “prime.”

 

Time for a petcock rebuild, but verify that your vacuum tube isn't plugged or collapsed

 

I'll check out a petcock rebuild kit... I know the vacuum tube isn't plugged. Is it pretty noticeable when it's collapsed?

Shouldn't it at least start up since i'm getting fuel when petcock is on "prime" ?

 

Well when you said ' it was when it was on PRI' I thought you meant it would start then.... my bad.

Either way, if you get fuel on PRI (since it is free-flow at that setting) and you don't get any when you are on RUN or RES (where there is vacuum needed to open the petcock), and the vacuum does not seem to open the petcock, it would point to a petcock issue

 

Got it. Do I need a whole new petcock or just new seals that come with a rebuild kit? And just to double check... the vacuum hose hooks in to the carb #3 intake boot, correct? Would it be worthwhile to try joining it to one of the other carb intake manifolds?

It was sputtering when I had it set to prime and it seemed like it wanted to start but I couldn’t get it. Is the vacuum line needed for it to start even when petcock is set to prime?

 

some petcocks are to far gone to rebuild but yes just the rebuild kit.

Rebuilding the Yamaha Vacuum Fuel Valve w/pics

If #3 is the open port then yes. Any port you want can be used. use caution with hose routing so you do not end up with a kink.

vacuum line runs on/run and reserve. prime is a gravity feed

How much gas do you have in your tank?


vacuum line is something you would want to replace when you rebuild your petcock. 4mm ID is the size

 

Plenty of gas. I guess my next step is getting that rebuild kit. Thanks guys

 

do you have a vacuum pump brake bleeder? hook a vacuum hose to petcock and fuel line into a container set to reserve apply vacuum and see if you get flow.

no pump? you can just suck on the hose for the petcock test

 

No pump, but that is a handy trick. I'll give it a shot.

Fuel should also come out when you do the petcock test with the petcock set to "ON" correct? And just to be sure I'm doing this right... the vacuum hose IS hooked up on both ends when I do the petcock test?

I'd hate to get a good mouthful of 'ol 87 and not have even done the test the right way

 

yes to on as well will work test both

vac hose goes to the vacuum nipple on petcock
the fuel nipple goes to a hose to drain into a container do not suck on this fuel hose