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