help?! No idle after a long day of wrenching...

Today I replaced my rear wheel, rebuilt the petcock, and installed new handlebars. Somewhere between those modifications (i'm guessing the wheel is innocent), my solid-running 1982 XJ650 Maxim is suddenly refusing to idle.

Oddly enough, when I had it on the jack stand and started it, it ran like a champ, but as soon as i dropped it off the stand it dropped to 500-700rpm and sputtered from there. I gave it some choke and it did nothing at all... eventually sputtering out.

I started it back up, this time putting it in gear and riding about three blocks manually revving the engine to keep it up, and as soon as i stopped at a stop sign, a quick sputtering death.

My first thought is maybe I messed up replacing the fuel lines... I feel like fuel isn't going where it's supposed to. That's total speculation, but when I removed the tank earlier I had accidentally left the vacuum and fuel lines connected, and they popped off with the tank, leaving me wondering where they came from. In my head I'm wondering if it was running fine on the jack stand because there was still some fuel in the system.

I also dont know if the new bars are a possible culprit... i can't really think of any way they could effect the idle but I figured I'd include the fact that they're different now.

I need help!

 

Mistake in petcock rebuid? Or you may have the lines swapped?

 

There are two Hose Connections on the Petc0ck.

One is the FUEL Outlet.
(On the Right Side. Gas will flow from it when the Petc0ck is set to PRI.

The other is for a Vacuum Hose connection which controls the Vacuum Operated On-Off Diaphragm Valve.
(Smaller. On the Vacuum Block. This connects the Vacuum Valve to an Intake Manifold Port. Any one will do. 3 is stock.)

If the Hose is not attached to the Manifold Port, ... and the Port NOT plugged-off ... the leak will case erratic performance.

 

I think I got the hoses on correctly... smaller hose on upper petcock nipple to airbox, larger hose on lower petcock nipple to carb.

I unplugged the fuel line and it's flowing gas from the petcock... not good, but definitely means there's fuel.

If I assembled the petcock incorrectly, would that somehow explain the extremely low idle? I meant to mention my choke lever is seemingly useless right now as well.

thanks for your help!

 

Without the bike running If you have the hose off the petcck and set to "prime" the gas should pour out like crazy and you should not get fuel if its set to "on"

 

sounds like not enough fuel (starving)

 

In prime, it's dumping fuel. In on or reserve, it's a slow drip. Not ideal, but before the rebuild it was spraying fuel out the side so it's an improvement... haha. So we definitely have fuel. As long as my hoses are correct we have vacuum...

is there a correlation between my choke lever being useless and this lack of idle?

 

you know, now that i think about it, the bike rides very similarly to the way my 83 seca 750 ran when it had a vacuum leak. does anybody have access to a hose diagram they'll post? or a photo or something. if i just plugged that vacuum hose into the wrong nipple i'm gonna feel like such an idiot...

also to add: i followed the choke cable to the carbs and lifted the lever manually and it still had no effect. must be a vacuum issue.

 

Leaking when no vacuum? Mmmmmm. Have you sucked on the pipe to confirm the petcock/diaphragm is opening- preferably with no petrol in the tank unless you like the taste of petrol....

 

I haven't, but I'm not looking forward to draining the tank AGAIN. I will if i have to but...

for the sake of discussion let's assume the petcock is fine and the vacuum is fine. Are these new bars a possible culprit? Searching around has shown me that a lot of riders experience poor idling after replacing bars, but i havent found any that idle lower than they did with their old bars.

im going to go adjust the throttle and see what happens. I may need to reroute all the cables as my choke cable is acting wonky... who knows!?

 

Highly unlikely unless the original bars somehow made the cable slightly taut but I'm probabl in the realms of fantasy there....

 

you might be onto something, i went from stock bars to clubmans which are much narrower and leave far more slack. I'm going to mess with my cable routing in the morning and see where it gets me. i'll keep this thread updated.

 

Okay, curiosity got the best of me. I went outside and untucked all the cables, and she fired right up. Choke worked fine, throttle worked fine, etc. All systems go... no choke for about 10 minutes. Then I come to a stoplight and BAM 5k rpm idle. So when it turns green I pull into a parking lot and she just sputters and dies.

I cuss. I plead. Nothing. Check all hoses, lines, etc. Let it sit for 15 minutes... Choke all the way, throttle pulled back all the way, and pressing the starter button for 10 seconds and she finally fires up. THANK YOU. Drive directly home, "manually choking" it with the throttle the entire way, because it dips below 1k rpm the second i let go. Take the corner before my house and almost slide out. WTF. Park it. Aaaand she's hemorrhaging oil. Like, everywhere. There's a stripe of it behind me on the road, and all over my rear tire.

Calling it a night. Looks like a long day tomorrow.

 

You've got serious carburetor/float issues; the petcock will only "enable" it.

The reason the bike is puking "oil" (it's not purely oil) everywhere is because your carburetor issue has caused the sump to get filled with gasoline and now this mixture is pumping out the breather. To confirm, open the oil filler and smell for gasoline.

You've likely got one or more stuck floats (unless you horribly overfilled it when you changed the oil.)

 

You're absolutely on point. Oil filler smells like gasoline.

I just did 1000 miles on this bike in the last two weekends, no issues besides a leaky petcock... carbs were torn apart and cleaned (by a mechanic) in January. so the carbs (as far as i can tell) were in fantastic shape before rebuilding the petcock.

What's your recommended procedure from here? I am planning to drain all the contaminated oil, and tear open the petcock and be sure I haven't somehow misassembled it.

At this point I'm just looking to get it running well enough to get it the 10 miles to the shop and have a mechanic check it out. I'm not really worried about spending a some money if it means a somewhat hassle-free (hah, right) summer.

 

YOU HAVE A STUCK (or mis-adjusted float.) The petcock only "enables" the problem; one or more carbs is DUMPING FUEL INTO THE MOTOR.

The float levels need to be wet-set; doing that will immediately reveal the problem.

Quite honestly, I wouldn't ride even 10 miles with my crankcase filling up with gasoline. These are plain-bearing motors so the possibility of main bearing/crankshaft damage is just too great.

If you're not up to it, pull the carbs, take them to the shop and tell them to WET-SET the floats to spec: http://www.xj4ever.com/setting%20fuel%20levels.pdf

Has this bike had its valve clearances checked/adjusted yet and a compression test run recently?

 

Great info, thank you. The bike has not had valve clearances checked nor has it had a compression test performed. I will read through that PDF when I'm home. Your help is very appreciated THANK YOU!

 

NO Hose from the Petc0ck is connected to the AIRBOX.

The Petc0ck FUEL Outlet ---> Carbs FUEL Supply.

The Petc0ck VACUUM Connection ---> INTAKE MANIFOLD VACUUM NIPPLE.

You may connect the Petc0ck Vacuum Hose to ANY of the (4) Intake Manifold Nipples.
The Stock arrangement is the Hose from Petc0ck -to- Manifold #3.

IF the Petc0ck is not getting Vacuum, ... NO Fuel will flow when the Petc0ckk is set to "ON ~ FUEL"

ALL 4 Manifold Test Ports must be Sealed Off.
One of them gets the Petc0ck Vacuum Line.
The other 3 have Rubber Cap and Speed Clamps.