82 XS650 Starts then dies

Cal Schilling

Cal Schilling

XS650 Addict
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Hello everyone I started and account here to look for help. After owning the bike for a while the head cracked on it and needed to be replaced. Well after replacing it I went back to college and the bike sat for sometime. I rebuilt the top end of the motor with new gaskets and seals. after a few years of it sitting around I got back into it (after graduation). Now here is where we are at the engine is rebuilt the timing is spot on. The cam shaft tensioner has been set to the tolerances. I have redone the valve spacing. I have cleaned the carburetor and gone over it with cleaner and a wire to get into all the little ports. Jets are cleaned 100% and I keep taking them apart to check because all the posts I see seem to lean towards that. I have replaced the throttle shaft seals because they were cracked. I have the manual and am no mechanic by any means but am learning a lot. Anyways the bike starts up after a few seconds of hitting the starter button. It then revs up to idle and about 5-10 seconds later it dies. If I give it more throttle it throttles up and then dies at the same time. I can not keep it running and I am running out of ideas on how to fix it. I would love some input from others who have worked on these bikes before. A little note on my carburetor is that it is the Mikuni BS34111 and has no fuel mixture screw. Any help or ideas would be great. I feel like I am so close but hit this road block.
 
Welcome to the forum, Cal Schilling.

80's XS650s have a TCI ignition, that's triggered by a small magnet in the alternator's rotor. The members here have found that the triggering magnet can become weak over the years, producing symptoms similar to yours. They cooked-up a simple test for this, simply unplug the charging system regulator before starting, and see if the symptom remains. More info can be found by doing a search on "rare earth magnet"...
 
TwoMany thank you for the reply. I unplugged the charging system regulator and the started I thought it may have ran a few seconds longer than usual but it still died right after starting. The battery is putting out 12.65V if that maters at all.
 
The bike only runs for a few seconds and then dies I really didn't have time to test anything. Thank you for the link I will read through it.
 
Cal Schilling said:
A little note on my carburetor is that it is the Mikuni BS34111 and has no fuel mixture screw. .
Click to expand...

Yes welcome to the site Cal. Would it be possible for you to post a picture of the carb from a topside angle between the manifolds and top of carb.
I'm thinking you have mix screws but haven't found/uncovered them. Pulling the cover caps and removal of the screw for cleaning the passage may help.
 
Weekendrider the manual I have states "The carburetor on the 1980 and later models.... d. There is no idle mixture adjust screw." But maybe I missed something. and here are some photos.
DSC_0125.JPG DSC_0126.JPG DSC_0127.JPG DSC_0128.JPG DSC_0129.JPG DSC_0130.JPG DSC_0131.JPG
Let me know if putting these as thumbnails works or if you want full photos.
 
Michaelo said:
Welcome Cal, 2m said that you have TCI, so I did a quick search and found this below...also, your saying the battery is putting out 12.65 volts, when it starts are you getting a spike in the charge at all?

http://www.xs650.com/threads/how-to-troubleshoot-the-tci-ignition-system.24161/
Click to expand...

I looked at the thread and got down to pick up coils and found that the grey wire gave no reading for resistance where the orange gave 777 ohms. I am not sure what that means yet (probably because I need to keep reading the thread)
 
Cal, the carbs pictured aren't familiar to me, but I am sure 5twins can help and other members way better than me. You do have the vacuum lines hooked up? I know it sounds like a stupid question but....well you just have to ask sometimes.
Since most of you are asleep now I bet there are plenty of knowledgeable members on tomorrow. I know 5twins did write a plethora of stuff on carbs.......

image.jpg


Also the grounding of the coils to the frame, I have mine grounded just above the engine mount bolt (I would send a picture but I've fractured my ankle and cannot get to it yet) if you have a dead earth, once the vibration starts (engine start up) it possibly could just die from not earthing out. In saying that though, it probably wouldn't start also....


image.png
 
Michaelo, It has been a long time since the bike has been this back together but I cannot recall if there was ever a vacuum line there. If I had a vacuum line I have no idea where it would hook up to other than the other side. I will look into the ground as I remember a motor mount with a ground up there. I havent reinstalled it because it got in the way while working on the bike.
 
weekendrider said:
...I'm thinking you have mix screws but haven't found/uncovered them. Pulling the cover caps and removal of the screw for cleaning the passage may help.
Click to expand...

Here's some BS34 idle/pilot servicing threads that go into what WeekendRider's describing:

http://www.xs650.com/threads/34-carbs-wondering-if-i-could-get-lucky-thinking-out-loud.6640/
http://www.xs650.com/threads/mikes-mixture-screw-kit.7258
http://www.xs650.com/threads/pilot-jet-heads-stripped.10584/
http://www.xs650.com/threads/bs34-pilot-screw-question.36519

Michaelo said:
... You do have the vacuum lines hooked up? I know it sounds like a stupid question but....well you just have to ask sometimes.
Click to expand...

Good eye there, Mick. An open vacuum line doesn't help matters.
 
I'm going to assume your vacuum line is still on the tank petcock. If you are trying to run the bike that barb on the intake will need to be capped or the line to the petcock reconnected.
Your mix screw cover/caps are still in place, to access you will need to pull the cap out. They were capped at the factory to satisfy EPA regulations. The factory settings are lean and most will set the mixture screw some richer around 2 1/4 - 2 1/2 turns out. The caps aren't that thick and it is easy to get into the mix screws if you aren't careful. That said it is a mod that done successfully by most newbies. Drill a little then look when the point of the drill starts to make that existing hole bigger you've gone far enough. Using a course thread screw to get a bite on it twist and pull the cap off.
cal's carb.JPG

Sorry about the quality. The phone cameras weren't as good 8 yrs. ago.
09-18-08_2147.jpg


09-18-08_2145.jpg
 
TwoManyXS1Bs said:
Good eye there, Mick. An open vacuum line doesn't help matters.
Click to expand...

Thanks 2M, ankle might be fractured but the brain is still working.....it does sound like the engine is starving for fuel, fires up, then not getting gas. Like anything with these, it's a process elimination. I've found from my experience that they are pretty forgiving, when it goes wrong there are always telltale signs of what the issue is....we complicate matters by assuming the it's a cluster fuck, where its sometimes something so simple.
That's my take on it anyway......from the underside of the globe
 
Ok this is starting to make some sense the barb is there and I was pretty sure it was capped like the other side I just cant find the cap I will find a way to plug it. As for the idle mixture screw OMFG!!!! I am getting the drill press set up first thing in the morning and I'll be pulling the carbs back off... again... Ok so for the mixture screw if I take it out how far should I turn it back in or is there a point where it will stop and I will back it off 2 1/4 - 2 1/2 turns? As for TwoMany I started reading through those threads and wow there is a lot of good information here. Thanks everyone for all the help I hope that tomorrow will bring it closer to running.
 
Before you take the mix screw out, screw it in till it lightly seats, too hard and you will deform the metering hole..
If you look in the head side of the throttle body you can see the hole in front of the butterfly plate. You can probably even feel the tip of the needle with your finger.
If you take the screw out and block the little holes in the throttle body with your finger you can use compressed air to back blow the circuit to clean it out(pilot jet removed). When you put it back in seat it lightly and then back off 2 1/4 turns to start.

The vacuum line operates the petcock by pulling a vacuum on a diaphragm valve in the petcock ( if OEM). One end goes on the barb the other to the barb on the back side of petcock. Again so many things can be swapped on these a picture of the petcock from the backside would help.

Helpful reading.
http://www.amckayltd.com/carbguide.pdf
 
Weekendrider here is a picture of the back of he petcock. Am in the process of taking the carbs back off to get to the idle mixture screw.
DSC_0378.JPG
I am assuming that the barb on the back in the vacuum line that hooks to the barb that is exposed. if not the barb needs to be covered which is how i think I received the bike. The previous owner didn't take care of the bike that well and I have learned a lot about how to maintain it while fixing it up.
 
Yep that's the one. A tube/hose from the intake manifold to the brass barb on the back of the petcock. If functioning correctly the petcock in the on or reserve won't flow fuel until a vacuum pulls/sucks the diaphragm and piston open. Prime by-passes that function. Some like this some don't. The biggest hazard is if the diaphragm develops a leak un-metered fuel fuel will flow from the tank to engine. While fixing your mix screws you may want to put some gas in the tank and see if in the on or reserve position you have fuel coming from that barb on the back. There is a weep hole in the plastic spacer that is supposed to let you know when this is happening but often it is blocked by dirt and gas residue. If it leaks and you decide to fix it take care when buying the kit. They changed the piston on the early ones compared to the later ones but the kit sellers don't tell you this.
 
OK the carbs mixture valve has been exposed and set to 2-1/4 and 2-1/2 turns out from bottoming out and the petcock is hooked up to the barb with a tube. I have the same problem where it starts and dies. I am going to upload a video of me attempting to start it twice.

 
r u using the choke? your idle should jump way up. that idle is way too low. pull the bowls off and clean the enrichener circuit.
when u uncovered your idle mix screws, did you remove them and really clean it all out good?
When you replaced the throttle shaft seals, are your plates centered in the bores?
 

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