XJ650 that runs great until it suddenly dies

The temps have warmed up a bit, so I found the motivation to rebuild the petcock. Everything was fairly easy except I lost the little check valve Bakelite disc that goes in the vacuum port. Is it possible to buy one or does someone have a spare disc laying around?

 

My bike runs great until it stops, too. Come to think of it, so do all of them.

Hmmm, even my car------

 

We have the discs, send us a message!

 

So the old girl now has a new check valve disc and a refreshed front brake system Thanks to XJ4Ever (only parts of the brake system that weren't replaced are metal).

Now that I've I got her put back together I decided to go take her for a spin... and didn't get out of the garage.

It's back to it's old tricks of the idle climbing a few 100 rpm (like it's leaning out, but I'm open to interpretations) and then suddenly dieing like it was shut off. The first time it did this, I had forgotten to change the petcock over, so it was still set to "prime". It died with the choke on and off. With the choke on, the battery was sitting at 11.5V when it died. It has a rebuilt petcock, new fuel cap, and new vacuum line (that's actually made for vacuum). I've checked the resistance of the ignition system and everything seemed correct (actual numbers are on a previous page)

Thoughts/Suggestions/Questions?

 

I'm with Dave... fuel issue. Time to go to Church!

The only reason not to think fuel is because of when you can sometimes restart it.... How are the contacts on your kill switch?

 

did you ever try riding it with the gas cap open?

 

So, have you done anything with the carbs yet? Still seems to me that it's a carb issue. Really sounds like floats are way off....and/or you have some clogged supply tubes

 

I threw a new fuel filter at it today (Ok, I may have installed it too) and tried running it again for the fun of it. Same old thing where it idles fine for a while then suddenly dies. I did run it with the fuel cap popped and that didn't change anything.

Also, I believe the rpms increasing only seems to happen with the choke on. If I've turned off the choke, it seems to just quit.

One other thing to mention is that the carb to engine boots are pretty old (original?) and have lots of cracking. The PO said (I know, I know...) he did the propane test and they weren't cracked all the way through anywhere. Of course, that was before this running issue got as bad as it is now.

Also, I have yet to do anything with the carbs yet so it's very possible they might need adjusting...

 

IT'S ALIVE! I finally reshimmed the valves (7 out of 8 were all on the bare minimum) and it's runs and runs and runs now. I do have a question about the clutch. When I really get on it, it starts to slip, which is a new behavior this spring. Now I did change the oil (Valvoline non-synthetic 20W-50 motorcycle oil) and I've put in about 3.3 quarts (3100 CCs) but it still seems lower than where the previous owner had it. When on the side stand, there's absolutely nothing in the site glass, but when pull the bike upright, oil flows into it. Clutch problem? oil problem?

 

Too much oil. 2500 cc + ~400 cc with a filter change. Drain or siphon the extra.
You check the oil level when on the center stand; engine stopped for at least five minutes.
There should never be oil in the sightglass when on the side stand, or with the engine running.
Your clutch may very well be slipping just due to wear or age.

 

I did replace the filter too (I forget not replacing it is a thing) so it's not super overfilled. The clutch engagement point has been way out at the end of the lever, so it definitely isn't very new. A case could be made that with properly shimmed valves, the thing might be making more power, causing the clutch to meet it's maker.

 

Overfilled is overfilled. Oil foaming is a bad thing. Drain the excess.
Time for new clutch friction plates.

 

I had similar issues with my Seca and it was old coils and I replaced them with the Dynacoils and there are several threads on here about it. It is an incredible help.

 

Well, it technically is/was running fine now.

Quick question though: is there any safety mechanism that causes the bike to not run if the rear running light is burnt out? The thing has now decided to only run momentarily now, and the most recent time it died was right after I released the brake light. Just noticed the tail is burnt out so I'm going to replace the bulb. Hoping it was a small bump in the road and I'm not still stuck in the same rut I've been in.

 

And I've answered my own question. Replaced the taillight, and it still cranks with no start. I'm too annoyed/disappointed/frustrated to do any diagnostics right now...

 

I think we're back at a bit of worn through insulation, or an internal break in a wire, or some other PITA to find fault.

 

Have you tried new plugs yet? Are the current plugs correct and gapped for your model?

Gary H.

 

Well, it looks like my issue might have been the battery ground being loose... *facepalm* Of course I didn't actually ride it tonight (feels like 32 degrees and misting) so we shall see if it holds up over a ride.

To answer your question Gary: The spark plugs were replaced this spring. The gap was checked on all four and they were properly gapped.

 

https://m.imgur.com/a/YJGjI

Found the clutch issue: the retaining wire for the final plain plate went rogue and beat up that plain plate and the adjacent friction plate.

 

The final plate is called the boss plate and is retained by the wire. It is different than the other plain plates. Make sure you replace it with a boss plate and not a standard plate. Chacal (Len) sells it.

Gary H.

 

Already sent Len a message to make sure I got the right stuff

 

Did you rebuild the petcock and replace the gas filter ? Maybe enough gas is getting through to
fill the float bowls slowly and the bike runs out of gas when demand increases . Polock was right
to suggest running it on prime.

 

Pretty sure the issue was solved with reshimming the valves. The fact that 7 out of the 8 valves were just out of spec makes me think that once the bike warmed up, the valves were staying open too long and the bike lost power that way. Now I just need to get the clutch back in the bike and see what I can break next!