XJ650 stalling issue

Hi,

I have a very strange issue with my new 82 XJ650J. I got the bike a few weeks ago and started fixing minor bits and pieces. Replaced petcock vacuum tube (old tube's walls were collapsing onto itself).

Now, the issue is whenever I brake quickly and the weight is shifted to the front, the bike stalls. I can also stall it by grabbing the handlebars and jerking forward to shift most of the weight onto front of the bike, regardless of gear.

What could be the reason for this? I have a petcock rebuild kit ready to install, but the bike stalls even on prime so not sure it is a vacuum issue.

Could it be low carb float levels or something electrical?

 

Sounds like a bad switch. Does it stall abruptly like when the kill switch is pushed or progressively like when you run out of gas??

 

It sounds "Ignition" related, ... Not Fuel.

 

It stops suddenly, RPMs drop to zero and it shuts off, does not try to restart.

I took the cutoff switch apart to install the start button and spring (was missing) and all connections are secure, but I can check again.

 

I also noticed if I shake it slightly (not hard enough to stall), the rpms will drop slightly and then recover. Sounds like something is shorting out?

 

Sidestand switch?

Or a loose connection somewhere; start in the headlight bucket (after checking the sidestand switch.)

 

It could also be the ignition switch. Try to move quickly your ignition key North-South-East-West while the engine runs. If the engine cuts you'll have your answer.

 

I tried that and wigling the key does not stall the engine.

I noticed that when I clutch in while in gear and sidestand down, it shuts off. Is this the proper behavior? I will try disconnecting the sidestand switch to see if it solves it.

 

Yes, it's part of the safety circuit, but not quite normal behavior. If everything's working correctly pulling the clutch in should ALLOW starting in gear with the sidestand UP.

If the sidestand is down it's supposed to be all stop unless you're in neutral.

 

Yup, that's what happens.

Alright, so I guess this is by design.

 

So, I wanted to eliminate the safety circuit as the cause of this problem.

I thought I could disconnect the safety cut-off switch, but it won't run at all. Somebody said it should start in neutral with the relay disconnected.

Another suggestion I found is to disconnect black+white stripe wire from the TCI, which should kill the safety circuit or side-stand circuit?

I guess I'll find out tomorrow..

 

I'm going to go back to the fuel. Sounds like the float settings are not correct and you're getting one of two things:

1. If the level is too HIGH, the sudden forward motion causes the carbs to swamp.

2. If the float level is too LOW, the sudden forward motion causes the level in the carbs to surge forward and away from the main jet, leaving it momentarily without fuel. So you basically 'run out of gas' for a moment.

Been there enough times.

Dave Fox

 

Yeah, I though this might the case too, just wanted to cover the electrical first. Another reason electrical is unlikely is I can't reproduce the cutoff by moving any wires around to short the system. Everything feels solid.

I wish it hadn't come to this, but I'll probably have to dig into the carbs if I can't find an electrical gremlin

 

Well........if you haven't been into the carbs, then you probably SHOULD. My own approach is: I only know what the condition of the carbs REALLY is when I go through them. Even if the PO did, or had a 'professional' go through them, it can't be 'proven' until you actually go in and look for yourself.

YMMV,

Dave F

 

Well, that fixed it. Float levels were too low on multiple carbs. Thanks for everyone's help!