HELP! Break down diagnosis needed....

[60ratrod]

I had 3 hot and one barely warm. I pulled the plug and checked spark on that cylinder, same pair of coils on both bikes, two different sets of wires, same results, no spark. Swap cylinders on both bikes, no spark. I'm known to have off the wall problems like this for what ever reason.

[Grimly]

Seeing that a GS coil is one winding that fires two wires at the same time and the ignition system uses a waste spark during the exhaust stroke...it aint gonna happen. The coil works or not. Never had a Dyna coil so I cant speak to thier construction...but a GS coil is just that..1 COIL. when its gone two wires go dead.

I wouldn't be too dogmatic about that - I've had several coils over the years that gradually failed when hot.

[BTreadz]

Wow! Thanks for all the help guys. I've just moved into a new house and haven't had time to tear into it yet. I'm going to borrow a compression tester this week to rule out the burt up valve/piston theory. I would think if it was running lean I'd have seen symptoms like a white plug or popping on decel etc...
When it died it didn't turn off like the key was switched off, it just lost power and then wouldn't idle when restarted after it died as I coasted to a stop on the side of the road. I had just filled up gas in a nowhere town in BC, and I filled the tank more fully than I normally would in anticipation of long ride to the next fill up.
What is my check for the petcock issue? Could one of my pilot jets be clogged? Nothing in my inline fuel filter...
I'm going to try and get into it this week. Not riding sucks!

[JTGS850GL]

If you feel you got bad gas then start by draining the float bowl and see if you have water in the gas. Gas and water separate and the water will settle to the bottom. It will look like two separate liquids with one on top of the other when you put it in a class container. The problem is that the water will be on the bottom and that is what ends up in the carbs. Obviously water wont burn.

[Macgyver]

Nothing in my inline fuel filter...

First thing I would do is get rid of the inline filter. Our bikes don't need them, and they tend to restrict fuel flow since we run on gravity and not a fuel pump.

Get rid of the inline filter, I learned this the hard way on my 650. I ditched the inline, and it cleared up my fuel delivery issues.

[BTreadz]

I put the compression tester to it tonight. Not good. Cylinder 1: 155psi, 2: 130, 3: 90, 4:95.
Plugs 2 & 3 were white. Ouch! I checked them all 1k miles ago about 1k after top end rebuild, and they all had good color. What happened? My plan is to check valves to see if they were too tight, and see if I can adjust to get compression back. Good plan?

[JTGS850GL]

You did do the compression check with the throttle wide open, right?

[BTreadz]

You did do the compression check with the throttle wide open, right?

Thanks JTG850GL! I forgot to hold the throttle WFO. Everything is within allowable limits. Cylinder 1: 162, 2: 135, 3: 142, 4:150


That's a relief and what I expected since I never heard any engine noise...What's my next step in the diagnosis? I haven't rebuilt my petcock or lined the tank (although it looked pretty good)...

[BTreadz]

Quick update. I have spark to all four plugs. Must be a petcock/tank/carb thing....

[JTGS850GL]

If you think it's petcock related, then don't try to re build it. The success rate on rebuilds is very low. Just pick up a new petcock.

[alke46]

First thing I would do is get rid of the inline filter. Our bikes don't need them, and they tend to restrict fuel flow since we run on gravity and not a fuel pump.

Get rid of the inline filter, I learned this the hard way on my 650. I ditched the inline, and it cleared up my fuel delivery issues.

Have you followed up with this yet? Best to eliminate all bad things that could be causing problems.

[BTreadz]

I will get some new plugs and try eliminating the inline filter. Wouldn't that be an easy fix.

[gustovh]

Clean your gas cap vent, a plugged one will cause your problems. If your tank can't vent a vacuum is formed and no not much gas can flow out the gas valve, it is only a few screws and only takes a couple minuets. I have had this happen on a couple bikes now.

V

[azr]

It's fine advice to get rid of the inline filter but don't worry about it right now as the bike has been running fine for a year with the inline filter there...so it's not the issue (unless it's plugged with fine rust sediment in which case you should have a look at the inside of your tank). It's pretty simple to check if your petcock is working properly. Take the tank off the bike, make sure the petcock is in the "run" position, of ANY gas is dripping out of it the petcock is toast. If no gas is dripping out attach a hose to the vacuum port, again make sure the lever is in the "run" position and suck on the the hose a bit (mimicking the vacuum your bike makes), gas should pour out of the petcock in a good stream, if it doesn't your petcock is toast. No need to test the "prime" setting but you can if you want to, gas should simply pour out when you turn it to "prime". This test will at least eliminate the petcock as being your problem.

[chuck hahn]

Least with compression numbesr that good youre relatively assured the piston and valves are unharmed. If they were holes the compression would show itself as way down..usually.