Gs450l abrupt loss of power?

[83Rabbit]

Got my 450 out today for the first time in a month and a half. While riding about 4 miles into my trip, the bike suddenly lost much of its power.
Still idles fine and runs without any odd noises or surges but it simply has no power, about a third or half of what it should.
Carbs were disassembled and thoroughly cleaned 200 miles ago. Choke on or off seems to make little to no difference.
Bike has 10k on it.
Any suggestions on what to look for?
Thanks

 

[Hornswaggle]

Sounds like maybe you lost a cylinder? Check to see if both cylinders are firing. Also check your battery voltage in case it's not charging though if it still spins over enough to start you should have enough juice to fire the coils. I'd pull the spark plugs to see if there is a difference between them which could indicate one not firing.


edit: Just noticed your other thread about carb issues and based on that I would start there. I've had snowmobiles act up like you describe and ended up being garbage floating around the float bowl and eventually plugging the jets. After shutting the engine off the garbage would fall away from the jet and the engine would restart and have power again until the jets got plugged again. If you are getting spark at both cyl. but one side isn't heating up you'll know where the problem is.

 

[Charlie G]

Is the petcock working?

cg

 

[83Rabbit]

I had carb issues, turned out to be a missing plug in the bowl. Replaced it, cleaned the carbs and reassembled, everything was great for 200 miles until now. Ill pull plug wires and see if it makes any difference and get back to ya.
Im assuming the petcock is working, I see fuel in the feed line to the carb, no bubbles.
Is there a screen in the petcock?
Im assuming ill be safe to ride it 7 miles home, ill baby it and go easy.

 

[83Rabbit]

Right cyliders not firing... Right pipe is warm, not hot at all. Gonna pull the plugs which are relatively new when I get home and swap them. Im guessing its either the coil, wire, or plug?

 

[Guest]

You may simply need new plug caps if they're still the originals.

Trim some HT lead off and stick a new NGK plug cap on if that's the case.

 

[83Rabbit]

You may simply need new plug caps if they're still the originals.

Trim some HT lead off and stick a new NGK plug cap on if that's the case.

Just run down to autozone or something and ask for NGK plug caps?

 

[83Rabbit]

Plug on the right side is actually sparking but its a yellow spark, weak, weak enough that it will only actually ignite the mixture a few times a minute, you can hear it pick up in idle for a split second and both cyls fire then it goes back to lame-ness.
Im gonna pull the tank later tonight or tomorrow and see whats up. Cycle junkyard near me says theyll do $25 for the coil and leads (used of course)

 

[Hornswaggle]

Sounds like you're getting it tracked down! With the seat and tank off it's a good time to go through all the electrical connectors and grounds and make sure the voltage to the coil is good. I went through that a few weeks ago when my bike needed a new R/R and for a couple dollars worth of insulated spade or bullet connectors, some new primary wire here and there to make sure everything had a good ground, and a couple hours of quality time in the man cave and the wiring should be good for another 30 years...

 

[SqDancerLynn1]

Before you go and buy coils make sure you have 12 volts on the coil...

 

[Guest]

Just run down to autozone or something and ask for NGK plug caps?

You should be able to do that. XB05F is what you want.

 

[83Rabbit]

so test to see if I have 12v at the coils by testing the leads before the coil?

Also is there a way to test the coils themselves with an ohm meter? If so what readings should I be looking for?

The right cylinder is sparking it just is a yellow spark whereas the left cyl is a bright blue spark, spark plug is not the issue, swapped plugs and same result.... I get the crap shocked out of me when I grab the boot / wire while its running.

Id like to be able to test the coil before I go out and buy anything at all.

 

[83Rabbit]

also compression on the right side is 150.

 

[Guest]

so test to see if I have 12v at the coils by testing the leads before the coil?

Also is there a way to test the coils themselves with an ohm meter? If so what readings should I be looking for?

The right cylinder is sparking it just is a yellow spark whereas the left cyl is a bright blue spark, spark plug is not the issue, swapped plugs and same result.... I get the crap shocked out of me when I grab the boot / wire while its running.

Id like to be able to test the coil before I go out and buy anything at all.

Yes, the Clymer should have the values to test for, I think it's 3 - 4 ohms on the primary side (pin to pin on the wiring harness connector) and maybe 25K ohms on the secondary, although I can't remember how to test that either...

If it's your plug cap that's the issue, the secondary test should show it up.

Give the cap that's on there now a big wiggle and twist and measure again and see if the reading changes. If so, that would be your problem.

One of my caps just about fell off when I got to sorting out the coils.

 

[83Rabbit]

OK, swapped the coils with the leads and the problem stayed on the right side...

Tested the coils and heres what I got

HT Tested from plug cap to rear coil mount
LT Tested from terminal to terminal on the coils with the wiring disconnected

Right side
HT: 21.29k Ohms
LT: 6.5-6.8 Ohms

Left Side
HT: 27.17k Ohms
LT: 6.2 Ohms


How do I test if I have 12v at the coil? with the key in the on position? With it running?
Left coil gets warm during running while right one is noticeably less warm. This could just be from the heat radiating from the left side of the engine (the side that is actually burning the mixture and thus creating more heat), I dont know.

 

[Guest]

Interesting, pretty sure the LT side should be 3 - 5 ohms, but they both sound consistent.

HT on the right looks a bit low, pretty sure it should be more like the left one, so plug cap might help there, at least they're cheap!

To test for 12v at the coil, simply turn ignition and kill switch on and measure between ground and the orange/white wire on the coils.

 

[83Rabbit]

hhhmmm ok well Ill check the voltage to the coils and then go from there, Ill also pull down the right carb and re-soak everything and go through it again for sh**s and giggles....

the actual ignition unit itself wouldnt be going bad would it? Where do these bikes get their signal to fire? stator/flywheel?
Thanks

 

[Guest]

It's certainly possible, but that typically is no spark, not weak spark.

You'll find the signal generator under the timing cover on the right side and the ignition module itself on the electrics tray under your left side cover...

 

[83Rabbit]

OK, Im STUMPED!

Got a Voltmeter, left side is about 10.5V, right side, the BEST I could get was 6.3, but mostly it measured mV it was so low. Power is so low it wont even light a test light, left side will easily light one....
But heres whats odd... when pulling the plug and cranking the starter, the plug sparks with no issues.... How could I have less than 1v with the key in the on position at the coil but the plug actually fire when its cranking???

Where do I go from here? Pull and replace all wiring related to the ignition? The only spade connectors I see for the system are the ones at the coil. Anything I can test next?

 

[BassCliff]

Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. 83Rabbit,

It sounds like you may have a lot of corrosion throughout your wiring harness. Check and clean all electrical connections and grounds from the headlight bucket to the tail light. See the troubleshooting tips on the electrical page of my little website. You might want to consider the coil relay mod.

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BassCliff