Cold #1 exhaust! Hot #2 exhaust! NO POWER!

[jrciamacco]

I have a 1980 GS450 L that's been giving me some problems lately.

Towards the end of the season last year I started up the bike and it fired but i noticed that the exaust out of the #1 Cylinder was significantly weaker than that of the other. The exaust was also ice cold even after 30 minutes of idle time. #2 exaust was at normal pressure and the pipe was hot. Could this me an electrical issue? I tried to pull out with it in this condition and it was very weak and had almost no power. Like I was pulling out in 6th gear. When I pulled it out for this year it started right up, but the problem is still the same! I'm a beginner with bike maintenance so any help would be greatly appreciated!

-Joe

[Tarbash 27]

Check The Spark Plug In That Cold Cylinder Because It Seems Fouled Out. If Its Not The Plug Make Sure The Carburetors Are Clean And Make Sure Its Getting Fuel.

[DaveT.]

Recently had an 850 with #1 cylinder not as hot as the others. Found that the emulsion tube in the #1 carb got cockeyed due to the guide pin being pushed out. This turned the fuel feed hole to the "off" position, not letting any fuel through the slow circuit. Pulled the main jet, pushed the guide pin back into place, put the main jet back in and wa-la! Hot exhaust on the #1 cylinder...

Just a suggestion.... 8-[

[jrciamacco]

Thanks, I have a clymer manual so I can rip into the carb and make sure everything is in the right place. I will also try new plugs and see if that fixes the problem. I'll update once I find out whats going on with it!!!

--Joe

[Hotblack]

It would be better to go right to the troubleshooting portion of your manual and systematically determine whether your problem is fuel or ignition related. Follow their advice, as it should involve checking simpler things first, progressing steadily to the more complicated/expensive things. You don't want to rip into your carbs, even on a twin, unless you've ruled out things like ANY ignition issue, or a leaky intake boot, stuck valve, etc.

[jrciamacco]

I took my carbs off and cleaned them up real good, but everything seemed to be the same in both carbs. Cleaned all the jets and the screens and put it all back together and fired it up and I've got the same problem. I swapped out the plug with an older one that I had replaced before, and I got the same result. checked the manifolds for leaks with soapy water and everything seems pretty tight. Any help would be greatly appreciated.

--Joe

[J_C]

Is this just a two cylinder? Can you swap the plug wires in a two cyl like you can swap wires from the same coil in a 4 cyl? That would at least eliminate it being electrical (I'm having the same problem too with mine.... I'm testing the wire swap tonight)

[jrciamacco]

I don't know about swapping the plug wires...will that do anything!!! I know that they each have their own seperate coil. anybody know if that will work! It is just a two cylinder so I'm a little iffy on it. Any other suggestions!!???

--Joe

[earlfor]

NO, you cannot swap only plug wires. That would result in your cylinders firing 180 degrees out of time. If you swap spark plug wires, you must switch the black and white wires on your coils. You have two coils. One coil will have an orange/white wire and a white wire, the other coil will have an orange/white wire and a black wire. You must swap the white and black wires AND swap your spark plug wires. If the other cylinder now gets hot and the one that was hot is now cold, you know the problem is either the coil, the spark plug wire or the points.

Earl

I don't know about swapping the plug wires...will that do anything!!! I know that they each have their own seperate coil. anybody know if that will work! It is just a two cylinder so I'm a little iffy on it. Any other suggestions!!???

--Joe

[jrciamacco]

I'll try that and see if it switches! Thanks for the advice. I'll let you know how it goes.

--Joe

[earlfor]

OK, I'm in and out of the tech pages, so if you answer and dont get a reply from me, and you want one, pm me. :-) I sometimes miss threads. LOL

Earl

I'll try that and see if it switches! Thanks for the advice. I'll let you know how it goes.

--Joe

[jrciamacco]

Ok...

I switched my plug wires and coils around and ran opposite cylinders off of them and the problem still existed the same. Cylinder 1 still was cold running off of Coil 2 and cylinder 2 still fired like normal off Coil 1. Still no power when pulling out as well. Does this eliminate the electrical system completely? If so Then I am gonna get the top end rebuilt. any help greatly appreciated!

--Joe

[Hotblack]

I didn't read weather you switched spark plugs or not, but that's the last link in the ignition system.

[jrciamacco]

Yeah I switched plugs too...same result...then I tried new plugs, same result as well

--Joe

[J_C]

From what little I know (And all I know is from reading books and this board) the cylinder needs three things in order to fire properly...

1. Fuel (Fuel/air mixture)
2. Spark
3. Compression

It seems as though you've tested the electrical, since you swapped the coil leads and the problem didn't follow. If you've already tested compression, the I would get into the carbs.

At least I hope that's the answer, since I'm in the same situation and I've tested 2 and 3, and all I have left to evaluate is the fuel (and potentially the valve clearances)