New to me GS450TX

[ssalmons]

Hello everyone, a few weeks ago I bought this beautiful blue 82 GS450TX. The original owner passed away in 1994, his son rode it one time in 1993 and parked it in his basement until I purchased it. The bike has under 1,300 miles, all the rubber and plastic are like new, the chrome cleaned up easily as well. I cleaned out the tank, fitted a new petcock, new fuel hose and filter, new oil and filter, new foam air filter, cleaned the carbs, put in a new battery and it fired up easily. Sounded great, hopped on to take a ride and had no power. Based on some others recommendations I put in a jet kit, cleaned the carbs again, then the bike was running like a champ! I took the kids for a ride around the neighborhood, having a good time, after 30 minutes it started sputtering and stalled. Now the bike backfires below 2,500 RPM. I put in new spark plugs, cleaned the carbs again, fresher gas, new o-rings on the intake boots, nothing seems to help. The left spark plug is white and right spark plug is black. Compression is 170 in both cylinders. I did not check valve clearance (yet) because it ran great for 30 minutes and mileage is so low. Any suggestions on where to look next?

I'm really excited to ride this bike. My dad had an 81 450L he bought new and I had an 82 650GL about 20 years ago I really liked as well.

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[xkaes]

Welcome to the Forum. Great find, for sure. I'm not familiar with that bike, but given the LOW mileage, I have to assume it's a simple problem. And since it has not been exposed to the elements, it's a problem with diagnosis. Have you checked the timing, gap, etc? You might just have a bad plug -- or two.
You'll get lots of suggestions soon -- but start with the easy stuff.

[Rich82GS750TZ]

If it's dying after running well for a short time, it could be as simple as gas cap not venting properly. If you run it a bit, then stop, remove the gas cap. If you hear or feel a whoosh of air or detect suction, this is a problem. Replace the seal, or the whole cap. I had to buy a cheap ebay cap just to rob the gasket from it and fit on my original cap. The ebay cap with the gasket was @$27 IIFC, and was supposed to fit my tank but didn't. The gasket was what I needed. I didn't have a venting problem, my gasket was just rotted. If the tank isn't venting, you may have to take the cap apart and clean.

[Gorminrider]

Yes there's a big list how about stuck float needle in the carb? the white plug might mean running out of gas there. The black plug might mean too much gas there

By the way, have to say, cleaning the carbs includes removing the jets ..idle jets especially get plugged (aka "stumbling below 2500")....and more to follow from others here

[Gorminrider]

By the way, Nice Bike!

There's a GOOD MANUAL here
GS450 Official Service Manual PDF

and also lots of info here:

BikeCliff's Website

[xkaes]

Since you have already "put in a jet kit, cleaned the carbs again" (twice), I'd assume that the carbs are not the problem -- unless you have some reason to think otherwise. Just be glad you only have TWO carbs to clean instead of a BANK!!!

[ssalmons]

Quick update for those that care. Before I ever put gas in the bike I checked for spark and found both had a very strong spark. I checked again today and found weak to no spark on the right cylinder. I had suspected the carb because the jet needles are pressed into the bowls (also previously documented on these forums) and I wasn't 100% certain they were fully clean. That might still be an issue but for now I'm switching focus to the ignition.

Based on the tests in the manual it appears the coils are good but regulator has failed and the ignitor box is failing. Hopefully I can get it fixed without spending a fortune. Thank you for sharing a link to the manual!

[xkaes]

Those parts should be easy to find and inexpensive. Keep us posted.

[Gorminrider]

There's a certain amount of trouble-shooting you can do on the Ignitor box ..check the sensors and their connections at the flywheel and on their way to the ignitor (look for chafe, pinches,tears in insulation); make sure the sensors are secure and not wobbly, that they have the right resistance testing for ohms (they are finely-wound coils inside)

Check connections. Seeing as it's ONE side that's suspect, there are tests to confirm the ignitor is really thrashed...look at bikecliffs might be there but I have stuff here if you can't find it.

ALWAYS and wherever, Check ground wires for "good connection" to the negative pole of your Frame and your battery. "Ground" wires are always Black/White stripe on these bikes unless aftermarket.

[ssalmons]

Quick update: new ignitor fixed the spark and bike is running mostly good. It still has no power from idle to 2,500 RPM so I suspect jet needle in the carb. For now I'm going to ride it and take another shot at cleaning the carbs when it gets cold. Then in the spring I'll be ready for carb tuning. Thanks everyone for your help.