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At wit's end, 1982 GS450T

  • Thread starter Thread starter KWC
  • Start date Start date
K

KWC

Guest
....was literally a little old man bike, 2900 miles - he sold it to a college kid who dropped it and dented the tank - then sold the bike to me running (but poorly) - invested in a NOS tank and now trying to get it to run properly with no luck.

Symptoms: will not fire consistently on the left cylinder, at idle, will fire about every 5 seconds and puff visible exhaust out (sounds more like a backfire), revved up it fires at about the same rate, enough to slightly warm the pipe, cylinder is getting fuel but possibly not enough? doesn't soak the plug or anything, under load (riding) the left cylinder seems to start firing for a few seconds and the bike surges ahead, then it cuts out, backfiring occasionally, right cylinder seems to run fine, bike responds to choke, but only on right cylinder

What I did to fuel system:

1. cleared out petcock, changed oil in case fuel in crankcase
2. replaced plugs
3. new intake boots with o-rings
4. new o-rings on the balancing ports
5. cleaned carbs in ultrasonic cleaner
6. checked slides for stickage, they are fine as are diaphrams
7. cleaned out all jets, passages, replaced idle air screw o-rings and set those at factory setting
8. set floats at level specified in the manual, apparently GS450's are different than literally all the others
9. with an electronic balancer on the carbs, the carbs appear to be drawing equally, spraying brake clean around carbs while running showed no obvious air leaks

What I did NOT do to fuel system

1. take apart the choke plungers (critical mistake?)

Valves:

1. checked these, they were on the tight side but within spec, both cylinders were the same
2. compression: both cylinders the same - within spec

Bike was still doing the exact same thing, so I went after the electrical system:

1. Both spark plugs seemed to have a fat spark with the threads grounded on the head, nevertheless i replaced the left coil with a good used one. no effect. Unplugged every connector in the ignition system and cleaned with contact cleaner and re-plugged in

2. Replaced pickup assembly with an other from a known running bike, no effect.

Questions:

1. Does this sound like a fuel or electrical issue? Anything I missed in the carbs? Is there an easy way to test the ignition box to see if it is failing? (odd way for one of these to fail though, intermittent spark on one cylinder) - plus, i believe the spark looked fine with the plug out and grounded.

I am at my wits end, the bike is a fabulous creampuff with only 2900 miles and will make someone very happy but after having the carbs off 3 times i am ready to chuck it in a lake.

Keith

 
Last edited:
Keith said...
"I am at my wits end, the bike is a fabulous creampuff with only 2900 miles and will make someone very happy but after having the carbs off 3 times i am ready to chuck it in a lake"

There's a big lake near me! But this bike is too pretty to dispose of it. There is some concern that ultrasonic cleaning might not get the job done in the tiny passages, even thought you said you cleaned them.You got a nice fat spark, so ignition system is good and most likely cam/crank timing is right, though it never hurts to be sure. Rather than be at wit's end, I'd do a proper carb dip, finish off with ultrasonic and eliminate the carbs as a problem.
 
tom203 said:
Rather than be at wit's end, I'd do a proper carb dip, finish off with ultrasonic and eliminate the carbs as a problem.
Click to expand...

Yes this.:D

Since you didn't take the choke system apart I assume you dipped the carbs assembled which is the incorrect method.

Fully break down the carbs - remove all parts. Then either soak in carb dip or give that ultrasonic thing another try.

Check the GS450 carb rebuild tutorial on basscliff's site, and/or check the version in my signature for some extra tips.

Good luck and hope you figure it out.
 
Also need to replace all o-rings inside carbs. How many turns out are the mixture screws? Bench sync. carbs and then sync. with proper tool. Also did you replace the sparkplug caps, sometimes they will break down. By the way beautiful bike, don't give up! terrylee
 
It appears that you are working through this "little issue".

My thought (from what you mention) is that it is an electrical issue. Have you checked the ohms resistance on the left coil?

Cut the plug lead back about 1/2" to make sure that there is a clean connection?

Battery fully charged and charging system putting out 14V+- at 4000 RPMs?
 
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