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Cut out over 5k rpm

4K views 61 replies 10 participants last post by  Sidecar Bob 
#1 ·
So I'm 18 years old abd heading off to college this fall. I got my motorcycle liscense and picked up 1982 gl500 back in December of 2019 and bought it to have a bike in college as i have been riding dirt bike since i was a little kid and wanted a street bike. I completely rebuilt the motor. Only left in the crank and cam shaft. The bike now idles ok, just needs idle turned up. But when i drive it it wont go over 5k rpm and only runs on the left cylinder over 5k rpm. I've read some about the ATU possibly causing that. I've cleaned and rejetted the carbs. I've also tried 2 different sets of stock carbs. I need help. I've rebuilt a couple dirt bikes and tons of snowmobiles but have never had an engine give me troubles like this thing has. Thank you.
 
#3 ·
Have you checked the pulse generators. See section 17 of FSM (link in my sig line.) should read 530 ohms +/- 50 ohm.
Did you reset the air gap on the ATU coils during install? Air gap .45-.65mm or .018- .026in
 
#13 ·
You need a bright light- at least a xenon.

The timing is checked through the round cover at the rear right of the motor on the back cover.

Drain .5 litre of oil and put bike on sidestand.

The timing marks show in the hole. You would be looking for LF and RF at idle and should see it move up to between the two full advance lines as the revs are increased. If it stays at baseline LF/RF the ATU aint ATUing.
 
#15 ·
Some of the fellers here know the 82 ignition system better than me {it's the only system I don't personally run} and can maybe give you advice on the possible modes of failure of the spark units and pulse generators.

This just based on one cylinder entirely dropping out.

But in the case of the spark units you can swap those from side to side and see if the fault follows. Ditto plugs, plug caps and ignition coils.

If you rule those out by swapping, test the advance and resistance check the pulse generators you will either have found the fault or ruled out most possible ignition faults.
 
#17 ·
I would check your plug cap resistance. You may have a faulty cap that goes open under load. Any cracking of the plastic is not a good sign should have 5k ohm resistance. There is the brass rod mod that works well using resistor plugs. Also check ign coils for any cracking. Test procedure is in the FSM as well.
 
#22 ·
I have a 1982 gl500. Ive cleaned carbs countless times, had multiple people look at it. I've ohmed out TAI system, I've hooked up a timing light and the timing advances. Rebuilt motor, done everything i can possibly think of I've been running it with no air filter. It will quit running on 2 cylinders after around 5k rpm. Doesn't get up to 5k rpm very fast either. Has a new petcock too
 
#23 ·
I have merged your threads. Please don't post multiple threads about the same problem as it only causes confusion when people answer in both places.

And please take the few minutes to add your location to your profile and your bike's model and model year to your signature.
 
#24 ·
Ive done everything i can think of to my 82 gl500 and it wont go over 5k rpm. At 5k the right cylinder quits firing. Ive done the carbs as well as i know carbs. Hooked up timing light. Rebuilt engine due to low compression. Done everything i know and am having issues. Its been a 7 month struggle. Thanks for any help.
 
#27 ·
Ive done everything i can think of to my 82 gl500 and it wont go over 5k rpm. At 5k the right cylinder quits firing.
Is this happening while riding or are these observations made with the bike in neutral in the shop? How are you determining that the right cylinder is the one cutting out at 5000 rpm?
 
#33 ·
The fact that the cylinder is dropping out under load is suggestive of a weak spark.
 
#37 ·
At 5000 rpm and not firing I would expect it to smell rich.
 
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