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backfiring and lack of power problems

  • Thread starter Thread starter chilids
  • Start date Start date
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chilids

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I have an 82 GS 450T that has treated me pretty well since I bought it 5 years ago except for a few problems here and there. Some of the minor problems have been ideling a little low, being cold blooded, and having to clean the carbs in the spring if I left gas in. Last summer the major problems started when the CDI box suddenly started smoking and died. It sat the rest of the summer and all winter long and this spring I bought a used cdi box off of ebay and popped it on. The bike fired up but sounded like it did back in the day when the carbs were dirty. I pulled the carbs and cleaned them and the bike still wasn't running right.

Now it is backfiring and running with about half the power. I can not remember if the backfiring was going on before I pulled the carbs or not. I can drive it down the road and it lags behind and occasionally catches and starts to take off for a second, leaving a very jerky ride.

One friend who does a lot of work in bikes thought it might be the timing because he says the cdi box and the stator have to be mached individually.

It is always the right side that backfires and that side runs cooler. the air out of the exhaust on the right side is cooler along with the pipes.

Any help would be appreciated. I could also use some help on how to adjust the timing or fix any of the other problems.
 
Seal the airbox and replace the intake boot o-rings. Sounds like a lean condition to me. Pull the spark plugs and see what color they are.
 
Have you stripped and dipped the carbs? Checked for good / strong spark on the right side? Synched the carbs? Float height set to spec? Checked for vaccume / air leaks? Petcock working correctly? Your timing should be set...non adjustable electronic ignition. Have you cleaned up all the grounds to the wiring harness? Let us know what you've done. :?
 
chilids said:
I have an 82 GS 450T that has treated me pretty well since I bought it 5 years ago except for a few problems here and there. Some of the minor problems have been ideling a little low, being cold blooded, and having to clean the carbs in the spring if I left gas in. Last summer the major problems started when the CDI box suddenly started smoking and died. It sat the rest of the summer and all winter long and this spring I bought a used cdi box off of ebay and popped it on. The bike fired up but sounded like it did back in the day when the carbs were dirty. I pulled the carbs and cleaned them and the bike still wasn't running right.

Now it is backfiring and running with about half the power. I can not remember if the backfiring was going on before I pulled the carbs or not. I can drive it down the road and it lags behind and occasionally catches and starts to take off for a second, leaving a very jerky ride.

One friend who does a lot of work in bikes thought it might be the timing because he says the cdi box and the stator have to be mached individually.

It is always the right side that backfires and that side runs cooler. the air out of the exhaust on the right side is cooler along with the pipes.

Any help would be appreciated. I could also use some help on how to adjust the timing or fix any of the other problems.
Click to expand...

1. Did you get your fuel line and vacuum line connected properly?

2. Sounds like a lean condition. Check your vacuum line from intake to petcock. Possibly a leak between the carbs and intake

3. Stock(factory) Ignition Timing is not externally adjustable.

4. I've never heard of matching the stator and cdi. In fact the stator does not even have to function, or exist for your bike to run if you have a fully charged battery. Some racers run total loss systems.

5. Sounds like the RH cylinder is running rich, maybe from a bad diaphram in the petcock.

Good luck.
 
I believe the petcock is working properly, I'm getting gas.

I'm not sure how to sync the carbs or what screw to adjust. The vacume line from the petcock to the carb is good. Would a small leak around the air box really cause that much of a problem? How would you recommend me finding the air leak? I've tightened up everything I can really think of. The air filter is also in pretty bad shape and I have a new one on the way. Thanks for the help
 
Just a small leak...no. However, add all the small leaks together, and you'll have a problem. Take Chef up on the O-ring advice at the intakes...If they have not been done, they need it. Also, all clamps at the airbox, between the airbox and the carbs, and at the intake rubbers. If the electricals all check out, it has to be a lean condition...not enough fuel or too much air. \\:D/
 
Air Screw on the carb

Air Screw on the carb

the airbox is tight as well as the boots from the airbox to the carbs and carbs to the engine. vacume tubes are all right and fine. I can't find the screw to adjust the air on the carb.
 
I'd replace your plugs. After having igniter problems (actually no CDI on these bikes, that box is called an "igniter"), you may have fouled a plug.

Also I don't know if you have mechanical timing advance on your model, but if the timing advance was handled by the igniter box, and you replaced it with one from a different model bike, you could have created a timing problem.

Check primary and secondary resistance on your coils, and resistance on your plug boots, too (do a search for how-to on those); if anything doesn't check out, replace it. Also arc a spare plug grounded against the motor in each plug boot; make sure you're getting a good hot spark on both. Plug the boots back in to the spark plugs in the motor, turn the bike on, and handle them a bit. Got a shock? Replace the boots.

Check voltage to your coils. You want as close to 12v as possible.

If all that checks out your ignition is fine. Move on to possible intake leaks or carb issues. But I'd start with a thorough check of ignition first, since that was your original problem.
 
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