back firing upon starting, help!

[ryanrod]

Hello all, I've got a 1982 Suzuki gs650, it's my only form of transportation, so I need it to run - even if it's just to a mechanic. I'll start by saying the carbs have been cleaned and tuned by a professional. Spark plugs are clean, and it's got good compression. However, it's been running like crap. Bogging all the time, tops out at 40 miles an hour (on the street). I think there's something wrong with the fuel/air, but the carbs are clean. How can I fix this or make this better?

 

[JJ]

Hello all, I've got a 1982 Suzuki gs650, it's my only form of transportation, so I need it to run - even if it's just to a mechanic. I'll start by saying the carbs have been cleaned and tuned by a professional. Spark plugs are clean, and it's got good compression. However, it's been running like crap. Bogging all the time, tops out at 40 miles an hour (on the street). I think there's something wrong with the fuel/air, but the carbs are clean. How can I fix this or make this better?

You didn't say when the carbs were supposedly cleaned and tuned by a "professional". Was it running crappy before they cleaned and tuned them, or did your problems start after the cleaning? You'd be surprised at the shortcuts that some "professionals" take, and the lies they will tell you. Did they synch and adjust them on the bike?

 

[Guest]

yep, wouldn't be the first "professional" to not do a good enough job on gs carbs.

 

[tom203]

Maintained properly, this thing will run well-50 +mpg- with more power than you'll likely need. How are you at mechanical stuff? Or...do you have oodles of cash waiting to be tossed?
Wait, you've joined here almost two years ago..... Did it suddenly behave badly? Any warning signs? What maintenance have you personally done?

 

[Guest]

Check your plug wires you might have crossed one.

 

[Who Dat?]

Poor starting (especially when cold) is often a symptom of tight valves. Have the clearances been checked?

 

[tkent02]

What are you using for an air box?

 

[loud et]

If the carbs were just recently removed, the airbox to carb boots may not be seated properly. They may have slipped off and are sucking too much air.
I doubt modern shops dip carbs completely for 24 hours. Maybe they just shoot it out with some carb cleaner and replaced the standard bits with a low grade rebuild kit.
Who knows.
Bench syncing is easy but very crucial. Who knows how deep they went into the carb rebuild process.
I am lucky to have learned a full and proper carb rebuild procedure and understand proper airbox and boot sealing and replacing the intake manifolds and o rings.
It sucks it's your only transportation, but these things gotta be right.

 

[ryanrod]

Maintained properly, this thing will run well-50 +mpg- with more power than you'll likely need. How are you at mechanical stuff? Or...do you have oodles of cash waiting to be tossed?
Wait, you've joined here almost two years ago..... Did it suddenly behave badly? Any warning signs? What maintenance have you personally done?

Thanks to those who replied.
I'm not afraid to get my hands dirty, I just don't want to mess anything up. I believe it has something to do with fuel/air - which is probably carburetors. I'll take a look at them and see what the dude actually did. It's got pod filters on it, no airbox unfortunately.

 

[tkent02]

Was it properly jetted for these pods?

 

[tom203]

You didn't say whether this poor running developed suddenly.... or it's been like this you've had bike.

Are the pods a new improved feature?

 

[Who Dat?]

Here, Tom, I fixed your question.

Are the pods a new "improved" feature?

 

[ryanrod]

So I drained the carbs and now it doesn't backfire upon starting up. I wish the previous owner kept the airbox, but I didn't know anything about these things when I bought it. It's been rejetted between 110 and 115 I want to say. It's been about a year since it's run good. I took a spill on it after manually screwing in a loose spark plug after the rejetting process. I'm having a buddy look at it. I'll report back with the results.

 

[Who Dat?]

So I drained the carbs and now it doesn't backfire upon starting up.

If you have truly drained the carbs, it's a wonder that it starts at all. How does it run with no gas in the carbs?

It's been rejetted between 110 and 115 I want to say.

It would really help to know, because 110 is stock. 115 is not really enough to compensate for pods, but it also depends on which pods you have. Different brands have different airflow abilities, which means they need different jetting.

One additional question: you have stock exhaust or a header on the bike? Yep, if you have a header, it requires different jetting, too.

 

[jdvorchak]

Really it sounds like you don't have the plug wires on the correct spark plug. Backfiring, bogging, won't go over 50 all point to spark issues. For a sanity check make sure that 1and4 are firing off the same coil and 2and3 are on the other.

I was working on a guys GS1100 last summer and noted that the PO had put aftermarket Dyna coils on it. That is a good thing but on the left coil one of the primary wires had come loose from the crimp on terminal. I cleaned it up and crimped on a new terminal and for the first time since that kid has owned that bike it ran on all 4 cylinders. His complaint was similar to yours. Poor mileage, bogging won't go over 40 mph...