Backfiring and odd idling

[DeePa]

As you know, i have an 85 200s which i am doing quite of bit of work to, but i dont plan on touching the motor. It runs like a champ except for 2 things.

In order to keep it idling, i have to up the idle speed (by the screw). Its probably around 2000 rpm by my guess. Even then, sometimes it will just start to really sputter and stall out. Starts right back up with the hand on the throttle and a quick pull. Should i have to hold the throttle to get her to start up again? If i dont it could take a good 10-15 pulls and even then it wont start.

Second thing. It backfires when its warm and cold when its in neutral when i rev the engine up. What causes backfiring. There is a champion plus in there now, and i have the correct NGK one coming, so that may make a difference. But what does backfiring mean? I ran a compression test, and got 90 psi, but i dont think i did it 100 % correctly. I have to do it again to find out.

If you can help me out, that'd be spectatcular

Thanks,
Mike

[86200s]

check the valve clearence if its good i would pull the head off and try getting a valve job.

[trikezilla]

Q: "WHAT CAUSES BACKFIRING?"

A: backfiring (on 4 stropkes) is commonlly caused by air leaks and holes in your exhaust system. somehow they trap gasses and cause a little "explosion"

[DeePa]

so could the exhaust manifold being loosly held onto the engine could be causing this? there is only one bolt holding it on because a stud is currently broken.

how about the rough idling??

[Tri-ZNate]

Since you have only one bolt holding the manafold I'd say put another in and it should be quieter if nothing else.

Rough idleing could just be a dirty carb.

[trikezilla]

I doubt a loose exhaust manifold could cause backfiring. IT would make it a little quieter if you put another one on there. Bacfiring can also be caused by all of your gas not being burned off. If it is not completly burned it will go out your exhaust..and can "explode" in there like i mentioned earlier. This leads me to my next point: If you fix the rough idling, it may not cause backfiring because you are getting all the correct gas and air ratios...allowing all of the gas to be burned off

[Oldshell4481]

yeah when i fixed the hole in my exhaust it stopped backfiring

[HaggLE]

You can also get backfiring caused by not enough advance on the ignition timing.

[hondaATCman]

I would say ignition timing or an air leak.

[Vealmonkey]

I had an 85 200x with a broken exhaust stud and it would back fire like crazy, spitting flame and the whole bit. I ended up having to get a used head as a previous owner had been a little too crazy trying to drill out a broken exhaust stud before. Once I replaced the head and new gaskets, especially exhaust, it was fine.