Weird, Puzzling Performance

[bjrpkr]

On the way home last week, I hit a bump rather hard and right after that my 1979 GS850 started running rough, felt like only 2 of 4 cylinders were firing. Well, first thing I thought was intake boots. Sure enough the O Rings were shot. Put in new O Rings. Same problem. Put in new plugs, no difference. I've checked the wiring from points to coils, everything looks OK. I fiddled with the timing a little and had a minor improvement. Makes me think something electrical. Plugs in cylinders 2 and 3 look slightly wet like I'm not getting good fire. My next step is new points and condensers. Anything you gurus can think of? I'm kind of stumped and summer is running out!

 

[BassCliff]

Hi,

Something like this happened to me once. After a lot of careful inspection I found one of my 12v coil wires had fallen off. I wrote up a little repair guide - CLICK HERE.

Take off the seat, tank, side covers, and look in the head light bucket for any loose, pinched, frayed wires or broken connections. Plug caps can be a problem but are cheap to replace.

Thank you for your indulgence,

BassCliff

 

[trippivot]

hit a bump and you think a intake o ring failed?

float needles can be effected by a major shock, a bad electrical connection can be made worse OR better.

Adjusting the points and getting an improvement has me thinking you might have more than 1 problem with your bike.

I'd start by checking that you have snappy blue spark on all 4 cylinders. Then I'd do resistance tests and voltage drop tests on the ignition system. Following the ignition diag. I'd go thru everything just to kick up potential problems and fix them now.

 

[Big T]

New points and condensors are a good start, a Dyna S would be better

Then, check the wires to the coils, the coils, the plug wires and the caps

 

[DanTheMan]

I had one of the air box mounting bolts fall out and the air box pulled a couple of the boots loose causing the very problem you describe. You might want to check that area as well.

 

[kdo58]

I have a 79 850 it started running bad, I cleaned the air filter and change the points, now it runs great.
cheapest place I have found points
http://www.procycledepot.com/home.html

 

[Guest]

I'd start with the simple and cheap stuff first. PLugs and wires. Good fire.
If not for the hitting of the bump I would think the problem to be fuel related.

I'm wondering, you had the carbs off to do the intake orings but ya didnt dip the carbs? I know its a few day process and your right, summer is running out. But still, you could be chasing this one around for a couple of weeks.
I usually install new(new) plugs no matter what. If no better then you'll have an extra set.

Keep us posted!