Hi i have just bought a 1991 sportster and I think its running quite rough compared to others I have seen. The bike is the 1200 and it has a Screaming Eagle air file and Carb and the tail pipes are the slash cut drag style ones. I was wondering if someone could point me towards the information I need to get the bike sorted and running better.

 

Are you sure something is wrong?
If its a rigid mounted motor, it will vibrate like a paint shaker.

If its a misfire, check the plug color/condition.

If it is NOT running right, the first place I would look is the carb, it may be plugged up or was never set up right for the mods the bike has.

If it runs ok, but vibrates excessivly, I would check all the hardware, motor mounts, frame bolts, etc.

The vibration on some older bikes was bad enough to crack things over time, and bolts falling off was not unusual...

Brett

 

Hi Brett
Thanks for replying

I have literally just checked the plugs and the gap looks way to big but I need to get a manual so I know the gap (unless someone here knows) and they were quite sooty but I think I should check them again after they have been gapped.

Thats the next thing the Carb I am quite at home jetting carbs did it loads in the 80's, but I need to find out more about the carb before I start playing

 

explain exactly what the bike is doing. Running rough isn't enough to go on. I had both an 88 and an 89 so I could help you with this. BTW.. the plugs will tell you just about everything with your bike. What exactly did they look like.

 

The plugs were quite sooty, and would indicate to me at least that it is running rich, but I am fresh to Harleys so I welcome any advice.

The bike requires no choke to start and won't tick over unless the throttle is held slightly open using the cruise control

 

Id say its running rich. Adjust the AF screw and see if it runs better. Its probably the heat that is affecting your af.

 

I would check the carb float and jet sizes, find out what stock was and see what is in there.
The air fuel screw just does idle mixture on most carbs, nothing above idle.

With a full hot motor, the air/fuel screw should be adjusted for the fastest idle speed, then you can tweak it a little bit each way to see where it idles best over a range of temps.

Make sure you have the correct plugs, and the correct gaps, and the wires are good, then check the carb...

Brett