Runs Rough

1982 KZ1000 LTD, 29,000 miles. I've been through just about everything on the bike. Fresh gas, plugs, coils, wires, oil, filter, air filter, chain, sprockets, tires, carbs cleaned, etc, etc.

The bike starts fine idles fine but seems to run rough until it gets above 3,000 RPM. If I bog the engine down just a little below 3K RPM (in any gear it seems) the bike will shudder and buck violently. I am also experiencing some minor backfireing on deceleration.

Carbs and I have bad karma but I'm thinking maybe that's my problem. Any suggestions would be greatly appreciated.

My buddy had the problem with backfiring during deceleration he cleaned the gas tank (ie kreem system) and it ran like a charm.

No other guesses?

Does it have a mechanical advancer?

pilots r plugged

Another thing that may help it out, Removing the smog system.

I think I can rule the advancer out. The pilots are what I will work on next. The smog system can be causing the backfiring but it shouldn't make the engine run rough below 3K RPM should it?

Check to make sure that you do not have any cracks in your fuel line.

I checked mine this year after changing the plugs and noticed a small crack.

After replacing it I experienced no further backfires and the performance increased by a factor of 10.

Something else to look into.

I haad a similar problem like that on my 650. Turns out the clamps on the intake boots had worked themselves loose, creating an air leak.
I could only hope it would be that simple for you.

Ok guy listen closely I had the same problem as you and I had to keep taking off the carbs to clean them, because junk kept clogging my jets. Where you actually have to start is your inline fuel filter if you have one and oil your advancer on the ignition. Also if you do take off the carbs, pull them out from the left side of the bike , but first take note of how the throttle cable is routed before pulling it out. Take the float bowls off and remove needle jets. Also unscrew the clamps that hold down the needle valve socket and check those filters to see if they are clogged and your main jets check for clogging there too.

Have you ever done a carb sync using either a vacuum gage or a mercury type stick gauge. In both cases the carbs must be within a certain range or this might happen. Also have you checked the valve clearances?

Vter Bob wrote:

.... The pilots are what I will work on next....

Are the carb Keihin CV type ? If so then when you have them off for the pilots check and see if you have transition holes. Open the throttle flap and look in and up. Just behind the hole for the pilot air screw may be three tiny holes. If there make sure they are clear. I use a fine pin with a right angle bend on mine (Keihin CV34).
Blocked transition holes can cause a stumble, chug chug at about 2,500 - 3,000 rpm on my 750.