Maintenance & Troubleshooting MIG Consumables MIG Welding

MIG Welder Birdnesting and Burnback: Causes and Fixes for Drive Rolls, Liners and Tips

Why MIG wire tangles at the drive rolls or welds itself to the contact tip, how to tell which part is causing it, and how to fix it.

Published November 4, 2026

MIG wire tangled in a birdnest at the drive rolls, and a burnback with the wire fused to the contact tip

In this guide

Quick answer: Birdnesting is when MIG wire tangles at the drive rolls because something further down the gun is stopping it. Burnback is when the wire melts back and welds itself to the contact tip. Both usually come from the same three parts: the drive rolls, the liner and the contact tip. Check them in that order, then check your wire speed, voltage and gun distance.

Birdnesting: Wire tangles at the drive rolls. Look for a block or drag further down the gun.
Burnback: Wire welds itself to the contact tip. Usually wire speed too slow, or the gun too close.
Main causes: Drive rolls, liner or contact tip that is the wrong size, worn, dirty or badly set.
Fix order: Start at the machine and work towards the tip.

What is birdnesting?

Birdnesting, also called a bird's nest, happens when the drive rolls keep pushing wire that cannot move forward. The wire buckles and wraps around the drive rolls inside the machine. The tangle shows up at the rolls, but the cause is almost always further down: a blocked contact tip, a liner that drags, or a gap the wire can bend into.

What is burnback?

Burnback happens when the wire melts faster than it feeds. The arc climbs back to the contact tip and welds the wire to it, so you see a small ball of metal on the end of the tip and the wire stops feeding.

Many machines also have a burnback setting. It keeps the wire live for a moment after you release the trigger, so the wire does not stick in the weld. Set too high, it can melt the wire back to the tip.

Swipe sideways to see the whole drawing.

A birdnest shows up at the drive rolls and a burnback at the contact tip, but both can start anywhere along the wire path.

Birdnesting: causes and fixes

Cause	How to tell	Fix
Drive roll tension too tight	Wire looks flattened or marked	Loosen it and reset with the test below
Wrong drive roll groove	Groove does not match the wire size or type	V-groove for solid wire, knurled for flux-cored, U-groove for aluminum
Gap at the drive rolls	Wire bends between the rolls and the gun	Fit the right wire guides and push the gun fully into the machine
Liner wrong size	Problem started after a new liner or wire size	Fit a liner made for your wire size
Liner cut too short, kinked or dirty	Wire is hard to pull through the gun by hand	Replace the liner and trim it with the cable laid straight
Contact tip blocked or too small	Spatter on the tip, or tip size does not match the wire	Fit a new tip that matches your wire size
Gun cable coiled or bent	Problem stops when the cable is straight	Keep the cable straight and use the shortest one that does the job
Soft wire in a long gun	Aluminum or thin wire through a long cable	Use a spool gun or a push-pull gun

See What size MIG gun do I need? for cable lengths and guns for soft wire, and shop necks and liners.

Burnback: causes and fixes

Cause	How to tell	Fix
Wire speed too slow for the voltage	The arc gets long and the wire melts back as you weld	Raise the wire speed or lower the voltage, starting from your machine's chart
Gun held too close	Tip and nozzle run very hot and collect spatter	Keep about 3/8 in. (10 mm) of wire sticking out for solid wire
Wire feed stutters	Wire speed changes while you weld	Reset drive roll tension and check the liner
Contact tip worn, wrong size or loose	Bore is oval, or the tip turns by hand	Fit a new tip of the right size and tighten it
Spatter on the tip	Spatter balls on the end of the tip and nozzle	Clean with MIG pliers, use anti-spatter, replace the tip when needed
Poor work clamp connection	Arc is unstable and the clamp gets warm	Clamp on clean, bare metal close to the weld
Burnback setting too high	Wire sticks to the tip right after you stop	Turn the setting down towards the middle

Swipe sideways to see the whole drawing.

With the right wire speed and gun distance, the arc stays at the work. Too close or too slow, and the heat reaches the contact tip.

Flux-cored wire usually needs more wire sticking out than solid wire, so check the spool label. Shop contact tips and anti-spatter.

How to set drive roll tension

Check the groove: the groove facing the wire must match your wire size and type.
Loosen the tension knob until the wire slips at the rolls when you pull the trigger.
Hold the gun about 1 in. (25 mm) from a block of wood and pull the trigger.
Tighten half a turn at a time until the wire stops slipping and curls against the wood.
Stop there, or add no more than another half turn.

Tension	What happens
Too loose	Wire slips, the feed stutters and the wire can burn back
Right	Wire feeds smoothly at a steady speed
Too tight	Wire gets flattened, the rolls and liner wear, and the wire birdnests if anything blocks it

Flux-cored wire is a soft tube, so it needs a knurled roll and less tension than solid wire. See the MIG wire size chart for the parts to match to each wire size.

Check the parts in this order

Work from the machine towards the tip, one part at a time, so you find the cause instead of guessing.

Spool: the hub brake should stop the spool when you release the trigger, without loose loops of wire.
Drive rolls: right groove, right size, not worn, tension set with the test above.
Wire guides and gun connection: no gap between the rolls and the gun, and the gun pushed fully in.
Liner: right size for the wire, clean, cut to the right length and free of kinks.
Contact tip: right size, not worn oval, free of spatter and screwed in tight. See our contact tip and nozzle compatibility guide.
Settings and technique: wire speed and voltage from the machine's chart, the right gun distance and a clean work clamp connection.

How to prevent birdnesting and burnback

Replace contact tips before the bore wears oval, and keep a few spares in the right size.
Clean spatter off the tip and nozzle during breaks.
Blow out the liner with dry compressed air when you change the wire spool.
Keep the gun cable straight, without loops, while you weld.
Store wire in a dry place so it does not rust and drag in the liner.

Safety when you fix a wire feed problem

Turn the machine off before you change the contact tip, liner or drive rolls, or untangle a birdnest.

On most machines the wire is electrically live whenever the trigger is pressed, so keep fingers clear of the drive rolls and point the gun away from yourself and others. The tip and nozzle stay hot after welding, so let them cool or wear welding gloves. Cut wire with pliers and hold the loose end, because it springs. In Canada, CSA W117.2 covers safety in welding, cutting and allied processes. Always follow your machine manual.

Frequently asked questions

Why does my MIG welder keep birdnesting?

The wire is blocked or dragging somewhere between the drive rolls and the contact tip, while the rolls keep pushing. Check the drive roll groove and tension, then the liner, then the contact tip. Too much drive roll tension makes it worse, because the rolls keep forcing wire that cannot move.

Why does my MIG wire keep burning back to the tip?

Usually the wire speed is too slow for the voltage, or the gun is held too close to the work. A feed that stutters, a worn tip or a poor work clamp connection can also cause it. Start from your machine's settings chart and keep about 3/8 in. (10 mm) of solid wire sticking out.

How tight should MIG drive rolls be?

Just tight enough that the wire does not slip. Loosen the tension until the wire slips, then tighten half a turn at a time until it feeds steadily into a block of wood. Add no more than another half turn.

Can the wrong contact tip cause birdnesting?

Yes. A tip that is too small or blocked with spatter stops the wire, so it tangles at the drive rolls. A tip that is too large lets the wire wander, which makes the arc unstable and can cause burnback. Use a tip that matches your wire size.

Can a MIG liner cause birdnesting?

Yes. A liner that is the wrong size, cut too short, kinked or full of dirt makes the wire drag. Fit a liner made for your wire size and trim it to length with the gun cable laid straight.

How do I fix a MIG burnback?

Turn the machine off, cut the wire, remove the contact tip and fit a new one. The bore of a tip with wire welded to it is usually damaged. Then find the cause, such as wire speed, gun distance or feeding, before you weld again.

What does the burnback setting do on a MIG welder?

It keeps the wire live for a moment after you release the trigger, so the end of the wire does not stick in the weld. Too low, and the wire sticks in the weld. Too high, and it can melt the wire back to the tip.

Does flux-cored wire birdnest more easily?

It can, because flux-cored wire is a soft tube that flattens under too much pressure. Use a knurled drive roll in the right size and less tension than you would use for solid wire.

Still getting birdnests or burnbacks?

Email a photo of your drive rolls, contact tip and machine rating plate to orders@mapindpro.com, call 905-919-1177, or visit our Toronto counter. We'll help you find the cause and the right parts.

Email us Call 905-919-1177 Shop contact tips

3625 Weston Road, Unit 10, Toronto, ON M9L 1V9. Monday to Thursday 8 am to 4:30 pm, Friday and Saturday 8 am to 12:30 pm.

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