400EX Head studs will pull the threads loose in the cylinder anytime that the cylinder gets too hot breaking down the aluminum. There are several causes of this including overheating of the cylinder during resleaving and poor matching of fuel octane to the engine.

Critical Note:

These heavy duty studs cannot be used if the cylinder was drilled and tapped for Helicoils or drilled and tapped for any other oversize studs with a differant thread diameter and pitch.

Installation Instructions

  You need to first drill and tap the cylinder to accept the new studs. 

Hole machining

7/16-inch course thread. Drill holes with a 3/8 inch bit. It is always best to have a machine shop do this procedure in a vertical mill to ensure proper alignment.

Be sure to hone cylinder after studs are installed. 

Install the new studs using Permatex sleeve retainer on the threads. 

Be sure to install to the correct height. 

The studs must be the correct distance out of the top of the cylinder. 

Front – 2.436”

Rear – 3.188”

Sides – 1.929”

Stock vs. Heavy duty

TRX400EX Heavy Duty Head Studs

  These head studs are for repairing the 400EX and XR 400 cylinder after the thread in the cylinder are damaged or can be installed in a new cylinder to help prevent head gaskets failing as quickly. They have shown to have over 70% more holding strength then the stock head studs due to the increased diameter and the longer threaded area on the studs.

  They can be installed with the cylinder on the quad but we prefer to machine the cylinder for the new studs on a mill for better accuracy.

400EX Heavy Duty Stud Kit.................... #01-001.........................- $59.95

You are welcome to send your cylinder in to us for stud installation. We have it machined in a Milling machine to ensure accurate drilling and tapping.

Head Stud Installation ............ $55.00

To order see Snure Interlocking or an authorized dealer near you

Head Gasket

This is a custom made head gasket. It is .005 thicker then stock to help lessen detonation related problems. It is a 3 piece stainless head gasket. It has an 89mm bore making it great for the 440 kits.

400EX Custom Head Gasket.......#01-002...............$49.95

To order see Snure Interlocking or an authorized dealer near you